diff --git a/clang/docs/DataFlowSanitizer.rst b/clang/docs/DataFlowSanitizer.rst
--- a/clang/docs/DataFlowSanitizer.rst
+++ b/clang/docs/DataFlowSanitizer.rst
@@ -140,59 +140,14 @@
 Example
 =======
 
+DataFlowSanitizer supports up to 8 labels, to achieve low CPU and code
+size overhead. Base labels are simply 8-bit unsigned integers that are
+powers of 2 (i.e. 1, 2, 4, 8, ..., 128), and union labels are created
+by ORing base labels.
+
 The following program demonstrates label propagation by checking that
 the correct labels are propagated.
 
-.. code-block:: c++
-
-  #include <sanitizer/dfsan_interface.h>
-  #include <assert.h>
-
-  int main(void) {
-    int i = 1;
-    dfsan_label i_label = dfsan_create_label("i", 0);
-    dfsan_set_label(i_label, &i, sizeof(i));
-
-    int j = 2;
-    dfsan_label j_label = dfsan_create_label("j", 0);
-    dfsan_set_label(j_label, &j, sizeof(j));
-
-    int k = 3;
-    dfsan_label k_label = dfsan_create_label("k", 0);
-    dfsan_set_label(k_label, &k, sizeof(k));
-
-    dfsan_label ij_label = dfsan_get_label(i + j);
-    assert(dfsan_has_label(ij_label, i_label));
-    assert(dfsan_has_label(ij_label, j_label));
-    assert(!dfsan_has_label(ij_label, k_label));
-
-    dfsan_label ijk_label = dfsan_get_label(i + j + k);
-    assert(dfsan_has_label(ijk_label, i_label));
-    assert(dfsan_has_label(ijk_label, j_label));
-    assert(dfsan_has_label(ijk_label, k_label));
-
-    return 0;
-  }
-
-fast16labels mode
-=================
-
-If you need 16 or fewer labels, you can use fast16labels instrumentation for
-less CPU and code size overhead.  To use fast16labels instrumentation, you'll
-need to specify `-fsanitize=dataflow -mllvm -dfsan-fast-16-labels` in your
-compile and link commands and use a modified API for creating and managing
-labels.
-
-In fast16labels mode, base labels are simply 16-bit unsigned integers that are
-powers of 2 (i.e. 1, 2, 4, 8, ..., 32768), and union labels are created by ORing
-base labels.  In this mode DFSan does not manage any label metadata, so the
-functions `dfsan_create_label`, `dfsan_union`, `dfsan_get_label_info`,
-`dfsan_has_label`, `dfsan_has_label_with_desc`, `dfsan_get_label_count`, and
-`dfsan_dump_labels` are unsupported.  Instead of using them, the user should
-maintain any necessary metadata about base labels themselves.
-
-For example:
-
 .. code-block:: c++
 
   #include <sanitizer/dfsan_interface.h>
@@ -216,6 +171,11 @@
     assert(!(ij_label & k_label));  // ij_label doesn't have k_label
     assert(ij_label == 3);  // Verifies all of the above
 
+    // Or, equivalently:
+    assert(dfsan_has_label(ij_label, i_label));
+    assert(dfsan_has_label(ij_label, j_label));
+    assert(!dfsan_has_label(ij_label, k_label));
+
     dfsan_label ijk_label = dfsan_get_label(i + j + k);
 
     assert(ijk_label & i_label);  // ijk_label has i_label
@@ -223,6 +183,11 @@
     assert(ijk_label & k_label);  // ijk_label has k_label
     assert(ijk_label == 7);  // Verifies all of the above
 
+    // Or, equivalently:
+    assert(dfsan_has_label(ijk_label, i_label));
+    assert(dfsan_has_label(ijk_label, j_label));
+    assert(dfsan_has_label(ijk_label, k_label));
+
     return 0;
   }
 
diff --git a/clang/docs/DataFlowSanitizerDesign.rst b/clang/docs/DataFlowSanitizerDesign.rst
--- a/clang/docs/DataFlowSanitizerDesign.rst
+++ b/clang/docs/DataFlowSanitizerDesign.rst
@@ -12,9 +12,7 @@
 a number of taint labels with any data stored in any memory region
 accessible by the program. The analysis is dynamic, which means that
 it operates on a running program, and tracks how the labels propagate
-through that program. The tool shall support a large (>100) number
-of labels, such that programs which operate on large numbers of data
-items may be analysed with each data item being tracked separately.
+through that program.
 
 Use Cases
 ---------
@@ -28,16 +26,13 @@
 Interface
 ---------
 
-A number of functions are provided which will create taint labels,
-attach labels to memory regions and extract the set of labels
-associated with a specific memory region. These functions are declared
-in the header file ``sanitizer/dfsan_interface.h``.
+A number of functions are provided which will attach taint labels to
+memory regions and extract the set of labels associated with a
+specific memory region. These functions are declared in the header
+file ``sanitizer/dfsan_interface.h``.
 
 .. code-block:: c
 
-  /// Creates and returns a base label with the given description and user data.
-  dfsan_label dfsan_create_label(const char *desc, void *userdata);
-
   /// Sets the label for each address in [addr,addr+size) to \c label.
   void dfsan_set_label(dfsan_label label, void *addr, size_t size);
 
@@ -53,93 +48,57 @@
   /// value.
   dfsan_label dfsan_get_label(long data);
 
-  /// Retrieves a pointer to the dfsan_label_info struct for the given label.
-  const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label);
-
   /// Returns whether the given label label contains the label elem.
   int dfsan_has_label(dfsan_label label, dfsan_label elem);
 
-  /// If the given label label contains a label with the description desc, returns
-  /// that label, else returns 0.
-  dfsan_label dfsan_has_label_with_desc(dfsan_label label, const char *desc);
+  /// Computes the union of \c l1 and \c l2, resulting in a union label.
+  dfsan_label dfsan_union(dfsan_label l1, dfsan_label l2);
 
 Taint label representation
 --------------------------
 
-As stated above, the tool must track a large number of taint
-labels. This poses an implementation challenge, as most multiple-label
-tainting systems assign one label per bit to shadow storage, and
-union taint labels using a bitwise or operation. This will not scale
-to clients which use hundreds or thousands of taint labels, as the
-label union operation becomes O(n) in the number of supported labels,
-and data associated with it will quickly dominate the live variable
-set, causing register spills and hampering performance.
-
-Instead, a low overhead approach is proposed which is best-case O(log\
-:sub:`2` n) during execution. The underlying assumption is that
-the required space of label unions is sparse, which is a reasonable
-assumption to make given that we are optimizing for the case where
-applications mostly copy data from one place to another, without often
-invoking the need for an actual union operation. The representation
-of a taint label is a 16-bit integer, and new labels are allocated
-sequentially from a pool. The label identifier 0 is special, and means
-that the data item is unlabelled.
-
-When a label union operation is requested at a join point (any
-arithmetic or logical operation with two or more operands, such as
-addition), the code checks whether a union is required, whether the
-same union has been requested before, and whether one union label
-subsumes the other. If so, it returns the previously allocated union
-label. If not, it allocates a new union label from the same pool used
-for new labels.
-
-Specifically, the instrumentation pass will insert code like this
-to decide the union label ``lu`` for a pair of labels ``l1``
-and ``l2``:
-
-.. code-block:: c
-
-  if (l1 == l2)
-    lu = l1;
-  else
-    lu = __dfsan_union(l1, l2);
-
-The equality comparison is outlined, to provide an early exit in
-the common cases where the program is processing unlabelled data, or
-where the two data items have the same label.  ``__dfsan_union`` is
-a runtime library function which performs all other union computation.
+We use an 8-bit unsigned integer for the representation of a
+label. The label identifier 0 is special, and means that the data item
+is unlabelled. This is optimizing for low CPU and code size overhead
+of the instrumentation. When a label union operation is requested at a
+join point (any arithmetic or logical operation with two or more
+operands, such as addition), we can simply OR the two labels in O(1).
 
-Further optimizations are possible, for example if ``l1`` is known
-at compile time to be zero (e.g. it is derived from a constant),
-``l2`` can be used for ``lu``, and vice versa.
+Users are responsible for managing the 8 integer labels (i.e., keeping
+track of what labels they have used so far, picking one that is yet
+unused, etc).
 
 Memory layout and label management
 ----------------------------------
 
-The following is the current memory layout for Linux/x86\_64:
+The following is the memory layout for Linux/x86\_64:
 
 +---------------+---------------+--------------------+
 |    Start      |    End        |        Use         |
 +===============+===============+====================+
 | 0x700000008000|0x800000000000 | application memory |
 +---------------+---------------+--------------------+
-| 0x200200000000|0x700000008000 |       unused       |
+| 0x300000000000|0x700000008000 |       unused       |
++---------------+---------------+--------------------+
+| 0x200000008000|0x300000000000 |       origin       |
++---------------+---------------+--------------------+
+| 0x200000000000|0x200000008000 |       unused       |
 +---------------+---------------+--------------------+
-| 0x200000000000|0x200200000000 |    union table     |
+| 0x100000008000|0x200000000000 |   shadow memory    |
 +---------------+---------------+--------------------+
-| 0x000000010000|0x200000000000 |   shadow memory    |
+| 0x000000010000|0x100000008000 |       unused       |
 +---------------+---------------+--------------------+
 | 0x000000000000|0x000000010000 | reserved by kernel |
 +---------------+---------------+--------------------+
 
-Each byte of application memory corresponds to two bytes of shadow
-memory, which are used to store its taint label. As for LLVM SSA
+Each byte of application memory corresponds to a single byte of shadow
+memory, which is used to store its taint label. As for LLVM SSA
 registers, we have not found it necessary to associate a label with
 each byte or bit of data, as some other tools do. Instead, labels are
 associated directly with registers.  Loads will result in a union of
-all shadow labels corresponding to bytes loaded (which most of the
-time will be short circuited by the initial comparison) and stores will
-result in a copy of the label to the shadow of all bytes stored to.
+all shadow labels corresponding to bytes loaded, and stores will
+result in a copy of the label of the stored value to the shadow of all
+bytes stored to.
 
 Propagating labels through arguments
 ------------------------------------
diff --git a/compiler-rt/include/sanitizer/dfsan_interface.h b/compiler-rt/include/sanitizer/dfsan_interface.h
--- a/compiler-rt/include/sanitizer/dfsan_interface.h
+++ b/compiler-rt/include/sanitizer/dfsan_interface.h
@@ -21,34 +21,15 @@
 extern "C" {
 #endif
 
-typedef uint16_t dfsan_label;
+typedef uint8_t dfsan_label;
 typedef uint32_t dfsan_origin;
 
-/// Stores information associated with a specific label identifier.  A label
-/// may be a base label created using dfsan_create_label, with associated
-/// text description and user data, or an automatically created union label,
-/// which represents the union of two label identifiers (which may themselves
-/// be base or union labels).
-struct dfsan_label_info {
-  // Fields for union labels, set to 0 for base labels.
-  dfsan_label l1;
-  dfsan_label l2;
-
-  // Fields for base labels.
-  const char *desc;
-  void *userdata;
-};
-
 /// Signature of the callback argument to dfsan_set_write_callback().
 typedef void (*dfsan_write_callback_t)(int fd, const void *buf, size_t count);
 
-/// Computes the union of \c l1 and \c l2, possibly creating a union label in
-/// the process.
+/// Computes the union of \c l1 and \c l2, resulting in a union label.
 dfsan_label dfsan_union(dfsan_label l1, dfsan_label l2);
 
-/// Creates and returns a base label with the given description and user data.
-dfsan_label dfsan_create_label(const char *desc, void *userdata);
-
 /// Sets the label for each address in [addr,addr+size) to \c label.
 void dfsan_set_label(dfsan_label label, void *addr, size_t size);
 
@@ -73,19 +54,9 @@
 /// Retrieves the label associated with the data at the given address.
 dfsan_label dfsan_read_label(const void *addr, size_t size);
 
-/// Retrieves a pointer to the dfsan_label_info struct for the given label.
-const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label);
-
 /// Returns whether the given label label contains the label elem.
 int dfsan_has_label(dfsan_label label, dfsan_label elem);
 
-/// If the given label label contains a label with the description desc, returns
-/// that label, else returns 0.
-dfsan_label dfsan_has_label_with_desc(dfsan_label label, const char *desc);
-
-/// Returns the number of labels allocated.
-size_t dfsan_get_label_count(void);
-
 /// Flushes the DFSan shadow, i.e. forgets about all labels currently associated
 /// with the application memory.  Use this call to start over the taint tracking
 /// within the same process.
@@ -99,12 +70,6 @@
 /// callback executes.  Pass in NULL to remove any callback.
 void dfsan_set_write_callback(dfsan_write_callback_t labeled_write_callback);
 
-/// Writes the labels currently used by the program to the given file
-/// descriptor. The lines of the output have the following format:
-///
-/// <label> <parent label 1> <parent label 2> <label description if any>
-void dfsan_dump_labels(int fd);
-
 /// Interceptor hooks.
 /// Whenever a dfsan's custom function is called the corresponding
 /// hook is called it non-zero. The hooks should be defined by the user.
diff --git a/compiler-rt/lib/dfsan/dfsan.h b/compiler-rt/lib/dfsan/dfsan.h
--- a/compiler-rt/lib/dfsan/dfsan.h
+++ b/compiler-rt/lib/dfsan/dfsan.h
@@ -18,21 +18,14 @@
 
 #include "dfsan_platform.h"
 
-using __sanitizer::u16;
 using __sanitizer::u32;
+using __sanitizer::u8;
 using __sanitizer::uptr;
 
 // Copy declarations from public sanitizer/dfsan_interface.h header here.
-typedef u16 dfsan_label;
+typedef u8 dfsan_label;
 typedef u32 dfsan_origin;
 
-struct dfsan_label_info {
-  dfsan_label l1;
-  dfsan_label l2;
-  const char *desc;
-  void *userdata;
-};
-
 extern "C" {
 void dfsan_add_label(dfsan_label label, void *addr, uptr size);
 void dfsan_set_label(dfsan_label label, void *addr, uptr size);
@@ -68,7 +61,7 @@
 void initialize_interceptors();
 
 inline dfsan_label *shadow_for(void *ptr) {
-  return (dfsan_label *) ((((uptr) ptr) & ShadowMask()) << 1);
+  return (dfsan_label *)(((uptr)ptr) & ShadowMask());
 }
 
 inline const dfsan_label *shadow_for(const void *ptr) {
@@ -76,7 +69,7 @@
 }
 
 inline uptr unaligned_origin_for(uptr ptr) {
-  return OriginAddr() + (ptr & ShadowMask());
+  return OriginAddr() - ShadowAddr() + (ptr & ShadowMask());
 }
 
 inline dfsan_origin *origin_for(void *ptr) {
@@ -98,6 +91,15 @@
   return is_shadow_addr_valid((uptr)ptr_s);
 }
 
+inline bool is_origin_addr_valid(uptr origin_addr) {
+  return (uptr)origin_addr >= OriginAddr() && (uptr)origin_addr < UnusedAddr();
+}
+
+inline bool has_valid_origin_addr(const void *ptr) {
+  const dfsan_origin *ptr_orig = origin_for(ptr);
+  return is_origin_addr_valid((uptr)ptr_orig);
+}
+
 void dfsan_copy_memory(void *dst, const void *src, uptr size);
 
 void dfsan_allocator_init();
diff --git a/compiler-rt/lib/dfsan/dfsan.cpp b/compiler-rt/lib/dfsan/dfsan.cpp
--- a/compiler-rt/lib/dfsan/dfsan.cpp
+++ b/compiler-rt/lib/dfsan/dfsan.cpp
@@ -36,14 +36,6 @@
 
 using namespace __dfsan;
 
-typedef atomic_uint16_t atomic_dfsan_label;
-static const dfsan_label kInitializingLabel = -1;
-
-static const uptr kNumLabels = 1 << (sizeof(dfsan_label) * 8);
-
-static atomic_dfsan_label __dfsan_last_label;
-static dfsan_label_info __dfsan_label_info[kNumLabels];
-
 Flags __dfsan::flags_data;
 
 // The size of TLS variables. These constants must be kept in sync with the ones
@@ -80,22 +72,22 @@
 // |                    |
 // |       unused       |
 // |                    |
-// +--------------------+ 0x300200000000 (kUnusedAddr)
-// |    union table     |
-// +--------------------+ 0x300000000000 (kUnionTableAddr)
+// +--------------------+ 0x300000000000 (kUnusedAddr)
 // |       origin       |
-// +--------------------+ 0x200000000000 (kOriginAddr)
+// +--------------------+ 0x200000008000 (kOriginAddr)
+// |       unused       |
+// +--------------------+ 0x200000000000
 // |   shadow memory    |
-// +--------------------+ 0x000000010000 (kShadowAddr)
+// +--------------------+ 0x100000008000 (kShadowAddr)
+// |       unused       |
+// +--------------------+ 0x000000010000
 // | reserved by kernel |
 // +--------------------+ 0x000000000000
 //
-// To derive a shadow memory address from an application memory address,
-// bits 44-46 are cleared to bring the address into the range
-// [0x000000008000,0x100000000000).  Then the address is shifted left by 1 to
-// account for the double byte representation of shadow labels and move the
-// address into the shadow memory range.  See the function shadow_for below.
-
+// To derive a shadow memory address from an application memory address, bits
+// 45-46 are cleared to bring the address into the range
+// [0x100000008000,0x200000000000).  See the function shadow_for below.
+//
 // On Linux/MIPS64, memory is laid out as follows:
 //
 // +--------------------+ 0x10000000000 (top of memory)
@@ -104,11 +96,11 @@
 // |                    |
 // |       unused       |
 // |                    |
-// +--------------------+ 0x2200000000 (kUnusedAddr)
-// |    union table     |
-// +--------------------+ 0x2000000000 (kUnionTableAddr)
+// +--------------------+ 0x2000000000 (kUnusedAddr)
 // |   shadow memory    |
-// +--------------------+ 0x0000010000 (kShadowAddr)
+// +--------------------+ 0x1000008000 (kShadowAddr)
+// |       unused       |
+// +--------------------+ 0x0000010000
 // | reserved by kernel |
 // +--------------------+ 0x0000000000
 
@@ -120,9 +112,7 @@
 // |                    |
 // |       unused       |
 // |                    |
-// +--------------------+ 0x1200000000 (kUnusedAddr)
-// |    union table     |
-// +--------------------+ 0x1000000000 (kUnionTableAddr)
+// +--------------------+ 0x1000000000 (kUnusedAddr)
 // |   shadow memory    |
 // +--------------------+ 0x0000010000 (kShadowAddr)
 // | reserved by kernel |
@@ -136,9 +126,7 @@
 // |                    |
 // |       unused       |
 // |                    |
-// +--------------------+ 0x1200000000 (kUnusedAddr)
-// |    union table     |
-// +--------------------+ 0x8000000000 (kUnionTableAddr)
+// +--------------------+ 0x8000000000 (kUnusedAddr)
 // |   shadow memory    |
 // +--------------------+ 0x0000010000 (kShadowAddr)
 // | reserved by kernel |
@@ -156,102 +144,19 @@
 // |                    |
 // |       unused       |
 // |                    |
-// +--------------------+ 0x1200000000 (kUnusedAddr)
-// |    union table     |
-// +--------------------+ 0x8000000000 (kUnionTableAddr)
+// +--------------------+ 0x8000000000 (kUnusedAddr)
 // |   shadow memory    |
 // +--------------------+ 0x0000010000 (kShadowAddr)
 // | reserved by kernel |
 // +--------------------+ 0x0000000000
 
-typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels];
-
 #ifdef DFSAN_RUNTIME_VMA
 // Runtime detected VMA size.
 int __dfsan::vmaSize;
 #endif
 
-static uptr UnusedAddr() {
-  return UnionTableAddr() + sizeof(dfsan_union_table_t);
-}
-
-static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) {
-  return &(*(dfsan_union_table_t *) UnionTableAddr())[l1][l2];
-}
-
-// Checks we do not run out of labels.
-static void dfsan_check_label(dfsan_label label) {
-  if (label == kInitializingLabel) {
-    Report("FATAL: DataFlowSanitizer: out of labels\n");
-    Die();
-  }
-}
-
-// Resolves the union of two unequal labels.  Nonequality is a precondition for
-// this function (the instrumentation pass inlines the equality test).
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE
-dfsan_label __dfsan_union(dfsan_label l1, dfsan_label l2) {
-  DCHECK_NE(l1, l2);
-
-  if (l1 == 0)
-    return l2;
-  if (l2 == 0)
-    return l1;
-
-  // If no labels have been created, yet l1 and l2 are non-zero, we are using
-  // fast16labels mode.
-  if (atomic_load(&__dfsan_last_label, memory_order_relaxed) == 0)
-    return l1 | l2;
-
-  if (l1 > l2)
-    Swap(l1, l2);
-
-  atomic_dfsan_label *table_ent = union_table(l1, l2);
-  // We need to deal with the case where two threads concurrently request
-  // a union of the same pair of labels.  If the table entry is uninitialized,
-  // (i.e. 0) use a compare-exchange to set the entry to kInitializingLabel
-  // (i.e. -1) to mark that we are initializing it.
-  dfsan_label label = 0;
-  if (atomic_compare_exchange_strong(table_ent, &label, kInitializingLabel,
-                                     memory_order_acquire)) {
-    // Check whether l2 subsumes l1.  We don't need to check whether l1
-    // subsumes l2 because we are guaranteed here that l1 < l2, and (at least
-    // in the cases we are interested in) a label may only subsume labels
-    // created earlier (i.e. with a lower numerical value).
-    if (__dfsan_label_info[l2].l1 == l1 ||
-        __dfsan_label_info[l2].l2 == l1) {
-      label = l2;
-    } else {
-      label =
-        atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
-      dfsan_check_label(label);
-      __dfsan_label_info[label].l1 = l1;
-      __dfsan_label_info[label].l2 = l2;
-    }
-    atomic_store(table_ent, label, memory_order_release);
-  } else if (label == kInitializingLabel) {
-    // Another thread is initializing the entry.  Wait until it is finished.
-    do {
-      internal_sched_yield();
-      label = atomic_load(table_ent, memory_order_acquire);
-    } while (label == kInitializingLabel);
-  }
-  return label;
-}
-
 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 dfsan_label __dfsan_union_load(const dfsan_label *ls, uptr n) {
-  dfsan_label label = ls[0];
-  for (uptr i = 1; i != n; ++i) {
-    dfsan_label next_label = ls[i];
-    if (label != next_label)
-      label = __dfsan_union(label, next_label);
-  }
-  return label;
-}
-
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE
-dfsan_label __dfsan_union_load_fast16labels(const dfsan_label *ls, uptr n) {
   dfsan_label label = ls[0];
   for (uptr i = 1; i != n; ++i)
     label |= ls[i];
@@ -301,24 +206,10 @@
   Die();
 }
 
-// Like __dfsan_union, but for use from the client or custom functions.  Hence
-// the equality comparison is done here before calling __dfsan_union.
+// Resolves the union of two labels.
 SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
 dfsan_union(dfsan_label l1, dfsan_label l2) {
-  if (l1 == l2)
-    return l1;
-  return __dfsan_union(l1, l2);
-}
-
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE
-dfsan_label dfsan_create_label(const char *desc, void *userdata) {
-  dfsan_label label =
-      atomic_fetch_add(&__dfsan_last_label, 1, memory_order_relaxed) + 1;
-  dfsan_check_label(label);
-  __dfsan_label_info[label].l1 = __dfsan_label_info[label].l2 = 0;
-  __dfsan_label_info[label].desc = desc;
-  __dfsan_label_info[label].userdata = userdata;
-  return label;
+  return l1 | l2;
 }
 
 // Return the origin of the first taint byte in the size bytes from the address
@@ -429,7 +320,7 @@
   // Align src up.
   uptr s = AlignUp((uptr)src);
   dfsan_origin *src_o = (dfsan_origin *)origin_for((void *)s);
-  u64 *src_s = (u64 *)shadow_for((void *)s);
+  u32 *src_s = (u32 *)shadow_for((void *)s);
   dfsan_origin *src_end = (dfsan_origin *)origin_for((void *)(s + (end - beg)));
   dfsan_origin *dst_o = (dfsan_origin *)origin_for((void *)beg);
   dfsan_origin last_src_o = 0;
@@ -465,7 +356,7 @@
     uptr s = AlignUp((uptr)src);
     dfsan_origin *src =
         (dfsan_origin *)origin_for((void *)(s + end - beg - kOriginAlign));
-    u64 *src_s = (u64 *)shadow_for((void *)(s + end - beg - kOriginAlign));
+    u32 *src_s = (u32 *)shadow_for((void *)(s + end - beg - kOriginAlign));
     dfsan_origin *src_begin = (dfsan_origin *)origin_for((void *)s);
     dfsan_origin *dst =
         (dfsan_origin *)origin_for((void *)(end - kOriginAlign));
@@ -628,7 +519,7 @@
 // origin chain with the previous ID o and the current stack trace. This is
 // used by instrumentation to reduce code size when too much code is inserted.
 extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_maybe_store_origin(
-    u16 s, void *p, uptr size, dfsan_origin o) {
+    dfsan_label s, void *p, uptr size, dfsan_origin o) {
   if (UNLIKELY(s)) {
     GET_CALLER_PC_BP_SP;
     (void)sp;
@@ -726,8 +617,7 @@
   }
 
   for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp)
-    if (*labelp != label)
-      *labelp = __dfsan_union(*labelp, label);
+    *labelp |= label;
 }
 
 // Unlike the other dfsan interface functions the behavior of this function
@@ -783,57 +673,9 @@
   __dfsan_set_label(label, origin, addr, size);
 }
 
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE
-const struct dfsan_label_info *dfsan_get_label_info(dfsan_label label) {
-  return &__dfsan_label_info[label];
-}
-
 extern "C" SANITIZER_INTERFACE_ATTRIBUTE int
 dfsan_has_label(dfsan_label label, dfsan_label elem) {
-  if (label == elem)
-    return true;
-  const dfsan_label_info *info = dfsan_get_label_info(label);
-  if (info->l1 != 0) {
-    return dfsan_has_label(info->l1, elem) || dfsan_has_label(info->l2, elem);
-  } else {
-    return false;
-  }
-}
-
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE dfsan_label
-dfsan_has_label_with_desc(dfsan_label label, const char *desc) {
-  const dfsan_label_info *info = dfsan_get_label_info(label);
-  if (info->l1 != 0) {
-    return dfsan_has_label_with_desc(info->l1, desc) ||
-           dfsan_has_label_with_desc(info->l2, desc);
-  } else {
-    return internal_strcmp(desc, info->desc) == 0;
-  }
-}
-
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr
-dfsan_get_label_count(void) {
-  dfsan_label max_label_allocated =
-      atomic_load(&__dfsan_last_label, memory_order_relaxed);
-
-  return static_cast<uptr>(max_label_allocated);
-}
-
-extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
-dfsan_dump_labels(int fd) {
-  dfsan_label last_label =
-      atomic_load(&__dfsan_last_label, memory_order_relaxed);
-  for (uptr l = 1; l <= last_label; ++l) {
-    char buf[64];
-    internal_snprintf(buf, sizeof(buf), "%u %u %u ", l,
-                      __dfsan_label_info[l].l1, __dfsan_label_info[l].l2);
-    WriteToFile(fd, buf, internal_strlen(buf));
-    if (__dfsan_label_info[l].l1 == 0 && __dfsan_label_info[l].desc) {
-      WriteToFile(fd, __dfsan_label_info[l].desc,
-                  internal_strlen(__dfsan_label_info[l].desc));
-    }
-    WriteToFile(fd, "\n", 1);
-  }
+  return (label & elem) == elem;
 }
 
 class Decorator : public __sanitizer::SanitizerCommonDecorator {
@@ -1068,22 +910,6 @@
 #endif
 }
 
-static void dfsan_fini() {
-  if (internal_strcmp(flags().dump_labels_at_exit, "") != 0) {
-    fd_t fd = OpenFile(flags().dump_labels_at_exit, WrOnly);
-    if (fd == kInvalidFd) {
-      Report("WARNING: DataFlowSanitizer: unable to open output file %s\n",
-             flags().dump_labels_at_exit);
-      return;
-    }
-
-    Report("INFO: DataFlowSanitizer: dumping labels to %s\n",
-           flags().dump_labels_at_exit);
-    dfsan_dump_labels(fd);
-    CloseFile(fd);
-  }
-}
-
 extern "C" void dfsan_flush() {
   if (!MmapFixedSuperNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr()))
     Die();
@@ -1115,11 +941,6 @@
 
   initialize_interceptors();
 
-  // Register the fini callback to run when the program terminates successfully
-  // or it is killed by the runtime.
-  Atexit(dfsan_fini);
-  AddDieCallback(dfsan_fini);
-
   // Set up threads
   DFsanTSDInit(DFsanTSDDtor);
 
@@ -1129,8 +950,6 @@
   SetCurrentThread(main_thread);
   main_thread->ThreadStart();
 
-  __dfsan_label_info[kInitializingLabel].desc = "<init label>";
-
   dfsan_init_is_running = false;
   dfsan_inited = true;
 }
diff --git a/compiler-rt/lib/dfsan/dfsan_flags.inc b/compiler-rt/lib/dfsan/dfsan_flags.inc
--- a/compiler-rt/lib/dfsan/dfsan_flags.inc
+++ b/compiler-rt/lib/dfsan/dfsan_flags.inc
@@ -26,9 +26,6 @@
     "(e.g., when comparing strings, ignore the fact that the output of the"
     "comparison might be data-dependent on the content of the strings). This"
     "applies only to the custom functions defined in 'custom.c'.")
-DFSAN_FLAG(const char *, dump_labels_at_exit, "", "The path of the file where "
-                                                  "to dump the labels when the "
-                                                  "program terminates.")
 DFSAN_FLAG(
      int, origin_history_size, Origin::kMaxDepth,
     "The limit of origin chain length. Non-positive values mean unlimited.")
diff --git a/compiler-rt/lib/dfsan/dfsan_platform.h b/compiler-rt/lib/dfsan/dfsan_platform.h
--- a/compiler-rt/lib/dfsan/dfsan_platform.h
+++ b/compiler-rt/lib/dfsan/dfsan_platform.h
@@ -14,41 +14,45 @@
 #ifndef DFSAN_PLATFORM_H
 #define DFSAN_PLATFORM_H
 
+#include "sanitizer_common/sanitizer_common.h"
+
 namespace __dfsan {
 
+using __sanitizer::uptr;
+
 #if defined(__x86_64__)
 struct Mapping {
-  static const uptr kShadowAddr = 0x10000;
-  static const uptr kOriginAddr = 0x200000000000;
-  static const uptr kUnionTableAddr = 0x300000000000;
+  static const uptr kShadowAddr = 0x100000008000;
+  static const uptr kOriginAddr = 0x200000008000;
+  static const uptr kUnusedAddr = 0x300000000000;
   static const uptr kAppAddr = 0x700000008000;
-  static const uptr kShadowMask = ~0x700000000000;
+  static const uptr kShadowMask = ~0x600000000000;
 };
 #elif defined(__mips64)
 struct Mapping {
-  static const uptr kShadowAddr = 0x10000;
-  static const uptr kUnionTableAddr = 0x2000000000;
+  static const uptr kShadowAddr = 0x1000008000;
+  static const uptr kUnusedAddr = 0x2000000000;
   static const uptr kAppAddr = 0xF000008000;
-  static const uptr kShadowMask = ~0xF000000000;
+  static const uptr kShadowMask = ~0xE000000000;
 };
 #elif defined(__aarch64__)
 struct Mapping39 {
   static const uptr kShadowAddr = 0x10000;
-  static const uptr kUnionTableAddr = 0x1000000000;
+  static const uptr kUnusedAddr = 0x1000000000;
   static const uptr kAppAddr = 0x7000008000;
   static const uptr kShadowMask = ~0x7800000000;
 };
 
 struct Mapping42 {
   static const uptr kShadowAddr = 0x10000;
-  static const uptr kUnionTableAddr = 0x8000000000;
+  static const uptr kUnusedAddr = 0x8000000000;
   static const uptr kAppAddr = 0x3ff00008000;
   static const uptr kShadowMask = ~0x3c000000000;
 };
 
 struct Mapping48 {
   static const uptr kShadowAddr = 0x10000;
-  static const uptr kUnionTableAddr = 0x8000000000;
+  static const uptr kUnusedAddr = 0x8000000000;
   static const uptr kAppAddr = 0xffff00008000;
   static const uptr kShadowMask = ~0xfffff0000000;
 };
@@ -64,7 +68,7 @@
 #if defined(__x86_64__)
   MAPPING_ORIGIN_ADDR,
 #endif
-  MAPPING_UNION_TABLE_ADDR,
+  MAPPING_UNUSED_ADDR,
   MAPPING_APP_ADDR,
   MAPPING_SHADOW_MASK
 };
@@ -77,7 +81,8 @@
     case MAPPING_ORIGIN_ADDR:
       return Mapping::kOriginAddr;
 #endif
-    case MAPPING_UNION_TABLE_ADDR: return Mapping::kUnionTableAddr;
+    case MAPPING_UNUSED_ADDR:
+      return Mapping::kUnusedAddr;
     case MAPPING_APP_ADDR: return Mapping::kAppAddr;
     case MAPPING_SHADOW_MASK: return Mapping::kShadowMask;
   }
@@ -113,9 +118,7 @@
 }
 
 ALWAYS_INLINE
-uptr UnionTableAddr() {
-  return MappingArchImpl<MAPPING_UNION_TABLE_ADDR>();
-}
+uptr UnusedAddr() { return MappingArchImpl<MAPPING_UNUSED_ADDR>(); }
 
 ALWAYS_INLINE
 uptr AppAddr() {
diff --git a/compiler-rt/lib/fuzzer/dataflow/DataFlow.cpp b/compiler-rt/lib/fuzzer/dataflow/DataFlow.cpp
--- a/compiler-rt/lib/fuzzer/dataflow/DataFlow.cpp
+++ b/compiler-rt/lib/fuzzer/dataflow/DataFlow.cpp
@@ -17,11 +17,9 @@
 // and also provides basic-block coverage for every input.
 //
 // Build:
-//   1. Compile this file (DataFlow.cpp) with -fsanitize=dataflow -mllvm
-//       -dfsan-fast-16-labels and -O2.
+//   1. Compile this file (DataFlow.cpp) with -fsanitize=dataflow and -O2.
 //   2. Compile DataFlowCallbacks.cpp with -O2 -fPIC.
 //   3. Build the fuzz target with -g -fsanitize=dataflow
-//       -mllvm -dfsan-fast-16-labels
 //       -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp
 //   4. Link those together with -fsanitize=dataflow
 //
@@ -82,7 +80,7 @@
   return __dft.PCsBeg[BlockIdx * 2 + 1] & PCFLAG_FUNC_ENTRY;
 }
 
-const int kNumLabels = 16;
+const int kNumLabels = 8;
 
 // Prints all instrumented functions.
 static int PrintFunctions() {
diff --git a/compiler-rt/test/dfsan/atomic.cpp b/compiler-rt/test/dfsan/atomic.cpp
--- a/compiler-rt/test/dfsan/atomic.cpp
+++ b/compiler-rt/test/dfsan/atomic.cpp
@@ -1,5 +1,5 @@
-// RUN: %clangxx_dfsan -mllvm -dfsan-fast-16-labels=true %s -fno-exceptions -o %t && %run %t
-// RUN: %clangxx_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -fno-exceptions -o %t && %run %t
+// RUN: %clangxx_dfsan %s -fno-exceptions -o %t && %run %t
+// RUN: %clangxx_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 %s -fno-exceptions -o %t && %run %t
 //
 // REQUIRES: x86_64-target-arch
 //
diff --git a/compiler-rt/test/dfsan/basic.c b/compiler-rt/test/dfsan/basic.c
--- a/compiler-rt/test/dfsan/basic.c
+++ b/compiler-rt/test/dfsan/basic.c
@@ -10,7 +10,7 @@
 
 int main(void) {
   int i = 1;
-  dfsan_label i_label = dfsan_create_label("i", 0);
+  dfsan_label i_label = 1;
   dfsan_set_label(i_label, &i, sizeof(i));
 
   dfsan_label new_label = dfsan_get_label(i);
@@ -19,7 +19,7 @@
   dfsan_label read_label = dfsan_read_label(&i, sizeof(i));
   assert(i_label == read_label);
 
-  dfsan_label j_label = dfsan_create_label("j", 0);
+  dfsan_label j_label = 2;
   dfsan_add_label(j_label, &i, sizeof(i));
 
   read_label = dfsan_read_label(&i, sizeof(i));
diff --git a/compiler-rt/test/dfsan/custom.cpp b/compiler-rt/test/dfsan/custom.cpp
--- a/compiler-rt/test/dfsan/custom.cpp
+++ b/compiler-rt/test/dfsan/custom.cpp
@@ -1,10 +1,10 @@
 // RUN: %clang_dfsan %s -o %t && DFSAN_OPTIONS="strict_data_dependencies=0" %run %t
 // RUN: %clang_dfsan -mllvm -dfsan-args-abi %s -o %t && DFSAN_OPTIONS="strict_data_dependencies=0" %run %t
-// RUN: %clang_dfsan -DFAST_16_LABELS -mllvm -dfsan-fast-16-labels %s -o %t && DFSAN_OPTIONS="strict_data_dependencies=0" %run %t
+// RUN: %clang_dfsan %s -o %t && DFSAN_OPTIONS="strict_data_dependencies=0" %run %t
 // RUN: %clang_dfsan -DSTRICT_DATA_DEPENDENCIES %s -o %t && %run %t
 // RUN: %clang_dfsan -DSTRICT_DATA_DEPENDENCIES -mllvm -dfsan-args-abi %s -o %t && %run %t
-// RUN: %clang_dfsan -DFAST_16_LABELS -DORIGIN_TRACKING -mllvm -dfsan-fast-16-labels -mllvm -dfsan-track-origins=1 -mllvm -dfsan-combine-pointer-labels-on-load=false -DSTRICT_DATA_DEPENDENCIES %s -o %t && %run %t
-// RUN: %clang_dfsan -DFAST_16_LABELS -DORIGIN_TRACKING -mllvm -dfsan-fast-16-labels -mllvm -dfsan-track-origins=1 -mllvm -dfsan-combine-pointer-labels-on-load=false %s -o %t && DFSAN_OPTIONS="strict_data_dependencies=0" %run %t
+// RUN: %clang_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -mllvm -dfsan-combine-pointer-labels-on-load=false -DSTRICT_DATA_DEPENDENCIES %s -o %t && %run %t
+// RUN: %clang_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -mllvm -dfsan-combine-pointer-labels-on-load=false %s -o %t && DFSAN_OPTIONS="strict_data_dependencies=0" %run %t
 //
 // Tests custom implementations of various glibc functions.
 //
@@ -1944,19 +1944,11 @@
 void test_fork() {}
 
 int main(void) {
-#ifdef FAST_16_LABELS
   i_label = 1;
   j_label = 2;
   k_label = 4;
   m_label = 8;
   n_label = 16;
-#else
-  i_label = dfsan_create_label("i", 0);
-  j_label = dfsan_create_label("j", 0);
-  k_label = dfsan_create_label("k", 0);
-  m_label = dfsan_create_label("m", 0);
-  n_label = dfsan_create_label("n", 0);
-#endif
   i_j_label = dfsan_union(i_label, j_label);
   assert(i_j_label != i_label);
   assert(i_j_label != j_label);
diff --git a/compiler-rt/test/dfsan/dump_labels.c b/compiler-rt/test/dfsan/dump_labels.c
deleted file mode 100644
--- a/compiler-rt/test/dfsan/dump_labels.c
+++ /dev/null
@@ -1,71 +0,0 @@
-// RUN: %clang_dfsan %s -o %t
-// RUN: DFSAN_OPTIONS=dump_labels_at_exit=/dev/stdout %run %t 2>&1 | FileCheck %s
-// RUN: DFSAN_OPTIONS=dump_labels_at_exit=/dev/stdout not %run %t c 2>&1 | FileCheck %s --check-prefix=CHECK-OOL
-// RUN: DFSAN_OPTIONS=dump_labels_at_exit=/dev/stdout not %run %t u 2>&1 | FileCheck %s --check-prefix=CHECK-OOL
-//
-// REQUIRES: x86_64-target-arch
-
-// Tests that labels are properly dumped at program termination.
-
-#include <sanitizer/dfsan_interface.h>
-#include <assert.h>
-#include <stdio.h>
-
-int main(int argc, char** argv) {
-  int i = 1;
-  dfsan_label i_label = dfsan_create_label("i", 0);
-  dfsan_set_label(i_label, &i, sizeof(i));
-
-  int j = 2;
-  dfsan_label j_label = dfsan_create_label("j", 0);
-  dfsan_set_label(j_label, &j, sizeof(j));
-
-  int k = 3;
-  dfsan_label k_label = dfsan_create_label("k", 0);
-  dfsan_set_label(k_label, &k, sizeof(k));
-
-  dfsan_label ij_label = dfsan_get_label(i + j);
-  dfsan_label ijk_label = dfsan_get_label(i + j + k);
-
-  fprintf(stderr, "i %d j %d k %d ij %d ijk %d\n", i_label, j_label, k_label,
-          ij_label, ijk_label);
-
-  // CHECK: 1 0 0 i
-  // CHECK: 2 0 0 j
-  // CHECK: 3 0 0 k
-  // CHECK: 4 1 2
-  // CHECK: 5 3 4
-
-  if (argc > 1) {
-    // Exhaust the labels.
-    unsigned long num_labels = 1 << (sizeof(dfsan_label) * 8);
-    for (unsigned long i =  ijk_label + 1; i < num_labels - 2; ++i) {
-      dfsan_label l = dfsan_create_label("l", 0);
-      assert(l == i);
-    }
-
-    // Consume the last available label.
-    dfsan_label l = dfsan_union(5, 6);
-    assert(l == num_labels - 2);
-
-    // Try to allocate another label (either explicitly or by unioning two
-    // existing labels), but expect a crash.
-    if (argv[1][0] == 'c') {
-      l = dfsan_create_label("l", 0);
-    } else {
-      l = dfsan_union(6, 7);
-    }
-
-    // CHECK-OOL: FATAL: DataFlowSanitizer: out of labels
-    // CHECK-OOL: 1 0 0 i
-    // CHECK-OOL: 2 0 0 j
-    // CHECK-OOL: 3 0 0 k
-    // CHECK-OOL: 4 1 2
-    // CHECK-OOL: 5 3 4
-    // CHECK-OOL: 6 0 0
-    // CHECK-OOL: 65534 5 6
-    // CHECK-OOL: 65535 0 0 <init label>
-  }
-
-  return 0;
-}
diff --git a/compiler-rt/test/dfsan/event_callbacks.c b/compiler-rt/test/dfsan/event_callbacks.c
--- a/compiler-rt/test/dfsan/event_callbacks.c
+++ b/compiler-rt/test/dfsan/event_callbacks.c
@@ -81,9 +81,9 @@
   assert(Argc == 2);
 
   int I = 1, J = 2;
-  LabelI = dfsan_create_label("I", 0);
+  LabelI = 1;
   dfsan_set_label(LabelI, &I, sizeof(I));
-  LabelJ = dfsan_create_label("J", 0);
+  LabelJ = 2;
   dfsan_set_label(LabelJ, &J, sizeof(J));
   LabelIJ = dfsan_union(LabelI, LabelJ);
 
@@ -113,7 +113,7 @@
   assert(I != J);
 
   LenArgv = strlen(Argv[1]);
-  LabelArgv = dfsan_create_label("Argv", 0);
+  LabelArgv = 4;
   dfsan_set_label(LabelArgv, Argv[1], LenArgv);
 
   char Buf[64];
diff --git a/compiler-rt/test/dfsan/fast16labels.c b/compiler-rt/test/dfsan/fast8labels.c
rename from compiler-rt/test/dfsan/fast16labels.c
rename to compiler-rt/test/dfsan/fast8labels.c
--- a/compiler-rt/test/dfsan/fast16labels.c
+++ b/compiler-rt/test/dfsan/fast8labels.c
@@ -1,10 +1,8 @@
-// RUN: %clang_dfsan %s -mllvm -dfsan-fast-16-labels -o %t
+// RUN: %clang_dfsan %s -o %t
 // RUN: %run %t
 //
 // REQUIRES: x86_64-target-arch
 //
-// Tests fast16labels mode.
-
 #include <sanitizer/dfsan_interface.h>
 
 #include <assert.h>
@@ -19,11 +17,11 @@
   int a = 10;
   int b = 20;
   dfsan_set_label(8, &a, sizeof(a));
-  dfsan_set_label(512, &b, sizeof(b));
+  dfsan_set_label(128, &b, sizeof(b));
   int c = foo(a, b);
   printf("A: 0x%x\n", dfsan_get_label(a));
   printf("B: 0x%x\n", dfsan_get_label(b));
   dfsan_label l = dfsan_get_label(c);
   printf("C: 0x%x\n", l);
-  assert(l == 520);  // OR of the other two labels.
+  assert(l == 136);  // OR of the other two labels.
 }
diff --git a/compiler-rt/test/dfsan/flags.c b/compiler-rt/test/dfsan/flags.c
--- a/compiler-rt/test/dfsan/flags.c
+++ b/compiler-rt/test/dfsan/flags.c
@@ -14,7 +14,7 @@
 
 int main(void) {
   int i = 1;
-  dfsan_label i_label = dfsan_create_label("i", 0);
+  dfsan_label i_label = 2;
   dfsan_set_label(i_label, &i, sizeof(i));
 
   // CHECK: WARNING: DataFlowSanitizer: call to uninstrumented function f
diff --git a/compiler-rt/test/dfsan/flush.c b/compiler-rt/test/dfsan/flush.c
--- a/compiler-rt/test/dfsan/flush.c
+++ b/compiler-rt/test/dfsan/flush.c
@@ -1,6 +1,6 @@
 // Tests dfsan_flush().
 // RUN: %clang_dfsan %s -o %t && %run %t
-// RUN: %clang_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && %run %t
+// RUN: %clang_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 %s -o %t && %run %t
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/fncall.c b/compiler-rt/test/dfsan/fncall.c
--- a/compiler-rt/test/dfsan/fncall.c
+++ b/compiler-rt/test/dfsan/fncall.c
@@ -10,19 +10,22 @@
 
 int f(int x) {
   int j = 2;
-  dfsan_label j_label = dfsan_create_label("j", 0);
+  dfsan_label j_label = 2;
   dfsan_set_label(j_label, &j, sizeof(j));
   return x + j;
 }
 
 int main(void) {
   int i = 1;
-  dfsan_label i_label = dfsan_create_label("i", 0);
+  dfsan_label i_label = 4;
   dfsan_set_label(i_label, &i, sizeof(i));
 
   dfsan_label ij_label = dfsan_get_label(f(i));
   assert(dfsan_has_label(ij_label, i_label));
-  assert(dfsan_has_label_with_desc(ij_label, "j"));
+
+  /* Must be consistent with the one in f(). */
+  dfsan_label j_label = 2;
+  assert(dfsan_has_label(ij_label, 2));
 
   return 0;
 }
diff --git a/compiler-rt/test/dfsan/fork.cpp b/compiler-rt/test/dfsan/fork.cpp
--- a/compiler-rt/test/dfsan/fork.cpp
+++ b/compiler-rt/test/dfsan/fork.cpp
@@ -2,10 +2,10 @@
 // Run a number of threads that create new chained origins, then fork
 // and verify that origin reads do not deadlock in the child process.
 //
-// RUN: %clangxx_dfsan -mllvm -dfsan-fast-16-labels=true %s -o %t
+// RUN: %clangxx_dfsan %s -o %t
 // RUN: %run %t 2>&1 | FileCheck %s
 //
-// RUN: %clangxx_dfsan -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t
+// RUN: %clangxx_dfsan -mllvm -dfsan-track-origins=1 %s -o %t
 // RUN: DFSAN_OPTIONS=store_context_size=1000,origin_history_size=0,origin_history_per_stack_limit=0 %run %t 2>&1 | FileCheck %s
 //
 // REQUIRES: x86_64-target-arch
diff --git a/compiler-rt/test/dfsan/interceptors.c b/compiler-rt/test/dfsan/interceptors.c
--- a/compiler-rt/test/dfsan/interceptors.c
+++ b/compiler-rt/test/dfsan/interceptors.c
@@ -1,5 +1,5 @@
-// RUN: %clang_dfsan -mllvm -dfsan-fast-16-labels -mllvm -dfsan-combine-pointer-labels-on-load=false %s -o %t && %run %t
-// RUN: %clang_dfsan -DORIGIN_TRACKING -mllvm -dfsan-fast-16-labels -mllvm -dfsan-track-origins=1 -mllvm -dfsan-combine-pointer-labels-on-load=false %s -o %t && %run %t
+// RUN: %clang_dfsan -mllvm -dfsan-combine-pointer-labels-on-load=false %s -o %t && %run %t
+// RUN: %clang_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -mllvm -dfsan-combine-pointer-labels-on-load=false %s -o %t && %run %t
 //
 // Tests custom implementations of various glibc functions.
 //
diff --git a/compiler-rt/test/dfsan/label_count.c b/compiler-rt/test/dfsan/label_count.c
deleted file mode 100644
--- a/compiler-rt/test/dfsan/label_count.c
+++ /dev/null
@@ -1,77 +0,0 @@
-// RUN: %clang_dfsan -DLIB -c %s -o %t.lib.o && \
-// RUN: %clang_dfsan       -c %s -o %t.o && \
-// RUN: %clang_dfsan %t.lib.o %t.o -o %t.bin && \
-// RUN: %run %t.bin
-
-// RUN: %clang_dfsan -mllvm -dfsan-args-abi -DLIB -c %s -o %t.lib.o && \
-// RUN: %clang_dfsan -mllvm -dfsan-args-abi -c %s -o %t.o && \
-// RUN: %clang_dfsan -mllvm -dfsan-args-abi %t.o %t.lib.o -o %t.bin && \
-// RUN: %run %t.bin
-//
-// REQUIRES: x86_64-target-arch
-
-#include <sanitizer/dfsan_interface.h>
-#include <assert.h>
-
-#ifdef LIB
-// Compiling this file with and without LIB defined allows this file to be
-// built as two separate translation units.  This ensures that the code
-// can not be optimized in a way that removes behavior we wish to test.  For
-// example, computing a value should cause labels to be allocated only if
-// the computation is actually done.  Putting the computation here prevents
-// the compiler from optimizing away the computation (and labeling) that
-// tests wish to verify.
-
-int add_in_separate_translation_unit(int a, int b) {
-  return a + b;
-}
-
-int multiply_in_separate_translation_unit(int a, int b) {
-  return a * b;
-}
-
-#else
-
-int add_in_separate_translation_unit(int i, int j);
-int multiply_in_separate_translation_unit(int i, int j);
-
-int main(void) {
-  size_t label_count;
-
-  // No labels allocated yet.
-  label_count = dfsan_get_label_count();
-  assert(0 == label_count);
-
-  int i = 1;
-  dfsan_label i_label = dfsan_create_label("i", 0);
-  dfsan_set_label(i_label, &i, sizeof(i));
-
-  // One label allocated for i.
-  label_count = dfsan_get_label_count();
-  assert(1u == label_count);
-
-  int j = 2;
-  dfsan_label j_label = dfsan_create_label("j", 0);
-  dfsan_set_label(j_label, &j, sizeof(j));
-
-  // Check that a new label was allocated for j.
-  label_count = dfsan_get_label_count();
-  assert(2u == label_count);
-
-  // Create a value that combines i and j.
-  int i_plus_j = add_in_separate_translation_unit(i, j);
-
-  // Check that a label was created for the union of i and j.
-  label_count = dfsan_get_label_count();
-  assert(3u == label_count);
-
-  // Combine i and j in a different way.  Check that the existing label is
-  // reused, and a new label is not created.
-  int j_times_i = multiply_in_separate_translation_unit(j, i);
-  label_count = dfsan_get_label_count();
-  assert(3u == label_count);
-  assert(dfsan_get_label(i_plus_j) == dfsan_get_label(j_times_i));
-
-  return 0;
-}
-#endif  // #ifdef LIB
diff --git a/compiler-rt/test/dfsan/origin_add_label.c b/compiler-rt/test/dfsan/origin_add_label.c
--- a/compiler-rt/test/dfsan/origin_add_label.c
+++ b/compiler-rt/test/dfsan/origin_add_label.c
@@ -1,10 +1,10 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/origin_branch.c b/compiler-rt/test/dfsan/origin_branch.c
--- a/compiler-rt/test/dfsan/origin_branch.c
+++ b/compiler-rt/test/dfsan/origin_branch.c
@@ -1,6 +1,6 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/origin_disabled.c b/compiler-rt/test/dfsan/origin_disabled.c
--- a/compiler-rt/test/dfsan/origin_disabled.c
+++ b/compiler-rt/test/dfsan/origin_disabled.c
@@ -1,6 +1,5 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-fast-16-labels=true %s -o %t && \
-// RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: %clang_dfsan -gmlt %s -o %t && %run %t >%t.out 2>&1
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/origin_invalid.c b/compiler-rt/test/dfsan/origin_invalid.c
--- a/compiler-rt/test/dfsan/origin_invalid.c
+++ b/compiler-rt/test/dfsan/origin_invalid.c
@@ -1,6 +1,6 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-fast-16-labels=true -mllvm -dfsan-track-origins=1 %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 // 
 // REQUIRES: x86_64-target-arch
 
@@ -8,13 +8,13 @@
 
 int main(int argc, char *argv[]) {
   uint64_t a = 10;
-  dfsan_set_label(8, &a, sizeof(a));
+  dfsan_set_label(1, &a, sizeof(a));
   size_t origin_addr =
-      (((size_t)&a & ~0x700000000000LL + 0x200000000000LL) & ~0x3UL);
+      (((size_t)&a & ~0x600000000000LL + 0x100000000000LL) & ~0x3UL);
   asm("mov %0, %%rax": :"r"(origin_addr));
   asm("movq $0, (%rax)");
   dfsan_print_origin_trace(&a, "invalid");
 }
 
-// CHECK: Taint value 0x8 (at {{.*}}) origin tracking (invalid)
-// CHECK: Taint value 0x8 (at {{.*}}) has invalid origin tracking. This can be a DFSan bug.
+// CHECK: Taint value 0x1 (at {{.*}}) origin tracking (invalid)
+// CHECK: Taint value 0x1 (at {{.*}}) has invalid origin tracking. This can be a DFSan bug.
diff --git a/compiler-rt/test/dfsan/origin_ld_lost.c b/compiler-rt/test/dfsan/origin_ld_lost.c
--- a/compiler-rt/test/dfsan/origin_ld_lost.c
+++ b/compiler-rt/test/dfsan/origin_ld_lost.c
@@ -1,6 +1,6 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 //
diff --git a/compiler-rt/test/dfsan/origin_ldst.c b/compiler-rt/test/dfsan/origin_ldst.c
--- a/compiler-rt/test/dfsan/origin_ldst.c
+++ b/compiler-rt/test/dfsan/origin_ldst.c
@@ -1,26 +1,26 @@
-// RUN: %clang_dfsan -gmlt -DTEST64 -DALIGN=8 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DTEST64 -DALIGN=8 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -DTEST32 -DALIGN=4 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DTEST32 -DALIGN=4 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -DALIGN=2 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DALIGN=2 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
-// rUN: %clang_dfsan -DTEST64 -DALIGN=5 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
-// rUN:     %run %t >%t.out 2>&1
-// rUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: %clang_dfsan -gmlt -DTEST64 -DALIGN=4 -mllvm -dfsan-track-origins=1 %s -o %t && \
+// RUN:     %run %t >%t.out 2>&1
+// RUN: FileCheck %s < %t.out
 //
-// rUN: %clang_dfsan -DTEST32 -DALIGN=3 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
-// rUN:     %run %t >%t.out 2>&1
-// rUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: %clang_dfsan -gmlt -DTEST32 -DALIGN=2 -mllvm -dfsan-track-origins=1 %s -o %t && \
+// RUN:     %run %t >%t.out 2>&1
+// RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -DALIGN=1 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DALIGN=1 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 //
diff --git a/compiler-rt/test/dfsan/origin_limit.c b/compiler-rt/test/dfsan/origin_limit.c
--- a/compiler-rt/test/dfsan/origin_limit.c
+++ b/compiler-rt/test/dfsan/origin_limit.c
@@ -1,7 +1,7 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t
 //
 // RUN: %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // RUN: DFSAN_OPTIONS=origin_history_size=2 %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK2 < %t.out
diff --git a/compiler-rt/test/dfsan/origin_memcpy.c b/compiler-rt/test/dfsan/origin_memcpy.c
--- a/compiler-rt/test/dfsan/origin_memcpy.c
+++ b/compiler-rt/test/dfsan/origin_memcpy.c
@@ -1,8 +1,8 @@
-// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK0 < %t.out
 // 
-// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK10 < %t.out
 //
diff --git a/compiler-rt/test/dfsan/origin_memmove.c b/compiler-rt/test/dfsan/origin_memmove.c
--- a/compiler-rt/test/dfsan/origin_memmove.c
+++ b/compiler-rt/test/dfsan/origin_memmove.c
@@ -1,8 +1,8 @@
-// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK0 < %t.out
 //
-// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK10 < %t.out
 //
diff --git a/compiler-rt/test/dfsan/origin_memset.c b/compiler-rt/test/dfsan/origin_memset.c
--- a/compiler-rt/test/dfsan/origin_memset.c
+++ b/compiler-rt/test/dfsan/origin_memset.c
@@ -1,8 +1,8 @@
-// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK0 < %t.out
 // 
-// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK10 < %t.out
 //
diff --git a/compiler-rt/test/dfsan/origin_overlapped.c b/compiler-rt/test/dfsan/origin_overlapped.c
--- a/compiler-rt/test/dfsan/origin_overlapped.c
+++ b/compiler-rt/test/dfsan/origin_overlapped.c
@@ -1,6 +1,6 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/origin_set_label.c b/compiler-rt/test/dfsan/origin_set_label.c
--- a/compiler-rt/test/dfsan/origin_set_label.c
+++ b/compiler-rt/test/dfsan/origin_set_label.c
@@ -1,10 +1,10 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 // 
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/origin_stack_trace.c b/compiler-rt/test/dfsan/origin_stack_trace.c
--- a/compiler-rt/test/dfsan/origin_stack_trace.c
+++ b/compiler-rt/test/dfsan/origin_stack_trace.c
@@ -1,8 +1,8 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
diff --git a/compiler-rt/test/dfsan/origin_track_ld.c b/compiler-rt/test/dfsan/origin_track_ld.c
--- a/compiler-rt/test/dfsan/origin_track_ld.c
+++ b/compiler-rt/test/dfsan/origin_track_ld.c
@@ -1,4 +1,4 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=2 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=2 %s -o %t && \
 // RUN:     %run %t > %t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
diff --git a/compiler-rt/test/dfsan/origin_unaligned_memtrans.c b/compiler-rt/test/dfsan/origin_unaligned_memtrans.c
--- a/compiler-rt/test/dfsan/origin_unaligned_memtrans.c
+++ b/compiler-rt/test/dfsan/origin_unaligned_memtrans.c
@@ -1,8 +1,8 @@
-// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=0 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK0 < %t.out
 // 
-// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DOFFSET=10 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s --check-prefix=CHECK10 < %t.out
 //
diff --git a/compiler-rt/test/dfsan/origin_untainted.c b/compiler-rt/test/dfsan/origin_untainted.c
--- a/compiler-rt/test/dfsan/origin_untainted.c
+++ b/compiler-rt/test/dfsan/origin_untainted.c
@@ -1,6 +1,6 @@
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-fast-16-labels=true -mllvm -dfsan-track-origins=1 %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
-// RUN: FileCheck %s --check-prefix=CHECK < %t.out
+// RUN: FileCheck %s < %t.out
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/origin_with_sigactions.c b/compiler-rt/test/dfsan/origin_with_sigactions.c
--- a/compiler-rt/test/dfsan/origin_with_sigactions.c
+++ b/compiler-rt/test/dfsan/origin_with_sigactions.c
@@ -3,19 +3,19 @@
 // Origin tracking uses ChainedOriginDepot that is not async signal safe, so we
 // do not track origins inside signal handlers.
 //
-// RUN: %clang_dfsan -gmlt -DUSE_SIGNAL_ACTION -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DUSE_SIGNAL_ACTION -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:      %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -DUSE_SIGNAL_ACTION -mllvm -dfsan-instrument-with-call-threshold=0 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -DUSE_SIGNAL_ACTION -mllvm -dfsan-instrument-with-call-threshold=0 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-instrument-with-call-threshold=0 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-instrument-with-call-threshold=0 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
diff --git a/compiler-rt/test/dfsan/origin_with_signals.cpp b/compiler-rt/test/dfsan/origin_with_signals.cpp
--- a/compiler-rt/test/dfsan/origin_with_signals.cpp
+++ b/compiler-rt/test/dfsan/origin_with_signals.cpp
@@ -3,11 +3,11 @@
 // Origin tracking uses ChainedOriginDepot that is not async signal safe, so we
 // do not track origins inside signal handlers.
 //
-// RUN: %clangxx_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clangxx_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
-// RUN: %clangxx_dfsan -gmlt -mllvm -dfsan-instrument-with-call-threshold=0 -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clangxx_dfsan -gmlt -mllvm -dfsan-instrument-with-call-threshold=0 -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
diff --git a/compiler-rt/test/dfsan/pair.cpp b/compiler-rt/test/dfsan/pair.cpp
--- a/compiler-rt/test/dfsan/pair.cpp
+++ b/compiler-rt/test/dfsan/pair.cpp
@@ -1,5 +1,5 @@
-// RUN: %clangxx_dfsan %s -mllvm -dfsan-fast-16-labels -mllvm -dfsan-track-select-control-flow=false -mllvm -dfsan-combine-pointer-labels-on-load=false -O0 -DO0 -o %t && %run %t
-// RUN: %clangxx_dfsan %s -mllvm -dfsan-fast-16-labels -mllvm -dfsan-track-select-control-flow=false -mllvm -dfsan-combine-pointer-labels-on-load=false -O1 -o %t && %run %t
+// RUN: %clangxx_dfsan %s -mllvm -dfsan-track-select-control-flow=false -mllvm -dfsan-combine-pointer-labels-on-load=false -O0 -DO0 -o %t && %run %t
+// RUN: %clangxx_dfsan %s -mllvm -dfsan-track-select-control-flow=false -mllvm -dfsan-combine-pointer-labels-on-load=false -O1 -o %t && %run %t
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/propagate.c b/compiler-rt/test/dfsan/propagate.c
--- a/compiler-rt/test/dfsan/propagate.c
+++ b/compiler-rt/test/dfsan/propagate.c
@@ -13,15 +13,15 @@
   assert(dfsan_union(0, 0) == 0);
 
   int i = 1;
-  dfsan_label i_label = dfsan_create_label("i", 0);
+  dfsan_label i_label = 1;
   dfsan_set_label(i_label, &i, sizeof(i));
 
   int j = 2;
-  dfsan_label j_label = dfsan_create_label("j", 0);
+  dfsan_label j_label = 2;
   dfsan_set_label(j_label, &j, sizeof(j));
 
   int k = 3;
-  dfsan_label k_label = dfsan_create_label("k", 0);
+  dfsan_label k_label = 4;
   dfsan_set_label(k_label, &k, sizeof(k));
 
   int k2 = 4;
diff --git a/compiler-rt/test/dfsan/pthread.c b/compiler-rt/test/dfsan/pthread.c
--- a/compiler-rt/test/dfsan/pthread.c
+++ b/compiler-rt/test/dfsan/pthread.c
@@ -1,10 +1,10 @@
-// RUN: %clang_dfsan -mllvm -dfsan-fast-16-labels=true %s -o %t && %run %t
+// RUN: %clang_dfsan %s -o %t && %run %t
 //
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
-// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && \
 // RUN:     %run %t >%t.out 2>&1
 // RUN: FileCheck %s < %t.out
 //
diff --git a/compiler-rt/test/dfsan/release_shadow_space.c b/compiler-rt/test/dfsan/release_shadow_space.c
--- a/compiler-rt/test/dfsan/release_shadow_space.c
+++ b/compiler-rt/test/dfsan/release_shadow_space.c
@@ -1,7 +1,7 @@
 // DFSAN_OPTIONS=no_huge_pages_for_shadow=false RUN: %clang_dfsan %s -o %t && setarch `uname -m` -R %run %t
 // DFSAN_OPTIONS=no_huge_pages_for_shadow=true RUN: %clang_dfsan %s -o %t && setarch `uname -m` -R %run %t
-// DFSAN_OPTIONS=no_huge_pages_for_shadow=false RUN: %clang_dfsan %s -DORIGIN_TRACKING -mllvm -dfsan-fast-16-labels -mllvm -dfsan-track-origins=1 -o %t && setarch `uname -m` -R %run %t
-// DFSAN_OPTIONS=no_huge_pages_for_shadow=true RUN: %clang_dfsan %s -DORIGIN_TRACKING -mllvm -dfsan-fast-16-labels -mllvm -dfsan-track-origins=1 -o %t && setarch `uname -m` -R %run %t
+// DFSAN_OPTIONS=no_huge_pages_for_shadow=false RUN: %clang_dfsan %s -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -o %t && setarch `uname -m` -R %run %t
+// DFSAN_OPTIONS=no_huge_pages_for_shadow=true RUN: %clang_dfsan %s -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -o %t && setarch `uname -m` -R %run %t
 //
 // REQUIRES: x86_64-target-arch
 
@@ -45,7 +45,7 @@
   size_t after_mmap = get_rss_kb();
 
   // store labels to all addresses. The overhead is 2x.
-  const dfsan_label label = dfsan_create_label("l", 0);
+  const dfsan_label label = 8;
   char val = 0xff;
   dfsan_set_label(label, &val, sizeof(val));
   memset(p, val, map_size);
diff --git a/compiler-rt/test/dfsan/sigaction.c b/compiler-rt/test/dfsan/sigaction.c
--- a/compiler-rt/test/dfsan/sigaction.c
+++ b/compiler-rt/test/dfsan/sigaction.c
@@ -1,6 +1,5 @@
-// RUN: %clang_dfsan -DUSE_SIGNAL_ACTION -mllvm -dfsan-fast-16-labels=true %s -o %t && \
-// RUN:     %run %t
-// RUN: %clang_dfsan -mllvm -dfsan-fast-16-labels=true %s -o %t && %run %t
+// RUN: %clang_dfsan -DUSE_SIGNAL_ACTION %s -o %t && %run %t
+// RUN: %clang_dfsan %s -o %t && %run %t
 //
 // REQUIRES: x86_64-target-arch
 
diff --git a/compiler-rt/test/dfsan/sigaction_stress_test.c b/compiler-rt/test/dfsan/sigaction_stress_test.c
--- a/compiler-rt/test/dfsan/sigaction_stress_test.c
+++ b/compiler-rt/test/dfsan/sigaction_stress_test.c
@@ -1,6 +1,6 @@
-// RUN: %clangxx_dfsan -mllvm -dfsan-fast-16-labels=true %s -o %t && %run %t
-// RUN: %clangxx_dfsan -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true %s -o %t && %run %t
-// RUN: %clangxx_dfsan -mllvm -dfsan-track-origins=1 -mllvm -dfsan-fast-16-labels=true -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && %run %t
+// RUN: %clangxx_dfsan %s -o %t && %run %t
+// RUN: %clangxx_dfsan -mllvm -dfsan-track-origins=1 %s -o %t && %run %t
+// RUN: %clangxx_dfsan -mllvm -dfsan-track-origins=1 -mllvm -dfsan-instrument-with-call-threshold=0 %s -o %t && %run %t
 //
 // Test that the state of shadows from a sigaction handler are consistent.
 //
diff --git a/compiler-rt/test/dfsan/struct.c b/compiler-rt/test/dfsan/struct.c
--- a/compiler-rt/test/dfsan/struct.c
+++ b/compiler-rt/test/dfsan/struct.c
@@ -1,6 +1,4 @@
-// RUN: %clang_dfsan %s -O1 -mllvm -dfsan-fast-16-labels=true -DFAST16_O1 -o %t && %run %t
-// RUN: %clang_dfsan %s -O1 -DO1 -o %t && %run %t
-// RUN: %clang_dfsan %s -O0 -mllvm -dfsan-fast-16-labels=true -DFAST16_O0 -o %t && %run %t
+// RUN: %clang_dfsan %s -O1 -o %t && %run %t
 // RUN: %clang_dfsan %s -O0 -DO0 -o %t && %run %t
 //
 // REQUIRES: x86_64-target-arch
@@ -40,13 +38,8 @@
 int main(void) {
   int i = 1;
   char *ptr = NULL;
-#if defined(FAST16_O1) || defined(FAST16_O0)
   dfsan_label i_label = 1;
   dfsan_label ptr_label = 2;
-#else
-  dfsan_label i_label = dfsan_create_label("i", 0);
-  dfsan_label ptr_label = dfsan_create_label("ptr", 0);
-#endif
   dfsan_set_label(i_label, &i, sizeof(i));
   dfsan_set_label(ptr_label, &ptr, sizeof(ptr));
 
@@ -56,12 +49,7 @@
 
   dfsan_label i1_label = dfsan_read_label(&i1, sizeof(i1));
   dfsan_label ptr1_label = dfsan_read_label(&ptr1, sizeof(ptr1));
-#if defined(O0) || defined(O1)
-  assert(dfsan_has_label(i1_label, i_label));
-  assert(dfsan_has_label(i1_label, ptr_label));
-  assert(dfsan_has_label(ptr1_label, i_label));
-  assert(dfsan_has_label(ptr1_label, ptr_label));
-#elif defined(FAST16_O0)
+#if defined(O0)
   assert(i1_label == (i_label | ptr_label));
   assert(ptr1_label == (i_label | ptr_label));
 #else
@@ -75,12 +63,7 @@
 
   dfsan_label i2_label = dfsan_read_label(&i2, sizeof(i2));
   dfsan_label ptr2_label = dfsan_read_label(&ptr2, sizeof(ptr2));
-#if defined(O0) || defined(O1)
-  assert(dfsan_has_label(i2_label, i_label));
-  assert(dfsan_has_label(i2_label, ptr_label));
-  assert(dfsan_has_label(ptr2_label, i_label));
-  assert(dfsan_has_label(ptr2_label, ptr_label));
-#elif defined(FAST16_O0)
+#if defined(O0)
   assert(i2_label == (i_label | ptr_label));
   assert(ptr2_label == (i_label | ptr_label));
 #else
@@ -94,12 +77,7 @@
 
   dfsan_label i3_label = dfsan_read_label(&i3, sizeof(i3));
   dfsan_label ptr3_label = dfsan_read_label(&ptr3, sizeof(ptr3));
-#if defined(O0) || defined(O1)
-  assert(dfsan_has_label(i3_label, i_label));
-  assert(dfsan_has_label(i3_label, ptr_label));
-  assert(dfsan_has_label(ptr3_label, i_label));
-  assert(dfsan_has_label(ptr3_label, ptr_label));
-#elif defined(FAST16_O0)
+#if defined(O0)
   assert(i3_label == (i_label | ptr_label));
   assert(ptr3_label == (i_label | ptr_label));
 #else
diff --git a/compiler-rt/test/fuzzer/dataflow.test b/compiler-rt/test/fuzzer/dataflow.test
--- a/compiler-rt/test/fuzzer/dataflow.test
+++ b/compiler-rt/test/fuzzer/dataflow.test
@@ -2,10 +2,10 @@
 REQUIRES: linux, x86_64
 
 # Build the tracer and the test.
-RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fsanitize=dataflow -mllvm -dfsan-fast-16-labels  %S/../../lib/fuzzer/dataflow/DataFlow.cpp -o  %t-DataFlow.o
+RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fsanitize=dataflow %S/../../lib/fuzzer/dataflow/DataFlow.cpp -o  %t-DataFlow.o
 RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fPIC                %S/../../lib/fuzzer/dataflow/DataFlowCallbacks.cpp -o  %t-DataFlowCallbacks.o
-RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -mllvm -dfsan-fast-16-labels -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/ThreeFunctionsTest.cpp     %t-DataFlow*.o -o %t-ThreeFunctionsTestDF
-RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -mllvm -dfsan-fast-16-labels -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/Labels20Test.cpp     %t-DataFlow*.o -o %t-Labels20TestDF
+RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/ThreeFunctionsTest.cpp     %t-DataFlow*.o -o %t-ThreeFunctionsTestDF
+RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/Labels20Test.cpp     %t-DataFlow*.o -o %t-Labels20TestDF
 RUN: %cpp_compiler %S/ThreeFunctionsTest.cpp -o %t-ThreeFunctionsTest
 
 # Dump the function list.
diff --git a/compiler-rt/test/fuzzer/only-some-bytes-fork.test b/compiler-rt/test/fuzzer/only-some-bytes-fork.test
--- a/compiler-rt/test/fuzzer/only-some-bytes-fork.test
+++ b/compiler-rt/test/fuzzer/only-some-bytes-fork.test
@@ -2,9 +2,9 @@
 REQUIRES: linux, x86_64
 
 # Build the tracer and the test.
-RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fsanitize=dataflow -mllvm -dfsan-fast-16-labels %S/../../lib/fuzzer/dataflow/DataFlow.cpp -o  %t-DataFlow.o
+RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fsanitize=dataflow %S/../../lib/fuzzer/dataflow/DataFlow.cpp -o  %t-DataFlow.o
 RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fPIC                %S/../../lib/fuzzer/dataflow/DataFlowCallbacks.cpp -o  %t-DataFlowCallbacks.o
-RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -mllvm -dfsan-fast-16-labels -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/OnlySomeBytesTest.cpp     %t-DataFlow*.o -o %t-DFT
+RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/OnlySomeBytesTest.cpp     %t-DataFlow*.o -o %t-DFT
 RUN: %cpp_compiler %S/OnlySomeBytesTest.cpp -o %t-Fuzz
 
 # Test that the fork mode can collect and use the DFT
diff --git a/compiler-rt/test/fuzzer/only-some-bytes.test b/compiler-rt/test/fuzzer/only-some-bytes.test
--- a/compiler-rt/test/fuzzer/only-some-bytes.test
+++ b/compiler-rt/test/fuzzer/only-some-bytes.test
@@ -2,9 +2,9 @@
 REQUIRES: linux, x86_64
 
 # Build the tracer and the test.
-RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fsanitize=dataflow -mllvm -dfsan-fast-16-labels %S/../../lib/fuzzer/dataflow/DataFlow.cpp -o  %t-DataFlow.o
+RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fsanitize=dataflow %S/../../lib/fuzzer/dataflow/DataFlow.cpp -o  %t-DataFlow.o
 RUN: %no_fuzzer_cpp_compiler -c -fno-sanitize=all -fPIC                %S/../../lib/fuzzer/dataflow/DataFlowCallbacks.cpp -o  %t-DataFlowCallbacks.o
-RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -mllvm -dfsan-fast-16-labels -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/OnlySomeBytesTest.cpp     %t-DataFlow*.o -o %t-DFT
+RUN: %no_fuzzer_cpp_compiler    -fno-sanitize=all -fsanitize=dataflow -fsanitize-coverage=trace-pc-guard,pc-table,bb,trace-cmp   %S/OnlySomeBytesTest.cpp     %t-DataFlow*.o -o %t-DFT
 RUN: %cpp_compiler %S/OnlySomeBytesTest.cpp -o %t-Fuzz
 
 # Prepare the inputs.
diff --git a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -18,11 +18,9 @@
 /// The analysis is based on automatic propagation of data flow labels (also
 /// known as taint labels) through a program as it performs computation.
 ///
-/// There are two possible memory layouts. In the first one, each byte of
-/// application memory is backed by a shadow memory byte. The shadow byte can
-/// represent up to 8 labels. To enable this you must specify the
-/// -dfsan-fast-8-labels flag. On Linux/x86_64, memory is then laid out as
-/// follows:
+/// Each byte of application memory is backed by a shadow memory byte. The
+/// shadow byte can represent up to 8 labels. On Linux/x86_64, memory is then
+/// laid out as follows:
 ///
 /// +--------------------+ 0x800000000000 (top of memory)
 /// | application memory |
@@ -30,11 +28,11 @@
 /// |                    |
 /// |       unused       |
 /// |                    |
-/// +--------------------+ 0x300200000000 (kUnusedAddr)
-/// |    union table     |
-/// +--------------------+ 0x300000000000 (kUnionTableAddr)
+/// +--------------------+ 0x300000000000 (kUnusedAddr)
 /// |       origin       |
 /// +--------------------+ 0x200000008000 (kOriginAddr)
+/// |       unused       |
+/// +--------------------+ 0x200000000000
 /// |   shadow memory    |
 /// +--------------------+ 0x100000008000 (kShadowAddr)
 /// |       unused       |
@@ -43,34 +41,9 @@
 /// +--------------------+ 0x000000000000
 ///
 ///
-/// In the second memory layout, each byte of application memory is backed by
-/// two bytes of shadow memory which hold the label. That means we can represent
-/// either 16 labels (with -dfsan-fast-16-labels flag) or 2^16 labels (on the
-/// default legacy mode) per byte. On Linux/x86_64, memory is then laid out as
-/// follows:
-///
-/// +--------------------+ 0x800000000000 (top of memory)
-/// | application memory |
-/// +--------------------+ 0x700000008000 (kAppAddr)
-/// |                    |
-/// |       unused       |
-/// |                    |
-/// +--------------------+ 0x300200000000 (kUnusedAddr)
-/// |    union table     |
-/// +--------------------+ 0x300000000000 (kUnionTableAddr)
-/// |       origin       |
-/// +--------------------+ 0x200000008000 (kOriginAddr)
-/// |   shadow memory    |
-/// +--------------------+ 0x000000010000 (kShadowAddr)
-/// | reserved by kernel |
-/// +--------------------+ 0x000000000000
-///
-///
-/// To derive a shadow memory address from an application memory address,
-/// bits 44-46 are cleared to bring the address into the range
-/// [0x000000008000,0x100000000000).  Then the address is shifted left by 1 to
-/// account for the double byte representation of shadow labels and move the
-/// address into the shadow memory range.  See the function
+/// To derive a shadow memory address from an application memory address, bits
+/// 45-46 are cleared to bring the address into the range
+/// [0x100000008000,0x200000000000). See the function
 /// DataFlowSanitizer::getShadowAddress below.
 ///
 /// For more information, please refer to the design document:
@@ -230,22 +203,6 @@
     cl::desc("Insert calls to __dfsan_*_callback functions on data events."),
     cl::Hidden, cl::init(false));
 
-// Use a distinct bit for each base label, enabling faster unions with less
-// instrumentation.  Limits the max number of base labels to 16.
-static cl::opt<bool> ClFast16Labels(
-    "dfsan-fast-16-labels",
-    cl::desc("Use more efficient instrumentation, limiting the number of "
-             "labels to 16."),
-    cl::Hidden, cl::init(false));
-
-// Use a distinct bit for each base label, enabling faster unions with less
-// instrumentation.  Limits the max number of base labels to 8.
-static cl::opt<bool> ClFast8Labels(
-    "dfsan-fast-8-labels",
-    cl::desc("Use more efficient instrumentation, limiting the number of "
-             "labels to 8."),
-    cl::Hidden, cl::init(false));
-
 // Controls whether the pass tracks the control flow of select instructions.
 static cl::opt<bool> ClTrackSelectControlFlow(
     "dfsan-track-select-control-flow",
@@ -387,6 +344,8 @@
   friend struct DFSanFunction;
   friend class DFSanVisitor;
 
+  enum { ShadowWidthBits = 8, ShadowWidthBytes = ShadowWidthBits / 8 };
+
   enum {
     OriginWidthBits = 32,
     OriginWidthBytes = OriginWidthBits / 8
@@ -428,15 +387,11 @@
     WK_Custom
   };
 
-  unsigned ShadowWidthBits;
-  unsigned ShadowWidthBytes;
-
   Module *Mod;
   LLVMContext *Ctx;
   Type *Int8Ptr;
   IntegerType *OriginTy;
   PointerType *OriginPtrTy;
-  ConstantInt *OriginBase;
   ConstantInt *ZeroOrigin;
   /// The shadow type for all primitive types and vector types.
   IntegerType *PrimitiveShadowTy;
@@ -444,14 +399,14 @@
   IntegerType *IntptrTy;
   ConstantInt *ZeroPrimitiveShadow;
   ConstantInt *ShadowPtrMask;
-  ConstantInt *ShadowPtrMul;
+  ConstantInt *ShadowBase;
+  ConstantInt *OriginBase;
   Constant *ArgTLS;
   ArrayType *ArgOriginTLSTy;
   Constant *ArgOriginTLS;
   Constant *RetvalTLS;
   Constant *RetvalOriginTLS;
   Constant *ExternalShadowMask;
-  FunctionType *DFSanUnionFnTy;
   FunctionType *DFSanUnionLoadFnTy;
   FunctionType *DFSanLoadLabelAndOriginFnTy;
   FunctionType *DFSanUnimplementedFnTy;
@@ -465,10 +420,7 @@
   FunctionType *DFSanChainOriginIfTaintedFnTy;
   FunctionType *DFSanMemOriginTransferFnTy;
   FunctionType *DFSanMaybeStoreOriginFnTy;
-  FunctionCallee DFSanUnionFn;
-  FunctionCallee DFSanCheckedUnionFn;
   FunctionCallee DFSanUnionLoadFn;
-  FunctionCallee DFSanUnionLoadFastLabelsFn;
   FunctionCallee DFSanLoadLabelAndOriginFn;
   FunctionCallee DFSanUnimplementedFn;
   FunctionCallee DFSanSetLabelFn;
@@ -510,7 +462,6 @@
   void initializeCallbackFunctions(Module &M);
   void initializeRuntimeFunctions(Module &M);
   void injectMetadataGlobals(Module &M);
-
   bool init(Module &M);
 
   /// Advances \p OriginAddr to point to the next 32-bit origin and then loads
@@ -518,19 +469,15 @@
   Value *loadNextOrigin(Instruction *Pos, Align OriginAlign,
                         Value **OriginAddr);
 
-  /// Returns whether fast8 or fast16 mode has been specified.
-  bool hasFastLabelsEnabled();
-
   /// Returns whether the given load byte size is amenable to inlined
   /// optimization patterns.
   bool hasLoadSizeForFastPath(uint64_t Size);
 
-  /// Returns whether the pass tracks origins. Support only fast16 mode in TLS
-  /// ABI mode.
+  /// Returns whether the pass tracks origins. Supports only TLS ABI mode.
   bool shouldTrackOrigins();
 
   /// Returns whether the pass tracks labels for struct fields and array
-  /// indices. Support only fast16 mode in TLS ABI mode.
+  /// indices. Supports only TLS ABI mode.
   bool shouldTrackFieldsAndIndices();
 
   /// Returns a zero constant with the shadow type of OrigTy.
@@ -590,7 +537,6 @@
 
   DenseSet<Instruction *> SkipInsts;
   std::vector<Value *> NonZeroChecks;
-  bool AvoidNewBlocks;
 
   struct CachedShadow {
     BasicBlock *Block; // The block where Shadow is defined.
@@ -608,9 +554,6 @@
   DFSanFunction(DataFlowSanitizer &DFS, Function *F, bool IsNativeABI)
       : DFS(DFS), F(F), IA(DFS.getInstrumentedABI()), IsNativeABI(IsNativeABI) {
     DT.recalculate(*F);
-    // FIXME: Need to track down the register allocator issue which causes poor
-    // performance in pathological cases with large numbers of basic blocks.
-    AvoidNewBlocks = F->size() > 1000;
   }
 
   /// Computes the shadow address for a given function argument.
@@ -702,15 +645,11 @@
   /// Returns the shadow value of an argument A.
   Value *getShadowForTLSArgument(Argument *A);
 
-  /// The fast path of loading shadow in legacy mode.
-  Value *loadLegacyShadowFast(Value *ShadowAddr, uint64_t Size,
-                              Align ShadowAlign, Instruction *Pos);
-
-  /// The fast path of loading shadow in fast-16-label mode.
+  /// The fast path of loading shadows.
   std::pair<Value *, Value *>
-  loadFast16ShadowFast(Value *ShadowAddr, Value *OriginAddr, uint64_t Size,
-                       Align ShadowAlign, Align OriginAlign, Value *FirstOrigin,
-                       Instruction *Pos);
+  loadShadowFast(Value *ShadowAddr, Value *OriginAddr, uint64_t Size,
+                 Align ShadowAlign, Align OriginAlign, Value *FirstOrigin,
+                 Instruction *Pos);
 
   Align getOriginAlign(Align InstAlignment);
 
@@ -820,14 +759,6 @@
 
 DataFlowSanitizer::DataFlowSanitizer(
     const std::vector<std::string> &ABIListFiles) {
-  if (ClFast8Labels && ClFast16Labels) {
-    report_fatal_error(
-        "cannot set both -dfsan-fast-8-labels and -dfsan-fast-16-labels");
-  }
-
-  ShadowWidthBits = ClFast8Labels ? 8 : 16;
-  ShadowWidthBytes = ShadowWidthBits / 8;
-
   std::vector<std::string> AllABIListFiles(std::move(ABIListFiles));
   llvm::append_range(AllABIListFiles, ClABIListFiles);
   // FIXME: should we propagate vfs::FileSystem to this constructor?
@@ -922,11 +853,6 @@
   return isa<ConstantAggregateZero>(V);
 }
 
-bool DataFlowSanitizer::hasFastLabelsEnabled() {
-  static const bool HasFastLabelsEnabled = ClFast8Labels || ClFast16Labels;
-  return HasFastLabelsEnabled;
-}
-
 bool DataFlowSanitizer::hasLoadSizeForFastPath(uint64_t Size) {
   uint64_t ShadowSize = Size * ShadowWidthBytes;
   return ShadowSize % 8 == 0 || ShadowSize == 4;
@@ -934,14 +860,12 @@
 
 bool DataFlowSanitizer::shouldTrackOrigins() {
   static const bool ShouldTrackOrigins =
-      ClTrackOrigins && getInstrumentedABI() == DataFlowSanitizer::IA_TLS &&
-      hasFastLabelsEnabled();
+      ClTrackOrigins && getInstrumentedABI() == DataFlowSanitizer::IA_TLS;
   return ShouldTrackOrigins;
 }
 
 bool DataFlowSanitizer::shouldTrackFieldsAndIndices() {
-  return getInstrumentedABI() == DataFlowSanitizer::IA_TLS &&
-         hasFastLabelsEnabled();
+  return getInstrumentedABI() == DataFlowSanitizer::IA_TLS;
 }
 
 Constant *DataFlowSanitizer::getZeroShadow(Type *OrigTy) {
@@ -1100,21 +1024,19 @@
   PrimitiveShadowPtrTy = PointerType::getUnqual(PrimitiveShadowTy);
   IntptrTy = DL.getIntPtrType(*Ctx);
   ZeroPrimitiveShadow = ConstantInt::getSigned(PrimitiveShadowTy, 0);
-  ShadowPtrMul = ConstantInt::getSigned(IntptrTy, ShadowWidthBytes);
-  OriginBase = ConstantInt::get(IntptrTy, 0x200000000000LL);
   ZeroOrigin = ConstantInt::getSigned(OriginTy, 0);
 
+  // TODO: these should be platform-specific and set in the switch-stmt below.
+  ShadowBase = ConstantInt::get(IntptrTy, 0x100000008000LL);
+  OriginBase = ConstantInt::get(IntptrTy, 0x200000008000LL);
+
   switch (TargetTriple.getArch()) {
   case Triple::x86_64:
-    ShadowPtrMask = ClFast8Labels
-                        ? ConstantInt::getSigned(IntptrTy, ~0x600000000000LL)
-                        : ConstantInt::getSigned(IntptrTy, ~0x700000000000LL);
+    ShadowPtrMask = ConstantInt::getSigned(IntptrTy, ~0x600000000000LL);
     break;
   case Triple::mips64:
   case Triple::mips64el:
-    ShadowPtrMask = ClFast8Labels
-                        ? ConstantInt::getSigned(IntptrTy, ~0xE000000000LL)
-                        : ConstantInt::getSigned(IntptrTy, ~0xF000000000LL);
+    ShadowPtrMask = ConstantInt::getSigned(IntptrTy, ~0xE000000000LL);
     break;
   case Triple::aarch64:
   case Triple::aarch64_be:
@@ -1125,9 +1047,6 @@
     report_fatal_error("unsupported triple");
   }
 
-  Type *DFSanUnionArgs[2] = {PrimitiveShadowTy, PrimitiveShadowTy};
-  DFSanUnionFnTy =
-      FunctionType::get(PrimitiveShadowTy, DFSanUnionArgs, /*isVarArg=*/false);
   Type *DFSanUnionLoadArgs[2] = {PrimitiveShadowPtrTy, IntptrTy};
   DFSanUnionLoadFnTy = FunctionType::get(PrimitiveShadowTy, DFSanUnionLoadArgs,
                                          /*isVarArg=*/false);
@@ -1306,32 +1225,6 @@
 
 // Initialize DataFlowSanitizer runtime functions and declare them in the module
 void DataFlowSanitizer::initializeRuntimeFunctions(Module &M) {
-  {
-    AttributeList AL;
-    AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
-                         Attribute::NoUnwind);
-    AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
-                         Attribute::ReadNone);
-    AL = AL.addAttribute(M.getContext(), AttributeList::ReturnIndex,
-                         Attribute::ZExt);
-    AL = AL.addParamAttribute(M.getContext(), 0, Attribute::ZExt);
-    AL = AL.addParamAttribute(M.getContext(), 1, Attribute::ZExt);
-    DFSanUnionFn =
-        Mod->getOrInsertFunction("__dfsan_union", DFSanUnionFnTy, AL);
-  }
-  {
-    AttributeList AL;
-    AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
-                         Attribute::NoUnwind);
-    AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
-                         Attribute::ReadNone);
-    AL = AL.addAttribute(M.getContext(), AttributeList::ReturnIndex,
-                         Attribute::ZExt);
-    AL = AL.addParamAttribute(M.getContext(), 0, Attribute::ZExt);
-    AL = AL.addParamAttribute(M.getContext(), 1, Attribute::ZExt);
-    DFSanCheckedUnionFn =
-        Mod->getOrInsertFunction("dfsan_union", DFSanUnionFnTy, AL);
-  }
   {
     AttributeList AL;
     AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
@@ -1343,17 +1236,6 @@
     DFSanUnionLoadFn =
         Mod->getOrInsertFunction("__dfsan_union_load", DFSanUnionLoadFnTy, AL);
   }
-  {
-    AttributeList AL;
-    AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
-                         Attribute::NoUnwind);
-    AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
-                         Attribute::ReadOnly);
-    AL = AL.addAttribute(M.getContext(), AttributeList::ReturnIndex,
-                         Attribute::ZExt);
-    DFSanUnionLoadFastLabelsFn = Mod->getOrInsertFunction(
-        "__dfsan_union_load_fast16labels", DFSanUnionLoadFnTy, AL);
-  }
   {
     AttributeList AL;
     AL = AL.addAttribute(M.getContext(), AttributeList::FunctionIndex,
@@ -1406,13 +1288,8 @@
         "__dfsan_maybe_store_origin", DFSanMaybeStoreOriginFnTy, AL);
   }
 
-  DFSanRuntimeFunctions.insert(DFSanUnionFn.getCallee()->stripPointerCasts());
-  DFSanRuntimeFunctions.insert(
-      DFSanCheckedUnionFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanUnionLoadFn.getCallee()->stripPointerCasts());
-  DFSanRuntimeFunctions.insert(
-      DFSanUnionLoadFastLabelsFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
       DFSanLoadLabelAndOriginFn.getCallee()->stripPointerCasts());
   DFSanRuntimeFunctions.insert(
@@ -1878,13 +1755,16 @@
 std::pair<Value *, Value *>
 DataFlowSanitizer::getShadowOriginAddress(Value *Addr, Align InstAlignment,
                                           Instruction *Pos) {
-  // Returns ((Addr & shadow_mask) + origin_base) & ~4UL
+  // Returns ((Addr & shadow_mask) + origin_base - shadow_base) & ~4UL
   IRBuilder<> IRB(Pos);
   Value *ShadowOffset = getShadowOffset(Addr, IRB);
   Value *ShadowPtr = getShadowAddress(Addr, Pos, ShadowOffset);
   Value *OriginPtr = nullptr;
   if (shouldTrackOrigins()) {
-    Value *OriginLong = IRB.CreateAdd(ShadowOffset, OriginBase);
+    static Value *OriginByShadowOffset = ConstantInt::get(
+        IntptrTy, OriginBase->getZExtValue() - ShadowBase->getZExtValue());
+
+    Value *OriginLong = IRB.CreateAdd(ShadowOffset, OriginByShadowOffset);
     const Align Alignment = llvm::assumeAligned(InstAlignment.value());
     // When alignment is >= 4, Addr must be aligned to 4, otherwise it is UB.
     // So Mask is unnecessary.
@@ -1900,15 +1780,11 @@
 Value *DataFlowSanitizer::getShadowAddress(Value *Addr, Instruction *Pos,
                                            Value *ShadowOffset) {
   IRBuilder<> IRB(Pos);
-
-  if (!ShadowPtrMul->isOne())
-    ShadowOffset = IRB.CreateMul(ShadowOffset, ShadowPtrMul);
-
   return IRB.CreateIntToPtr(ShadowOffset, PrimitiveShadowPtrTy);
 }
 
 Value *DataFlowSanitizer::getShadowAddress(Value *Addr, Instruction *Pos) {
-  // Returns (Addr & shadow_mask) x 2
+  // Returns (Addr & shadow_mask)
   IRBuilder<> IRB(Pos);
   Value *ShadowOffset = getShadowOffset(Addr, IRB);
   return getShadowAddress(Addr, Pos, ShadowOffset);
@@ -1961,37 +1837,8 @@
   Value *PV2 = collapseToPrimitiveShadow(V2, Pos);
 
   IRBuilder<> IRB(Pos);
-  if (DFS.hasFastLabelsEnabled()) {
-    CCS.Block = Pos->getParent();
-    CCS.Shadow = IRB.CreateOr(PV1, PV2);
-  } else if (AvoidNewBlocks) {
-    CallInst *Call = IRB.CreateCall(DFS.DFSanCheckedUnionFn, {PV1, PV2});
-    Call->addAttribute(AttributeList::ReturnIndex, Attribute::ZExt);
-    Call->addParamAttr(0, Attribute::ZExt);
-    Call->addParamAttr(1, Attribute::ZExt);
-
-    CCS.Block = Pos->getParent();
-    CCS.Shadow = Call;
-  } else {
-    BasicBlock *Head = Pos->getParent();
-    Value *Ne = IRB.CreateICmpNE(PV1, PV2);
-    BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
-        Ne, Pos, /*Unreachable=*/false, DFS.ColdCallWeights, &DT));
-    IRBuilder<> ThenIRB(BI);
-    CallInst *Call = ThenIRB.CreateCall(DFS.DFSanUnionFn, {PV1, PV2});
-    Call->addAttribute(AttributeList::ReturnIndex, Attribute::ZExt);
-    Call->addParamAttr(0, Attribute::ZExt);
-    Call->addParamAttr(1, Attribute::ZExt);
-
-    BasicBlock *Tail = BI->getSuccessor(0);
-    PHINode *Phi =
-        PHINode::Create(DFS.PrimitiveShadowTy, 2, "", &Tail->front());
-    Phi->addIncoming(Call, Call->getParent());
-    Phi->addIncoming(PV1, Head);
-
-    CCS.Block = Tail;
-    CCS.Shadow = Phi;
-  }
+  CCS.Block = Pos->getParent();
+  CCS.Shadow = IRB.CreateOr(PV1, PV2);
 
   std::set<Value *> UnionElems;
   if (V1Elems != ShadowElements.end()) {
@@ -2116,7 +1963,7 @@
   return IRB.CreateAlignedLoad(OriginTy, *OriginAddr, OriginAlign);
 }
 
-std::pair<Value *, Value *> DFSanFunction::loadFast16ShadowFast(
+std::pair<Value *, Value *> DFSanFunction::loadShadowFast(
     Value *ShadowAddr, Value *OriginAddr, uint64_t Size, Align ShadowAlign,
     Align OriginAlign, Value *FirstOrigin, Instruction *Pos) {
   const bool ShouldTrackOrigins = DFS.shouldTrackOrigins();
@@ -2135,7 +1982,7 @@
   // Specifically, when the shadow size in bytes (i.e., loaded bytes x shadow
   // per byte) is either:
   // - a multiple of 8  (common)
-  // - equal to 4       (only for load32 in fast-8 mode)
+  // - equal to 4       (only for load32)
   //
   // For the second case, we can fit the wide shadow in a 32-bit integer. In all
   // other cases, we use a 64-bit integer to hold the wide shadow.
@@ -2204,84 +2051,6 @@
               : DFS.ZeroOrigin};
 }
 
-Value *DFSanFunction::loadLegacyShadowFast(Value *ShadowAddr, uint64_t Size,
-                                           Align ShadowAlign,
-                                           Instruction *Pos) {
-  // Fast path for the common case where each byte has identical shadow: load
-  // shadow 64 (or 32) bits at a time, fall out to a __dfsan_union_load call if
-  // any shadow is non-equal.
-  BasicBlock *FallbackBB = BasicBlock::Create(*DFS.Ctx, "", F);
-  IRBuilder<> FallbackIRB(FallbackBB);
-  CallInst *FallbackCall = FallbackIRB.CreateCall(
-      DFS.DFSanUnionLoadFn, {ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size)});
-  FallbackCall->addAttribute(AttributeList::ReturnIndex, Attribute::ZExt);
-
-  const uint64_t ShadowSize = Size * DFS.ShadowWidthBytes;
-  assert(Size >= 4 && "Not large enough load size for fast path!");
-
-  // Same as in loadFast16AShadowsFast. In the case of load32, we can fit the
-  // wide shadow in a 32-bit integer instead.
-  Type *WideShadowTy =
-      ShadowSize == 4 ? Type::getInt32Ty(*DFS.Ctx) : Type::getInt64Ty(*DFS.Ctx);
-
-  // Compare each of the shadows stored in the loaded 64 bits to each other,
-  // by computing (WideShadow rotl ShadowWidthBits) == WideShadow.
-  IRBuilder<> IRB(Pos);
-  unsigned WideShadowBitWidth = WideShadowTy->getIntegerBitWidth();
-  Value *WideAddr = IRB.CreateBitCast(ShadowAddr, WideShadowTy->getPointerTo());
-  Value *WideShadow =
-      IRB.CreateAlignedLoad(WideShadowTy, WideAddr, ShadowAlign);
-  Value *TruncShadow = IRB.CreateTrunc(WideShadow, DFS.PrimitiveShadowTy);
-  Value *ShlShadow = IRB.CreateShl(WideShadow, DFS.ShadowWidthBits);
-  Value *ShrShadow =
-      IRB.CreateLShr(WideShadow, WideShadowBitWidth - DFS.ShadowWidthBits);
-  Value *RotShadow = IRB.CreateOr(ShlShadow, ShrShadow);
-  Value *ShadowsEq = IRB.CreateICmpEQ(WideShadow, RotShadow);
-
-  BasicBlock *Head = Pos->getParent();
-  BasicBlock *Tail = Head->splitBasicBlock(Pos->getIterator());
-
-  if (DomTreeNode *OldNode = DT.getNode(Head)) {
-    std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());
-
-    DomTreeNode *NewNode = DT.addNewBlock(Tail, Head);
-    for (auto *Child : Children)
-      DT.changeImmediateDominator(Child, NewNode);
-  }
-
-  // In the following code LastBr will refer to the previous basic block's
-  // conditional branch instruction, whose true successor is fixed up to point
-  // to the next block during the loop below or to the tail after the final
-  // iteration.
-  BranchInst *LastBr = BranchInst::Create(FallbackBB, FallbackBB, ShadowsEq);
-  ReplaceInstWithInst(Head->getTerminator(), LastBr);
-  DT.addNewBlock(FallbackBB, Head);
-
-  const uint64_t BytesPerWideShadow = WideShadowBitWidth / DFS.ShadowWidthBits;
-
-  for (uint64_t ByteOfs = BytesPerWideShadow; ByteOfs < Size;
-       ByteOfs += BytesPerWideShadow) {
-    BasicBlock *NextBB = BasicBlock::Create(*DFS.Ctx, "", F);
-    DT.addNewBlock(NextBB, LastBr->getParent());
-    IRBuilder<> NextIRB(NextBB);
-    WideAddr = NextIRB.CreateGEP(WideShadowTy, WideAddr,
-                                 ConstantInt::get(DFS.IntptrTy, 1));
-    Value *NextWideShadow =
-        NextIRB.CreateAlignedLoad(WideShadowTy, WideAddr, ShadowAlign);
-    ShadowsEq = NextIRB.CreateICmpEQ(WideShadow, NextWideShadow);
-    LastBr->setSuccessor(0, NextBB);
-    LastBr = NextIRB.CreateCondBr(ShadowsEq, FallbackBB, FallbackBB);
-  }
-
-  LastBr->setSuccessor(0, Tail);
-  FallbackIRB.CreateBr(Tail);
-  PHINode *Shadow =
-      PHINode::Create(DFS.PrimitiveShadowTy, 2, "", &Tail->front());
-  Shadow->addIncoming(FallbackCall, FallbackBB);
-  Shadow->addIncoming(TruncShadow, LastBr->getParent());
-  return Shadow;
-}
-
 std::pair<Value *, Value *> DFSanFunction::loadShadowOriginSansLoadTracking(
     Value *Addr, uint64_t Size, Align InstAlignment, Instruction *Pos) {
   const bool ShouldTrackOrigins = DFS.shouldTrackOrigins();
@@ -2369,21 +2138,14 @@
   }
   }
   bool HasSizeForFastPath = DFS.hasLoadSizeForFastPath(Size);
-  bool HasFastLabelsEnabled = DFS.hasFastLabelsEnabled();
-
-  if (HasFastLabelsEnabled && HasSizeForFastPath)
-    return loadFast16ShadowFast(ShadowAddr, OriginAddr, Size, ShadowAlign,
-                                OriginAlign, Origin, Pos);
 
-  if (!AvoidNewBlocks && HasSizeForFastPath)
-    return {loadLegacyShadowFast(ShadowAddr, Size, ShadowAlign, Pos), Origin};
+  if (HasSizeForFastPath)
+    return loadShadowFast(ShadowAddr, OriginAddr, Size, ShadowAlign,
+                          OriginAlign, Origin, Pos);
 
   IRBuilder<> IRB(Pos);
-  FunctionCallee &UnionLoadFn = HasFastLabelsEnabled
-                                    ? DFS.DFSanUnionLoadFastLabelsFn
-                                    : DFS.DFSanUnionLoadFn;
   CallInst *FallbackCall = IRB.CreateCall(
-      UnionLoadFn, {ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size)});
+      DFS.DFSanUnionLoadFn, {ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size)});
   FallbackCall->addAttribute(AttributeList::ReturnIndex, Attribute::ZExt);
   return {FallbackCall, Origin};
 }
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/abilist.ll b/llvm/test/Instrumentation/DataFlowSanitizer/abilist.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/abilist.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/abilist.ll
@@ -1,6 +1,4 @@
 ; RUN: opt < %s -dfsan -dfsan-args-abi -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-args-abi -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-args-abi -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/abilist_aggregate.ll b/llvm/test/Instrumentation/DataFlowSanitizer/abilist_aggregate.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/abilist_aggregate.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/abilist_aggregate.ll
@@ -1,6 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s --check-prefixes=CHECK,TLS_ABI
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s --check-prefixes=CHECK,TLS_ABI
-; RUN: opt < %s -dfsan -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s --check-prefixes=CHECK,LEGACY
+; RUN: opt < %s -dfsan -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s --check-prefixes=CHECK,TLS_ABI
 ; RUN: opt < %s -dfsan -dfsan-args-abi -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s --check-prefixes=CHECK,ARGS_ABI
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
@@ -33,19 +31,12 @@
   ; TLS_ABI-NEXT: %[[#REG+10]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } %[[#REG+9]], i[[#SBITS]] %[[#REG+8]], 1
   ; TLS_ABI: store { i[[#SBITS]], i[[#SBITS]] } %[[#REG+10]], { i[[#SBITS]], i[[#SBITS]] }* bitcast ([100 x i64]* @__dfsan_retval_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN]]
 
-  ; LEGACY: @"dfs$call_functional"
-  ; LEGACY: [[B:%.*]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([100 x i64]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: [[A:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; LEGACY: [[U:%.*]] = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext [[A]], i[[#SBITS]] zeroext [[B]])
-  ; LEGACY: [[PH:%.*]] = phi i[[#SBITS]] [ [[U]], {{.*}} ], [ [[A]], {{.*}} ]
-  ; LEGACY: store i[[#SBITS]] [[PH]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-
-  ; ARGS_ABI: @"dfs$call_functional"
-  ; ARGS_ABI: [[U:%.*]]  = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext %2, i[[#SBITS]] zeroext %3)
-  ; ARGS_ABI: [[PH:%.*]] = phi i[[#SBITS]] [ %7, {{.*}} ], [ %2, {{.*}} ]
-  ; ARGS_ABI: [[R0:%.*]] = insertvalue { { i1, i7 }, i[[#SBITS]] } undef, { i1, i7 } %r, 0
-  ; ARGS_ABI: [[R1:%.*]] = insertvalue { { i1, i7 }, i[[#SBITS]] } [[R0]], i[[#SBITS]] [[PH]], 1
-  ; ARGS_ABI: ret { { i1, i7 }, i[[#SBITS]] } [[R1]]
+  ; ARGS_ABI: @"dfs$call_functional"({ i32, i1 } %0, [2 x i7] %1, i[[#SBITS]] %2, i[[#SBITS]] %3)
+  ; ARGS_ABI: %[[#U:]]  = or i[[#SBITS]] %2, %3
+  ; ARGS_ABI: %r = call { i1, i7 } @functional({ i32, i1 } %0, [2 x i7] %1)
+  ; ARGS_ABI: %[[#R:]] = insertvalue { { i1, i7 }, i[[#SBITS]] } undef, { i1, i7 } %r, 0
+  ; ARGS_ABI: %[[#R+1]] = insertvalue { { i1, i7 }, i[[#SBITS]] } %[[#R]], i[[#SBITS]] %[[#U]], 1
+  ; ARGS_ABI: ret { { i1, i7 }, i[[#SBITS]] } %[[#R+1]]
 
   %r = call {i1, i7} @functional({i32, i1} %a, [2 x i7] %b)
   ret {i1, i7} %r
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/arith.ll b/llvm/test/Instrumentation/DataFlowSanitizer/arith.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/arith.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/arith.ll
@@ -7,13 +7,12 @@
 
 define i8 @add(i8 %a, i8 %b) {
   ; CHECK: @"dfs$add"
-  ; CHECK-DAG: %[[ALABEL:.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[ARGTLSTYPE:\[100 x i64\]]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; CHECK-DAG: %[[BLABEL:.*]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[ARGTLSTYPE]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK: %[[UNION:.*]] = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext %[[ALABEL]], i[[#SBITS]] zeroext %[[BLABEL]])
-  ; CHECK: %[[ADDLABEL:.*]] = phi i[[#SBITS]] [ %[[UNION]], {{.*}} ], [ %[[ALABEL]], {{.*}} ]
-  ; CHECK: add i8
-  ; CHECK: store i[[#SBITS]] %[[ADDLABEL]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK: ret i8
+  ; CHECK-DAG: %[[#ALABEL:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[ARGTLSTYPE:\[100 x i64\]]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
+  ; CHECK-DAG: %[[#BLABEL:]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[ARGTLSTYPE]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK: %[[#UNION:]] = or i[[#SBITS]] %[[#ALABEL]], %[[#BLABEL]]
+  ; CHECK: %c = add i8 %a, %b
+  ; CHECK: store i[[#SBITS]] %[[#UNION]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK: ret i8 %c
   %c = add i8 %a, %b
   ret i8 %c
 }
@@ -22,10 +21,10 @@
   ; CHECK: @"dfs$sub"
   ; CHECK: load{{.*}}__dfsan_arg_tls
   ; CHECK: load{{.*}}__dfsan_arg_tls
-  ; CHECK: call{{.*}}__dfsan_union
-  ; CHECK: sub i8
+  ; CHECK: or i[[#SBITS]]
+  ; CHECK: %c = sub i8 %a, %b
   ; CHECK: store{{.*}}__dfsan_retval_tls
-  ; CHECK: ret i8
+  ; CHECK: ret i8 %c
   %c = sub i8 %a, %b
   ret i8 %c
 }
@@ -34,10 +33,10 @@
   ; CHECK: @"dfs$mul"
   ; CHECK: load{{.*}}__dfsan_arg_tls
   ; CHECK: load{{.*}}__dfsan_arg_tls
-  ; CHECK: call{{.*}}__dfsan_union
-  ; CHECK: mul i8
+  ; CHECK: or i[[#SBITS]]
+  ; CHECK: %c = mul i8 %a, %b
   ; CHECK: store{{.*}}__dfsan_retval_tls
-  ; CHECK: ret i8
+  ; CHECK: ret i8 %c
   %c = mul i8 %a, %b
   ret i8 %c
 }
@@ -46,10 +45,10 @@
   ; CHECK: @"dfs$sdiv"
   ; CHECK: load{{.*}}__dfsan_arg_tls
   ; CHECK: load{{.*}}__dfsan_arg_tls
-  ; CHECK: call{{.*}}__dfsan_union
-  ; CHECK: sdiv i8
+  ; CHECK: or i[[#SBITS]]
+  ; CHECK: %c = sdiv i8 %a, %b
   ; CHECK: store{{.*}}__dfsan_retval_tls
-  ; CHECK: ret i8
+  ; CHECK: ret i8 %c
   %c = sdiv i8 %a, %b
   ret i8 %c
 }
@@ -58,10 +57,10 @@
   ; CHECK: @"dfs$udiv"
   ; CHECK: load{{.*}}__dfsan_arg_tls
   ; CHECK: load{{.*}}__dfsan_arg_tls
-  ; CHECK: call{{.*}}__dfsan_union
-  ; CHECK: udiv i8
+  ; CHECK: or i[[#SBITS]]
+  ; CHECK: %c = udiv i8 %a, %b
   ; CHECK: store{{.*}}__dfsan_retval_tls
-  ; CHECK: ret i8
+  ; CHECK: ret i8 %c
   %c = udiv i8 %a, %b
   ret i8 %c
 }
@@ -69,9 +68,9 @@
 define double @fneg(double %a) {
   ; CHECK: @"dfs$fneg"
   ; CHECK: load{{.*}}__dfsan_arg_tls
-  ; CHECK: fneg double
+  ; CHECK: %c = fneg double %a
   ; CHECK: store{{.*}}__dfsan_retval_tls
-  ; CHECK: ret double
+  ; CHECK: ret double %c
   %c = fneg double %a
   ret double %c
 }
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/array.ll b/llvm/test/Instrumentation/DataFlowSanitizer/array.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/array.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/array.ll
@@ -1,15 +1,9 @@
-; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,LEGACY
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-event-callbacks=true -S | FileCheck %s --check-prefixes=CHECK,EVENT_CALLBACKS
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-event-callbacks=true -S | FileCheck %s --check-prefixes=CHECK,EVENT_CALLBACKS
+; RUN: opt < %s -dfsan -dfsan-event-callbacks=true -S | FileCheck %s --check-prefixes=CHECK,EVENT_CALLBACKS
 ; RUN: opt < %s -dfsan -dfsan-args-abi -S | FileCheck %s --check-prefixes=CHECK,ARGS_ABI
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,FAST
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_LOAD_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-combine-pointer-labels-on-store=true -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-debug-nonzero-labels -S | FileCheck %s --check-prefixes=CHECK,DEBUG_NONZERO_LABELS
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -S | FileCheck %s --check-prefixes=CHECK,FAST
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_LOAD_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-combine-pointer-labels-on-store=true -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-debug-nonzero-labels -S | FileCheck %s --check-prefixes=CHECK,DEBUG_NONZERO_LABELS
+; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,FAST
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_LOAD_PTR
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-store=true -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
+; RUN: opt < %s -dfsan -dfsan-debug-nonzero-labels -S | FileCheck %s --check-prefixes=CHECK,DEBUG_NONZERO_LABELS
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -102,13 +96,6 @@
   ; FAST: [[S1:%.*]] = insertvalue [1 x i[[#SBITS]]] undef, i[[#SBITS]] [[U]], 0
   ; FAST: store [1 x i[[#SBITS]]] [[S1]], [1 x i[[#SBITS]]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to [1 x i[[#SBITS]]]*), align [[ALIGN]]
 
-  ; LEGACY: @"dfs$load_array1"
-  ; LEGACY: [[P:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: [[L:%.*]] = load i[[#SBITS]], i[[#SBITS]]* {{.*}}, align [[#SBYTES]]
-  ; LEGACY: [[U:%.*]] = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext [[L]], i[[#SBITS]] zeroext [[P]])
-  ; LEGACY: [[PH:%.*]] = phi i[[#SBITS]] [ [[U]], {{.*}} ], [ [[L]], {{.*}} ]
-  ; LEGACY: store i[[#SBITS]] [[PH]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-
   %a = load [1 x i1], [1 x i1]* %p
   ret [1 x i1] %a
 }
@@ -164,13 +151,6 @@
   ; FAST: [[S4:%.*]] = insertvalue [4 x i[[#SBITS]]] [[S3]], i[[#SBITS]] [[O]], 3
   ; FAST: store [4 x i[[#SBITS]]] [[S4]], [4 x i[[#SBITS]]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to [4 x i[[#SBITS]]]*), align 2
 
-  ; LEGACY: @"dfs$load_array4"
-  ; LEGACY: [[P:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: [[PH1:%.*]] = phi i[[#SBITS]]
-  ; LEGACY: [[U:%.*]] = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext [[PH1]], i[[#SBITS]] zeroext [[P]])
-  ; LEGACY: [[PH:%.*]] = phi i[[#SBITS]] [ [[U]], {{.*}} ], [ [[PH1]], {{.*}} ]
-  ; LEGACY: store i[[#SBITS]] [[PH]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-
   %a = load [4 x i1], [4 x i1]* %p
   ret [4 x i1] %a
 }
@@ -220,13 +200,6 @@
 }
 
 define void @store_array2([2 x i1] %a, [2 x i1]* %p) {
-  ; LEGACY: @"dfs$store_array2"
-  ; LEGACY: [[S:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: [[SP0:%.*]] = getelementptr i[[#SBITS]], i[[#SBITS]]* [[SP:%.*]], i32 0
-  ; LEGACY: store i[[#SBITS]] [[S]], i[[#SBITS]]* [[SP0]], align [[#SBYTES]]
-  ; LEGACY: [[SP1:%.*]] = getelementptr i[[#SBITS]], i[[#SBITS]]* [[SP]], i32 1
-  ; LEGACY: store i[[#SBITS]] [[S]], i[[#SBITS]]* [[SP1]], align [[#SBYTES]]
-
   ; EVENT_CALLBACKS: @"dfs$store_array2"
   ; EVENT_CALLBACKS: [[E12:%.*]] = or i[[#SBITS]]
   ; EVENT_CALLBACKS: [[P:%.*]] = bitcast [2 x i1]* %p to i8*
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/atomics.ll b/llvm/test/Instrumentation/DataFlowSanitizer/atomics.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/atomics.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/atomics.ll
@@ -1,9 +1,6 @@
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,CHECK16
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true -dfsan-instrument-with-call-threshold=0 -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,CHECK16,CHECK_ORIGIN
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -dfsan-instrument-with-call-threshold=0 -S | FileCheck %s --check-prefixes=CHECK,CHECK16,CHECK_ORIGIN
+; RUN: opt < %s -dfsan -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1 -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
+; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-instrument-with-call-threshold=0 -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -21,7 +18,6 @@
   ; CHECK-NOT:         @__dfsan_arg_tls
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
@@ -42,7 +38,6 @@
   ; CHECK-NOT:         @__dfsan_arg_tls
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
@@ -65,7 +60,6 @@
   ; CHECK-NOT:         @__dfsan_arg_tls
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
@@ -89,7 +83,6 @@
   ; CHECK-NOT:         @__dfsan_arg_tls
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
@@ -213,7 +206,6 @@
   ; CHECK_ORIGIN-NOT:  35184372088832
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
@@ -234,7 +226,6 @@
   ; CHECK_ORIGIN-NOT:  35184372088832
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
@@ -255,7 +246,6 @@
   ; CHECK_ORIGIN-NOT:  35184372088832
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
@@ -276,7 +266,6 @@
   ; CHECK_ORIGIN-NOT:  35184372088832
   ; CHECK:             %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:        %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT:      %[[#SHADOW_ADDR:INTP+2]] = mul i64 %[[#INTP+1]], 2
   ; CHECK-NEXT:        %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:        %[[#SHADOW_PTR64:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#NUM_BITS:mul(SBITS,4)]]*
   ; CHECK-NEXT:        store i[[#NUM_BITS]] 0, i[[#NUM_BITS]]* %[[#SHADOW_PTR64]], align [[#SBYTES]]
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/basic.ll b/llvm/test/Instrumentation/DataFlowSanitizer/basic.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/basic.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/basic.ll
@@ -1,6 +1,5 @@
-; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,CHECK_NO_ORIGIN -DSHADOW_MASK=-123145302310913
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN -DSHADOW_MASK=-123145302310913
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN -DSHADOW_MASK=-105553116266497
+; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,CHECK_NO_ORIGIN -DSHADOW_MASK=-105553116266497   --dump-input-context=100
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN -DSHADOW_MASK=-105553116266497  --dump-input-context=100
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -35,20 +34,11 @@
 ; CHECK: declare void @__dfsan_mem_transfer_callback(i[[#SBITS]]*, i64)
 ; CHECK: declare void @__dfsan_cmp_callback(i[[#SBITS]])
 
-; CHECK: ; Function Attrs: nounwind readnone
-; CHECK-NEXT: declare zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext, i[[#SBITS]] zeroext) #0
-
-; CHECK: ; Function Attrs: nounwind readnone
-; CHECK-NEXT: declare zeroext i[[#SBITS]] @dfsan_union(i[[#SBITS]] zeroext, i[[#SBITS]] zeroext) #0
-
-; CHECK: ; Function Attrs: nounwind readonly
-; CHECK-NEXT: declare zeroext i[[#SBITS]] @__dfsan_union_load(i[[#SBITS]]*, i64) #1
-
 ; CHECK: ; Function Attrs: nounwind readonly
-; CHECK-NEXT: declare zeroext i[[#SBITS]] @__dfsan_union_load_fast16labels(i[[#SBITS]]*, i64) #1
+; CHECK-NEXT: declare zeroext i[[#SBITS]] @__dfsan_union_load(i[[#SBITS]]*, i64)
 
 ; CHECK: ; Function Attrs: nounwind readonly
-; CHECK-NEXT: declare zeroext i64 @__dfsan_load_label_and_origin(i8*, i64) #1
+; CHECK-NEXT: declare zeroext i64 @__dfsan_load_label_and_origin(i8*, i64)
 
 ; CHECK: declare void @__dfsan_unimplemented(i8*)
 ; CHECK: declare void @__dfsan_set_label(i[[#SBITS]] zeroext, i32 zeroext, i8*, i64)
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/call.ll b/llvm/test/Instrumentation/DataFlowSanitizer/call.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/call.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/call.ll
@@ -1,6 +1,4 @@
 ; RUN: opt < %s -dfsan -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels -S | FileCheck %s
 ; RUN: opt < %s -passes=dfsan -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/dont_combine_offset_labels_on_gep.ll b/llvm/test/Instrumentation/DataFlowSanitizer/dont_combine_offset_labels_on_gep.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/dont_combine_offset_labels_on_gep.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/dont_combine_offset_labels_on_gep.ll
@@ -1,5 +1,5 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-combine-offset-labels-on-gep=false -dfsan-fast-8-labels=true -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
-; RUN: opt < %s -dfsan -dfsan-combine-offset-labels-on-gep=false -dfsan-fast-8-labels=true -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-combine-offset-labels-on-gep=false -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-combine-offset-labels-on-gep=false -dfsan-track-origins=1 -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/external_mask.ll b/llvm/test/Instrumentation/DataFlowSanitizer/external_mask.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/external_mask.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/external_mask.ll
@@ -1,15 +1,12 @@
-; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,CHECK16
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,CHECK16
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -S | FileCheck %s --check-prefixes=CHECK
+; RUN: opt < %s -dfsan -S | FileCheck %s
 target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64-unknown-linux-gnu"
 
 define i32 @test(i32 %a, i32* nocapture readonly %b) #0 {
-; CHECK: @"dfs$test"
-; CHECK: %[[RV:.*]] load{{.*}}__dfsan_shadow_ptr_mask
-; CHECK: ptrtoint i32* {{.*}} to i64
-; CHECK: and {{.*}}%[[RV:.*]]
-; CHECK16: mul i64
+  ; CHECK: @"dfs$test"
+  ; CHECK: %[[RV:.*]] load{{.*}}__dfsan_shadow_ptr_mask
+  ; CHECK: ptrtoint i32* {{.*}} to i64
+  ; CHECK: and {{.*}}%[[RV:.*]]
   %1 = load i32, i32* %b, align 4
   %2 = add nsw i32 %1, %a
   ret i32 %2
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/fast16labels.ll b/llvm/test/Instrumentation/DataFlowSanitizer/fast16labels.ll
deleted file mode 100644
--- a/llvm/test/Instrumentation/DataFlowSanitizer/fast16labels.ll
+++ /dev/null
@@ -1,172 +0,0 @@
-; Test that -dfsan-fast-16-labels mode uses inline ORs rather than calling
-; __dfsan_union or __dfsan_union_load.
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -S | FileCheck %s --implicit-check-not="call{{.*}}__dfsan_union" --check-prefixes=CHECK,CHECK16
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels -S | FileCheck %s --implicit-check-not="call{{.*}}__dfsan_union" --check-prefixes=CHECK,CHECK8
-target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
-target triple = "x86_64-unknown-linux-gnu"
-
-; CHECK: @__dfsan_arg_tls = external thread_local(initialexec) global [[TLS_ARR:\[100 x i64\]]]
-; CHECK: @__dfsan_retval_tls = external thread_local(initialexec) global [[TLS_ARR]]
-; CHECK: @__dfsan_shadow_width_bits = weak_odr constant i32 [[#SBITS:]]
-; CHECK: @__dfsan_shadow_width_bytes = weak_odr constant i32 [[#SBYTES:]]
-
-define i8 @add(i8 %a, i8 %b) {
-  ; CHECK-LABEL: define i8 @"dfs$add"
-  ; CHECK-DAG: %[[ALABEL:.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; CHECK-DAG: %[[BLABEL:.*]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK: %[[ADDLABEL:.*]] = or i[[#SBITS]] %[[ALABEL]], %[[BLABEL]]
-  ; CHECK: %c = add i8 %a, %b
-  ; CHECK: store i[[#SBITS]] %[[ADDLABEL]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK: ret i8 %c
-  %c = add i8 %a, %b
-  ret i8 %c
-}
-
-define i8 @load8(i8* %p) {
-  ; CHECK-LABEL:  define i8 @"dfs$load8"
-  ; CHECK-SAME:   (i8* %[[PADDR:.*]])
-  ; CHECK-NEXT:   %[[#ARG:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   %[[#R:]] = ptrtoint i8* %[[PADDR]] to i64
-  ; CHECK-NEXT:   %[[#PS:R+1]] = and i64 %[[#R]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT: %[[#PS:R+2]] = mul i64 %[[#R+1]], 2
-  ; CHECK-NEXT:   %[[#SADDR:]] = inttoptr i64 %[[#PS]] to i[[#SBITS]]*
-  ; CHECK-NEXT:   %[[#S:]] = load i[[#SBITS]], i[[#SBITS]]* %[[#SADDR]]
-  ; CHECK-NEXT:   %[[#S_OUT:S+1]] = or i[[#SBITS]] %[[#S]], %[[#ARG]]
-  ; CHECK-NEXT:   %a = load i8, i8* %p
-  ; CHECK-NEXT:   store i[[#SBITS]] %[[#S_OUT]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   ret i8 %a
-
-  %a = load i8, i8* %p
-  ret i8 %a
-}
-
-define i16 @load16(i16* %p) {
-  ; CHECK-LABEL:  define i16 @"dfs$load16"
-  ; CHECK-SAME:   (i16* %[[PADDR:.*]])
-  ; CHECK-NEXT:   %[[#ARG:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   %[[#R:]] = ptrtoint i16* %[[PADDR]] to i64
-  ; CHECK-NEXT:   %[[#PS:R+1]] = and i64 %[[#R]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT: %[[#PS:R+2]] = mul i64 %[[#R+1]], 2
-  ; CHECK-NEXT:   %[[#SADDR:]]  = inttoptr i64 %[[#PS]] to i[[#SBITS]]*
-  ; CHECK-NEXT:   %[[#SADDR+1]] = getelementptr i[[#SBITS]], i[[#SBITS]]* %[[#SADDR]], i64 1
-  ; CHECK-NEXT:   %[[#S:]]  = load i[[#SBITS]], i[[#SBITS]]* %[[#SADDR]]
-  ; CHECK-NEXT:   %[[#S+1]] = load i[[#SBITS]], i[[#SBITS]]* %[[#SADDR+1]]
-  ; CHECK-NEXT:   %[[#S+2]] = or i[[#SBITS]] %[[#S]], %[[#S+1]]
-  ; CHECK-NEXT:   %[[#S_OUT:S+3]] = or i[[#SBITS]] %[[#S+2]], %[[#ARG]]
-  ; CHECK-NEXT:   %a = load i16, i16* %p
-  ; CHECK-NEXT:   store i[[#SBITS]] %[[#S_OUT]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   ret i16 %a
-
-  %a = load i16, i16* %p
-  ret i16 %a
-}
-
-define i32 @load32(i32* %p) {
-  ; CHECK-LABEL: define i32 @"dfs$load32"
-  ; CHECK-SAME:   (i32* %[[PADDR:.*]])
-  ; CHECK-NEXT:   %[[#ARG:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   %[[#R:]] = ptrtoint i32* %[[PADDR]] to i64
-  ; CHECK-NEXT:   %[[#PS:R+1]] = and i64 %[[#R]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT: %[[#PS:R+2]] = mul i64 %[[#R+1]], 2
-  ; CHECK-NEXT:   %[[#SADDR:]] = inttoptr i64 %[[#PS]] to i[[#SBITS]]*
-  ; CHECK-NEXT:   %[[#SADDR+1]] = bitcast i[[#SBITS]]* %[[#SADDR]] to i[[#WBITS:mul(SBITS,4)]]*
-  ; CHECK-NEXT:   %[[#WS:]]  = load i[[#WBITS]], i[[#WBITS]]* %[[#SADDR+1]]
-  ; CHECK-NEXT:   %[[#WS+1]] = lshr i[[#WBITS]] %[[#WS]], [[#mul(SBITS,2)]]
-  ; CHECK-NEXT:   %[[#WS+2]] = or i[[#WBITS]] %[[#WS]], %[[#WS+1]]
-  ; CHECK-NEXT:   %[[#WS+3]] = lshr i[[#WBITS]] %[[#WS+2]], [[#SBITS]]
-  ; CHECK-NEXT:   %[[#WS+4]] = or i[[#WBITS]] %[[#WS+2]], %[[#WS+3]]
-  ; CHECK-NEXT:   %[[#WS+5]] = trunc i[[#WBITS]] %[[#WS+4]] to i[[#SBITS]]
-  ; CHECK-NEXT:   %[[#S_OUT:WS+6]] = or i[[#SBITS]] %[[#WS+5]], %[[#ARG]]
-  ; CHECK-NEXT:   %a = load i32, i32* %p
-  ; CHECK-NEXT:   store i[[#SBITS]] %[[#S_OUT]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   ret i32 %a
-
-  %a = load i32, i32* %p
-  ret i32 %a
-}
-
-define i64 @load64(i64* %p) {
-  ; CHECK-LABEL:  define i64 @"dfs$load64"
-  ; CHECK-SAME:   (i64* %[[PADDR:.*]])
-  ; CHECK-NEXT:   %[[#ARG:]]        = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   %[[#R:]]          = ptrtoint i64* %[[PADDR]] to i64
-  ; CHECK-NEXT:   %[[#PS:R+1]]      = and i64 %[[#R]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT: %[[#PS:R+2]]      = mul i64 %[[#R+1]], 2
-  ; CHECK-NEXT:   %[[#SADDR:]]      = inttoptr i64 %[[#PS]] to i[[#SBITS]]*
-  ; CHECK-NEXT:   %[[#SADDR+1]]     = bitcast i[[#SBITS]]* %[[#SADDR]] to i64*
-  ; CHECK-NEXT:   %[[#WS:]]         = load i64, i64* %[[#SADDR+1]]
-
-  ; COMM: On fast16, the 2x64 shadow bits need to be ORed first.
-  ; CHECK16-NEXT: %[[#SADDR_NEXT:]] = getelementptr i64, i64* %[[#SADDR+1]], i64 1
-  ; CHECK16-NEXT: %[[#WS_NEXT:]]    = load i64, i64* %[[#SADDR_NEXT]]
-  ; CHECK16-NEXT: %[[#WS:]]         = or i64 %[[#WS]], %[[#WS_NEXT]]
-  ; CHECK16-NEXT: %[[#WS+1]]        = lshr i64 %[[#WS]], 32
-  ; CHECK16-NEXT: %[[#WS+2]]        = or i64 %[[#WS]], %[[#WS+1]]
-  ; CHECK16-NEXT: %[[#WS+3]]        = lshr i64 %[[#WS+2]], 16
-  ; CHECK16-NEXT: %[[#WS+4]]        = or i64 %[[#WS+2]], %[[#WS+3]]
-  ; CHECK16-NEXT: %[[#WS+5]]        = trunc i64 %[[#WS+4]] to i[[#SBITS]]
-  ; CHECK16-NEXT: %[[#S_OUT:]]      = or i[[#SBITS]] %[[#WS+5]], %[[#ARG]]
-
-  ; COMM: On fast8, no need to OR the wide shadow but one more shift is needed.
-  ; CHECK8-NEXT: %[[#WS+1]]         = lshr i64 %[[#WS]], 32
-  ; CHECK8-NEXT: %[[#WS+2]]         = or i64 %[[#WS]], %[[#WS+1]]
-  ; CHECK8-NEXT: %[[#WS+3]]         = lshr i64 %[[#WS+2]], 16
-  ; CHECK8-NEXT: %[[#WS+4]]         = or i64 %[[#WS+2]], %[[#WS+3]]
-  ; CHECK8-NEXT: %[[#WS+5]]         = lshr i64 %[[#WS+4]], 8
-  ; CHECK8-NEXT: %[[#WS+6]]         = or i64 %[[#WS+4]], %[[#WS+5]]
-  ; CHECK8-NEXT: %[[#WS+7]]         = trunc i64 %[[#WS+6]] to i[[#SBITS]]
-  ; CHECK8-NEXT: %[[#S_OUT:]]       = or i[[#SBITS]] %[[#WS+7]], %[[#ARG]]
-
-  ; CHECK-NEXT:   %a = load i64, i64* %p
-  ; CHECK-NEXT:   store i[[#SBITS]] %[[#S_OUT]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   ret i64 %a
-
-  %a = load i64, i64* %p
-  ret i64 %a
-}
-
-define i128 @load128(i128* %p) {
-  ; CHECK-LABEL:  define i128 @"dfs$load128"
-  ; CHECK-SAME:   (i128* %[[PADDR:.*]])
-  ; CHECK-NEXT:   %[[#ARG:]]    = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT:   %[[#R:]]      = ptrtoint i128* %[[PADDR]] to i64
-  ; CHECK-NEXT:   %[[#PS:R+1]]  = and i64 %[[#R]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT: %[[#PS:R+2]]  = mul i64 %[[#R+1]], 2
-  ; CHECK-NEXT:   %[[#SADDR:]]  = inttoptr i64 %[[#PS]] to i[[#SBITS]]*
-  ; CHECK-NEXT:   %[[#SADDR+1]] = bitcast i[[#SBITS]]* %[[#SADDR]] to i64*
-  ; CHECK-NEXT:   %[[#S:]]      = load i64, i64* %[[#SADDR+1]]
-  ; CHECK-NEXT:   %[[#S+1]]     = getelementptr i64, i64* %[[#SADDR+1]], i64 1
-  ; CHECK-NEXT:   %[[#S+2]]     = load i64, i64* %[[#S+1]]
-  ; CHECK-NEXT:   %[[#WS:S+3]]  = or i64 %[[#S]], %[[#S+2]]
-
-  ; COMM: On fast16, we need to OR 4x64bits for the wide shadow, before ORing its bytes.
-  ; CHECK16-NEXT: %[[#S+4]]     = getelementptr i64, i64* %[[#S+1]], i64 1
-  ; CHECK16-NEXT: %[[#S+5]]     = load i64, i64* %[[#S+4]]
-  ; CHECK16-NEXT: %[[#S+6]]     = or i64 %[[#S+3]], %[[#S+5]]
-  ; CHECK16-NEXT: %[[#S+7]]     = getelementptr i64, i64* %[[#S+4]], i64 1
-  ; CHECK16-NEXT: %[[#S+8]]     = load i64, i64* %[[#S+7]]
-  ; CHECK16-NEXT: %[[#WS:S+9]]  = or i64 %[[#S+6]], %[[#S+8]]
-  ; CHECK16-NEXT: %[[#WS+1]]    = lshr i64 %[[#WS]], 32
-  ; CHECK16-NEXT: %[[#WS+2]]    = or i64 %[[#WS]], %[[#WS+1]]
-  ; CHECK16-NEXT: %[[#WS+3]]    = lshr i64 %[[#WS+2]], 16
-  ; CHECK16-NEXT: %[[#WS+4]]    = or i64 %[[#WS+2]], %[[#WS+3]]
-  ; CHECK16-NEXT: %[[#WS+5]]    = trunc i64 %[[#WS+4]] to i[[#SBITS]]
-  ; CHECK16-NEXT: %[[#S_OUT:]]  = or i[[#SBITS]] %[[#WS+5]], %[[#ARG]]
-
-  ; COMM: On fast8, we need to OR 2x64bits for the wide shadow, before ORing its bytes (one more shift).
-  ; CHECK8-NEXT: %[[#WS+1]]     = lshr i64 %[[#WS]], 32
-  ; CHECK8-NEXT: %[[#WS+2]]     = or i64 %[[#WS]], %[[#WS+1]]
-  ; CHECK8-NEXT: %[[#WS+3]]     = lshr i64 %[[#WS+2]], 16
-  ; CHECK8-NEXT: %[[#WS+4]]     = or i64 %[[#WS+2]], %[[#WS+3]]
-  ; CHECK8-NEXT: %[[#WS+5]]     = lshr i64 %[[#WS+4]], 8
-  ; CHECK8-NEXT: %[[#WS+6]]     = or i64 %[[#WS+4]], %[[#WS+5]]
-  ; CHECK8-NEXT: %[[#WS+7]]     = trunc i64 %[[#WS+6]] to i[[#SBITS]]
-  ; CHECK8-NEXT: %[[#S_OUT:]]   = or i[[#SBITS]] %[[#WS+7]], %[[#ARG]]
-
-  ; CHECK-NEXT: %a = load i128, i128* %p
-  ; CHECK-NEXT: store i[[#SBITS]] %[[#S_OUT]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; CHECK-NEXT: ret i128 %a
-
-  %a = load i128, i128* %p
-  ret i128 %a
-}
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/load.ll b/llvm/test/Instrumentation/DataFlowSanitizer/load.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/load.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/load.ll
@@ -1,176 +1,156 @@
-; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-load=1 -S | FileCheck %s --check-prefix=COMBINE_PTR_LABEL
-; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-load=0 -S | FileCheck %s --check-prefix=NO_COMBINE_PTR_LABEL
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-load=true -S | FileCheck %s --check-prefixes=CHECK,COMBINE_LOAD_PTR
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
+; CHECK: @__dfsan_arg_tls = external thread_local(initialexec) global [[TLS_ARR:\[100 x i64\]]]
+; CHECK: @__dfsan_retval_tls = external thread_local(initialexec) global [[TLS_ARR]]
+; CHECK: @__dfsan_shadow_width_bits = weak_odr constant i32 [[#SBITS:]]
+; CHECK: @__dfsan_shadow_width_bytes = weak_odr constant i32 [[#SBYTES:]]
+
+
 define {} @load0({}* %p) {
-  ; COMBINE_PTR_LABEL: @"dfs$load0"
-  ; COMBINE_PTR_LABEL: load
-  ; COMBINE_PTR_LABEL-NOT: load
+  ; CHECK-LABEL:           @"dfs$load0"
+  ; CHECK-NEXT:            %a = load {}, {}* %p, align 1
+  ; CHECK-NEXT:            store {} zeroinitializer, {}* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to {}*), align [[ALIGN:2]]
+  ; CHECK-NEXT:            ret {} %a
 
-  ; NO_COMBINE_PTR_LABEL: @"dfs$load0"
-  ; NO_COMBINE_PTR_LABEL: load
-  ; NO_COMBINE_PTR_LABEL-NOT: load
   %a = load {}, {}* %p
   ret {} %a
 }
 
 define i8 @load8(i8* %p) {
-  ; COMBINE_PTR_LABEL: @"dfs$load8"
-  ; COMBINE_PTR_LABEL: load i16, i16*
-  ; COMBINE_PTR_LABEL: ptrtoint i8* {{.*}} to i64
-  ; COMBINE_PTR_LABEL: and i64
-  ; COMBINE_PTR_LABEL: mul i64
-  ; COMBINE_PTR_LABEL: inttoptr i64
-  ; COMBINE_PTR_LABEL: load i16, i16*
-  ; COMBINE_PTR_LABEL: icmp ne i16
-  ; COMBINE_PTR_LABEL: call zeroext i16 @__dfsan_union
-  ; COMBINE_PTR_LABEL: load i8, i8*
-  ; COMBINE_PTR_LABEL: store i16 {{.*}} @__dfsan_retval_tls
-  ; COMBINE_PTR_LABEL: ret i8
-
-  ; NO_COMBINE_PTR_LABEL: @"dfs$load8"
-  ; NO_COMBINE_PTR_LABEL: ptrtoint i8*
-  ; NO_COMBINE_PTR_LABEL: and i64
-  ; NO_COMBINE_PTR_LABEL: mul i64
-  ; NO_COMBINE_PTR_LABEL: inttoptr i64 {{.*}} to i16*
-  ; NO_COMBINE_PTR_LABEL: load i16, i16*
-  ; NO_COMBINE_PTR_LABEL: load i8, i8*
-  ; NO_COMBINE_PTR_LABEL: store i16 {{.*}} @__dfsan_retval_tls
-  ; NO_COMBINE_PTR_LABEL: ret i8
+  ; CHECK-LABEL:           @"dfs$load8"
+  ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i8* %p to i64
+  ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
+  ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
+  ; CHECK-NEXT:            %[[#SHADOW:]] = load i[[#SBITS]], i[[#SBITS]]* %[[#SHADOW_PTR]]
+  ; COMBINE_LOAD_PTR-NEXT: %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#PS]]
+  ; CHECK-NEXT:            %a = load i8, i8* %p
+  ; CHECK-NEXT:            store i[[#SBITS]] %[[#SHADOW]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            ret i8 %a
 
   %a = load i8, i8* %p
   ret i8 %a
 }
 
 define i16 @load16(i16* %p) {
-  ; COMBINE_PTR_LABEL: @"dfs$load16"
-  ; COMBINE_PTR_LABEL: ptrtoint i16*
-  ; COMBINE_PTR_LABEL: and i64
-  ; COMBINE_PTR_LABEL: mul i64
-  ; COMBINE_PTR_LABEL: inttoptr i64 {{.*}} i16*
-  ; COMBINE_PTR_LABEL: getelementptr i16
-  ; COMBINE_PTR_LABEL: load i16, i16*
-  ; COMBINE_PTR_LABEL: load i16, i16*
-  ; COMBINE_PTR_LABEL: icmp ne
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-  ; COMBINE_PTR_LABEL: icmp ne i16
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-  ; COMBINE_PTR_LABEL: load i16, i16*
-  ; COMBINE_PTR_LABEL: store {{.*}} @__dfsan_retval_tls
-  ; COMBINE_PTR_LABEL: ret i16
-
-  ; NO_COMBINE_PTR_LABEL: @"dfs$load16"
-  ; NO_COMBINE_PTR_LABEL: ptrtoint i16*
-  ; NO_COMBINE_PTR_LABEL: and i64
-  ; NO_COMBINE_PTR_LABEL: mul i64
-  ; NO_COMBINE_PTR_LABEL: inttoptr i64 {{.*}} i16*
-  ; NO_COMBINE_PTR_LABEL: getelementptr i16, i16*
-  ; NO_COMBINE_PTR_LABEL: load i16, i16*
-  ; NO_COMBINE_PTR_LABEL: load i16, i16*
-  ; NO_COMBINE_PTR_LABEL: icmp ne i16
-  ; NO_COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-  ; NO_COMBINE_PTR_LABEL: load i16, i16*
-  ; NO_COMBINE_PTR_LABEL: store i16 {{.*}} @__dfsan_retval_tls
-  ; NO_COMBINE_PTR_LABEL: ret i16
+  ; CHECK-LABEL:           @"dfs$load16"
+  ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i16* %p to i64
+  ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#MASK]]
+  ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
+  ; CHECK-NEXT:            %[[#SHADOW_PTR+1]] = getelementptr i[[#SBITS]], i[[#SBITS]]* %[[#SHADOW_PTR]], i64 1
+  ; CHECK-NEXT:            %[[#SHADOW:]]  = load i[[#SBITS]], i[[#SBITS]]* %[[#SHADOW_PTR]]
+  ; CHECK-NEXT:            %[[#SHADOW+1]] = load i[[#SBITS]], i[[#SBITS]]* %[[#SHADOW_PTR+1]]
+
+  ; CHECK-NEXT:            %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#SHADOW+1]]
+  ; COMBINE_LOAD_PTR-NEXT: %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#PS]]
+  ; CHECK-NEXT:            %a = load i16, i16* %p
+  ; CHECK-NEXT:            store i[[#SBITS]] %[[#SHADOW]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            ret i16 %a
 
   %a = load i16, i16* %p
   ret i16 %a
 }
 
 define i32 @load32(i32* %p) {
-  ; COMBINE_PTR_LABEL: @"dfs$load32"
-  ; COMBINE_PTR_LABEL: ptrtoint i32*
-  ; COMBINE_PTR_LABEL: and i64
-  ; COMBINE_PTR_LABEL: mul i64
-  ; COMBINE_PTR_LABEL: inttoptr i64 {{.*}} i16*
-  ; COMBINE_PTR_LABEL: bitcast i16* {{.*}} i64*
-  ; COMBINE_PTR_LABEL: load i64, i64*
-  ; COMBINE_PTR_LABEL: trunc i64 {{.*}} i16
-  ; COMBINE_PTR_LABEL: shl i64
-  ; COMBINE_PTR_LABEL: lshr i64
-  ; COMBINE_PTR_LABEL: or i64
-  ; COMBINE_PTR_LABEL: icmp eq i64
-  ; COMBINE_PTR_LABEL: icmp ne i16
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-  ; COMBINE_PTR_LABEL: load i32, i32*
-  ; COMBINE_PTR_LABEL: store i16 {{.*}} @__dfsan_retval_tls
-  ; COMBINE_PTR_LABEL: ret i32
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union_load
-
-  ; NO_COMBINE_PTR_LABEL: @"dfs$load32"
-  ; NO_COMBINE_PTR_LABEL: ptrtoint i32*
-  ; NO_COMBINE_PTR_LABEL: and i64
-  ; NO_COMBINE_PTR_LABEL: mul i64
-  ; NO_COMBINE_PTR_LABEL: inttoptr i64 {{.*}} i16*
-  ; NO_COMBINE_PTR_LABEL: bitcast i16* {{.*}} i64*
-  ; NO_COMBINE_PTR_LABEL: load i64, i64*
-  ; NO_COMBINE_PTR_LABEL: trunc i64 {{.*}} i16
-  ; NO_COMBINE_PTR_LABEL: shl i64
-  ; NO_COMBINE_PTR_LABEL: lshr i64
-  ; NO_COMBINE_PTR_LABEL: or i64
-  ; NO_COMBINE_PTR_LABEL: icmp eq i64
-  ; NO_COMBINE_PTR_LABEL: load i32, i32*
-  ; NO_COMBINE_PTR_LABEL: store i16 {{.*}} @__dfsan_retval_tls
-  ; NO_COMBINE_PTR_LABEL: ret i32
-  ; NO_COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union_load
-  
+  ; CHECK-LABEL:           @"dfs$load32"
+  ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i32* %p to i64
+  ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#MASK]]
+  ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_PTR:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i[[#WSBITS:mul(SBITS,4)]]*
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = load i[[#WSBITS]], i[[#WSBITS]]* %[[#WIDE_SHADOW_PTR]], align [[#SBYTES]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i[[#WSBITS]] %[[#WIDE_SHADOW]], [[#mul(SBITS,2)]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i[[#WSBITS]] %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i[[#WSBITS]] %[[#WIDE_SHADOW]], [[#SBITS]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i[[#WSBITS]] %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#SHADOW:]] = trunc i[[#WSBITS]] %[[#WIDE_SHADOW]] to i[[#SBITS]]
+  ; COMBINE_LOAD_PTR-NEXT: %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#PS]]
+  ; CHECK-NEXT:            %a = load i32, i32* %p, align 4
+  ; CHECK-NEXT:            store i[[#SBITS]] %[[#SHADOW]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            ret i32 %a
 
   %a = load i32, i32* %p
   ret i32 %a
 }
 
 define i64 @load64(i64* %p) {
-  ; COMBINE_PTR_LABEL: @"dfs$load64"
-  ; COMBINE_PTR_LABEL: ptrtoint i64*
-  ; COMBINE_PTR_LABEL: and i64
-  ; COMBINE_PTR_LABEL: mul i64
-  ; COMBINE_PTR_LABEL: inttoptr i64 {{.*}} i16*
-  ; COMBINE_PTR_LABEL: bitcast i16* {{.*}} i64*
-  ; COMBINE_PTR_LABEL: load i64, i64*
-  ; COMBINE_PTR_LABEL: trunc i64 {{.*}} i16
-  ; COMBINE_PTR_LABEL: shl i64
-  ; COMBINE_PTR_LABEL: lshr i64
-  ; COMBINE_PTR_LABEL: or i64
-  ; COMBINE_PTR_LABEL: icmp eq i64
-  ; COMBINE_PTR_LABEL: icmp ne i16
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-  ; COMBINE_PTR_LABEL: load i64, i64*
-  ; COMBINE_PTR_LABEL: store i16 {{.*}} @__dfsan_retval_tls
-  ; COMBINE_PTR_LABEL: ret i64
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union_load
-  ; COMBINE_PTR_LABEL: getelementptr i64, i64* {{.*}} i64
-  ; COMBINE_PTR_LABEL: load i64, i64*
-  ; COMBINE_PTR_LABEL: icmp eq i64
-
-  ; NO_COMBINE_PTR_LABEL: @"dfs$load64"
-  ; NO_COMBINE_PTR_LABEL: ptrtoint i64*
-  ; NO_COMBINE_PTR_LABEL: and i64
-  ; NO_COMBINE_PTR_LABEL: mul i64
-  ; NO_COMBINE_PTR_LABEL: inttoptr i64 {{.*}} i16*
-  ; NO_COMBINE_PTR_LABEL: bitcast i16* {{.*}} i64*
-  ; NO_COMBINE_PTR_LABEL: load i64, i64*
-  ; NO_COMBINE_PTR_LABEL: trunc i64 {{.*}} i16
-  ; NO_COMBINE_PTR_LABEL: shl i64
-  ; NO_COMBINE_PTR_LABEL: lshr i64
-  ; NO_COMBINE_PTR_LABEL: or i64
-  ; NO_COMBINE_PTR_LABEL: icmp eq i64
-  ; NO_COMBINE_PTR_LABEL: load i64, i64*
-  ; NO_COMBINE_PTR_LABEL: store i16 {{.*}} @__dfsan_retval_tls
-  ; NO_COMBINE_PTR_LABEL: ret i64
-  ; NO_COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union_load
-  ; NO_COMBINE_PTR_LABEL: getelementptr i64, i64* {{.*}} i64
-  ; NO_COMBINE_PTR_LABEL: load i64, i64*
-  ; NO_COMBINE_PTR_LABEL: icmp eq i64
+  ; CHECK-LABEL:           @"dfs$load64"
+  ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i64* %p to i64
+  ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#MASK]]
+  ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_PTR:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i64*
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = load i64, i64* %[[#WIDE_SHADOW_PTR]], align [[#SBYTES]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
+  ; COMBINE_LOAD_PTR-NEXT: %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#PS]]
+  ; CHECK-NEXT:            %a = load i64, i64* %p, align 8
+  ; CHECK-NEXT:            store i[[#SBITS]] %[[#SHADOW]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            ret i64 %a
 
   %a = load i64, i64* %p
   ret i64 %a
 }
 
+define i128 @load128(i128* %p) {
+  ; CHECK-LABEL:           @"dfs$load128"
+  ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i128* %p to i64
+  ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#MASK]]
+  ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_PTR:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i64*
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = load i64, i64* %[[#WIDE_SHADOW_PTR]], align [[#SBYTES]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_PTR2:]] = getelementptr i64, i64* %[[#WIDE_SHADOW_PTR]], i64 1
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW2:]] = load i64, i64* %[[#WIDE_SHADOW_PTR2]], align [[#SBYTES]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW2]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
+  ; COMBINE_LOAD_PTR-NEXT: %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#PS]]
+  ; CHECK-NEXT:            %a = load i128, i128* %p, align 8
+  ; CHECK-NEXT:            store i[[#SBITS]] %[[#SHADOW]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            ret i128 %a
+
+  %a = load i128, i128* %p
+  ret i128 %a
+}
+
+
+define i17 @load17(i17* %p) {
+  ; CHECK-LABEL:           @"dfs$load17"
+  ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i17* %p to i64
+  ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#MASK]]
+  ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
+  ; CHECK-NEXT:            %[[#SHADOW:]] = call zeroext i8 @__dfsan_union_load(i[[#SBITS]]* %[[#SHADOW_PTR]], i64 3)
+  ; COMBINE_LOAD_PTR-NEXT: %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#PS]]
+  ; CHECK-NEXT:            %a = load i17, i17* %p
+  ; CHECK-NEXT:            store i[[#SBITS]] %[[#SHADOW]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            ret i17 %a
+
+  %a = load i17, i17* %p
+  ret i17 %a
+}
+
 @X = constant i1 1
 define i1 @load_global() {
-  ; NO_COMBINE_PTR_LABEL: @"dfs$load_global"
-  ; NO_COMBINE_PTR_LABEL: store i16 0, i16* bitcast ([100 x i64]* @__dfsan_retval_tls to i16*), align 2
+  ; CHECK-LABEL:           @"dfs$load_global"
+  ; CHECK-NEXT:            %a = load i1, i1* @X
+  ; CHECK-NEXT:            store i[[#SBITS]] 0, i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
+  ; CHECK-NEXT:            ret i1 %a
 
   %a = load i1, i1* @X
   ret i1 %a
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/musttailcall.ll b/llvm/test/Instrumentation/DataFlowSanitizer/musttailcall.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/musttailcall.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/musttailcall.ll
@@ -1,7 +1,5 @@
 ; RUN: opt < %s -dfsan -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -dfsan-track-origins=1 -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
+; RUN: opt < %s -dfsan -dfsan-track-origins=1 -S | FileCheck %s --check-prefixes=CHECK,CHECK_ORIGIN
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_abilist.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_abilist.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_abilist.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_abilist.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -dfsan-abilist=%S/Inputs/abilist.txt -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_cached_shadows.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_cached_shadows.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_cached_shadows.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_cached_shadows.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -S | FileCheck %s
 ;
 ; %15 and %17 have the same key in shadow cache. They should not reuse the same
 ; shadow because their blocks do not dominate each other. Origin tracking
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_call.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_call.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_call.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_call.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_load.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_load.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_load.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_load.ll
@@ -1,7 +1,5 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels -S | FileCheck %s --check-prefixes=CHECK,CHECK8,COMBINE_LOAD_PTR
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,CHECK8
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels -S | FileCheck %s --check-prefixes=CHECK,CHECK16,COMBINE_LOAD_PTR
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,CHECK16
+; RUN: opt < %s -dfsan -dfsan-track-origins=1 -S | FileCheck %s --check-prefixes=CHECK,COMBINE_LOAD_PTR
+; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -38,7 +36,6 @@
   ; CHECK-LABEL:  @"dfs$load_escaped_alloca"
   ; CHECK:        %[[#INTP:]] = ptrtoint i16* %p to i64
   ; CHECK-NEXT:   %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT: %[[#SHADOW_ADDR:]] = mul i64 %[[#SHADOW_ADDR]], 2
   ; CHECK-NEXT:   %[[#SHADOW_PTR0:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:   %[[#ORIGIN_OFFSET:]] = add i64 %[[#INTP+1]], [[#%.10d,ORIGIN_MASK:]]
   ; CHECK-NEXT:   %[[#ORIGIN_ADDR:]] = and i64 %[[#ORIGIN_OFFSET]], -4
@@ -76,7 +73,6 @@
 
   ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i1* %p to i64
   ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#MASK]]
-  ; CHECK16-NEXT:          %[[#SHADOW_ADDR:]] = mul i64 %[[#SHADOW_ADDR]], 2
   ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:            %[[#ORIGIN_OFFSET:]] = add i64 %[[#INTP+1]], [[#ORIGIN_MASK]]
   ; CHECK-NEXT:            %[[#ORIGIN_ADDR:]] = and i64 %[[#ORIGIN_OFFSET]], -4
@@ -104,7 +100,6 @@
 
   ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i16* %p to i64
   ; CHECK-NEXT:            %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#MASK]]
-  ; CHECK16-NEXT:          %[[#SHADOW_ADDR:]] = mul i64 %[[#SHADOW_ADDR]], 2
   ; CHECK-NEXT:            %[[#SHADOW_PTR0:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:            %[[#ORIGIN_OFFSET:]] = add i64 %[[#INTP+1]], [[#ORIGIN_MASK]]
   ; CHECK-NEXT:            %[[#ORIGIN_ADDR:]] = and i64 %[[#ORIGIN_OFFSET]], -4
@@ -133,9 +128,8 @@
   ; COMBINE_LOAD_PTR-NEXT: %[[#PO:]] = load i32, i32* getelementptr inbounds ([200 x i32], [200 x i32]* @__dfsan_arg_origin_tls, i64 0, i64 0), align 4
   ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
 
-  ; CHECK:                 %[[#INTP:]] = ptrtoint i32* %p to i64
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i32* %p to i64
   ; CHECK-NEXT:            %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#MASK]]
-  ; CHECK16-NEXT:          %[[#SHADOW_ADDR:]] = mul i64 %[[#SHADOW_ADDR]], 2
   ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:            %[[#ORIGIN_ADDR:]] = add i64 %[[#INTP+1]], [[#ORIGIN_MASK]]
   ; CHECK-NEXT:            %[[#ORIGIN_PTR:]] = inttoptr i64 %[[#ORIGIN_ADDR]] to i32*
@@ -166,41 +160,26 @@
   ; COMBINE_LOAD_PTR-NEXT: %[[#PO:]] = load i32, i32* getelementptr inbounds ([200 x i32], [200 x i32]* @__dfsan_arg_origin_tls, i64 0, i64 0), align 4
   ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
 
-  ; CHECK:                 %[[#INTP:]] = ptrtoint i64* %p to i64
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i64* %p to i64
   ; CHECK-NEXT:            %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#MASK]]
-  ; CHECK16-NEXT:          %[[#SHADOW_ADDR:]] = mul i64 %[[#SHADOW_ADDR]], 2
   ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:            %[[#ORIGIN_ADDR:]] = add i64 %[[#INTP+1]], [[#ORIGIN_MASK]]
   ; CHECK-NEXT:            %[[#ORIGIN_PTR:]] = inttoptr i64 %[[#ORIGIN_ADDR]] to i32*
   ; CHECK-NEXT:            %[[#ORIGIN:]] = load i32, i32* %[[#ORIGIN_PTR]], align 8
   ; CHECK-NEXT:            %[[#WIDE_SHADOW_PTR:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i64*
   ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = load i64, i64* %[[#WIDE_SHADOW_PTR]], align [[#SBYTES]]
-
-  ; COMM: On fast16, the 2x64 shadow bits need to be ORed first.
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW_PTR2:]] = getelementptr i64, i64* %[[#WIDE_SHADOW_PTR]], i64 1
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW2:]] = load i64, i64* %[[#WIDE_SHADOW_PTR2]], align [[#SBYTES]]
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW2]]
-  ; CHECK16-NEXT:          %[[#ORIGIN_PTR2:]] = getelementptr i32, i32* %[[#ORIGIN_PTR]], i64 1
-  ; CHECK16-NEXT:          %[[#ORIGIN2:]] = load i32, i32* %[[#ORIGIN_PTR2]], align 8
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK16-NEXT:          %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
-  ; CHECK16-NEXT:          %[[#SHADOW_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW2]], 0
-  ; CHECK16-NEXT:          %[[#ORIGIN:]] = select i1 %[[#SHADOW_NZ]], i32 %[[#ORIGIN2]], i32 %[[#ORIGIN]]
-
-  ; COMM: On fast8, no need to OR the wide shadow but one more shift is needed.
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_LO:]] = shl i64 %[[#WIDE_SHADOW]], 32
-  ; CHECK8-NEXT:           %[[#ORIGIN_PTR2:]] = getelementptr i32, i32* %[[#ORIGIN_PTR]], i64 1
-  ; CHECK8-NEXT:           %[[#ORIGIN2:]] = load i32, i32* %[[#ORIGIN_PTR2]], align 8
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 8
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK8-NEXT:           %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_LO:]] = shl i64 %[[#WIDE_SHADOW]], 32
+  ; CHECK-NEXT:            %[[#ORIGIN2_PTR:]] = getelementptr i32, i32* %[[#ORIGIN_PTR]], i64 1
+  ; CHECK-NEXT:            %[[#ORIGIN2:]] = load i32, i32* %[[#ORIGIN2_PTR]], align 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
+  ; CHECK-NEXT:            %[[#SHADOW_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW_LO]], 0
+  ; CHECK-NEXT:            %[[#ORIGIN:]] = select i1 %[[#SHADOW_NZ]], i32 %[[#ORIGIN]], i32 %[[#ORIGIN2]]
   ; CHECK8-NEXT:           %[[#SHADOW_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW_LO]], 0
   ; CHECK8-NEXT:           %[[#ORIGIN:]] = select i1 %[[#SHADOW_NZ]], i32 %[[#ORIGIN]], i32 %[[#ORIGIN2]]
 
@@ -246,66 +225,38 @@
   ; COMBINE_LOAD_PTR-NEXT: %[[#PO:]] = load i32, i32* getelementptr inbounds ([200 x i32], [200 x i32]* @__dfsan_arg_origin_tls, i64 0, i64 0), align 4
   ; COMBINE_LOAD_PTR-NEXT: %[[#PS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
 
-  ; CHECK:                 %[[#INTP:]] = ptrtoint i128* %p to i64
+  ; CHECK-NEXT:            %[[#INTP:]] = ptrtoint i128* %p to i64
   ; CHECK-NEXT:            %[[#SHADOW_ADDR:INTP+1]] = and i64 %[[#INTP]], [[#MASK]]
-  ; CHECK16-NEXT:          %[[#SHADOW_ADDR:]] = mul i64 %[[#SHADOW_ADDR]], 2
   ; CHECK-NEXT:            %[[#SHADOW_PTR:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
-  ; CHECK-NEXT:            %[[#ORIGIN_ADDR:]] = add i64 %[[#INTP+1]], [[#ORIGIN_MASK]]
-  ; CHECK-NEXT:            %[[#ORIGIN_PTR:]] = inttoptr i64 %[[#ORIGIN_ADDR]] to i32*
-  ; CHECK-NEXT:            %[[#ORIGIN:]] = load i32, i32* %[[#ORIGIN_PTR]], align 8
-  ; CHECK-NEXT:            %[[#WIDE_SHADOW_PTR:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i64*
-  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = load i64, i64* %[[#WIDE_SHADOW_PTR]], align [[#SBYTES]]
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_LO:]] = shl i64 %[[#WIDE_SHADOW]], 32
-  ; CHECK8-NEXT:           %[[#ORIGIN_PTR2:]] = getelementptr i32, i32* %[[#ORIGIN_PTR]], i64 1
-  ; CHECK8-NEXT:           %[[#ORIGIN2:]] = load i32, i32* %[[#ORIGIN_PTR2]], align 8
-  ; CHECK-NEXT:            %[[#WIDE_SHADOW_PTR2:]] = getelementptr i64, i64* %[[#WIDE_SHADOW_PTR]], i64 1
-  ; CHECK-NEXT:            %[[#WIDE_SHADOW2:]] = load i64, i64* %[[#WIDE_SHADOW_PTR2]], align [[#SBYTES]]
-  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW2]]
-
-  ; COMM: On fast16, we need to OR 4x64bits for the wide shadow, before ORing its bytes.
-  ; CHECK16-NEXT:          %[[#ORIGIN_PTR2:]] = getelementptr i32, i32* %[[#ORIGIN_PTR]], i64 1
-  ; CHECK16-NEXT:          %[[#ORIGIN2:]] = load i32, i32* %[[#ORIGIN_PTR2]], align 8
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW_PTR3:]] = getelementptr i64, i64* %[[#WIDE_SHADOW_PTR2]], i64 1
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW3:]] = load i64, i64* %[[#WIDE_SHADOW_PTR3]], align [[#SBYTES]]
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW3]]
-  ; CHECK16-NEXT:          %[[#ORIGIN_PTR3:]] = getelementptr i32, i32* %[[#ORIGIN_PTR2]], i64 1
-  ; CHECK16-NEXT:          %[[#ORIGIN3:]] = load i32, i32* %[[#ORIGIN_PTR3]], align 8
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW_PTR4:]] = getelementptr i64, i64* %[[#WIDE_SHADOW_PTR3]], i64 1
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW4:]] = load i64, i64* %[[#WIDE_SHADOW_PTR4]], align [[#SBYTES]]
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW4]]
-  ; CHECK16-NEXT:          %[[#ORIGIN_PTR4:]] = getelementptr i32, i32* %[[#ORIGIN_PTR3]], i64 1
-  ; CHECK16-NEXT:          %[[#ORIGIN4:]] = load i32, i32* %[[#ORIGIN_PTR4]], align 8
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
-  ; CHECK16-NEXT:          %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK16-NEXT:          %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
-  ; CHECK16-NEXT:          %[[#SHADOW2_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW2]], 0
-  ; CHECK16-NEXT:          %[[#ORIGIN:]] = select i1 %[[#SHADOW2_NZ]], i32 %[[#ORIGIN2]], i32 %[[#ORIGIN]]
-  ; CHECK16-NEXT:          %[[#SHADOW3_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW3]], 0
-  ; CHECK16-NEXT:          %[[#ORIGIN:]] = select i1 %[[#SHADOW3_NZ]], i32 %[[#ORIGIN3]], i32 %[[#ORIGIN]]
-  ; CHECK16-NEXT:          %[[#SHADOW4_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW4]], 0
-  ; CHECK16-NEXT:          %[[#ORIGIN:]] = select i1 %[[#SHADOW4_NZ]], i32 %[[#ORIGIN4]], i32 %[[#ORIGIN]]
-  
-  ; COMM: On fast8, we need to OR 2x64bits for the wide shadow, before ORing its bytes (one more shift).
-  ; CHECK8-NEXT:           %[[#ORIGIN_PTR3:]] = getelementptr i32, i32* %[[#ORIGIN_PTR2]], i64 1
-  ; CHECK8-NEXT:           %[[#ORIGIN3:]] = load i32, i32* %[[#ORIGIN_PTR3]], align 8
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW2_LO:]] = shl i64 %[[#WIDE_SHADOW2]], 32
-  ; CHECK8-NEXT:           %[[#ORIGIN_PTR4:]] = getelementptr i32, i32* %[[#ORIGIN_PTR3]], i64 1
-  ; CHECK8-NEXT:           %[[#ORIGIN4:]] = load i32, i32* %[[#ORIGIN_PTR4]], align 8
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 8
-  ; CHECK8-NEXT:           %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
-  ; CHECK8-NEXT:           %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
-  ; CHECK8-NEXT:           %[[#SHADOW_LO_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW_LO]], 0
-  ; CHECK8-NEXT:           %[[#ORIGIN:]] = select i1 %[[#SHADOW_LO_NZ]], i32 %[[#ORIGIN]], i32 %[[#ORIGIN2]]
-  ; CHECK8-NEXT:           %[[#SHADOW2_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW2]], 0
-  ; CHECK8-NEXT:           %[[#ORIGIN:]] = select i1 %[[#SHADOW2_NZ]], i32 %[[#ORIGIN4]], i32 %[[#ORIGIN]]
-  ; CHECK8-NEXT:           %[[#SHADOW2_LO_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW2_LO]], 0
-  ; CHECK8-NEXT:           %[[#ORIGIN:]] = select i1 %[[#SHADOW2_LO_NZ]], i32 %[[#ORIGIN3]], i32 %[[#ORIGIN]]
+  ; CHECK-NEXT:            %[[#ORIGIN_ADDR:]] = add i64 %[[#SHADOW_ADDR]], [[#ORIGIN_MASK]]
+  ; CHECK-NEXT:            %[[#ORIGIN1_PTR:]] = inttoptr i64 %[[#ORIGIN_ADDR]] to i32*
+  ; CHECK-NEXT:            %[[#ORIGIN1:]] = load i32, i32* %[[#ORIGIN1_PTR]], align 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW1_PTR:]] = bitcast i[[#SBITS]]* %[[#SHADOW_PTR]] to i64*
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW1:]] = load i64, i64* %[[#WIDE_SHADOW1_PTR]], align [[#SBYTES]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW1_LO:]] = shl i64 %[[#WIDE_SHADOW1]], 32
+  ; CHECK-NEXT:            %[[#ORIGIN2_PTR:]] = getelementptr i32, i32* %[[#ORIGIN1_PTR]], i64 1
+  ; CHECK-NEXT:            %[[#ORIGIN2:]] = load i32, i32* %[[#ORIGIN2_PTR]], align 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW2_PTR:]] = getelementptr i64, i64* %[[#WIDE_SHADOW1_PTR]], i64 1
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW2:]] = load i64, i64* %[[#WIDE_SHADOW2_PTR]], align [[#SBYTES]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW1]], %[[#WIDE_SHADOW2]]
+  ; CHECK-NEXT:            %[[#ORIGIN3_PTR:]] = getelementptr i32, i32* %[[#ORIGIN2_PTR]], i64 1
+  ; CHECK-NEXT:            %[[#ORIGIN3:]] = load i32, i32* %[[#ORIGIN3_PTR]], align 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW2_LO:]] = shl i64 %[[#WIDE_SHADOW2]], 32
+  ; CHECK-NEXT:            %[[#ORIGIN4_PTR:]] = getelementptr i32, i32* %[[#ORIGIN3_PTR]], i64 1
+  ; CHECK-NEXT:            %[[#ORIGIN4:]] = load i32, i32* %[[#ORIGIN4_PTR]], align 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 32
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 16
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW_SHIFTED:]] = lshr i64 %[[#WIDE_SHADOW]], 8
+  ; CHECK-NEXT:            %[[#WIDE_SHADOW:]] = or i64 %[[#WIDE_SHADOW]], %[[#WIDE_SHADOW_SHIFTED]]
+  ; CHECK-NEXT:            %[[#SHADOW:]] = trunc i64 %[[#WIDE_SHADOW]] to i[[#SBITS]]
+  ; CHECK-NEXT:            %[[#SHADOW1_LO_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW1_LO]], 0
+  ; CHECK-NEXT:            %[[#ORIGIN12:]] = select i1 %[[#SHADOW1_LO_NZ]], i32 %[[#ORIGIN1]], i32 %[[#ORIGIN2]]
+  ; CHECK-NEXT:            %[[#SHADOW2_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW2]], 0
+  ; CHECK-NEXT:            %[[#ORIGIN124:]] = select i1 %[[#SHADOW2_NZ]], i32 %[[#ORIGIN4]], i32 %[[#ORIGIN12]]
+  ; CHECK-NEXT:            %[[#SHADOW2_LO_NZ:]] = icmp ne i64 %[[#WIDE_SHADOW2_LO]], 0
+  ; CHECK-NEXT:            %[[#ORIGIN:]] = select i1 %[[#SHADOW2_LO_NZ]], i32 %[[#ORIGIN3]], i32 %[[#ORIGIN124]]
 
   ; COMBINE_LOAD_PTR-NEXT: %[[#SHADOW:]] = or i[[#SBITS]] %[[#SHADOW]], %[[#PS]]
   ; COMBINE_LOAD_PTR-NEXT: %[[#NZ:]] = icmp ne i[[#SBITS]] %[[#PS]], 0
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_mem_intrinsic.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_mem_intrinsic.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_mem_intrinsic.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_mem_intrinsic.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_other_ops.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_other_ops.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_other_ops.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_other_ops.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_phi.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_phi.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_phi.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_phi.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_select.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_select.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_select.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_select.ll
@@ -1,7 +1,5 @@
-; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=1 -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s --check-prefixes=CHECK,TRACK_CONTROL_FLOW
-; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=0 -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -S | FileCheck %s --check-prefixes=CHECK,NO_TRACK_CONTROL_FLOW
-; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=1 -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,TRACK_CONTROL_FLOW
-; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=0 -dfsan-track-origins=1 -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,NO_TRACK_CONTROL_FLOW
+; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=1 -dfsan-track-origins=1  -S | FileCheck %s --check-prefixes=CHECK,TRACK_CONTROL_FLOW
+; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=0 -dfsan-track-origins=1  -S | FileCheck %s --check-prefixes=CHECK,NO_TRACK_CONTROL_FLOW
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_store.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_store.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_store.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_store.ll
@@ -1,7 +1,5 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels -dfsan-combine-pointer-labels-on-store -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels -S | FileCheck %s --check-prefixes=CHECK,CHECK16
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels -dfsan-combine-pointer-labels-on-store -S | FileCheck %s --check-prefixes=CHECK,CHECK16,COMBINE_STORE_PTR
+; RUN: opt < %s -dfsan -dfsan-track-origins=1 -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-combine-pointer-labels-on-store -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -55,7 +53,6 @@
   ; CHECK-NEXT:   %[[#AS:]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
   ; CHECK:        %[[#INTP:]] = ptrtoint i16* %p to i64
   ; CHECK-NEXT:   %[[#SHADOW_ADDR:]] = and i64 %[[#INTP]], [[#%.10d,MASK:]]
-  ; CHECK16-NEXT: %[[#SHADOW_ADDR:]] = mul i64 %[[#SHADOW_ADDR]], 2
   ; CHECK-NEXT:   %[[#SHADOW_PTR0:]] = inttoptr i64 %[[#SHADOW_ADDR]] to i[[#SBITS]]*
   ; CHECK-NEXT:   %[[#ORIGIN_OFFSET:]] = add i64 %[[#INTP+1]], [[#%.10d,ORIGIN_MASK:]]
   ; CHECK-NEXT:   %[[#ORIGIN_ADDR:]] = and i64 %[[#ORIGIN_OFFSET]], -4
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_store_threshold.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_store_threshold.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_store_threshold.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_store_threshold.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-8-labels=true  -dfsan-instrument-with-call-threshold=0 -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=1 -dfsan-fast-16-labels=true -dfsan-instrument-with-call-threshold=0 -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=1  -dfsan-instrument-with-call-threshold=0 -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/origin_track_load.ll b/llvm/test/Instrumentation/DataFlowSanitizer/origin_track_load.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/origin_track_load.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/origin_track_load.ll
@@ -1,5 +1,4 @@
-; RUN: opt < %s -dfsan -dfsan-track-origins=2 -dfsan-fast-8-labels -S | FileCheck %s
-; RUN: opt < %s -dfsan -dfsan-track-origins=2 -dfsan-fast-16-labels -S | FileCheck %s
+; RUN: opt < %s -dfsan -dfsan-track-origins=2 -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/phi.ll b/llvm/test/Instrumentation/DataFlowSanitizer/phi.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/phi.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/phi.ll
@@ -1,6 +1,4 @@
-; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,LEGACY
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,FAST
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -S | FileCheck %s --check-prefixes=CHECK,FAST
+; RUN: opt < %s -dfsan -S | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -8,15 +6,11 @@
 ; CHECK: @__dfsan_shadow_width_bytes = weak_odr constant i32 [[#SBYTES:]]
 
 define {i32, i32} @test({i32, i32} %a, i1 %c) {
-  ; LEGACY: [[AL:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: [[PL:%.*]] = phi i[[#SBITS]] [ [[AL]], %T ], [ [[AL]], %F ]
-  ; LEGACY: store i[[#SBITS]] [[PL]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-
-  ; FAST: [[AL:%.*]] = load { i[[#SBITS]], i[[#SBITS]] }, { i[[#SBITS]], i[[#SBITS]] }* bitcast ([100 x i64]* @__dfsan_arg_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN:2]]
-  ; FAST: [[AL0:%.*]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } [[AL]], i[[#SBITS]] 0, 0
-  ; FAST: [[AL1:%.*]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } [[AL]], i[[#SBITS]] 0, 1
-  ; FAST: [[PL:%.*]] = phi { i[[#SBITS]], i[[#SBITS]] } [ [[AL0]], %T ], [ [[AL1]], %F ]
-  ; FAST: store { i[[#SBITS]], i[[#SBITS]] } [[PL]], { i[[#SBITS]], i[[#SBITS]] }* bitcast ([100 x i64]* @__dfsan_retval_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN]]
+  ; CHECK: %[[#AL:]] = load { i[[#SBITS]], i[[#SBITS]] }, { i[[#SBITS]], i[[#SBITS]] }* bitcast ([100 x i64]* @__dfsan_arg_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN:2]]
+  ; CHECK: %[[#AL0:]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } %[[#AL]], i[[#SBITS]] 0, 0
+  ; CHECK: %[[#AL1:]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } %[[#AL]], i[[#SBITS]] 0, 1
+  ; CHECK: %[[#PL:]] = phi { i[[#SBITS]], i[[#SBITS]] } [ %[[#AL0]], %T ], [ %[[#AL1]], %F ]
+  ; CHECK: store { i[[#SBITS]], i[[#SBITS]] } %[[#PL]], { i[[#SBITS]], i[[#SBITS]] }* bitcast ([100 x i64]* @__dfsan_retval_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN]]
 
 entry:
   br i1 %c, label %T, label %F
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/select.ll b/llvm/test/Instrumentation/DataFlowSanitizer/select.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/select.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/select.ll
@@ -1,9 +1,5 @@
-; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=1 -S | FileCheck %s --check-prefixes=CHECK,TRACK_CF,TRACK_CF_LEGACY
-; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=0 -S | FileCheck %s --check-prefixes=CHECK,NO_TRACK_CF,NO_TRACK_CF_LEGACY
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -dfsan-track-select-control-flow=1 -S | FileCheck %s --check-prefixes=CHECK,TRACK_CF,TRACK_CF_FAST
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -dfsan-track-select-control-flow=0 -S | FileCheck %s --check-prefixes=CHECK,NO_TRACK_CF,NO_TRACK_CF_FAST
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels -dfsan-track-select-control-flow=1 -S | FileCheck %s --check-prefixes=CHECK,TRACK_CF,TRACK_CF_FAST
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels -dfsan-track-select-control-flow=0 -S | FileCheck %s --check-prefixes=CHECK,NO_TRACK_CF,NO_TRACK_CF_FAST
+; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=true -S | FileCheck %s --check-prefixes=CHECK,TRACK_CF
+; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=false -S | FileCheck %s --check-prefixes=CHECK,NO_TRACK_CF
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -18,11 +14,7 @@
   ; TRACK_CF: %[[#R+1]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN]]
   ; TRACK_CF: %[[#R+2]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
   ; TRACK_CF: %[[#R+3]] = select i1 %c, i[[#SBITS]] %[[#R+1]], i[[#SBITS]] %[[#R]]
-  ; TRACK_CF_LEGACY: %[[#R+4]] = icmp ne i[[#SBITS]] %[[#R+2]], %[[#R+3]]
-  ; TRACK_CF_LEGACY: %[[#R+6]] = call {{.*}} i[[#SBITS]] @__dfsan_union(i[[#SBITS]] {{.*}} %[[#R+2]], i[[#SBITS]] {{.*}} %[[#R+3]])
-  ; TRACK_CF_LEGACY: %[[#RO:]] = phi i[[#SBITS]] [ %[[#R+6]], {{.*}} ], [ %[[#R+2]], {{.*}} ]
-  ; COMM: The union is simply an OR when fast labels are used.
-  ; TRACK_CF_FAST: %[[#RO:]] = or i[[#SBITS]] %[[#R+2]], %[[#R+3]]
+  ; TRACK_CF: %[[#RO:]] = or i[[#SBITS]] %[[#R+2]], %[[#R+3]]
   ; TRACK_CF: %a = select i1 %c, i8 %t, i8 %f
   ; TRACK_CF: store i[[#SBITS]] %[[#RO]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
   ; TRACK_CF: ret i8 %a
@@ -44,11 +36,7 @@
   ; TRACK_CF: @"dfs$select8e"
   ; TRACK_CF: %[[#R:]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN]]
   ; TRACK_CF: %[[#R+1]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; TRACK_CF_LEGACY: %[[#R+2]] = icmp ne i[[#SBITS]] %[[#R+1]], %[[#R]]
-  ; TRACK_CF_LEGACY: %[[#R+4]] = call {{.*}} i[[#SBITS]] @__dfsan_union(i[[#SBITS]] {{.*}} %[[#R+1]], i[[#SBITS]] {{.*}} %[[#R]])
-  ; TRACK_CF_LEGACY: %[[#RO:]] = phi i[[#SBITS]] [ %[[#R+4]], {{.*}} ], [ %[[#R+1]], {{.*}} ]
-  ; COMM: The union is simply an OR when fast labels are used.
-  ; TRACK_CF_FAST: %[[#RO:]] = or i[[#SBITS]] %[[#R+1]], %[[#R]]
+  ; TRACK_CF: %[[#RO:]] = or i[[#SBITS]] %[[#R+1]], %[[#R]]
   ; TRACK_CF: %a = select i1 %c, i8 %tf, i8 %tf
   ; TRACK_CF: store i[[#SBITS]] %[[#RO]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
   ; TRACK_CF: ret i8 %a
@@ -69,15 +57,8 @@
   ; TRACK_CF: %[[#R:]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 4) to i[[#SBITS]]*), align [[ALIGN:2]]
   ; TRACK_CF: %[[#R+1]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN]]
   ; TRACK_CF: %[[#R+2]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; TRACK_CF_LEGACY: %[[#R+3]] = icmp ne i[[#SBITS]] %[[#R+1]], %[[#R]]
-  ; TRACK_CF_LEGACY: %[[#R+5]] = call {{.*}} i[[#SBITS]] @__dfsan_union(i[[#SBITS]] {{.*}} %[[#R+1]], i[[#SBITS]] zeroext %[[#R]])
-  ; TRACK_CF_LEGACY: %[[#R+7]] = phi i[[#SBITS]] [ %[[#R+5]], {{.*}} ], [ %[[#R+1]], {{.*}} ]
-  ; TRACK_CF_LEGACY: %[[#R+8]] = icmp ne i[[#SBITS]] %[[#R+2]], %[[#R+7]]
-  ; TRACK_CF_LEGACY: %[[#R+10]] = call {{.*}} i[[#SBITS]] @__dfsan_union(i[[#SBITS]] {{.*}} %[[#R+2]], i[[#SBITS]] zeroext %[[#R+7]])
-  ; TRACK_CF_LEGACY: %[[#RO:]] = phi i[[#SBITS]] [ %[[#R+10]], {{.*}} ], [ %[[#R+2]], {{.*}} ]
-  ; COMM: The union is simply an OR when fast labels are used.
-  ; TRACK_CF_FAST: %[[#R+3]] = or i[[#SBITS]] %[[#R+1]], %[[#R]]
-  ; TRACK_CF_FAST: %[[#RO:]] = or i[[#SBITS]] %[[#R+2]], %[[#R+3]]
+  ; TRACK_CF: %[[#R+3]] = or i[[#SBITS]] %[[#R+1]], %[[#R]]
+  ; TRACK_CF: %[[#RO:]] = or i[[#SBITS]] %[[#R+2]], %[[#R+3]]
   ; TRACK_CF: %a = select <4 x i1> %c, <4 x i8> %t, <4 x i8> %f
   ; TRACK_CF: store i[[#SBITS]] %[[#RO]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
   ; TRACK_CF: ret <4 x i8> %a
@@ -86,11 +67,7 @@
   ; NO_TRACK_CF: %[[#R:]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 4) to i[[#SBITS]]*), align [[ALIGN:2]]
   ; NO_TRACK_CF: %[[#R+1]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN]]
   ; NO_TRACK_CF: %[[#R+2]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; NO_TRACK_CF_LEGACY: %[[#R+3]] = icmp ne i[[#SBITS]] %[[#R+1]], %[[#R]]
-  ; NO_TRACK_CF_LEGACY: %[[#R+5]] = call {{.*}} i[[#SBITS]] @__dfsan_union(i[[#SBITS]] {{.*}} %[[#R+1]], i[[#SBITS]] {{.*}} %[[#R]])
-  ; NO_TRACK_CF_LEGACY: %[[#RO:]] = phi i[[#SBITS]] [ %6, {{.*}} ], [ %2, {{.*}} ]
-  ; COMM: The union is simply an OR when fast labels are used.
-  ; NO_TRACK_CF_FAST: %[[#RO:]] = or i[[#SBITS]] %[[#R+1]], %[[#R]]
+  ; NO_TRACK_CF: %[[#RO:]] = or i[[#SBITS]] %[[#R+1]], %[[#R]]
   ; NO_TRACK_CF: %a = select <4 x i1> %c, <4 x i8> %t, <4 x i8> %f
   ; NO_TRACK_CF: store i[[#SBITS]] %[[#RO]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
   ; NO_TRACK_CF: ret <4 x i8> %a
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/shadow-args-zext.ll b/llvm/test/Instrumentation/DataFlowSanitizer/shadow-args-zext.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/shadow-args-zext.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/shadow-args-zext.ll
@@ -1,6 +1,4 @@
 ; RUN: opt -mtriple=x86_64-unknown-linux-gnu < %s -dfsan -S --dfsan-abilist=%S/Inputs/shadow-args-abilist.txt | FileCheck %s
-; RUN: opt -mtriple=x86_64-unknown-linux-gnu < %s -dfsan -S --dfsan-abilist=%S/Inputs/shadow-args-abilist.txt -dfsan-fast-16-labels | FileCheck %s
-; RUN: opt -mtriple=x86_64-unknown-linux-gnu < %s -dfsan -S --dfsan-abilist=%S/Inputs/shadow-args-abilist.txt -dfsan-fast-8-labels | FileCheck %s
 
 ; REQUIRES: x86-registered-target
 
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/store.ll b/llvm/test/Instrumentation/DataFlowSanitizer/store.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/store.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/store.ll
@@ -1,9 +1,5 @@
-; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-store=1 -S | FileCheck %s --check-prefixes=CHECK,CHECK16,COMBINE_PTR_LABEL
-; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-store=0 -S | FileCheck %s --check-prefixes=CHECK,CHECK16,NO_COMBINE_PTR_LABEL
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -dfsan-combine-pointer-labels-on-store=1 -S | FileCheck %s --check-prefixes=CHECK,CHECK16,COMBINE_PTR_LABEL_FAST
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels -dfsan-combine-pointer-labels-on-store=0 -S | FileCheck %s --check-prefixes=CHECK,CHECK16,NO_COMBINE_PTR_LABEL
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels -dfsan-combine-pointer-labels-on-store=1 -S | FileCheck %s --check-prefixes=CHECK,COMBINE_PTR_LABEL_FAST
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels -dfsan-combine-pointer-labels-on-store=0 -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_PTR_LABEL
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-store=1 -S | FileCheck %s --check-prefixes=CHECK,COMBINE_PTR_LABEL
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-store=0 -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_PTR_LABEL
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -23,19 +19,10 @@
 define void @store8(i8 %v, i8* %p) {
   ; CHECK-LABEL:       @"dfs$store8"
   ; CHECK:             load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-
   ; COMBINE_PTR_LABEL: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL: icmp ne i[[#SBITS]]
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-
-  ; COMM: When not in legacy mode, the three instructions above will
-  ;        be replaced with the following:
-  ; COMBINE_PTR_LABEL_FAST: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL_FAST: or i[[#SBITS]]
-
+  ; COMBINE_PTR_LABEL: or i[[#SBITS]]
   ; CHECK:             ptrtoint i8* {{.*}} i64
   ; CHECK-NEXT:        and i64
-  ; CHECK16-NEXT:      mul i64
   ; CHECK-NEXT:        inttoptr i64 {{.*}} i[[#SBITS]]*
   ; CHECK-NEXT:        getelementptr i[[#SBITS]], i[[#SBITS]]*
   ; CHECK-NEXT:        store i[[#SBITS]]
@@ -49,19 +36,10 @@
 define void @store16(i16 %v, i16* %p) {
   ; CHECK-LABEL:       @"dfs$store16"
   ; CHECK:             load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-
   ; COMBINE_PTR_LABEL: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL: icmp ne i[[#SBITS]]
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-
-  ; COMM: When not in legacy mode, the three instructions above will
-  ;        be replaced with the following:
-  ; COMBINE_PTR_LABEL_FAST: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL_FAST: or i[[#SBITS]]
-
+  ; COMBINE_PTR_LABEL: or i[[#SBITS]]
   ; CHECK:             ptrtoint i16* {{.*}} i64
   ; CHECK-NEXT:        and i64
-  ; CHECK16-NEXT:      mul i64
   ; CHECK-NEXT:        inttoptr i64 {{.*}} i[[#SBITS]]*
   ; CHECK-NEXT:        getelementptr i[[#SBITS]], i[[#SBITS]]*
   ; CHECK-NEXT:        store i[[#SBITS]]
@@ -77,19 +55,10 @@
 define void @store32(i32 %v, i32* %p) {
   ; CHECK-LABEL:       @"dfs$store32"
   ; CHECK:             load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-
   ; COMBINE_PTR_LABEL: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL: icmp ne i[[#SBITS]]
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-
-  ; COMM: When not in legacy mode, the three instructions above will
-  ;        be replaced with the following:
-  ; COMBINE_PTR_LABEL_FAST: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL_FAST: or i[[#SBITS]]
-
+  ; COMBINE_PTR_LABEL: or i[[#SBITS]]
   ; CHECK:             ptrtoint i32* {{.*}} i64
   ; CHECK-NEXT:        and i64
-  ; CHECK16-NEXT:      mul i64
   ; CHECK-NEXT:        inttoptr i64 {{.*}} i[[#SBITS]]*
   ; CHECK-NEXT:        getelementptr i[[#SBITS]], i[[#SBITS]]*
   ; CHECK-NEXT:        store i[[#SBITS]]
@@ -109,19 +78,10 @@
 define void @store64(i64 %v, i64* %p) {
   ; CHECK-LABEL:       @"dfs$store64"
   ; CHECK:             load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-
   ; COMBINE_PTR_LABEL: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL: icmp ne i[[#SBITS]]
-  ; COMBINE_PTR_LABEL: call {{.*}} @__dfsan_union
-
-  ; COMM: When not in legacy mode, the three instructions above will
-  ;       be replaced with the following:
-  ; COMBINE_PTR_LABEL_FAST: load i[[#SBITS]], i[[#SBITS]]* {{.*}} @__dfsan_arg_tls
-  ; COMBINE_PTR_LABEL_FAST: or i[[#SBITS]]
-
+  ; COMBINE_PTR_LABEL: or i[[#SBITS]]
   ; CHECK:             ptrtoint i64* {{.*}} i64
   ; CHECK-NEXT:        and i64
-  ; CHECK16-NEXT:      mul i64
   ; CHECK-NEXT:        inttoptr i64 {{.*}} i[[#SBITS]]*
   ; CHECK-COUNT-8:     insertelement {{.*}} i[[#SBITS]]
   ; CHECK-NEXT:        bitcast i[[#SBITS]]* {{.*}} <8 x i[[#SBITS]]>*
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/struct.ll b/llvm/test/Instrumentation/DataFlowSanitizer/struct.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/struct.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/struct.ll
@@ -1,16 +1,10 @@
-; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,LEGACY
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-event-callbacks=true -S | FileCheck %s --check-prefixes=CHECK,EVENT_CALLBACKS
+; RUN: opt < %s -dfsan -dfsan-event-callbacks=true -S | FileCheck %s --check-prefixes=CHECK,EVENT_CALLBACKS
 ; RUN: opt < %s -dfsan -dfsan-args-abi -S | FileCheck %s --check-prefixes=CHECK,ARGS_ABI
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,FAST
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_LOAD_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-combine-pointer-labels-on-store=true -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-track-select-control-flow=false -S | FileCheck %s --check-prefixes=CHECK,NO_SELECT_CONTROL
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -dfsan-debug-nonzero-labels -S | FileCheck %s --check-prefixes=CHECK,DEBUG_NONZERO_LABELS
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -S | FileCheck %s --check-prefixes=CHECK,FAST
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_LOAD_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-combine-pointer-labels-on-store=true -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-track-select-control-flow=false -S | FileCheck %s --check-prefixes=CHECK,NO_SELECT_CONTROL
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -dfsan-debug-nonzero-labels -S | FileCheck %s --check-prefixes=CHECK,DEBUG_NONZERO_LABELS
+; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,FAST
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-load=false -S | FileCheck %s --check-prefixes=CHECK,NO_COMBINE_LOAD_PTR
+; RUN: opt < %s -dfsan -dfsan-combine-pointer-labels-on-store=true -S | FileCheck %s --check-prefixes=CHECK,COMBINE_STORE_PTR
+; RUN: opt < %s -dfsan -dfsan-track-select-control-flow=false -S | FileCheck %s --check-prefixes=CHECK,NO_SELECT_CONTROL
+; RUN: opt < %s -dfsan -dfsan-debug-nonzero-labels -S | FileCheck %s --check-prefixes=CHECK,DEBUG_NONZERO_LABELS
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -91,11 +85,6 @@
   ; FAST: %[[#R+9]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } %[[#R+8]], i[[#SBITS]] %[[#R+7]], 1
   ; FAST: store { i[[#SBITS]], i[[#SBITS]] } %[[#R+9]], { i[[#SBITS]], i[[#SBITS]] }* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN]]
 
-  ; LEGACY: @"dfs$select_struct"
-  ; LEGACY: [[U:%.*]] = call zeroext i[[#SBITS]] @__dfsan_union
-  ; LEGACY: [[P:%.*]] = phi i[[#SBITS]] [ [[U]],
-  ; LEGACY: store i[[#SBITS]] [[P]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align 2
-
   %s = select i1 %c, {i1, i32} %a, {i1, i32} %b
   ret {i1, i32} %s
 }
@@ -109,13 +98,6 @@
   ; FAST: [[S1:%.*]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } [[S0]], i[[#SBITS]] [[E01]], 1
   ; FAST: store { i[[#SBITS]], i[[#SBITS]] } [[S1]], { i[[#SBITS]], i[[#SBITS]] }* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN]]
 
-  ; LEGACY: @"dfs$asm_struct"
-  ; LEGACY: [[E1:%.*]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: [[E0:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; LEGACY: [[E01:%.*]] = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext [[E0]], i[[#SBITS]] zeroext [[E1]])
-  ; LEGACY: [[P:%.*]] = phi i[[#SBITS]] [ [[E01]], {{.*}} ], [ [[E0]], {{.*}} ]
-  ; LEGACY: store i[[#SBITS]] [[P]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
-
 entry:
   %a = call { i32, i32 } asm "", "=r,=r,r,r,~{dirflag},~{fpsr},~{flags}"(i32 %0, i32 %1)
   ret { i32, i32 } %a
@@ -124,9 +106,6 @@
 define {i32, i32} @const_struct() {
   ; FAST: @"dfs$const_struct"
   ; FAST: store { i[[#SBITS]], i[[#SBITS]] } zeroinitializer, { i[[#SBITS]], i[[#SBITS]] }* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to { i[[#SBITS]], i[[#SBITS]] }*), align 2
-
-  ; LEGACY: @"dfs$const_struct"
-  ; LEGACY: store i[[#SBITS]] 0, i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align 2
   ret {i32, i32} { i32 42, i32 11 }
 }
 
@@ -136,9 +115,6 @@
   ; FAST: [[EM:%.*]] = extractvalue { i[[#SBITS]], i[[#SBITS]] } [[SM]], 0
   ; FAST: store i[[#SBITS]] [[EM]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
 
-  ; LEGACY: @"dfs$extract_struct"
-  ; LEGACY: [[SM:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: store i[[#SBITS]] [[SM]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
   %e2 = extractvalue {i1, i5} %s, 0
   ret i1 %e2
 }
@@ -149,13 +125,6 @@
   ; FAST: [[SM:%.*]] = load { i[[#SBITS]], i[[#SBITS]] }, { i[[#SBITS]], i[[#SBITS]] }* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN]]
   ; FAST: [[SM1:%.*]] = insertvalue { i[[#SBITS]], i[[#SBITS]] } [[SM]], i[[#SBITS]] [[EM]], 1
   ; FAST: store { i[[#SBITS]], i[[#SBITS]] } [[SM1]], { i[[#SBITS]], i[[#SBITS]] }* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to { i[[#SBITS]], i[[#SBITS]] }*), align [[ALIGN]]
-
-  ; LEGACY: @"dfs$insert_struct"
-  ; LEGACY: [[EM:%.*]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([[TLS_ARR]]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN:2]]
-  ; LEGACY: [[SM:%.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-  ; LEGACY: [[U:%.*]] = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext [[SM]], i[[#SBITS]] zeroext [[EM]])
-  ; LEGACY: [[P:%.*]] = phi i[[#SBITS]] [ [[U]], {{.*}} ], [ [[SM]], {{.*}} ]
-  ; LEGACY: store i[[#SBITS]] [[P]], i[[#SBITS]]* bitcast ([[TLS_ARR]]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]
   %s1 = insertvalue {i1, i5} %s, i5 %e1, 1
   ret {i1, i5} %s1
 }
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/union-large.ll b/llvm/test/Instrumentation/DataFlowSanitizer/union-large.ll
deleted file mode 100644
--- a/llvm/test/Instrumentation/DataFlowSanitizer/union-large.ll
+++ /dev/null
@@ -1,3014 +0,0 @@
-; RUN: opt < %s -dfsan -S | FileCheck %s
-target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
-target triple = "x86_64-unknown-linux-gnu"
-
-; Check that we use dfsan_union in large functions instead of __dfsan_union.
-
-; CHECK-LABEL: @"dfs$foo"
-define i32 @foo(i32 %a, i32 %b) {
-bb0:
-  br label %bb1
-
-bb1:
-  br label %bb2
-
-bb2:
-  br label %bb3
-
-bb3:
-  br label %bb4
-
-bb4:
-  br label %bb5
-
-bb5:
-  br label %bb6
-
-bb6:
-  br label %bb7
-
-bb7:
-  br label %bb8
-
-bb8:
-  br label %bb9
-
-bb9:
-  br label %bb10
-
-bb10:
-  br label %bb11
-
-bb11:
-  br label %bb12
-
-bb12:
-  br label %bb13
-
-bb13:
-  br label %bb14
-
-bb14:
-  br label %bb15
-
-bb15:
-  br label %bb16
-
-bb16:
-  br label %bb17
-
-bb17:
-  br label %bb18
-
-bb18:
-  br label %bb19
-
-bb19:
-  br label %bb20
-
-bb20:
-  br label %bb21
-
-bb21:
-  br label %bb22
-
-bb22:
-  br label %bb23
-
-bb23:
-  br label %bb24
-
-bb24:
-  br label %bb25
-
-bb25:
-  br label %bb26
-
-bb26:
-  br label %bb27
-
-bb27:
-  br label %bb28
-
-bb28:
-  br label %bb29
-
-bb29:
-  br label %bb30
-
-bb30:
-  br label %bb31
-
-bb31:
-  br label %bb32
-
-bb32:
-  br label %bb33
-
-bb33:
-  br label %bb34
-
-bb34:
-  br label %bb35
-
-bb35:
-  br label %bb36
-
-bb36:
-  br label %bb37
-
-bb37:
-  br label %bb38
-
-bb38:
-  br label %bb39
-
-bb39:
-  br label %bb40
-
-bb40:
-  br label %bb41
-
-bb41:
-  br label %bb42
-
-bb42:
-  br label %bb43
-
-bb43:
-  br label %bb44
-
-bb44:
-  br label %bb45
-
-bb45:
-  br label %bb46
-
-bb46:
-  br label %bb47
-
-bb47:
-  br label %bb48
-
-bb48:
-  br label %bb49
-
-bb49:
-  br label %bb50
-
-bb50:
-  br label %bb51
-
-bb51:
-  br label %bb52
-
-bb52:
-  br label %bb53
-
-bb53:
-  br label %bb54
-
-bb54:
-  br label %bb55
-
-bb55:
-  br label %bb56
-
-bb56:
-  br label %bb57
-
-bb57:
-  br label %bb58
-
-bb58:
-  br label %bb59
-
-bb59:
-  br label %bb60
-
-bb60:
-  br label %bb61
-
-bb61:
-  br label %bb62
-
-bb62:
-  br label %bb63
-
-bb63:
-  br label %bb64
-
-bb64:
-  br label %bb65
-
-bb65:
-  br label %bb66
-
-bb66:
-  br label %bb67
-
-bb67:
-  br label %bb68
-
-bb68:
-  br label %bb69
-
-bb69:
-  br label %bb70
-
-bb70:
-  br label %bb71
-
-bb71:
-  br label %bb72
-
-bb72:
-  br label %bb73
-
-bb73:
-  br label %bb74
-
-bb74:
-  br label %bb75
-
-bb75:
-  br label %bb76
-
-bb76:
-  br label %bb77
-
-bb77:
-  br label %bb78
-
-bb78:
-  br label %bb79
-
-bb79:
-  br label %bb80
-
-bb80:
-  br label %bb81
-
-bb81:
-  br label %bb82
-
-bb82:
-  br label %bb83
-
-bb83:
-  br label %bb84
-
-bb84:
-  br label %bb85
-
-bb85:
-  br label %bb86
-
-bb86:
-  br label %bb87
-
-bb87:
-  br label %bb88
-
-bb88:
-  br label %bb89
-
-bb89:
-  br label %bb90
-
-bb90:
-  br label %bb91
-
-bb91:
-  br label %bb92
-
-bb92:
-  br label %bb93
-
-bb93:
-  br label %bb94
-
-bb94:
-  br label %bb95
-
-bb95:
-  br label %bb96
-
-bb96:
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-
-bb97:
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-
-bb98:
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-
-bb99:
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-
-bb100:
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-
-bb101:
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-
-bb102:
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-
-bb103:
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-
-bb104:
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-
-bb105:
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-
-bb106:
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-
-bb107:
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-
-bb108:
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-
-bb109:
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-
-bb110:
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-
-bb111:
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-
-bb112:
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-
-bb113:
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-
-bb114:
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-
-bb115:
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-
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-
-bb117:
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-
-bb118:
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-
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-
-bb120:
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-
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-
-bb136:
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-
-bb137:
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-
-bb138:
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-
-bb139:
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-
-bb140:
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-
-bb141:
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-
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-
-bb143:
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-
-bb144:
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-
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-
-bb146:
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-  br label %bb601
-
-bb601:
-  br label %bb602
-
-bb602:
-  br label %bb603
-
-bb603:
-  br label %bb604
-
-bb604:
-  br label %bb605
-
-bb605:
-  br label %bb606
-
-bb606:
-  br label %bb607
-
-bb607:
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-
-bb608:
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-
-bb609:
-  br label %bb610
-
-bb610:
-  br label %bb611
-
-bb611:
-  br label %bb612
-
-bb612:
-  br label %bb613
-
-bb613:
-  br label %bb614
-
-bb614:
-  br label %bb615
-
-bb615:
-  br label %bb616
-
-bb616:
-  br label %bb617
-
-bb617:
-  br label %bb618
-
-bb618:
-  br label %bb619
-
-bb619:
-  br label %bb620
-
-bb620:
-  br label %bb621
-
-bb621:
-  br label %bb622
-
-bb622:
-  br label %bb623
-
-bb623:
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-
-bb624:
-  br label %bb625
-
-bb625:
-  br label %bb626
-
-bb626:
-  br label %bb627
-
-bb627:
-  br label %bb628
-
-bb628:
-  br label %bb629
-
-bb629:
-  br label %bb630
-
-bb630:
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-
-bb631:
-  br label %bb632
-
-bb632:
-  br label %bb633
-
-bb633:
-  br label %bb634
-
-bb634:
-  br label %bb635
-
-bb635:
-  br label %bb636
-
-bb636:
-  br label %bb637
-
-bb637:
-  br label %bb638
-
-bb638:
-  br label %bb639
-
-bb639:
-  br label %bb640
-
-bb640:
-  br label %bb641
-
-bb641:
-  br label %bb642
-
-bb642:
-  br label %bb643
-
-bb643:
-  br label %bb644
-
-bb644:
-  br label %bb645
-
-bb645:
-  br label %bb646
-
-bb646:
-  br label %bb647
-
-bb647:
-  br label %bb648
-
-bb648:
-  br label %bb649
-
-bb649:
-  br label %bb650
-
-bb650:
-  br label %bb651
-
-bb651:
-  br label %bb652
-
-bb652:
-  br label %bb653
-
-bb653:
-  br label %bb654
-
-bb654:
-  br label %bb655
-
-bb655:
-  br label %bb656
-
-bb656:
-  br label %bb657
-
-bb657:
-  br label %bb658
-
-bb658:
-  br label %bb659
-
-bb659:
-  br label %bb660
-
-bb660:
-  br label %bb661
-
-bb661:
-  br label %bb662
-
-bb662:
-  br label %bb663
-
-bb663:
-  br label %bb664
-
-bb664:
-  br label %bb665
-
-bb665:
-  br label %bb666
-
-bb666:
-  br label %bb667
-
-bb667:
-  br label %bb668
-
-bb668:
-  br label %bb669
-
-bb669:
-  br label %bb670
-
-bb670:
-  br label %bb671
-
-bb671:
-  br label %bb672
-
-bb672:
-  br label %bb673
-
-bb673:
-  br label %bb674
-
-bb674:
-  br label %bb675
-
-bb675:
-  br label %bb676
-
-bb676:
-  br label %bb677
-
-bb677:
-  br label %bb678
-
-bb678:
-  br label %bb679
-
-bb679:
-  br label %bb680
-
-bb680:
-  br label %bb681
-
-bb681:
-  br label %bb682
-
-bb682:
-  br label %bb683
-
-bb683:
-  br label %bb684
-
-bb684:
-  br label %bb685
-
-bb685:
-  br label %bb686
-
-bb686:
-  br label %bb687
-
-bb687:
-  br label %bb688
-
-bb688:
-  br label %bb689
-
-bb689:
-  br label %bb690
-
-bb690:
-  br label %bb691
-
-bb691:
-  br label %bb692
-
-bb692:
-  br label %bb693
-
-bb693:
-  br label %bb694
-
-bb694:
-  br label %bb695
-
-bb695:
-  br label %bb696
-
-bb696:
-  br label %bb697
-
-bb697:
-  br label %bb698
-
-bb698:
-  br label %bb699
-
-bb699:
-  br label %bb700
-
-bb700:
-  br label %bb701
-
-bb701:
-  br label %bb702
-
-bb702:
-  br label %bb703
-
-bb703:
-  br label %bb704
-
-bb704:
-  br label %bb705
-
-bb705:
-  br label %bb706
-
-bb706:
-  br label %bb707
-
-bb707:
-  br label %bb708
-
-bb708:
-  br label %bb709
-
-bb709:
-  br label %bb710
-
-bb710:
-  br label %bb711
-
-bb711:
-  br label %bb712
-
-bb712:
-  br label %bb713
-
-bb713:
-  br label %bb714
-
-bb714:
-  br label %bb715
-
-bb715:
-  br label %bb716
-
-bb716:
-  br label %bb717
-
-bb717:
-  br label %bb718
-
-bb718:
-  br label %bb719
-
-bb719:
-  br label %bb720
-
-bb720:
-  br label %bb721
-
-bb721:
-  br label %bb722
-
-bb722:
-  br label %bb723
-
-bb723:
-  br label %bb724
-
-bb724:
-  br label %bb725
-
-bb725:
-  br label %bb726
-
-bb726:
-  br label %bb727
-
-bb727:
-  br label %bb728
-
-bb728:
-  br label %bb729
-
-bb729:
-  br label %bb730
-
-bb730:
-  br label %bb731
-
-bb731:
-  br label %bb732
-
-bb732:
-  br label %bb733
-
-bb733:
-  br label %bb734
-
-bb734:
-  br label %bb735
-
-bb735:
-  br label %bb736
-
-bb736:
-  br label %bb737
-
-bb737:
-  br label %bb738
-
-bb738:
-  br label %bb739
-
-bb739:
-  br label %bb740
-
-bb740:
-  br label %bb741
-
-bb741:
-  br label %bb742
-
-bb742:
-  br label %bb743
-
-bb743:
-  br label %bb744
-
-bb744:
-  br label %bb745
-
-bb745:
-  br label %bb746
-
-bb746:
-  br label %bb747
-
-bb747:
-  br label %bb748
-
-bb748:
-  br label %bb749
-
-bb749:
-  br label %bb750
-
-bb750:
-  br label %bb751
-
-bb751:
-  br label %bb752
-
-bb752:
-  br label %bb753
-
-bb753:
-  br label %bb754
-
-bb754:
-  br label %bb755
-
-bb755:
-  br label %bb756
-
-bb756:
-  br label %bb757
-
-bb757:
-  br label %bb758
-
-bb758:
-  br label %bb759
-
-bb759:
-  br label %bb760
-
-bb760:
-  br label %bb761
-
-bb761:
-  br label %bb762
-
-bb762:
-  br label %bb763
-
-bb763:
-  br label %bb764
-
-bb764:
-  br label %bb765
-
-bb765:
-  br label %bb766
-
-bb766:
-  br label %bb767
-
-bb767:
-  br label %bb768
-
-bb768:
-  br label %bb769
-
-bb769:
-  br label %bb770
-
-bb770:
-  br label %bb771
-
-bb771:
-  br label %bb772
-
-bb772:
-  br label %bb773
-
-bb773:
-  br label %bb774
-
-bb774:
-  br label %bb775
-
-bb775:
-  br label %bb776
-
-bb776:
-  br label %bb777
-
-bb777:
-  br label %bb778
-
-bb778:
-  br label %bb779
-
-bb779:
-  br label %bb780
-
-bb780:
-  br label %bb781
-
-bb781:
-  br label %bb782
-
-bb782:
-  br label %bb783
-
-bb783:
-  br label %bb784
-
-bb784:
-  br label %bb785
-
-bb785:
-  br label %bb786
-
-bb786:
-  br label %bb787
-
-bb787:
-  br label %bb788
-
-bb788:
-  br label %bb789
-
-bb789:
-  br label %bb790
-
-bb790:
-  br label %bb791
-
-bb791:
-  br label %bb792
-
-bb792:
-  br label %bb793
-
-bb793:
-  br label %bb794
-
-bb794:
-  br label %bb795
-
-bb795:
-  br label %bb796
-
-bb796:
-  br label %bb797
-
-bb797:
-  br label %bb798
-
-bb798:
-  br label %bb799
-
-bb799:
-  br label %bb800
-
-bb800:
-  br label %bb801
-
-bb801:
-  br label %bb802
-
-bb802:
-  br label %bb803
-
-bb803:
-  br label %bb804
-
-bb804:
-  br label %bb805
-
-bb805:
-  br label %bb806
-
-bb806:
-  br label %bb807
-
-bb807:
-  br label %bb808
-
-bb808:
-  br label %bb809
-
-bb809:
-  br label %bb810
-
-bb810:
-  br label %bb811
-
-bb811:
-  br label %bb812
-
-bb812:
-  br label %bb813
-
-bb813:
-  br label %bb814
-
-bb814:
-  br label %bb815
-
-bb815:
-  br label %bb816
-
-bb816:
-  br label %bb817
-
-bb817:
-  br label %bb818
-
-bb818:
-  br label %bb819
-
-bb819:
-  br label %bb820
-
-bb820:
-  br label %bb821
-
-bb821:
-  br label %bb822
-
-bb822:
-  br label %bb823
-
-bb823:
-  br label %bb824
-
-bb824:
-  br label %bb825
-
-bb825:
-  br label %bb826
-
-bb826:
-  br label %bb827
-
-bb827:
-  br label %bb828
-
-bb828:
-  br label %bb829
-
-bb829:
-  br label %bb830
-
-bb830:
-  br label %bb831
-
-bb831:
-  br label %bb832
-
-bb832:
-  br label %bb833
-
-bb833:
-  br label %bb834
-
-bb834:
-  br label %bb835
-
-bb835:
-  br label %bb836
-
-bb836:
-  br label %bb837
-
-bb837:
-  br label %bb838
-
-bb838:
-  br label %bb839
-
-bb839:
-  br label %bb840
-
-bb840:
-  br label %bb841
-
-bb841:
-  br label %bb842
-
-bb842:
-  br label %bb843
-
-bb843:
-  br label %bb844
-
-bb844:
-  br label %bb845
-
-bb845:
-  br label %bb846
-
-bb846:
-  br label %bb847
-
-bb847:
-  br label %bb848
-
-bb848:
-  br label %bb849
-
-bb849:
-  br label %bb850
-
-bb850:
-  br label %bb851
-
-bb851:
-  br label %bb852
-
-bb852:
-  br label %bb853
-
-bb853:
-  br label %bb854
-
-bb854:
-  br label %bb855
-
-bb855:
-  br label %bb856
-
-bb856:
-  br label %bb857
-
-bb857:
-  br label %bb858
-
-bb858:
-  br label %bb859
-
-bb859:
-  br label %bb860
-
-bb860:
-  br label %bb861
-
-bb861:
-  br label %bb862
-
-bb862:
-  br label %bb863
-
-bb863:
-  br label %bb864
-
-bb864:
-  br label %bb865
-
-bb865:
-  br label %bb866
-
-bb866:
-  br label %bb867
-
-bb867:
-  br label %bb868
-
-bb868:
-  br label %bb869
-
-bb869:
-  br label %bb870
-
-bb870:
-  br label %bb871
-
-bb871:
-  br label %bb872
-
-bb872:
-  br label %bb873
-
-bb873:
-  br label %bb874
-
-bb874:
-  br label %bb875
-
-bb875:
-  br label %bb876
-
-bb876:
-  br label %bb877
-
-bb877:
-  br label %bb878
-
-bb878:
-  br label %bb879
-
-bb879:
-  br label %bb880
-
-bb880:
-  br label %bb881
-
-bb881:
-  br label %bb882
-
-bb882:
-  br label %bb883
-
-bb883:
-  br label %bb884
-
-bb884:
-  br label %bb885
-
-bb885:
-  br label %bb886
-
-bb886:
-  br label %bb887
-
-bb887:
-  br label %bb888
-
-bb888:
-  br label %bb889
-
-bb889:
-  br label %bb890
-
-bb890:
-  br label %bb891
-
-bb891:
-  br label %bb892
-
-bb892:
-  br label %bb893
-
-bb893:
-  br label %bb894
-
-bb894:
-  br label %bb895
-
-bb895:
-  br label %bb896
-
-bb896:
-  br label %bb897
-
-bb897:
-  br label %bb898
-
-bb898:
-  br label %bb899
-
-bb899:
-  br label %bb900
-
-bb900:
-  br label %bb901
-
-bb901:
-  br label %bb902
-
-bb902:
-  br label %bb903
-
-bb903:
-  br label %bb904
-
-bb904:
-  br label %bb905
-
-bb905:
-  br label %bb906
-
-bb906:
-  br label %bb907
-
-bb907:
-  br label %bb908
-
-bb908:
-  br label %bb909
-
-bb909:
-  br label %bb910
-
-bb910:
-  br label %bb911
-
-bb911:
-  br label %bb912
-
-bb912:
-  br label %bb913
-
-bb913:
-  br label %bb914
-
-bb914:
-  br label %bb915
-
-bb915:
-  br label %bb916
-
-bb916:
-  br label %bb917
-
-bb917:
-  br label %bb918
-
-bb918:
-  br label %bb919
-
-bb919:
-  br label %bb920
-
-bb920:
-  br label %bb921
-
-bb921:
-  br label %bb922
-
-bb922:
-  br label %bb923
-
-bb923:
-  br label %bb924
-
-bb924:
-  br label %bb925
-
-bb925:
-  br label %bb926
-
-bb926:
-  br label %bb927
-
-bb927:
-  br label %bb928
-
-bb928:
-  br label %bb929
-
-bb929:
-  br label %bb930
-
-bb930:
-  br label %bb931
-
-bb931:
-  br label %bb932
-
-bb932:
-  br label %bb933
-
-bb933:
-  br label %bb934
-
-bb934:
-  br label %bb935
-
-bb935:
-  br label %bb936
-
-bb936:
-  br label %bb937
-
-bb937:
-  br label %bb938
-
-bb938:
-  br label %bb939
-
-bb939:
-  br label %bb940
-
-bb940:
-  br label %bb941
-
-bb941:
-  br label %bb942
-
-bb942:
-  br label %bb943
-
-bb943:
-  br label %bb944
-
-bb944:
-  br label %bb945
-
-bb945:
-  br label %bb946
-
-bb946:
-  br label %bb947
-
-bb947:
-  br label %bb948
-
-bb948:
-  br label %bb949
-
-bb949:
-  br label %bb950
-
-bb950:
-  br label %bb951
-
-bb951:
-  br label %bb952
-
-bb952:
-  br label %bb953
-
-bb953:
-  br label %bb954
-
-bb954:
-  br label %bb955
-
-bb955:
-  br label %bb956
-
-bb956:
-  br label %bb957
-
-bb957:
-  br label %bb958
-
-bb958:
-  br label %bb959
-
-bb959:
-  br label %bb960
-
-bb960:
-  br label %bb961
-
-bb961:
-  br label %bb962
-
-bb962:
-  br label %bb963
-
-bb963:
-  br label %bb964
-
-bb964:
-  br label %bb965
-
-bb965:
-  br label %bb966
-
-bb966:
-  br label %bb967
-
-bb967:
-  br label %bb968
-
-bb968:
-  br label %bb969
-
-bb969:
-  br label %bb970
-
-bb970:
-  br label %bb971
-
-bb971:
-  br label %bb972
-
-bb972:
-  br label %bb973
-
-bb973:
-  br label %bb974
-
-bb974:
-  br label %bb975
-
-bb975:
-  br label %bb976
-
-bb976:
-  br label %bb977
-
-bb977:
-  br label %bb978
-
-bb978:
-  br label %bb979
-
-bb979:
-  br label %bb980
-
-bb980:
-  br label %bb981
-
-bb981:
-  br label %bb982
-
-bb982:
-  br label %bb983
-
-bb983:
-  br label %bb984
-
-bb984:
-  br label %bb985
-
-bb985:
-  br label %bb986
-
-bb986:
-  br label %bb987
-
-bb987:
-  br label %bb988
-
-bb988:
-  br label %bb989
-
-bb989:
-  br label %bb990
-
-bb990:
-  br label %bb991
-
-bb991:
-  br label %bb992
-
-bb992:
-  br label %bb993
-
-bb993:
-  br label %bb994
-
-bb994:
-  br label %bb995
-
-bb995:
-  br label %bb996
-
-bb996:
-  br label %bb997
-
-bb997:
-  br label %bb998
-
-bb998:
-  br label %bb999
-
-bb999:
-  br label %bb1000
-
-bb1000:
-  ; CHECK: call{{.*}}@dfsan_union
-  ; CHECK-NOT: phi
-  %ab = mul i32 %a, %b
-  ret i32 %ab
-}
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/union.ll b/llvm/test/Instrumentation/DataFlowSanitizer/union.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/union.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/union.ll
@@ -2,6 +2,9 @@
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
+; CHECK: @__dfsan_shadow_width_bits = weak_odr constant i32 [[#SBITS:]]
+; CHECK: @__dfsan_shadow_width_bytes = weak_odr constant i32 [[#SBYTES:]]
+
 @a = common global i32 0
 @b = common global i32 0
 
@@ -9,10 +12,10 @@
 
 ; CHECK-LABEL: @"dfs$f"
 define void @f(i32 %x, i32 %y) {
-  ; CHECK: call{{.*}}__dfsan_union
+  ; CHECK: or i[[#SBITS]]
   %xay = add i32 %x, %y
   store i32 %xay, i32* @a
-  ; CHECK-NOT: call{{.*}}__dfsan_union
+  ; CHECK-NOT: or i[[#SBITS]]
   %xmy = mul i32 %x, %y
   store i32 %xmy, i32* @b
   ret void
@@ -26,13 +29,13 @@
   br i1 %p, label %l1, label %l2
 
 l1:
-  ; CHECK: call{{.*}}__dfsan_union
+  ; CHECK: or i[[#SBITS]]
   %xay = add i32 %x, %y
   store i32 %xay, i32* @a
   br label %l3
 
 l2:
-  ; CHECK: call{{.*}}__dfsan_union
+  ; CHECK: or i[[#SBITS]]
   %xmy = mul i32 %x, %y
   store i32 %xmy, i32* @b
   br label %l3
@@ -45,9 +48,9 @@
 
 ; CHECK-LABEL: @"dfs$h"
 define i32 @h(i32 %x, i32 %y) {
-  ; CHECK: call{{.*}}__dfsan_union
+  ; CHECK: or i[[#SBITS]]
   %xay = add i32 %x, %y
-  ; CHECK-NOT: call{{.*}}__dfsan_union
+  ; CHECK-NOT: or i[[#SBITS]]
   %xayax = add i32 %xay, %x
   ret i32 %xayax
 }
diff --git a/llvm/test/Instrumentation/DataFlowSanitizer/vector.ll b/llvm/test/Instrumentation/DataFlowSanitizer/vector.ll
--- a/llvm/test/Instrumentation/DataFlowSanitizer/vector.ll
+++ b/llvm/test/Instrumentation/DataFlowSanitizer/vector.ll
@@ -1,7 +1,5 @@
-; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,TLS_ABI,TLS_ABI_LEGACY
 ; RUN: opt < %s -dfsan -dfsan-args-abi -S | FileCheck %s --check-prefixes=CHECK,ARGS_ABI
-; RUN: opt < %s -dfsan -dfsan-fast-16-labels=true -S | FileCheck %s --check-prefixes=CHECK,TLS_ABI,TLS_ABI_FAST
-; RUN: opt < %s -dfsan -dfsan-fast-8-labels=true -S | FileCheck %s --check-prefixes=CHECK,TLS_ABI,TLS_ABI_FAST
+; RUN: opt < %s -dfsan -S | FileCheck %s --check-prefixes=CHECK,TLS_ABI
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
@@ -37,12 +35,7 @@
   ; TLS_ABI-LABEL: @"dfs$icmp_vector"
   ; TLS_ABI-NEXT: %[[B:.*]] = load i[[#SBITS]], i[[#SBITS]]* inttoptr (i64 add (i64 ptrtoint ([100 x i64]* @__dfsan_arg_tls to i64), i64 2) to i[[#SBITS]]*), align [[ALIGN:2]]
   ; TLS_ABI-NEXT: %[[A:.*]] = load i[[#SBITS]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_arg_tls to i[[#SBITS]]*), align [[ALIGN]]
-
-  ; TLS_ABI_LEGACY: %[[U:.*]] = call zeroext i[[#SBITS]] @__dfsan_union(i[[#SBITS]] zeroext %[[A]], i[[#SBITS]] zeroext %[[B]])
-  ; TLS_ABI_LEGACY: %[[L:.*]] = phi i[[#SBITS]] [ %[[U]], {{.*}} ], [ %[[A]], {{.*}} ]
-
-  ; COM: With fast labels enabled, union is just an OR.
-  ; TLS_ABI_FAST: %[[L:.*]] = or i[[#SBITS]] %[[A]], %[[B]]
+  ; TLS_ABI:       %[[L:.*]] = or i[[#SBITS]] %[[A]], %[[B]]
 
   ; TLS_ABI: %r = icmp eq <4 x i8> %a, %b
   ; TLS_ABI: store i[[#SBITS]] %[[L]], i[[#SBITS]]* bitcast ([100 x i64]* @__dfsan_retval_tls to i[[#SBITS]]*), align [[ALIGN]]