Index: lib/ubsan/ubsan_checks.inc
===================================================================
--- lib/ubsan/ubsan_checks.inc
+++ lib/ubsan/ubsan_checks.inc
@@ -21,6 +21,7 @@
 UBSAN_CHECK(NullPointerUse, "null-pointer-use", "null")
 UBSAN_CHECK(PointerOverflow, "pointer-overflow", "pointer-overflow")
 UBSAN_CHECK(MisalignedPointerUse, "misaligned-pointer-use", "alignment")
+UBSAN_CHECK(AlignmentAssumption, "alignment-assumption", "alignment")
 UBSAN_CHECK(InsufficientObjectSize, "insufficient-object-size", "object-size")
 UBSAN_CHECK(SignedIntegerOverflow, "signed-integer-overflow",
             "signed-integer-overflow")
Index: lib/ubsan/ubsan_handlers.h
===================================================================
--- lib/ubsan/ubsan_handlers.h
+++ lib/ubsan/ubsan_handlers.h
@@ -24,6 +24,12 @@
   unsigned char TypeCheckKind;
 };
 
+struct AlignmentAssumptionData {
+  SourceLocation Loc;
+  SourceLocation AssumptionLoc;
+  const TypeDescriptor &Type;
+};
+
 #define UNRECOVERABLE(checkname, ...) \
   extern "C" SANITIZER_INTERFACE_ATTRIBUTE NORETURN \
     void __ubsan_handle_ ## checkname( __VA_ARGS__ );
@@ -39,6 +45,11 @@
 /// type.
 RECOVERABLE(type_mismatch_v1, TypeMismatchData *Data, ValueHandle Pointer)
 
+/// \brief Handle a runtime alignment assumption check failure,
+/// caused by a misaligned pointer.
+RECOVERABLE(alignment_assumption, AlignmentAssumptionData *Data,
+            ValueHandle Pointer, ValueHandle Alignment, ValueHandle Offset)
+
 struct OverflowData {
   SourceLocation Loc;
   const TypeDescriptor &Type;
Index: lib/ubsan/ubsan_handlers.cc
===================================================================
--- lib/ubsan/ubsan_handlers.cc
+++ lib/ubsan/ubsan_handlers.cc
@@ -106,6 +106,62 @@
   Die();
 }
 
+static void handleAlignmentAssumptionImpl(AlignmentAssumptionData *Data,
+                                          ValueHandle Pointer,
+                                          ValueHandle Alignment,
+                                          ValueHandle Offset,
+                                          ReportOptions Opts) {
+  Location Loc = Data->Loc.acquire();
+  SourceLocation AssumptionLoc = Data->AssumptionLoc.acquire();
+
+  ErrorType ET = ErrorType::AlignmentAssumption;
+
+  if (ignoreReport(Loc.getSourceLocation(), Opts, ET))
+    return;
+
+  ScopedReport R(Opts, Loc, ET);
+
+  uptr RealPointer = Pointer - Offset;
+  uptr LSB = LeastSignificantSetBitIndex(RealPointer);
+  uptr ActualAlignment = uptr(1) << LSB;
+
+  uptr Mask = Alignment - 1;
+  uptr MisAlignmentOffset = RealPointer & Mask;
+
+  if (!Offset) {
+    Diag(Loc, DL_Error, ET,
+         "assumption of %0 byte alignment for pointer of type %1 failed")
+        << Alignment << Data->Type;
+  } else {
+    Diag(Loc, DL_Error, ET,
+         "assumption of %0 byte alignment (with offset of %1 byte) for pointer "
+         "of type %2 failed")
+        << Alignment << Offset << Data->Type;
+  }
+
+  if (!AssumptionLoc.isInvalid())
+    Diag(AssumptionLoc, DL_Note, ET, "alignment assumption was specified here");
+
+  Diag(RealPointer, DL_Note, ET,
+       "address is %0 aligned, misalignment offset is %1 bytes")
+      << ActualAlignment << MisAlignmentOffset;
+}
+
+void __ubsan::__ubsan_handle_alignment_assumption(AlignmentAssumptionData *Data,
+                                                  ValueHandle Pointer,
+                                                  ValueHandle Alignment,
+                                                  ValueHandle Offset) {
+  GET_REPORT_OPTIONS(false);
+  handleAlignmentAssumptionImpl(Data, Pointer, Alignment, Offset, Opts);
+}
+void __ubsan::__ubsan_handle_alignment_assumption_abort(
+    AlignmentAssumptionData *Data, ValueHandle Pointer, ValueHandle Alignment,
+    ValueHandle Offset) {
+  GET_REPORT_OPTIONS(true);
+  handleAlignmentAssumptionImpl(Data, Pointer, Alignment, Offset, Opts);
+  Die();
+}
+
 /// \brief Common diagnostic emission for various forms of integer overflow.
 template <typename T>
 static void handleIntegerOverflowImpl(OverflowData *Data, ValueHandle LHS,
Index: lib/ubsan_minimal/ubsan_minimal_handlers.cc
===================================================================
--- lib/ubsan_minimal/ubsan_minimal_handlers.cc
+++ lib/ubsan_minimal/ubsan_minimal_handlers.cc
@@ -95,6 +95,7 @@
   HANDLER_NORECOVER(name, msg)
 
 HANDLER(type_mismatch, "type-mismatch")
+HANDLER(alignment_assumption, "alignment-assumption")
 HANDLER(add_overflow, "add-overflow")
 HANDLER(sub_overflow, "sub-overflow")
 HANDLER(mul_overflow, "mul-overflow")
Index: test/fuzzer/AlignmentAssumptionTest.cpp
===================================================================
--- /dev/null
+++ test/fuzzer/AlignmentAssumptionTest.cpp
@@ -0,0 +1,27 @@
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+
+// Test for alignment assumption failure.
+
+#include <assert.h>
+#include <climits>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <iostream>
+
+static volatile int32_t Sink;
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  assert(Data);
+  if (Size > 0 && Data[0] == 'H') {
+    Sink = 1;
+    if (Size > 1 && Data[1] == 'i') {
+      Sink = 2;
+      if (Size > 2 && Data[2] == '!') {
+        __builtin_assume_aligned(Data, 0x80000000);
+      }
+    }
+  }
+  return 0;
+}
Index: test/fuzzer/fuzzer-alignment-assumption.test
===================================================================
--- /dev/null
+++ test/fuzzer/fuzzer-alignment-assumption.test
@@ -0,0 +1,7 @@
+RUN: rm -f %t-AlignmentAssumptionTest-Ubsan
+RUN: %cpp_compiler -fsanitize=alignment -fno-sanitize-recover=all %S/AlignmentAssumptionTest.cpp -o %t-AlignmentAssumptionTest-Ubsan
+RUN: not %run %t-AlignmentAssumptionTest-Ubsan 2>&1 | FileCheck %s
+CHECK: AlignmentAssumptionTest.cpp:22:34:  runtime error: assumption of 2147483648 byte alignment for pointer of type 'const {{.*}} *' (aka 'const unsigned char *') failed
+CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+CHECK: Test unit written to ./crash-
Index: test/ubsan/TestCases/Pointer/alignment-assumption-attribute-align_value-on-lvalue.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-attribute-align_value-on-lvalue.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+typedef char ** __attribute__((align_value(0x80000000))) aligned_char;
+
+struct ac_struct {
+  aligned_char a;
+};
+
+char **load_from_ac_struct(struct ac_struct* x) {
+  return x->a;
+}
+
+int main(int argc, char* argv[]) {
+  struct ac_struct x;
+  x.a = argv; // FIXME: it is weird that this does not also have an assumption.
+  load_from_ac_struct(&x);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-7]]:13: runtime error: assumption of 2147483648 byte alignment for pointer of type 'aligned_char' (aka 'char **') failed
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-15]]:32: note: alignment assumption was specified here
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-attribute-align_value-on-paramvar.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-attribute-align_value-on-paramvar.cpp
@@ -0,0 +1,24 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+char** passthrough(__attribute__((align_value(0x80000000))) char **x) {
+  return x;
+}
+
+int main(int argc, char* argv[]) {
+  passthrough(argv);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-5]]:10: runtime error: assumption of 2147483648 byte alignment for pointer of type 'char **' failed
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-7]]:35: note: alignment assumption was specified here
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  // FIXME: shouldn't there be an assumption on the caller's side too?
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-attribute-alloc_align-on-function-variable.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-attribute-alloc_align-on-function-variable.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+char **__attribute__((alloc_align(2)))
+passthrough(char **x, unsigned long alignment) {
+  return x;
+}
+
+unsigned long alignment;
+
+int main(int argc, char* argv[]) {
+  alignment = 0x80000000;
+
+  passthrough(argv, alignment);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-1]]:3: runtime error: assumption of 2147483648 byte alignment for pointer of type 'char **' failed
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-12]]:23: note: alignment assumption was specified here
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-attribute-alloc_align-on-function.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-attribute-alloc_align-on-function.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+char **__attribute__((alloc_align(2)))
+passthrough(char **x, unsigned long alignment) {
+  return x;
+}
+
+int main(int argc, char* argv[]) {
+  passthrough(argv, 0x80000000);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-1]]:3: runtime error: assumption of 2147483648 byte alignment for pointer of type 'char **' failed
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-8]]:23: note: alignment assumption was specified here
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-attribute-assume_aligned-on-function-two-params.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-attribute-assume_aligned-on-function-two-params.cpp
@@ -0,0 +1,22 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+char ** __attribute__((assume_aligned(0x80000000, 42))) passthrough(char** x) {
+  return x;
+}
+
+int main(int argc, char* argv[]) {
+  passthrough(argv);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-1]]:3: runtime error: assumption of 2147483648 byte alignment (with offset of 42 byte) for pointer of type 'char **' failed
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-7]]:24: note: alignment assumption was specified here
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-attribute-assume_aligned-on-function.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-attribute-assume_aligned-on-function.cpp
@@ -0,0 +1,22 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+char ** __attribute__((assume_aligned(0x80000000))) passthrough(char** x) {
+  return x;
+}
+
+int main(int argc, char* argv[]) {
+  passthrough(argv);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-1]]:3: runtime error: assumption of 2147483648 byte alignment for pointer of type 'char **' failed
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-7]]:24: note: alignment assumption was specified here
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-blacklist.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-blacklist.cpp
@@ -0,0 +1,19 @@
+// FIXME: https://code.google.com/p/address-sanitizer/issues/detail?id=316
+// I'm not sure this is actually *that* issue, but this seems oddly similar to the other XFAIL'ed cases.
+// XFAIL: android
+// UNSUPPORTED: ios
+
+// RUN: %clang -fsanitize=alignment -fno-sanitize-recover=alignment                           -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption "
+
+// RUN: rm -f %tmp
+// RUN: echo "[alignment]" >> %tmp
+// RUN: echo "fun:main" >> %tmp
+// RUN: %clang -fsanitize=alignment -fno-sanitize-recover=alignment -fsanitize-blacklist=%tmp -O0 %s -o %t && %run %t 2>&1
+
+int main(int argc, char* argv[]) {
+  __builtin_assume_aligned(argv, 0x80000000);
+  // CHECK: {{.*}}alignment-assumption-blacklist.cpp:[[@LINE-1]]:28: runtime error: assumption of 2147483648 byte alignment for pointer of type 'char **' failed
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-builtin_assume_aligned-three-params-variable.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-builtin_assume_aligned-three-params-variable.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+volatile long offset;
+
+int main(int argc, char* argv[]) {
+  offset = 42;
+
+  __builtin_assume_aligned(argv, 0x80000000, offset);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-1]]:28: runtime error: assumption of 2147483648 byte alignment (with offset of 42 byte) for pointer of type 'char **' failed
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-builtin_assume_aligned-three-params.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-builtin_assume_aligned-three-params.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+int main(int argc, char* argv[]) {
+  __builtin_assume_aligned(argv, 0x80000000, 42);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-1]]:28: runtime error: assumption of 2147483648 byte alignment (with offset of 42 byte) for pointer of type 'char **' failed
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-builtin_assume_aligned-two-params.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-builtin_assume_aligned-two-params.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang   -x c   -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+int main(int argc, char* argv[]) {
+  __builtin_assume_aligned(argv, 0x80000000);
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-1]]:28: runtime error: assumption of 2147483648 byte alignment for pointer of type 'char **' failed
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-openmp.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-openmp.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang   -x c   -fsanitize=alignment -fopenmp-simd -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -fopenmp-simd -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -fopenmp-simd -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c   -fsanitize=alignment -fopenmp-simd -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+// RUN: %clang   -x c++ -fsanitize=alignment -fopenmp-simd -O0 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -fopenmp-simd -O1 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -fopenmp-simd -O2 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+// RUN: %clang   -x c++ -fsanitize=alignment -fopenmp-simd -O3 %s -o %t && %run %t 2>&1 | FileCheck %s --implicit-check-not=" assumption " --implicit-check-not="note:" --implicit-check-not="error:"
+
+int main(int argc, char* argv[]) {
+#pragma omp for simd aligned(argv : 0x40000000)
+  for(int x = 0; x < 1; x++)
+    argv[x] = argv[x];
+  // CHECK: {{.*}}alignment-assumption-{{.*}}.cpp:[[@LINE-3]]:30: runtime error: assumption of 1073741824 byte alignment for pointer of type 'char **' failed
+  // CHECK: 0x{{.*}}: note: address is {{.*}} aligned, misalignment offset is {{.*}} byte
+
+  return 0;
+}
Index: test/ubsan/TestCases/Pointer/alignment-assumption-summary.cpp
===================================================================
--- /dev/null
+++ test/ubsan/TestCases/Pointer/alignment-assumption-summary.cpp
@@ -0,0 +1,11 @@
+// RUN: %clangxx -fsanitize=alignment %s -o %t
+// RUN: %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-NOTYPE
+// RUN: %env_ubsan_opts=report_error_type=1 %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-TYPE
+// REQUIRES: !ubsan-standalone && !ubsan-standalone-static
+
+int main(int argc, char* argv[]) {
+  __builtin_assume_aligned(argv, 0x80000000);
+  // CHECK-NOTYPE: SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior {{.*}}summary.cpp:[[@LINE-1]]:28
+  // CHECK-TYPE: SUMMARY: UndefinedBehaviorSanitizer: alignment-assumption {{.*}}summary.cpp:[[@LINE-2]]:28
+  return 0;
+}
Index: test/ubsan_minimal/TestCases/alignment-assumption.c
===================================================================
--- /dev/null
+++ test/ubsan_minimal/TestCases/alignment-assumption.c
@@ -0,0 +1,11 @@
+// RUN: %clang -fsanitize=alignment %s -o %t && %run %t 2>&1 | FileCheck %s --check-prefixes=CHECK
+
+int main(int argc, char* argv[]) {
+// CHECK-NOT: alignment-assumption
+
+  __builtin_assume_aligned(argv, 0x80000000);
+// CHECK: alignment-assumption
+// CHECK-NOT: alignment-assumption
+
+  return 0;
+}