[IR] Add llvm.dbg.addr, a control-dependent version of llvm.dbg.declare

[rnk]

Summary

This implements the design discussed on llvm-dev for better tracking of
variables that live in memory through optimizations:

http://lists.llvm.org/pipermail/llvm-dev/2017-September/117222.html

This is tracked as PR34136

llvm.dbg.addr is intended to be produced and used in almost precisely
the same way as llvm.dbg.declare is today, with the exception that it is
control-dependent. That means that dbg.addr should always have a
position in the instruction stream, and it will allow passes that
optimize memory operations on local variables to insert llvm.dbg.value
calls to reflect deleted stores. See SourceLevelDebugging.rst for more
details.

The main drawback to generating DBG_VALUE machine instrs is that they
usually cause LLVM to emit a location list for DW_AT_location. The next
step will be to teach DwarfDebug.cpp how to recognize more DBG_VALUE
ranges as not needing a location list, and possibly start setting
DW_AT_start_offset for variables whose lifetimes begin mid-scope.

[aprantl]

llvm/docs/SourceLevelDebugging.rst

202

please add a DILocation (!dbg !4), since it actually is an integral part of the intrinsic.

205

"exactly one" ?

221

I find this somewhat confusing for the reader since the above paragraph makes it sound like there can also only be one dbg.addr.

222

control-flow-dependent?

llvm/include/llvm/IR/IntrinsicInst.h

130

/// Methods for ...
/// @{
...
/// @}

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

5144

control flow ?

llvm/lib/IR/DIBuilder.cpp

28

What would break (besides IR testcases) if we made this the default immediately?

llvm/lib/IR/Verifier.cpp

4006

that string correct?

llvm/lib/Transforms/Scalar/SROA.cpp

4105

These are no longer just dbg.declares, are they?

llvm/lib/Transforms/Utils/Local.cpp

1254

Should this be a verifier error?

llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp

106

These are no longer just dbg.declares, are they?

248

These are no longer just dbg.declares, are they?

llvm/test/Transforms/SROA/dbg-addr-diamond.ll

42

strip the tbaa stuff?

[rnk]

llvm/docs/SourceLevelDebugging.rst

221

Hm, the above paragraph was meant to clarify that the frontend should generate one call, but optimizations may introduce more dbg.addrs. Hopefully now it's clear?

222

"control dependence" is a pretty common compiler concept, I think it's clearer to keep this short.

llvm/lib/IR/DIBuilder.cpp

28

Our -O0 DWARF would probably become much larger and much worse. llvm.dbg.addr always generates DBG_VALUE instructions that may be lost, and even if they survive CodeGen, they usually lead to the creation of a single entry location list, which is larger than an inline exprloc.

We could work around this by using the MF side table if there is exactly one llvm.dbg.addr and optnone is set, but I want to see what the quality degradation is first to see if it is viable to improve DwarfDebug.cpp to standardize on DBG_VALUE and eliminate the side table.

llvm/lib/IR/Verifier.cpp

4006

Oops, fixed.

llvm/lib/Transforms/Scalar/SROA.cpp

4105

The naming is inconsistent here and elsewhere. For this transition period when they can be either addrs or declares, I'd rather leave the naming alone until we flip the default and standardize on dbg.addr.

llvm/lib/Transforms/Utils/Local.cpp

1254

Actually, I think this is bug. A single alloca may hold multiple variables at different offsets. I tried to construct a unit test for this, but it was difficult and fragile so I deleted it. There's also no correctness issue with multiple variables living at the same location in memory, either.

I tried to put together a real-world test case with inalloca on windows x86:

struct NonTrivial {
  NonTrivial() : x(1) {}
  NonTrivial(const NonTrivial &) = default;
  ~NonTrivial() {}
  int x;
};
static int inalloca(NonTrivial a, int b, int c) {
  return a.x + b + c;
}
extern "C" int f() {
  return inalloca(NonTrivial(), 2, 3);
}

Clang will generate a single alloca to hold a, b, and c, and I would like it if we could inline and SROA away everything while tracking their values (1, 2, and 3). However, there are compounding issues here that move this out of scope for this patch.

[rnk]

• update

[probinson]

llvm/lib/IR/IntrinsicInst.cpp

27

With no other changes in the file, I'm guessing you don't actually need this?

llvm/lib/Transforms/Scalar/SROA.cpp

4141–4142

Preceding comment is no longer fully correct.

[rnk]

• rebase
• implement Paul's comments

[rnk]

ping

[aprantl]

llvm/lib/Transforms/Utils/Local.cpp

1101

llvm.dbg.decl?

Either the comment is not up to date, or the signature shouldn't change.
Side-note: the comment should also be moved into the header.

1143

ditto

1237

move comment into header
/// Finds all llvm.dbg.declare and llvm.debug.addr intrinsics describing local variables ...

llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp

106

ping

948

NFC follow-up to make this into
auto AI ?

[aprantl]

Couple of (stylistic) inline comments, but otherwise looking good!

llvm/docs/SourceLevelDebugging.rst

 <LangRef.html#specialized-metadata>`_, first-class subclasses of ``Metadata``.
 
 .. _format_common_intrinsics:
 
 Debugger intrinsic functions
 ----------------------------
 
 LLVM uses several intrinsic functions (name prefixed with "``llvm.dbg``") to
-provide debug information at various points in generated code.
+track source local variables through optimization and code generation.
 
-``llvm.dbg.declare``
+``llvm.dbg.addr``
 ^^^^^^^^^^^^^^^^^^^^
 
 .. code-block:: llvm
 
-  void @llvm.dbg.declare(metadata, metadata, metadata)
+  void @llvm.dbg.addr(metadata, metadata, metadata)
 
-This intrinsic provides information about a local element (e.g., variable).  The
-first argument is metadata holding the alloca for the variable.  The second
-argument is a `local variable <LangRef.html#dilocalvariable>`_ containing a
-description of the variable.  The third argument is a `complex expression
-<LangRef.html#diexpression>`_.  An `llvm.dbg.declare` instrinsic describes the
-*location* of a source variable.
+This intrinsic provides information about a local element (e.g., variable).
+The first argument is metadata holding the address of variable, typically a
+static alloca in the function entry block.  The second argument is a
+`local variable <LangRef.html#dilocalvariable>`_ containing a description of
+the variable.  The third argument is a `complex expression
+<LangRef.html#diexpression>`_.  An `llvm.dbg.addr` intrinsic describes the
+*address* of a source variable.
 
 .. code-block:: llvm
 
     %i.addr = alloca i32, align 4
-    call void @llvm.dbg.declare(metadata i32* %i.addr, metadata !1, metadata !2), !dbg !3
+    call void @llvm.dbg.addr(metadata i32* %i.addr, metadata !1,
+                             metadata !DIExpression()), !dbg !2
     !1 = !DILocalVariable(name: "i", ...) ; int i
-    !2 = !DIExpression()
-    !3 = !DILocation(...)
+    !2 = !DILocation(...)
     ...
     %buffer = alloca [256 x i8], align 8
     ; The address of i is buffer+64.
-    call void @llvm.dbg.declare(metadata [256 x i8]* %buffer, metadata !1, metadata !2)
-    !1 = !DILocalVariable(name: "i", ...) ; int i
-    !2 = !DIExpression(DW_OP_plus, 64)
+    call void @llvm.dbg.addr(metadata [256 x i8]* %buffer, metadata !3,
+                             metadata !DIExpression(DW_OP_plus, 64))
+    !3 = !DILocalVariable(name: "i", ...) ; int i
+
+A frontend should generate one call to ``llvm.dbg.addr`` at the point of
+declaration of a source variable. Optimization passes that fully promote the
+variable from memory to SSA values will replace this call with possibly
+multiple calls to `llvm.dbg.value`. Passes that delete stores are effectively
+partial promotion, and they will insert a mix of calls to ``llvm.dbg.value``
+and ``llvm.dbg.addr`` to track the source variable value when it is available.
+
+
+``llvm.dbg.declare``
+^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: llvm
+
+  void @llvm.dbg.declare(metadata, metadata, metadata)
+
+This intrinsic is identical to `llvm.dbg.addr`, except that there can only be
+one call to `llvm.dbg.declare` for a given concrete `local variable
+<LangRef.html#dilocalvariable>`_. It is not control-dependent, meaning that if
+a call to `llvm.dbg.declare` exists and has a valid location argument, that
+address is considered to be the true home of the variable across its entire
+lifetime. This makes it hard for optimizations to preserve accurate debug info
+in the presence of ``llvm.dbg.declare``, so we are transitioning away from it,
+and we plan to deprecate it in future LLVM releases.
 
 
 ``llvm.dbg.value``
 ^^^^^^^^^^^^^^^^^^
 
 .. code-block:: llvm
 
   void @llvm.dbg.value(metadata, metadata, metadata)
.. code-block:: c
   3.    int Y = 22;
   4.    {
   5.      int Z = 23;
   6.      Z = X;
   7.    }
   8.    X = Y;
   9.  }
 
+.. FIXME: Update the following example to use llvm.dbg.addr once that is the
+   default in clang.
+
 Compiled to LLVM, this function would be represented like this:
 
 .. code-block:: text
 
   ; Function Attrs: nounwind ssp uwtable
   define void @foo() #0 !dbg !4 {
   entry:
     %X = alloca i32, align 4

llvm/include/llvm/IR/IntrinsicInst.h

namespace llvm {
   /// This is the common base class for debug info intrinsics.
   class DbgInfoIntrinsic : public IntrinsicInst {
   public:
     /// Get the location corresponding to the variable referenced by the debug
     /// info intrinsic.  Depending on the intrinsic, this could be the
     /// variable's value or its address.
     Value *getVariableLocation(bool AllowNullOp = true) const;
 
+    /// Does this describe the address of a local variable. True for dbg.addr
+    /// and dbg.declare, but not dbg.value, which describes its value.
+    bool isAddressOfVariable() const {
+      return getIntrinsicID() != Intrinsic::dbg_value;
+    }
+
     DILocalVariable *getVariable() const {
       return cast<DILocalVariable>(getRawVariable());
     }
 
     DIExpression *getExpression() const {
       return cast<DIExpression>(getRawExpression());
     }
 
     Metadata *getRawVariable() const {
       return cast<MetadataAsValue>(getArgOperand(1))->getMetadata();
     }
 
     Metadata *getRawExpression() const {
       return cast<MetadataAsValue>(getArgOperand(2))->getMetadata();
     }
 
     // Methods for support type inquiry through isa, cast, and dyn_cast:
     static bool classof(const IntrinsicInst *I) {
       switch (I->getIntrinsicID()) {
       case Intrinsic::dbg_declare:
       case Intrinsic::dbg_value:
+      case Intrinsic::dbg_addr:
         return true;
       default: return false;
       }
     }
     static bool classof(const Value *V) {
       return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
     }
   };
 
   /// This represents the llvm.dbg.declare instruction.
   class DbgDeclareInst : public DbgInfoIntrinsic {
   public:
     Value *getAddress() const { return getVariableLocation(); }
 
     // Methods for support type inquiry through isa, cast, and dyn_cast:
     static bool classof(const IntrinsicInst *I) {
       return I->getIntrinsicID() == Intrinsic::dbg_declare;
     }
     static bool classof(const Value *V) {
       return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
     }
   };
 
+  /// This represents the llvm.dbg.addr instruction.
+  class DbgAddrIntrinsic : public DbgInfoIntrinsic {
+  public:
+    Value *getAddress() const { return getVariableLocation(); }
+
+    // Methods for support type inquiry through isa, cast, and dyn_cast:
+    static bool classof(const IntrinsicInst *I) {
+      return I->getIntrinsicID() == Intrinsic::dbg_addr;
+    }
+    static bool classof(const Value *V) {
+      return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
+    }
+  };
+
   /// This represents the llvm.dbg.value instruction.
   class DbgValueInst : public DbgInfoIntrinsic {
   public:
     Value *getValue() const {
       return getVariableLocation(/* AllowNullOp = */ false);
     }
 
     // Methods for support type inquiry through isa, cast, and dyn_cast:

llvm/include/llvm/IR/Intrinsics.td

 
 // None of these intrinsics accesses memory at all...but that doesn't
 // mean the optimizers can change them aggressively.  Special handling
 // needed in a few places. These synthetic intrinsics have no
 // side-effects and just mark information about their operands.
 let IntrProperties = [IntrNoMem, IntrSpeculatable] in {
   def int_dbg_declare      : Intrinsic<[],
                                        [llvm_metadata_ty,
                                         llvm_metadata_ty,
                                         llvm_metadata_ty]>;
   def int_dbg_value        : Intrinsic<[],
                                        [llvm_metadata_ty,
                                         llvm_metadata_ty,
                                         llvm_metadata_ty]>;
+  def int_dbg_addr         : Intrinsic<[],
+                                       [llvm_metadata_ty,
+                                        llvm_metadata_ty,
+                                        llvm_metadata_ty]>;
 }
 
 //===------------------ Exception Handling Intrinsics----------------------===//
 //
 
 // The result of eh.typeid.for depends on the enclosing function, but inside a
 // given function it is 'const' and may be CSE'd etc.
 def int_eh_typeid_for : Intrinsic<[llvm_i32_ty], [llvm_ptr_ty], [IntrNoMem]>;

llvm/include/llvm/Transforms/Utils/Local.h

 // program.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H
 #define LLVM_TRANSFORMS_UTILS_LOCAL_H
 
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/TinyPtrVector.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/GetElementPtrTypeIterator.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Operator.h"
 
 namespace llvm {
 
 class User;
 class BasicBlock;
 class Function;
 class BranchInst;
 class Instruction;
 class CallInst;
 class DbgDeclareInst;
+class DbgInfoIntrinsic;
 class DbgValueInst;
 class StoreInst;
 class LoadInst;
 class Value;
 class PHINode;
 class AllocaInst;
 class AssumptionCache;
 class ConstantExpr;

 }
 
 ///===---------------------------------------------------------------------===//
 ///  Dbg Intrinsic utilities
 ///
 
 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
 /// that has an associated llvm.dbg.decl intrinsic.
-void ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+void ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
                                      StoreInst *SI, DIBuilder &Builder);
 
 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
 /// that has an associated llvm.dbg.decl intrinsic.
-void ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+void ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
                                      LoadInst *LI, DIBuilder &Builder);
 
 /// Inserts a llvm.dbg.value intrinsic after a phi of an alloca'd value
 /// that has an associated llvm.dbg.decl intrinsic.
-void ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+void ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
                                      PHINode *LI, DIBuilder &Builder);
 
 /// Lowers llvm.dbg.declare intrinsics into appropriate set of
 /// llvm.dbg.value intrinsics.
 bool LowerDbgDeclare(Function &F);
 
-/// Finds the llvm.dbg.declare intrinsic corresponding to an alloca, if any.
-DbgDeclareInst *FindAllocaDbgDeclare(Value *V);
+/// Finds debug info intrinsics describing local variables at this address.
+TinyPtrVector<DbgInfoIntrinsic *> FindDbgAddrUses(Value *V);
 
 /// Finds the llvm.dbg.value intrinsics describing a value.
 void findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V);
 
 /// Replaces llvm.dbg.declare instruction when the address it describes
 /// is replaced with a new value. If Deref is true, an additional DW_OP_deref is
 /// prepended to the expression. If Offset is non-zero, a constant displacement
 /// is added to the expression (after the optional Deref). Offset can be

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

CLI.setDebugLoc(sdl).setChain(getRoot()).setLibCallee(
         DAG.getExternalSymbol(TLI.getLibcallName(LibraryCall),
                               TLI.getPointerTy(DAG.getDataLayout())),
         std::move(Args));
 
     std::pair<SDValue, SDValue> CallResult = TLI.LowerCallTo(CLI);
     DAG.setRoot(CallResult.second);
     return nullptr;
   }
+  case Intrinsic::dbg_addr:
   case Intrinsic::dbg_declare: {
-    const DbgDeclareInst &DI = cast<DbgDeclareInst>(I);
+    const DbgInfoIntrinsic &DI = cast<DbgInfoIntrinsic>(I);
     DILocalVariable *Variable = DI.getVariable();
     DIExpression *Expression = DI.getExpression();
-    const Value *Address = DI.getAddress();
     assert(Variable && "Missing variable");
-    if (!Address) {
-      DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
-      return nullptr;
-    }
 
     // Check if address has undef value.
-    if (isa<UndefValue>(Address) ||
+    const Value *Address = DI.getVariableLocation();
+    if (!Address || isa<UndefValue>(Address) ||
         (Address->use_empty() && !isa<Argument>(Address))) {
       DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
       return nullptr;
     }
 
-    // Static allocas are handled more efficiently in the variable frame index
-    // side table.
-    if (const auto *AI =
-            dyn_cast<AllocaInst>(Address->stripInBoundsConstantOffsets()))
-      if (AI->isStaticAlloca() && FuncInfo.StaticAllocaMap.count(AI))
-        return nullptr;
+    bool isParameter = Variable->isParameter() || isa<Argument>(Address);
 
-    // Byval arguments with frame indices were already handled after argument
-    // lowering and before isel.
-    if (const auto *Arg =
-            dyn_cast<Argument>(Address->stripInBoundsConstantOffsets()))
-      if (FuncInfo.getArgumentFrameIndex(Arg) != INT_MAX)
-        return nullptr;
+    // Check if this variable can be described by a frame index, typically
+    // either as a static alloca or a byval parameter.
+    int FI = INT_MAX;
+    if (const auto *AI =
+            dyn_cast<AllocaInst>(Address->stripInBoundsConstantOffsets())) {
+      if (AI->isStaticAlloca()) {
+        auto I = FuncInfo.StaticAllocaMap.find(AI);
+        if (I != FuncInfo.StaticAllocaMap.end())
+          FI = I->second;
+      }
+    } else if (const auto *Arg = dyn_cast<Argument>(
+                   Address->stripInBoundsConstantOffsets())) {
+      FI = FuncInfo.getArgumentFrameIndex(Arg);
+    }
+
+    // llvm.dbg.addr is control dependent and always generates indirect
+    // DBG_VALUE instructions. llvm.dbg.declare is handled as a frame index in
+    // the MachineFunction variable table.
+    if (FI != INT_MAX) {
+      if (Intrinsic == Intrinsic::dbg_addr)
+        DAG.AddDbgValue(DAG.getFrameIndexDbgValue(Variable, Expression, FI, dl,
+                                                  SDNodeOrder),
+                        getRoot().getNode(), isParameter);
+    }
 
     SDValue &N = NodeMap[Address];
     if (!N.getNode() && isa<Argument>(Address))
       // Check unused arguments map.
       N = UnusedArgNodeMap[Address];
     SDDbgValue *SDV;
     if (N.getNode()) {
       if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
         Address = BCI->getOperand(0);
       // Parameters are handled specially.
-      bool isParameter = Variable->isParameter() || isa<Argument>(Address);
       auto FINode = dyn_cast<FrameIndexSDNode>(N.getNode());
       if (isParameter && FINode) {
         // Byval parameter. We have a frame index at this point.
         SDV = DAG.getFrameIndexDbgValue(Variable, Expression,
                                         FINode->getIndex(), dl, SDNodeOrder);
       } else if (isa<Argument>(Address)) {
         // Address is an argument, so try to emit its dbg value using
         // virtual register info from the FuncInfo.ValueMap.

llvm/lib/IR/DIBuilder.cpp

 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/Debug.h"
 
 using namespace llvm;
 using namespace llvm::dwarf;
 
+cl::opt<bool>
+    UseDbgAddr("use-dbg-addr",
+                llvm::cl::desc("Use llvm.dbg.addr for all local variables"),
+                cl::init(false));
+
 DIBuilder::DIBuilder(Module &m, bool AllowUnresolvedNodes)
   : M(m), VMContext(M.getContext()), CUNode(nullptr),
       DeclareFn(nullptr), ValueFn(nullptr),
       AllowUnresolvedNodes(AllowUnresolvedNodes) {}
 
 void DIBuilder::trackIfUnresolved(MDNode *N) {
   if (!N)
     return;
static Value *getDbgIntrinsicValueImpl(LLVMContext &VMContext, Value *V) {
   return MetadataAsValue::get(VMContext, ValueAsMetadata::get(V));
 }
 
 static Instruction *withDebugLoc(Instruction *I, const DILocation *DL) {
   I->setDebugLoc(const_cast<DILocation *>(DL));
   return I;
 }
 
+static Function *getDeclareIntrin(Module &M) {
+  return Intrinsic::getDeclaration(&M, UseDbgAddr ? Intrinsic::dbg_addr
+                                                  : Intrinsic::dbg_declare);
+}
+
 Instruction *DIBuilder::insertDeclare(Value *Storage, DILocalVariable *VarInfo,
                                       DIExpression *Expr, const DILocation *DL,
                                       Instruction *InsertBefore) {
   assert(VarInfo && "empty or invalid DILocalVariable* passed to dbg.declare");
   assert(DL && "Expected debug loc");
   assert(DL->getScope()->getSubprogram() ==
              VarInfo->getScope()->getSubprogram() &&
          "Expected matching subprograms");
   if (!DeclareFn)
-    DeclareFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_declare);
+    DeclareFn = getDeclareIntrin(M);
 
   trackIfUnresolved(VarInfo);
   trackIfUnresolved(Expr);
   Value *Args[] = {getDbgIntrinsicValueImpl(VMContext, Storage),
                    MetadataAsValue::get(VMContext, VarInfo),
                    MetadataAsValue::get(VMContext, Expr)};
   return withDebugLoc(CallInst::Create(DeclareFn, Args, "", InsertBefore), DL);
 }
 
 Instruction *DIBuilder::insertDeclare(Value *Storage, DILocalVariable *VarInfo,
                                       DIExpression *Expr, const DILocation *DL,
                                       BasicBlock *InsertAtEnd) {
   assert(VarInfo && "empty or invalid DILocalVariable* passed to dbg.declare");
   assert(DL && "Expected debug loc");
   assert(DL->getScope()->getSubprogram() ==
              VarInfo->getScope()->getSubprogram() &&
          "Expected matching subprograms");
   if (!DeclareFn)
-    DeclareFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_declare);
+    DeclareFn = getDeclareIntrin(M);
 
   trackIfUnresolved(VarInfo);
   trackIfUnresolved(Expr);
   Value *Args[] = {getDbgIntrinsicValueImpl(VMContext, Storage),
                    MetadataAsValue::get(VMContext, VarInfo),
                    MetadataAsValue::get(VMContext, Expr)};
 
   // If this block already has a terminator then insert this intrinsic

llvm/lib/IR/IntrinsicInst.cpp

 // type pointer to empty struct { }*.  To access the real item of interest the
 // cast instruction needs to be stripped away.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/IR/Constants.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//
 /// DbgInfoIntrinsic - This is the common base class for debug info intrinsics

llvm/lib/IR/Verifier.cpp

case Intrinsic::experimental_constrained_nearbyint:
     visitConstrainedFPIntrinsic(
         cast<ConstrainedFPIntrinsic>(*CS.getInstruction()));
     break;
   case Intrinsic::dbg_declare: // llvm.dbg.declare
     Assert(isa<MetadataAsValue>(CS.getArgOperand(0)),
            "invalid llvm.dbg.declare intrinsic call 1", CS);
     visitDbgIntrinsic("declare", cast<DbgInfoIntrinsic>(*CS.getInstruction()));
     break;
+  case Intrinsic::dbg_addr: // llvm.dbg.addr
   case Intrinsic::dbg_value: // llvm.dbg.value
     visitDbgIntrinsic("value", cast<DbgInfoIntrinsic>(*CS.getInstruction()));
     break;
   case Intrinsic::memcpy:
   case Intrinsic::memmove:
   case Intrinsic::memset: {
     ConstantInt *AlignCI = dyn_cast<ConstantInt>(CS.getArgOperand(3));
     Assert(AlignCI,
            "alignment argument of memory intrinsics must be a constant int",
            CS);

llvm/lib/Transforms/Scalar/SROA.cpp

for (auto &P : AS.partitions()) {
     ++NumPartitions;
   }
 
   NumAllocaPartitions += NumPartitions;
   MaxPartitionsPerAlloca.updateMax(NumPartitions);
 
   // Migrate debug information from the old alloca to the new alloca(s)
   // and the individual partitions.
-  if (DbgDeclareInst *DbgDecl = FindAllocaDbgDeclare(&AI)) {
-    auto *Var = DbgDecl->getVariable();
-    auto *Expr = DbgDecl->getExpression();
+  TinyPtrVector<DbgInfoIntrinsic *> DbgDeclares = FindDbgAddrUses(&AI);
+  if (!DbgDeclares.empty()) {
+    auto *Var = DbgDeclares.front()->getVariable();
+    auto *Expr = DbgDeclares.front()->getExpression();
     DIBuilder DIB(*AI.getModule(), /*AllowUnresolved*/ false);
     uint64_t AllocaSize = DL.getTypeSizeInBits(AI.getAllocatedType());
     for (auto Fragment : Fragments) {
       // Create a fragment expression describing the new partition or reuse AI's
       // expression if there is only one partition.
       auto *FragmentExpr = Expr;
       if (Fragment.Size < AllocaSize || Expr->isFragment()) {
         // If this alloca is already a scalar replacement of a larger aggregate,
for (auto Fragment : Fragments) {
                  "new fragment is outside of original fragment");
           Start -= OrigFragment->OffsetInBits;
         }
         FragmentExpr =
             DIExpression::createFragmentExpression(Expr, Start, Size);
       }
 
       // Remove any existing dbg.declare intrinsic describing the same alloca.
-      if (DbgDeclareInst *OldDDI = FindAllocaDbgDeclare(Fragment.Alloca))
-        OldDDI->eraseFromParent();
+      for (DbgInfoIntrinsic *OldDII : FindDbgAddrUses(Fragment.Alloca))
+        OldDII->eraseFromParent();
 
       DIB.insertDeclare(Fragment.Alloca, Var, FragmentExpr,
-                        DbgDecl->getDebugLoc(), &AI);
+                        DbgDeclares.front()->getDebugLoc(), &AI);
     }
   }
   return Changed;
 }
 
 /// \brief Clobber a use with undef, deleting the used value if it becomes dead.
 void SROA::clobberUse(Use &U) {
   Value *OldV = U;
for (Use &Operand : I->operands())
         // Zero out the operand and see if it becomes trivially dead.
         Operand = nullptr;
         if (isInstructionTriviallyDead(U))
           DeadInsts.insert(U);
       }
 
     if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
       DeletedAllocas.insert(AI);
-      if (DbgDeclareInst *DbgDecl = FindAllocaDbgDeclare(AI))
-        DbgDecl->eraseFromParent();
+      for (DbgInfoIntrinsic *OldDII : FindDbgAddrUses(AI))
+        OldDII->eraseFromParent();
     }
 
     ++NumDeleted;
     I->eraseFromParent();
   }
 }
 
 /// \brief Promote the allocas, using the best available technique.

llvm/lib/Transforms/Utils/Local.cpp

for (auto *DVI : DbgValues) {
     assert(DVI->getValue() == APN);
     if ((DVI->getVariable() == DIVar) && (DVI->getExpression() == DIExpr))
       return true;
   }
   return false;
 }
 
 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
 /// that has an associated llvm.dbg.decl intrinsic.
-void llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
                                            StoreInst *SI, DIBuilder &Builder) {
-  auto *DIVar = DDI->getVariable();
+  assert(DII->isAddressOfVariable());
+  auto *DIVar = DII->getVariable();
   assert(DIVar && "Missing variable");
-  auto *DIExpr = DDI->getExpression();
+  auto *DIExpr = DII->getExpression();
   Value *DV = SI->getOperand(0);
 
   // If an argument is zero extended then use argument directly. The ZExt
   // may be zapped by an optimization pass in future.
   Argument *ExtendedArg = nullptr;
   if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
     ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
   if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
     ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
   if (ExtendedArg) {
-    // If this DDI was already describing only a fragment of a variable, ensure
+    // If this DII was already describing only a fragment of a variable, ensure
     // that fragment is appropriately narrowed here.
     // But if a fragment wasn't used, describe the value as the original
     // argument (rather than the zext or sext) so that it remains described even
     // if the sext/zext is optimized away. This widens the variable description,
     // leaving it up to the consumer to know how the smaller value may be
     // represented in a larger register.
     if (auto Fragment = DIExpr->getFragmentInfo()) {
       unsigned FragmentOffset = Fragment->OffsetInBits;
       SmallVector<uint64_t, 3> Ops(DIExpr->elements_begin(),
                                    DIExpr->elements_end() - 3);
       Ops.push_back(dwarf::DW_OP_LLVM_fragment);
       Ops.push_back(FragmentOffset);
-      const DataLayout &DL = DDI->getModule()->getDataLayout();
+      const DataLayout &DL = DII->getModule()->getDataLayout();
       Ops.push_back(DL.getTypeSizeInBits(ExtendedArg->getType()));
       DIExpr = Builder.createExpression(Ops);
     }
     DV = ExtendedArg;
   }
   if (!LdStHasDebugValue(DIVar, DIExpr, SI))
-    Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, DDI->getDebugLoc(),
+    Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, DII->getDebugLoc(),
                                     SI);
 }
 
 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
 /// that has an associated llvm.dbg.decl intrinsic.
-void llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
                                            LoadInst *LI, DIBuilder &Builder) {
-  auto *DIVar = DDI->getVariable();
-  auto *DIExpr = DDI->getExpression();
+  auto *DIVar = DII->getVariable();
+  auto *DIExpr = DII->getExpression();
   assert(DIVar && "Missing variable");
 
   if (LdStHasDebugValue(DIVar, DIExpr, LI))
     return;
 
   // We are now tracking the loaded value instead of the address. In the
   // future if multi-location support is added to the IR, it might be
   // preferable to keep tracking both the loaded value and the original
   // address in case the alloca can not be elided.
   Instruction *DbgValue = Builder.insertDbgValueIntrinsic(
-      LI, DIVar, DIExpr, DDI->getDebugLoc(), (Instruction *)nullptr);
+      LI, DIVar, DIExpr, DII->getDebugLoc(), (Instruction *)nullptr);
   DbgValue->insertAfter(LI);
 }
 
 /// Inserts a llvm.dbg.value intrinsic after a phi
 /// that has an associated llvm.dbg.decl intrinsic.
-void llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
                                            PHINode *APN, DIBuilder &Builder) {
-  auto *DIVar = DDI->getVariable();
-  auto *DIExpr = DDI->getExpression();
+  auto *DIVar = DII->getVariable();
+  auto *DIExpr = DII->getExpression();
   assert(DIVar && "Missing variable");
 
   if (PhiHasDebugValue(DIVar, DIExpr, APN))
     return;
 
   BasicBlock *BB = APN->getParent();
   auto InsertionPt = BB->getFirstInsertionPt();
 
   // The block may be a catchswitch block, which does not have a valid
   // insertion point.
   // FIXME: Insert dbg.value markers in the successors when appropriate.
   if (InsertionPt != BB->end())
-    Builder.insertDbgValueIntrinsic(APN, DIVar, DIExpr, DDI->getDebugLoc(),
+    Builder.insertDbgValueIntrinsic(APN, DIVar, DIExpr, DII->getDebugLoc(),
                                     &*InsertionPt);
 }
 
 /// Determine whether this alloca is either a VLA or an array.
 static bool isArray(AllocaInst *AI) {
   return AI->isArrayAllocation() ||
     AI->getType()->getElementType()->isArrayTy();
 }
if (AI && !isArray(AI)) {
         }
       }
       DDI->eraseFromParent();
     }
   }
   return true;
 }
 
-/// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the
-/// alloca 'V', if any.
-DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) {
-  if (auto *L = LocalAsMetadata::getIfExists(V))
-    if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
-      for (User *U : MDV->users())
-        if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
-          return DDI;
+/// Finds all intrinsics declaring local variables as living in the memory that
+/// 'V' points to. This may include a mix of dbg.declare and
+/// dbg.value+DW_OP_deref intrinsics, but they must all agree about which
+/// variable is stored there.
+TinyPtrVector<DbgInfoIntrinsic *> llvm::FindDbgAddrUses(Value *V) {
+  auto *L = LocalAsMetadata::getIfExists(V);
+  if (!L)
+    return {};
+  auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L);
+  if (!MDV)
+    return {};
+
+  TinyPtrVector<DbgInfoIntrinsic *> Declares;
+  for (User *U : MDV->users()) {
+    if (auto *DII = dyn_cast<DbgInfoIntrinsic>(U))
+      if (DII->isAddressOfVariable())
+        Declares.push_back(DII);
+  }
+
+  // Return nothing if the locations or DILocalVariables disagree.
+  DILocalVariable *Local =
+      Declares.empty() ? nullptr : Declares.front()->getVariable();
+  for (DbgInfoIntrinsic *DII : Declares) {
+    if (DII->getVariable() != Local)
+      return {};
+  }
 
-  return nullptr;
+  return Declares;
 }
 
 void llvm::findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V) {
   if (auto *L = LocalAsMetadata::getIfExists(V))
     if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
       for (User *U : MDV->users())
         if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U))
           DbgValues.push_back(DVI);
 }
 
-
 bool llvm::replaceDbgDeclare(Value *Address, Value *NewAddress,
                              Instruction *InsertBefore, DIBuilder &Builder,
                              bool Deref, int Offset) {
-  DbgDeclareInst *DDI = FindAllocaDbgDeclare(Address);
-  if (!DDI)
-    return false;
-  DebugLoc Loc = DDI->getDebugLoc();
-  auto *DIVar = DDI->getVariable();
-  auto *DIExpr = DDI->getExpression();
+  auto DbgAddrs = FindDbgAddrUses(Address);
+  for (DbgInfoIntrinsic *DII : DbgAddrs) {
+    DebugLoc Loc = DII->getDebugLoc();
+    auto *DIVar = DII->getVariable();
+    auto *DIExpr = DII->getExpression();
     assert(DIVar && "Missing variable");
     DIExpr = DIExpression::prepend(DIExpr, Deref, Offset);
     // Insert llvm.dbg.declare immediately after the original alloca, and remove
     // old llvm.dbg.declare.
     Builder.insertDeclare(NewAddress, DIVar, DIExpr, Loc, InsertBefore);
-  DDI->eraseFromParent();
-  return true;
+    DII->eraseFromParent();
+  }
+  return !DbgAddrs.empty();
 }
 
 bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
                                       DIBuilder &Builder, bool Deref, int Offset) {
   return replaceDbgDeclare(AI, NewAllocaAddress, AI->getNextNode(), Builder,
                            Deref, Offset);
 }
 

llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp

struct AllocaInfo {
   SmallVector<BasicBlock *, 32> DefiningBlocks;
   SmallVector<BasicBlock *, 32> UsingBlocks;
 
   StoreInst *OnlyStore;
   BasicBlock *OnlyBlock;
   bool OnlyUsedInOneBlock;
 
   Value *AllocaPointerVal;
-  DbgDeclareInst *DbgDeclare;
+  TinyPtrVector<DbgInfoIntrinsic*> DbgDeclares;
 
   void clear() {
     DefiningBlocks.clear();
     UsingBlocks.clear();
     OnlyStore = nullptr;
     OnlyBlock = nullptr;
     OnlyUsedInOneBlock = true;
     AllocaPointerVal = nullptr;
-    DbgDeclare = nullptr;
+    DbgDeclares.clear();
   }
 
   /// Scan the uses of the specified alloca, filling in the AllocaInfo used
   /// by the rest of the pass to reason about the uses of this alloca.
   void AnalyzeAlloca(AllocaInst *AI) {
     clear();
 
     // As we scan the uses of the alloca instruction, keep track of stores,
for (auto UI = AI->user_begin(), E = AI->user_end(); UI != E;) {
       if (OnlyUsedInOneBlock) {
         if (!OnlyBlock)
           OnlyBlock = User->getParent();
         else if (OnlyBlock != User->getParent())
           OnlyUsedInOneBlock = false;
       }
     }
 
-    DbgDeclare = FindAllocaDbgDeclare(AI);
+    DbgDeclares = FindDbgAddrUses(AI);
   }
 };
 
 // Data package used by RenamePass()
 class RenamePassData {
 public:
   typedef std::vector<Value *> ValVector;
 
struct PromoteMem2Reg {
   /// If we are updating an AliasSetTracker, then for each alloca that is of
   /// pointer type, we keep track of what to copyValue to the inserted PHI
   /// nodes here.
   std::vector<Value *> PointerAllocaValues;
 
   /// For each alloca, we keep track of the dbg.declare intrinsic that
   /// describes it, if any, so that we can convert it to a dbg.value
   /// intrinsic if the alloca gets promoted.
-  SmallVector<DbgDeclareInst *, 8> AllocaDbgDeclares;
+  SmallVector<TinyPtrVector<DbgInfoIntrinsic *>, 8> AllocaDbgDeclares;
 
   /// The set of basic blocks the renamer has already visited.
   ///
   SmallPtrSet<BasicBlock *, 16> Visited;
 
   /// Contains a stable numbering of basic blocks to avoid non-determinstic
   /// behavior.
   DenseMap<BasicBlock *, unsigned> BBNumbers;
static bool rewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
   }
 
   // Finally, after the scan, check to see if the store is all that is left.
   if (!Info.UsingBlocks.empty())
     return false; // If not, we'll have to fall back for the remainder.
 
   // Record debuginfo for the store and remove the declaration's
   // debuginfo.
-  if (DbgDeclareInst *DDI = Info.DbgDeclare) {
+  for (DbgInfoIntrinsic *DII : Info.DbgDeclares) {
     DIBuilder DIB(*AI->getModule(), /*AllowUnresolved*/ false);
-    ConvertDebugDeclareToDebugValue(DDI, Info.OnlyStore, DIB);
-    DDI->eraseFromParent();
-    LBI.deleteValue(DDI);
+    ConvertDebugDeclareToDebugValue(DII, Info.OnlyStore, DIB);
+    DII->eraseFromParent();
+    LBI.deleteValue(DII);
   }
   // Remove the (now dead) store and alloca.
   Info.OnlyStore->eraseFromParent();
   LBI.deleteValue(Info.OnlyStore);
 
   AI->eraseFromParent();
   LBI.deleteValue(AI);
   return true;
for (auto UI = AI->user_begin(), E = AI->user_end(); UI != E;) {
     LI->eraseFromParent();
     LBI.deleteValue(LI);
   }
 
   // Remove the (now dead) stores and alloca.
   while (!AI->use_empty()) {
     StoreInst *SI = cast<StoreInst>(AI->user_back());
     // Record debuginfo for the store before removing it.
-    if (DbgDeclareInst *DDI = Info.DbgDeclare) {
+    for (DbgInfoIntrinsic *DII : Info.DbgDeclares) {
       DIBuilder DIB(*AI->getModule(), /*AllowUnresolved*/ false);
-      ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+      ConvertDebugDeclareToDebugValue(DII, SI, DIB);
     }
     SI->eraseFromParent();
     LBI.deleteValue(SI);
   }
 
   AI->eraseFromParent();
   LBI.deleteValue(AI);
 
   // The alloca's debuginfo can be removed as well.
-  if (DbgDeclareInst *DDI = Info.DbgDeclare) {
-    DDI->eraseFromParent();
-    LBI.deleteValue(DDI);
+  for (DbgInfoIntrinsic *DII : Info.DbgDeclares) {
+    DII->eraseFromParent();
+    LBI.deleteValue(DII);
   }
 
   ++NumLocalPromoted;
   return true;
 }
 
 void PromoteMem2Reg::run() {
   Function &F = *DT.getRoot()->getParent();
for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
     // now.
     if (BBNumbers.empty()) {
       unsigned ID = 0;
       for (auto &BB : F)
         BBNumbers[&BB] = ID++;
     }
 
     // Remember the dbg.declare intrinsic describing this alloca, if any.
-    if (Info.DbgDeclare)
-      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare;
+    if (!Info.DbgDeclares.empty())
+      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclares;
 
     // Keep the reverse mapping of the 'Allocas' array for the rename pass.
     AllocaLookup[Allocas[AllocaNum]] = AllocaNum;
 
     // At this point, we're committed to promoting the alloca using IDF's, and
     // the standard SSA construction algorithm.  Determine which blocks need PHI
     // nodes and see if we can optimize out some work by avoiding insertion of
     // dead phi nodes.
for (Instruction *A : Allocas) {
     // unreachable basic blocks that were not processed by walking the dominator
     // tree. Just delete the users now.
     if (!A->use_empty())
       A->replaceAllUsesWith(UndefValue::get(A->getType()));
     A->eraseFromParent();
   }
 
   // Remove alloca's dbg.declare instrinsics from the function.
-  for (DbgDeclareInst *DDI : AllocaDbgDeclares)
-    if (DDI)
-      DDI->eraseFromParent();
+  for (auto &Declares : AllocaDbgDeclares)
+    for (auto *DII : Declares)
+      DII->eraseFromParent();
 
   // Loop over all of the PHI nodes and see if there are any that we can get
   // rid of because they merge all of the same incoming values.  This can
   // happen due to undef values coming into the PHI nodes.  This process is
   // iterative, because eliminating one PHI node can cause others to be removed.
   bool EliminatedAPHI = true;
   while (EliminatedAPHI) {
     EliminatedAPHI = false;
if (PhiToAllocaMap.count(APN)) {
         unsigned AllocaNo = PhiToAllocaMap[APN];
 
         // Add N incoming values to the PHI node.
         for (unsigned i = 0; i != NumEdges; ++i)
           APN->addIncoming(IncomingVals[AllocaNo], Pred);
 
         // The currently active variable for this block is now the PHI.
         IncomingVals[AllocaNo] = APN;
-        if (DbgDeclareInst *DDI = AllocaDbgDeclares[AllocaNo])
-          ConvertDebugDeclareToDebugValue(DDI, APN, DIB);
+        for (DbgInfoIntrinsic *DII : AllocaDbgDeclares[AllocaNo])
+          ConvertDebugDeclareToDebugValue(DII, APN, DIB);
 
         // Get the next phi node.
         ++PNI;
         APN = dyn_cast<PHINode>(PNI);
         if (!APN)
           break;
 
         // Verify that it is missing entries.  If not, it is not being inserted
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
       BB->getInstList().erase(LI);
     } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
       // Delete this instruction and mark the name as the current holder of the
       // value
       AllocaInst *Dest = dyn_cast<AllocaInst>(SI->getPointerOperand());
       if (!Dest)
         continue;
 
       DenseMap<AllocaInst *, unsigned>::iterator ai = AllocaLookup.find(Dest);
       if (ai == AllocaLookup.end())
         continue;
 
       // what value were we writing?
       IncomingVals[ai->second] = SI->getOperand(0);
       // Record debuginfo for the store before removing it.
-      if (DbgDeclareInst *DDI = AllocaDbgDeclares[ai->second])
-        ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+      for (DbgInfoIntrinsic *DII : AllocaDbgDeclares[ai->second])
+        ConvertDebugDeclareToDebugValue(DII, SI, DIB);
       BB->getInstList().erase(SI);
     }
   }
 
   // 'Recurse' to our successors.
   succ_iterator I = succ_begin(BB), E = succ_end(BB);
   if (I == E)
     return;

llvm/test/DebugInfo/X86/dbg-addr-dse.ll

+; RUN: llc %s -o %t.s
+; RUN: llvm-mc %t.s -filetype=obj -triple=x86_64-windows-msvc -o %t.o
+; RUN: FileCheck %s < %t.s --check-prefix=ASM
+; RUN: llvm-dwarfdump %t.o | FileCheck %s --check-prefix=DWARF
+
+; In this example, the variable lives mostly in memory, but at the point of the
+; assignment to global, it lives nowhere, and is described as the constant
+; value 1.
+
+; C source:
+;
+; void escape(int *);
+; extern int global;
+; void f(int x) {
+;   escape(&x);
+;   x = 1; // DSE should delete and insert dbg.value(i32 1)
+;   global = x;
+;   x = 2; // DSE should insert dbg.addr
+;   escape(&x);
+; }
+
+; ModuleID = 'dse.c'
+source_filename = "dse.c"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.0.24215"
+
+declare void @llvm.dbg.addr(metadata, metadata, metadata) #2
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+declare void @escape(i32*)
+
+@global = external global i32, align 4
+
+; Function Attrs: nounwind uwtable
+define void @f(i32 %x) #0 !dbg !8 {
+entry:
+  %x.addr = alloca i32, align 4
+  store i32 %x, i32* %x.addr, align 4
+  call void @llvm.dbg.addr(metadata i32* %x.addr, metadata !13, metadata !DIExpression()), !dbg !18
+  call void @escape(i32* %x.addr), !dbg !19
+  call void @llvm.dbg.value(metadata i32 1, metadata !13, metadata !DIExpression()), !dbg !20
+  store i32 1, i32* @global, align 4, !dbg !22
+  call void @llvm.dbg.addr(metadata i32* %x.addr, metadata !13, metadata !DIExpression()), !dbg !23
+  store i32 2, i32* %x.addr, align 4, !dbg !23
+  call void @escape(i32* %x.addr), !dbg !24
+  ret void, !dbg !25
+}
+
+; ASM-LABEL: f: # @f
+; ASM: movl    %ecx, [[OFF_X:[0-9]+]](%rsp)
+; ASM: #DEBUG_VALUE: f:x <- [DW_OP_plus_uconst [[OFF_X]]] [%RSP+0]
+; ASM: callq   escape
+; ASM: #DEBUG_VALUE: f:x <- 1
+; ASM: movl    $1, global(%rip)
+; ASM: #DEBUG_VALUE: f:x <- [DW_OP_plus_uconst [[OFF_X]]] [%RSP+0]
+; ASM: movl    $2, [[OFF_X]](%rsp)
+; ASM: callq   escape
+; ASM: retq
+
+; DWARF:      DW_TAG_formal_parameter
+; DWARF-NEXT:   DW_AT_location        (0x00000000
+; DWARF-NEXT:      {{[^:]*}}: DW_OP_breg7 RSP+{{[0-9]+}}
+; DWARF-NEXT:      {{[^:]*}}: DW_OP_consts +1, DW_OP_stack_value
+; DWARF-NEXT:      {{[^:]*}}: DW_OP_breg7 RSP+{{[0-9]+}})
+; DWARF-NEXT:   DW_AT_name    ("x")
+
+attributes #0 = { nounwind uwtable }
+attributes #2 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "dse.c", directory: "C:\5Csrc\5Cllvm-project\5Cbuild")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 6.0.0 "}
+!8 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !9, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !12)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null, !11}
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !{!13}
+!13 = !DILocalVariable(name: "x", arg: 1, scope: !8, file: !1, line: 3, type: !11)
+!14 = !{!15, !15, i64 0}
+!15 = !{!"int", !16, i64 0}
+!16 = !{!"omnipotent char", !17, i64 0}
+!17 = !{!"Simple C/C++ TBAA"}
+!18 = !DILocation(line: 3, column: 12, scope: !8)
+!19 = !DILocation(line: 4, column: 3, scope: !8)
+!20 = !DILocation(line: 5, column: 5, scope: !8)
+!21 = !DILocation(line: 6, column: 12, scope: !8)
+!22 = !DILocation(line: 6, column: 10, scope: !8)
+!23 = !DILocation(line: 7, column: 5, scope: !8)
+!24 = !DILocation(line: 8, column: 3, scope: !8)
+!25 = !DILocation(line: 9, column: 1, scope: !8)

llvm/test/DebugInfo/X86/dbg-addr.ll

+; RUN: llc %s -o %t.s
+; RUN: llvm-mc -triple x86_64--linux %t.s -filetype=obj -o %t.o
+; RUN: FileCheck < %t.s %s
+; RUN: llvm-dwarfdump %t.o | FileCheck %s --check-prefix=DWARF
+
+; Unlike dbg.declare, dbg.addr should be lowered to DBG_VALUE instructions. It
+; is control-dependent.
+
+; CHECK-LABEL: use_dbg_addr:
+; CHECK: #DEBUG_VALUE: use_dbg_addr:o <- [%RSP+0]
+
+; FIXME: Avoid the use of a single-location location list and use
+; DW_AT_start_offset instead.
+
+; DWARF: DW_TAG_variable
+; DWARF-NEXT:              DW_AT_location (0x00000000
+; DWARF-NEXT:                          0x{{.*}} - 0x{{.*}}: DW_OP_breg7 RSP+0)
+; DWARF-NEXT:              DW_AT_name ("o")
+
+
+; ModuleID = 't.c'
+source_filename = "t.c"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+%struct.Foo = type { i32 }
+
+; Function Attrs: noinline nounwind uwtable
+define void @use_dbg_addr() #0 !dbg !7 {
+entry:
+  %o = alloca %struct.Foo, align 4
+  call void @llvm.dbg.addr(metadata %struct.Foo* %o, metadata !10, metadata !15), !dbg !16
+  call void @escape_foo(%struct.Foo* %o), !dbg !17
+  ret void, !dbg !18
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.addr(metadata, metadata, metadata) #1
+
+declare void @escape_foo(%struct.Foo*)
+
+attributes #0 = { noinline nounwind uwtable }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "t.c", directory: "C:\5Csrc\5Cllvm-project\5Cbuild")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 6.0.0 "}
+!7 = distinct !DISubprogram(name: "use_dbg_addr", scope: !1, file: !1, line: 3, type: !8, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !DILocalVariable(name: "o", scope: !7, file: !1, line: 4, type: !11)
+!11 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Foo", file: !1, line: 1, size: 32, elements: !12)
+!12 = !{!13}
+!13 = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !11, file: !1, line: 1, baseType: !14, size: 32)
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !DIExpression()
+!16 = !DILocation(line: 4, column: 14, scope: !7)
+!17 = !DILocation(line: 5, column: 3, scope: !7)
+!18 = !DILocation(line: 6, column: 1, scope: !7)

llvm/test/Transforms/Mem2Reg/dbg-addr-inline-dse.ll

+; RUN: opt -mem2reg -S < %s | FileCheck %s -implicit-check-not="call void @llvm.dbg.addr"
+
+; This example is intended to simulate this pass pipeline, which may not exist
+; in practice:
+; 1. DSE f from the original C source
+; 2. Inline escape
+; 3. mem2reg
+; This exercises the corner case of multiple llvm.dbg.addr intrinsics.
+
+; C source:
+;
+; void escape(int *px) { ++*px; }
+; extern int global;
+; void f(int x) {
+;   escape(&x);
+;   x = 1; // DSE should delete and insert dbg.value(i32 1)
+;   global = x;
+;   x = 2; // DSE should insert dbg.addr
+;   escape(&x);
+; }
+
+; ModuleID = 'dse.c'
+source_filename = "dse.c"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.0.24215"
+
+declare void @llvm.dbg.addr(metadata, metadata, metadata) #2
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+@global = external global i32, align 4
+
+; Function Attrs: nounwind uwtable
+define void @f(i32 %x) #0 !dbg !8 {
+entry:
+  %x.addr = alloca i32, align 4
+  store i32 %x, i32* %x.addr, align 4
+  call void @llvm.dbg.addr(metadata i32* %x.addr, metadata !13, metadata !DIExpression()), !dbg !18
+  %ld.1 = load i32, i32* %x.addr, align 4, !dbg !19
+  %inc.1 = add nsw i32 %ld.1, 1, !dbg !19
+  store i32 %inc.1, i32* %x.addr, align 4, !dbg !19
+  call void @llvm.dbg.value(metadata i32 1, metadata !13, metadata !DIExpression()), !dbg !20
+  store i32 1, i32* @global, align 4, !dbg !22
+  call void @llvm.dbg.addr(metadata i32* %x.addr, metadata !13, metadata !DIExpression()), !dbg !23
+  store i32 2, i32* %x.addr, align 4, !dbg !23
+  %ld.2 = load i32, i32* %x.addr, align 4, !dbg !19
+  %inc.2 = add nsw i32 %ld.2, 1, !dbg !19
+  store i32 %inc.2, i32* %x.addr, align 4, !dbg !19
+  ret void, !dbg !25
+}
+
+; CHECK-LABEL: define void @f(i32 %x)
+; CHECK: call void @llvm.dbg.value(metadata i32 %x, metadata !13, metadata !DIExpression())
+; CHECK: %inc.1 = add nsw i32 %x, 1
+; CHECK: call void @llvm.dbg.value(metadata i32 %inc.1, metadata !13, metadata !DIExpression())
+; CHECK: call void @llvm.dbg.value(metadata i32 1, metadata !13, metadata !DIExpression())
+; CHECK: store i32 1, i32* @global, align 4
+; CHECK: call void @llvm.dbg.value(metadata i32 2, metadata !13, metadata !DIExpression())
+; CHECK: %inc.2 = add nsw i32 2, 1
+; CHECK: call void @llvm.dbg.value(metadata i32 %inc.2, metadata !13, metadata !DIExpression())
+; CHECK: ret void
+
+attributes #0 = { nounwind uwtable }
+attributes #2 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "dse.c", directory: "C:\5Csrc\5Cllvm-project\5Cbuild")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 6.0.0 "}
+!8 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !9, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !12)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null, !11}
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !{!13}
+!13 = !DILocalVariable(name: "x", arg: 1, scope: !8, file: !1, line: 3, type: !11)
+!14 = !{!15, !15, i64 0}
+!15 = !{!"int", !16, i64 0}
+!16 = !{!"omnipotent char", !17, i64 0}
+!17 = !{!"Simple C/C++ TBAA"}
+!18 = !DILocation(line: 3, column: 12, scope: !8)
+!19 = !DILocation(line: 4, column: 3, scope: !8)
+!20 = !DILocation(line: 5, column: 5, scope: !8)
+!21 = !DILocation(line: 6, column: 12, scope: !8)
+!22 = !DILocation(line: 6, column: 10, scope: !8)
+!23 = !DILocation(line: 7, column: 5, scope: !8)
+!24 = !DILocation(line: 8, column: 3, scope: !8)
+!25 = !DILocation(line: 9, column: 1, scope: !8)

llvm/test/Transforms/Mem2Reg/dbg-addr.ll

+; RUN: opt -mem2reg -S < %s | FileCheck %s
+
+; ModuleID = 'newvars.c'
+source_filename = "newvars.c"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.0.24215"
+
+; Function Attrs: nounwind uwtable
+define i32 @if_else(i32 %cond, i32 %a, i32 %b) !dbg !8 {
+entry:
+  %x = alloca i32, align 4
+  call void @llvm.dbg.addr(metadata i32* %x, metadata !16, metadata !DIExpression()), !dbg !26
+  store i32 %a, i32* %x, align 4, !dbg !26, !tbaa !17
+  %tobool = icmp ne i32 %cond, 0, !dbg !28
+  br i1 %tobool, label %if.then, label %if.else, !dbg !30
+
+if.then:                                          ; preds = %entry
+  store i32 0, i32* %x, align 4, !dbg !31, !tbaa !17
+  br label %if.end, !dbg !33
+
+if.else:                                          ; preds = %entry
+  store i32 %b, i32* %x, align 4, !dbg !36, !tbaa !17
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %rv = load i32, i32* %x, align 4, !dbg !37, !tbaa !17
+  ret i32 %rv, !dbg !39
+}
+
+; CHECK-LABEL: define i32 @if_else({{.*}})
+; CHECK: entry:
+; CHECK-NOT:   alloca i32
+; CHECK:   call void @llvm.dbg.value(metadata i32 %a, metadata ![[X_LOCAL:[0-9]+]], metadata !DIExpression())
+; CHECK: if.then:                                          ; preds = %entry
+; CHECK:   call void @llvm.dbg.value(metadata i32 0, metadata ![[X_LOCAL]], metadata !DIExpression())
+; CHECK: if.else:                                          ; preds = %entry
+; CHECK:   call void @llvm.dbg.value(metadata i32 %b, metadata ![[X_LOCAL]], metadata !DIExpression())
+; CHECK: if.end:                                           ; preds = %if.else, %if.then
+; CHECK:   %[[PHI:[^ ]*]] = phi i32 [ 0, %if.then ], [ %b, %if.else ]
+; CHECK:   call void @llvm.dbg.value(metadata i32 %[[PHI]], metadata ![[X_LOCAL]], metadata !DIExpression())
+; CHECK:   ret i32
+
+; CHECK: ![[X_LOCAL]] = !DILocalVariable(name: "x", {{.*}})
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+declare void @llvm.dbg.addr(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "newvars.c", directory: "C:\5Csrc\5Cllvm-project\5Cbuild")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 6.0.0 "}
+!8 = distinct !DISubprogram(name: "if_else", scope: !1, file: !1, line: 1, type: !9, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !12)
+!9 = !DISubroutineType(types: !10)
+!10 = !{!11, !11, !11, !11}
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !{!13, !14, !15, !16}
+!13 = !DILocalVariable(name: "b", arg: 3, scope: !8, file: !1, line: 1, type: !11)
+!14 = !DILocalVariable(name: "a", arg: 2, scope: !8, file: !1, line: 1, type: !11)
+!15 = !DILocalVariable(name: "cond", arg: 1, scope: !8, file: !1, line: 1, type: !11)
+!16 = !DILocalVariable(name: "x", scope: !8, file: !1, line: 2, type: !11)
+!17 = !{!18, !18, i64 0}
+!18 = !{!"int", !19, i64 0}
+!19 = !{!"omnipotent char", !20, i64 0}
+!20 = !{!"Simple C/C++ TBAA"}
+!22 = !DILocation(line: 1, column: 34, scope: !8)
+!23 = !DILocation(line: 1, column: 27, scope: !8)
+!24 = !DILocation(line: 1, column: 17, scope: !8)
+!25 = !DILocation(line: 2, column: 3, scope: !8)
+!26 = !DILocation(line: 2, column: 7, scope: !8)
+!27 = !DILocation(line: 2, column: 11, scope: !8)
+!28 = !DILocation(line: 3, column: 7, scope: !29)
+!29 = distinct !DILexicalBlock(scope: !8, file: !1, line: 3, column: 7)
+!30 = !DILocation(line: 3, column: 7, scope: !8)
+!31 = !DILocation(line: 4, column: 7, scope: !32)
+!32 = distinct !DILexicalBlock(scope: !29, file: !1, line: 3, column: 13)
+!33 = !DILocation(line: 5, column: 3, scope: !32)
+!34 = !DILocation(line: 6, column: 9, scope: !35)
+!35 = distinct !DILexicalBlock(scope: !29, file: !1, line: 5, column: 10)
+!36 = !DILocation(line: 6, column: 7, scope: !35)
+!37 = !DILocation(line: 8, column: 10, scope: !8)
+!38 = !DILocation(line: 9, column: 1, scope: !8)
+!39 = !DILocation(line: 8, column: 3, scope: !8)

llvm/test/Transforms/SROA/dbg-addr-diamond.ll

+; RUN: opt -use-dbg-addr -sroa -S < %s | FileCheck %s
+
+; ModuleID = '<stdin>'
+source_filename = "newvars.c"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.0.24215"
+
+%struct.Pair = type { i32, i32 }
+
+@pair = internal global %struct.Pair zeroinitializer
+
+; Function Attrs: nounwind uwtable
+define void @if_else(i32 %cond, i32 %a, i32 %b) !dbg !8 {
+entry:
+  %p = alloca %struct.Pair, align 4
+  %0 = bitcast %struct.Pair* %p to i8*, !dbg !25
+  call void @llvm.dbg.addr(metadata %struct.Pair* %p, metadata !20, metadata !DIExpression()), !dbg !26
+  %x = getelementptr inbounds %struct.Pair, %struct.Pair* %p, i32 0, i32 0, !dbg !27
+  store i32 %a, i32* %x, align 4, !dbg !28, !tbaa !29
+  %y = getelementptr inbounds %struct.Pair, %struct.Pair* %p, i32 0, i32 1, !dbg !34
+  store i32 %b, i32* %y, align 4, !dbg !35, !tbaa !36
+  %tobool = icmp ne i32 %cond, 0, !dbg !37
+  br i1 %tobool, label %if.then, label %if.else, !dbg !39
+
+if.then:                                          ; preds = %entry
+  %x1 = getelementptr inbounds %struct.Pair, %struct.Pair* %p, i32 0, i32 0, !dbg !40
+  store i32 0, i32* %x1, align 4, !dbg !42, !tbaa !29
+  %y2 = getelementptr inbounds %struct.Pair, %struct.Pair* %p, i32 0, i32 1, !dbg !43
+  store i32 %a, i32* %y2, align 4, !dbg !44, !tbaa !36
+  br label %if.end, !dbg !45
+
+if.else:                                          ; preds = %entry
+  %x3 = getelementptr inbounds %struct.Pair, %struct.Pair* %p, i32 0, i32 0, !dbg !46
+  store i32 %b, i32* %x3, align 4, !dbg !48, !tbaa !29
+  %y4 = getelementptr inbounds %struct.Pair, %struct.Pair* %p, i32 0, i32 1, !dbg !49
+  store i32 0, i32* %y4, align 4, !dbg !50, !tbaa !36
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %1 = bitcast %struct.Pair* %p to i8*, !dbg !51
+  %2 = bitcast %struct.Pair* @pair to i8*, !dbg !51
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %2, i8* %1, i64 8, i32 4, i1 false), !dbg !51, !tbaa.struct !52
+  ret void
+}
+
+; CHECK-LABEL: define void @if_else(i32 %cond, i32 %a, i32 %b)
+; CHECK: entry:
+; CHECK:   call void @llvm.dbg.value(metadata i32 %a, metadata ![[PVAR:[0-9]+]], metadata ![[XFRAG:DIExpression\(DW_OP_LLVM_fragment, 0, 32\)]])
+; CHECK:   call void @llvm.dbg.value(metadata i32 %b, metadata ![[PVAR]], metadata ![[YFRAG:DIExpression\(DW_OP_LLVM_fragment, 32, 32\)]])
+; CHECK: if.then:
+; CHECK:   call void @llvm.dbg.value(metadata i32 0, metadata ![[PVAR]], metadata ![[XFRAG]])
+; CHECK:   call void @llvm.dbg.value(metadata i32 %a, metadata ![[PVAR]], metadata ![[YFRAG]])
+; CHECK: if.else:
+; CHECK:   call void @llvm.dbg.value(metadata i32 %b, metadata ![[PVAR]], metadata ![[XFRAG]])
+; CHECK:   call void @llvm.dbg.value(metadata i32 0, metadata ![[PVAR]], metadata ![[YFRAG]])
+; CHECK: if.end:
+; CHECK:   %p.sroa.4.0 = phi i32 [ %a, %if.then ], [ 0, %if.else ]
+; CHECK:   %p.sroa.0.0 = phi i32 [ 0, %if.then ], [ %b, %if.else ]
+; CHECK:   call void @llvm.dbg.value(metadata i32 %p.sroa.0.0, metadata ![[PVAR]], metadata ![[XFRAG]])
+; CHECK:   call void @llvm.dbg.value(metadata i32 %p.sroa.4.0, metadata ![[PVAR]], metadata ![[YFRAG]])
+
+; CHECK: ![[PVAR]] = !DILocalVariable(name: "p", {{.*}})
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1) #2
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.addr(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 6.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "newvars.c", directory: "C:\5Csrc\5Cllvm-project\5Cbuild")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 6.0.0 "}
+!8 = distinct !DISubprogram(name: "if_else", scope: !1, file: !1, line: 2, type: !9, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !16)
+!9 = !DISubroutineType(types: !10)
+!10 = !{!11, !14, !14, !14}
+!11 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Pair", file: !1, line: 1, size: 64, elements: !12)
+!12 = !{!13, !15}
+!13 = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !11, file: !1, line: 1, baseType: !14, size: 32)
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !DIDerivedType(tag: DW_TAG_member, name: "y", scope: !11, file: !1, line: 1, baseType: !14, size: 32, offset: 32)
+!16 = !{!17, !18, !19, !20}
+!17 = !DILocalVariable(name: "b", arg: 3, scope: !8, file: !1, line: 2, type: !14)
+!18 = !DILocalVariable(name: "a", arg: 2, scope: !8, file: !1, line: 2, type: !14)
+!19 = !DILocalVariable(name: "cond", arg: 1, scope: !8, file: !1, line: 2, type: !14)
+!20 = !DILocalVariable(name: "p", scope: !8, file: !1, line: 3, type: !11)
+!22 = !DILocation(line: 2, column: 42, scope: !8)
+!23 = !DILocation(line: 2, column: 35, scope: !8)
+!24 = !DILocation(line: 2, column: 25, scope: !8)
+!25 = !DILocation(line: 3, column: 3, scope: !8)
+!26 = !DILocation(line: 3, column: 15, scope: !8)
+!27 = !DILocation(line: 4, column: 5, scope: !8)
+!28 = !DILocation(line: 4, column: 7, scope: !8)
+!29 = !{!30, !31, i64 0}
+!30 = !{!"Pair", !31, i64 0, !31, i64 4}
+!31 = !{!"int", !32, i64 0}
+!32 = !{!"omnipotent char", !33, i64 0}
+!33 = !{!"Simple C/C++ TBAA"}
+!34 = !DILocation(line: 5, column: 5, scope: !8)
+!35 = !DILocation(line: 5, column: 7, scope: !8)
+!36 = !{!30, !31, i64 4}
+!37 = !DILocation(line: 6, column: 7, scope: !38)
+!38 = distinct !DILexicalBlock(scope: !8, file: !1, line: 6, column: 7)
+!39 = !DILocation(line: 6, column: 7, scope: !8)
+!40 = !DILocation(line: 7, column: 7, scope: !41)
+!41 = distinct !DILexicalBlock(scope: !38, file: !1, line: 6, column: 13)
+!42 = !DILocation(line: 7, column: 9, scope: !41)
+!43 = !DILocation(line: 8, column: 7, scope: !41)
+!44 = !DILocation(line: 8, column: 9, scope: !41)
+!45 = !DILocation(line: 9, column: 3, scope: !41)
+!46 = !DILocation(line: 10, column: 7, scope: !47)
+!47 = distinct !DILexicalBlock(scope: !38, file: !1, line: 9, column: 10)
+!48 = !DILocation(line: 10, column: 9, scope: !47)
+!49 = !DILocation(line: 11, column: 7, scope: !47)
+!50 = !DILocation(line: 11, column: 9, scope: !47)
+!51 = !DILocation(line: 13, column: 10, scope: !8)
+!52 = !{i64 0, i64 4, !53, i64 4, i64 4, !53}
+!53 = !{!31, !31, i64 0}
+!54 = !DILocation(line: 14, column: 1, scope: !8)