[Debuginfo][Salvaging] (5/7) Support for DW_OP_implicit_pointer for named and unnamed variables (second strategy).

[alok]

Summary

This patch stems from D84112.
This patch includes improvement in debuginfo salvaging.

[jmorse]

Could you elaborate on why module-level information needs to be preserved? As mentioned on llvm-dev, I think you might have missed a place where promotion from stack to SSA/values happens -- IMHO we shouldn't add module-level debuginfo-tracking unless it's absolutely necessary.

llvm/include/llvm/IR/Module.h

205

You'll need to use a value handle (WeakVH perhaps) to store Value references, to avoid storing pointers that become dangling pointers later. The comment should indicate what's being mapped -- I believe it's old alloca to the DILocalVariable, because insertVarAddressMap inserts the second operand of a dbg.declare?

In addition, it looks like salvageDebugInfoForDbgValues never dereferences the mapped value, so could this instead be a set instead of a map?

llvm/lib/IR/Instruction.cpp

81–82

Does this make the debug-info metadata code in the Instruction destructor redundant?

800–803

The rest of Instruction.cpp is very detail-agnostic, and it seems out of place to check the DWARF version here (and presumably meaningless for CodeView). Could this be turned into a more generic compile option, or target option, so that it's less DWARF specific?

(It might be that LLVM doesn't support such a form of option).

812–813

Quite a lot of this function is now dedicated to "if we're an alloca being deleted, that had associated dbg.declares". IMO, it's clearer to put that code into a separate function.

llvm/test/DebugInfo/X86/implicit_pointer_temp_dyn_alloc.cc

2–3

We can't call clang from within llvm as it's not guaranteed to be built. Getting the unoptimised IR with -O0 -gdwarf-5 -emit-llvm -S -Xclang -disable-O0-optnone, and writing a normal lit test for that, would be best.

You might also want to put an end-to-end Dexter test into the debuginfo-tests.

llvm/unittests/IR/DebugInfoTest.cpp

186

This should be a positive test that the dbg.value points at a correct thing, not that it doesn't point at an undef. There are a variety of other Values it could point at by mistake.

[alok]

Updated to re-base.

[djtodoro]

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

312

Can we leave this here in Local ?

llvm/lib/IR/Instruction.cpp

797

nit: Preserve

822

why only for DWARF 5?
There is dw_op_gnu_implicit_pointer for the later version ?

822

Please add a comment describing what we are doing here.

825

Please use early continue here.

[djtodoro]

llvm/lib/IR/Instruction.cpp

822

'later version' --> I meant earlier

llvm/include/llvm/IR/Instruction.h

 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <utility>
 
 namespace llvm {
 
 class BasicBlock;
+class DbgVariableIntrinsic;
 class FastMathFlags;
 class MDNode;
 class Module;
 struct AAMDNodes;
 
 template <> struct ilist_alloc_traits<Instruction> {
   static inline void deleteNode(Instruction *V);
 };
void dropUnknownNonDebugMetadata(unsigned ID1, unsigned ID2) {
     unsigned IDs[] = {ID1, ID2};
     return dropUnknownNonDebugMetadata(IDs);
   }
   /// @}
 
   /// Sets the metadata on this instruction from the AAMDNodes structure.
   void setAAMetadata(const AAMDNodes &N);
 
+  /// Given DIExpression \p DIExpr operating on this instruction, write the
+  /// effects of this instruction into the returned DIExpression, or return
+  /// nullptr if it cannot be salvaged. \p StackVal: whether DW_OP_stack_value
+  /// should be appended to the expression.
+  DIExpression *salvageDebugInfoImpl(DIExpression *SrcDIExpr,
+                                     bool WithStackValue);
+
+  /// Implementation of salvageDebugInfo, applying only to instructions in
+  /// \p DbgUsers, rather than all debug users of this instruction.
+  void salvageDebugInfoForDbgValues(ArrayRef<DbgVariableIntrinsic *> DbgUsers);
+
+  /// Assuming this instruction is going to be deleted, attempt to salvage
+  /// debug users by writing the effect of this instruction in a DIExpression.
+  /// Returns true if any debug users were updated.
+  void salvageDebugInfo();
+
   /// Retrieve the raw weight values of a conditional branch or select.
   /// Returns true on success with profile weights filled in.
   /// Returns false if no metadata or invalid metadata was found.
   bool extractProfMetadata(uint64_t &TrueVal, uint64_t &FalseVal) const;
 
   /// Retrieve total raw weight values of a branch.
   /// Returns true on success with profile total weights filled in.
   /// Returns false if no metadata was found.

llvm/include/llvm/IR/Module.h

 #include <cstdint>
 #include <iterator>
 #include <memory>
 #include <string>
 #include <vector>
 
 namespace llvm {
 
+class DbgVariableIntrinsic;
 class Error;
 class FunctionType;
 class GVMaterializer;
 class LLVMContext;
 class MemoryBuffer;
 class ModuleSummaryIndex;
 class Pass;
 class RandomNumberGenerator;
private:
   Materializer;                   ///< Used to materialize GlobalValues
   std::string ModuleID;           ///< Human readable identifier for the module
   std::string SourceFileName;     ///< Original source file name for module,
                                   ///< recorded in bitcode.
   std::string TargetTriple;       ///< Platform target triple Module compiled on
                                   ///< Format: (arch)(sub)-(vendor)-(sys0-(abi)
   NamedMDSymTabType NamedMDSymTab;  ///< NamedMDNode names.
   DataLayout DL;                  ///< DataLayout associated with the module
+  /// Instruction combiner optimization deletes debugdeclare intrinsic,
+  /// cases when debugdeclare instrinsic is deleted from caller while callee
+  /// is later inlined, which makes opportunity to create DW_OP_implicit_pointer
+  /// we will preserve location of variable in DenseMap to use later
+  DenseMap<Value *, Value *> VarAddrMap;
 
   friend class Constant;
 
 /// @}
 /// @name Constructors
 /// @{
 public:
   /// The Module constructor. Note that there is no default constructor. You
   /// must provide a name for the module upon construction.
   explicit Module(StringRef ModuleID, LLVMContext& C);
   /// The module destructor. This will dropAllReferences.
   ~Module();
 
+  void insertVarAddressMap(DbgVariableIntrinsic *DDI);
+
+  Value *findVarAddressMap(Value *Var);
+
   /// @}
   /// @name Module Level Accessors
   /// @{
 
   /// Get the module identifier which is, essentially, the name of the module.
   /// @returns the module identifier as a string
   const std::string &getModuleIdentifier() const { return ModuleID; }
 
   /// Returns the number of non-debug IR instructions in the module.
   /// This is equivalent to the sum of the IR instruction counts of each
   /// function contained in the module.

llvm/include/llvm/IR/Value.h

 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_IR_VALUE_H
 #define LLVM_IR_VALUE_H
 
 #include "llvm-c/Types.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/IR/Use.h"
 #include "llvm/Support/Alignment.h"
 #include "llvm/Support/CBindingWrapping.h"
 #include "llvm/Support/Casting.h"
 #include <cassert>
 #include <iterator>
 #include <memory>
 
 namespace llvm {
 
 class APInt;
 class Argument;
 class BasicBlock;
 class Constant;
 class ConstantData;
 class ConstantAggregate;
 class DataLayout;
+class DbgVariableIntrinsic;
 class Function;
 class GlobalAlias;
 class GlobalIFunc;
 class GlobalIndirectSymbol;
 class GlobalObject;
 class GlobalValue;
 class GlobalVariable;
 class InlineAsm;
for (use_iterator UI = use_begin(), E = use_end(); UI != E;) {
       Use &U = *UI;
       ++UI;
       if (!ShouldReplace(U))
         continue;
       U.set(New);
     }
   }
 
+  /// Finds the debug info intrinsics describing this value.
+  void findDbgUsers(SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers);
+
   /// replaceUsesOutsideBlock - Go through the uses list for this definition and
   /// make each use point to "V" instead of "this" when the use is outside the
   /// block. 'This's use list is expected to have at least one element.
   /// Unlike replaceAllUsesWith() this function does not support basic block
   /// values or constant users.
   void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
 
   //----------------------------------------------------------------------

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

 
 /// Like \c FindDbgAddrUses, but only returns dbg.declare intrinsics, not
 /// dbg.addr.
 TinyPtrVector<DbgDeclareInst *> FindDbgDeclareUses(Value *V);
 
 /// Finds the llvm.dbg.value intrinsics describing a value.
 void findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V);
 
-/// Finds the debug info intrinsics describing a value.
-void findDbgUsers(SmallVectorImpl<DbgVariableIntrinsic *> &DbgInsts, 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
 /// (between the optional Deref operations). Offset can be negative.
 bool replaceDbgDeclare(Value *Address, Value *NewAddress, DIBuilder &Builder,
                        uint8_t DIExprFlags, int Offset);
 
 /// Replaces multiple llvm.dbg.value instructions when the alloca it describes
 /// is replaced with a new value. If Offset is non-zero, a constant displacement
 /// is added to the expression (after the mandatory Deref). Offset can be
 /// negative. New llvm.dbg.value instructions are inserted at the locations of
 /// the instructions they replace.
 void replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
                               DIBuilder &Builder, int Offset = 0);
 
-/// Assuming the instruction \p I is going to be deleted, attempt to salvage
-/// debug users of \p I by writing the effect of \p I in a DIExpression. If it
-/// cannot be salvaged changes its debug uses to undef.
-void salvageDebugInfo(Instruction &I);
-
-
-/// Implementation of salvageDebugInfo, applying only to instructions in
-/// \p Insns, rather than all debug users from findDbgUsers( \p I).
-/// Returns true if any debug users were updated.
-/// Mark undef if salvaging cannot be completed.
-void salvageDebugInfoForDbgValues(Instruction &I,
-                                  ArrayRef<DbgVariableIntrinsic *> Insns);
-
-/// Given an instruction \p I and DIExpression \p DIExpr operating on it, write
-/// the effects of \p I into the returned DIExpression, or return nullptr if
-/// it cannot be salvaged. \p StackVal: whether DW_OP_stack_value should be
-/// appended to the expression.
-DIExpression *salvageDebugInfoImpl(Instruction &I, DIExpression *DIExpr,
-                                   bool StackVal);
+/// Finds alloca where the value comes from.
+AllocaInst *findAllocaForValue(Value *V,
+                               DenseMap<Value *, AllocaInst *> &AllocaForValue);
 
 /// Point debug users of \p From to \p To or salvage them. Use this function
 /// only when replacing all uses of \p From with \p To, with a guarantee that
 /// \p From is going to be deleted.
 ///
 /// Follow these rules to prevent use-before-def of \p To:
 ///   . If \p To is a linked Instruction, set \p DomPoint to \p To.
 ///   . If \p To is an unlinked Instruction, set \p DomPoint to the Instruction

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

void SelectionDAGBuilder::salvageUnresolvedDbgValue(DanglingDebugInfo &DDI) {
   if (handleDebugValue(V, Var, Expr, DL, InstDL, SDOrder))
     return;
 
   // Attempt to salvage back through as many instructions as possible. Bail if
   // a non-instruction is seen, such as a constant expression or global
   // variable. FIXME: Further work could recover those too.
   while (isa<Instruction>(V)) {
     Instruction &VAsInst = *cast<Instruction>(V);
-    DIExpression *NewExpr = salvageDebugInfoImpl(VAsInst, Expr, StackValue);
+    DIExpression *NewExpr = VAsInst.salvageDebugInfoImpl(Expr, StackValue);
 
     // If we cannot salvage any further, and haven't yet found a suitable debug
     // expression, bail out.
     if (!NewExpr)
       break;
 
     // New value and expr now represent this debuginfo.
     V = VAsInst.getOperand(0);

llvm/lib/IR/DebugInfoMetadata.cpp

void DIExpression::appendOffset(SmallVectorImpl<uint64_t> &Ops,
   } else if (Offset < 0) {
     Ops.push_back(dwarf::DW_OP_constu);
     Ops.push_back(-Offset);
     Ops.push_back(dwarf::DW_OP_minus);
   }
 }
 
 bool DIExpression::extractIfOffset(int64_t &Offset) const {
-  if (getNumElements() == 0) {
+  unsigned numElements = getNumElements();
+
+  if (numElements == 0) {
     Offset = 0;
     return true;
   }
 
-  if (getNumElements() == 2 && Elements[0] == dwarf::DW_OP_plus_uconst) {
+  if (Elements[numElements - 1] == dwarf::DW_OP_stack_value)
+    numElements--;
+
+  if (numElements == 2 && Elements[0] == dwarf::DW_OP_plus_uconst) {
     Offset = Elements[1];
     return true;
   }
 
-  if (getNumElements() == 3 && Elements[0] == dwarf::DW_OP_constu) {
+  if (numElements == 3 && Elements[0] == dwarf::DW_OP_constu) {
     if (Elements[2] == dwarf::DW_OP_plus) {
       Offset = Elements[1];
       return true;
     }
     if (Elements[2] == dwarf::DW_OP_minus) {
       Offset = -Elements[1];
       return true;
     }

llvm/lib/IR/Instruction.cpp

 //===-- Instruction.cpp - Implement the Instruction class -----------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Instruction class for the IR library.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/Instruction.h"
-#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/IR/Constants.h"
+#include "llvm/IR/DIBuilder.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/Type.h"
 using namespace llvm;
 
 Instruction::Instruction(Type *ty, unsigned it, Use *Ops, unsigned NumOps,
                          Instruction *InsertBefore)
   : User(ty, Value::InstructionVal + it, Ops, NumOps), Parent(nullptr) {
 
const Function *Instruction::getFunction() const {
   return getParent()->getParent();
 }
 
 void Instruction::removeFromParent() {
   getParent()->getInstList().remove(getIterator());
 }
 
 iplist<Instruction>::iterator Instruction::eraseFromParent() {
+  // Try to preserve debug information attached to the instruction.
+  salvageDebugInfo();
+
   return getParent()->getInstList().erase(getIterator());
 }
 
 /// Insert an unlinked instruction into a basic block immediately before the
 /// specified instruction.
 void Instruction::insertBefore(Instruction *InsertPos) {
   InsertPos->getParent()->getInstList().insert(InsertPos->getIterator(), this);
 }

 #include "llvm/IR/Instruction.def"
 #undef HANDLE_INST
   }
 
   New->SubclassOptionalData = SubclassOptionalData;
   New->copyMetadata(*this);
   return New;
 }
+
+void Instruction::salvageDebugInfo() {
+  SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
+
+  // Return false if any of the operand is already deleted
+  for (unsigned i = 0; i < getNumOperands(); ++i)
+    if (!getOperand(i))
+      return;
+
+  // preserve the information we may need later when called function from
+  // current function is inlined. We need this information for
+  // DW_OP_implicit_pointer.
+  if (auto DDI = dyn_cast<DbgVariableIntrinsic>(this))
+    if (getModule()->getDwarfVersion() >= 5)
+      if (DDI->isAddressOfVariable())
+        getModule()->insertVarAddressMap(DDI);
+
+  findDbgUsers(DbgUsers);
+  if (DbgUsers.empty())
+    return;
+
+  salvageDebugInfoForDbgValues(DbgUsers);
+}
+
+void Instruction::salvageDebugInfoForDbgValues(
+    ArrayRef<DbgVariableIntrinsic *> DbgUsers) {
+  auto &Ctx = getContext();
+  bool Salvaged = false;
+  auto wrapMD = [&](Value *V) {
+    return MetadataAsValue::get(Ctx, ValueAsMetadata::get(V));
+  };
+  Value *DebugDeclareAddress = nullptr;
+  SmallVector<StoreInst *, 1> StoreInsts;
+
+  if (getModule()->getDwarfVersion() >= 5) {
+    if (isa<AllocaInst>(*this)) {
+      for (auto *DII : DbgUsers) {
+        if (DII->isAddressOfVariable()) {
+          if (const llvm::MetadataAsValue *MDV =
+                  dyn_cast<llvm::MetadataAsValue>(DII->getOperand(1)))
+            if (isa<DILocalVariable>(MDV->getMetadata())) {
+              DebugDeclareAddress = DII->getOperand(1);
+            }
+          break;
+        }
+      }
+    }
+
+    if (!DebugDeclareAddress)
+      DebugDeclareAddress = getModule()->findVarAddressMap(this);
+
+    if (!DebugDeclareAddress) {
+      StoreInst *SI;
+      for (auto &AIUse : uses()) {
+        User *U = AIUse.getUser();
+        if ((SI = dyn_cast<StoreInst>(U)) && SI->getOperand(1) == this)
+          StoreInsts.push_back(SI);
+      }
+    }
+  }
+
+  for (auto *DII : DbgUsers) {
+    // Do not add DW_OP_stack_value for DbgDeclare and DbgAddr, because they
+    // are implicitly pointing out the value as a DWARF memory location
+    // description.
+    bool StackValue = isa<DbgValueInst>(DII);
+
+    DIExpression *DIExpr =
+        salvageDebugInfoImpl(DII->getExpression(), StackValue);
+
+    // salvageDebugInfoImpl should fail on examining the first element of
+    // DbgUsers, or none of them.
+    if (!DIExpr)
+      continue;
+
+    int64_t ExprOffset = 0;
+
+    // It is AllocaInst and either of below is true then continue
+    //   - We failed to get the variable description, or
+    //   - Current instruction is not llvm.dbg.value, or
+    //   - Current instruction doesnt have constant offset
+    if (!StoreInsts.empty()) {
+      if (!DII->getExpression()->extractIfOffset(ExprOffset))
+        continue;
+    } else if (isa<AllocaInst>(this) &&
+               (!DebugDeclareAddress || DII->isAddressOfVariable() ||
+                !DII->getExpression()->extractIfOffset(ExprOffset)))
+      continue;
+
+    if (!StoreInsts.empty()) {
+      DIBuilder DIB(*getModule(), /*AllowUnresolved*/ false);
+
+      DIExpression *DIExpr = DII->getExpression();
+
+      for (auto *SI : StoreInsts) {
+        Value *ReplVal = SI->getOperand(0);
+        DIExpression *DIExprNew = DIExpression::get(
+            DIExpr->getContext(), {dwarf::DW_OP_LLVM_implicit_pointer});
+
+        if (!StackValue)
+          DIB.insertDbgValueIntrinsic(ReplVal, DII->getVariable(), DIExprNew,
+                                      DII->getDebugLoc(), SI);
+        else {
+          DII->setOperand(0, wrapMD(ReplVal));
+          DII->setOperand(2, MetadataAsValue::get(Ctx, DIExprNew));
+        }
+      }
+      Salvaged = true;
+    } else if (!isa<AllocaInst>(this)) {
+      DII->setOperand(0, wrapMD(getOperand(0)));
+      DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr));
+      Salvaged = true;
+    }
+  }
+
+  if (Salvaged)
+    return;
+
+  for (auto *DII : DbgUsers) {
+    Value *Undef = UndefValue::get(getType());
+    DII->setOperand(0, MetadataAsValue::get(DII->getContext(),
+                                            ValueAsMetadata::get(Undef)));
+  }
+}
+
+DIExpression *Instruction::salvageDebugInfoImpl(DIExpression *SrcDIExpr,
+                                                bool WithStackValue) {
+  auto &M = *getModule();
+  auto &DL = M.getDataLayout();
+
+  // Apply a vector of opcodes to the source DIExpression.
+  auto doSalvage = [&](SmallVectorImpl<uint64_t> &Ops) -> DIExpression * {
+    DIExpression *DIExpr = SrcDIExpr;
+    if (!Ops.empty()) {
+      DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, WithStackValue);
+    }
+    return DIExpr;
+  };
+
+  // Apply the given offset to the source DIExpression.
+  auto applyOffset = [&](uint64_t Offset) -> DIExpression * {
+    SmallVector<uint64_t, 8> Ops;
+    DIExpression::appendOffset(Ops, Offset);
+    return doSalvage(Ops);
+  };
+
+  // initializer-list helper for applying operators to the source DIExpression.
+  auto applyOps = [&](ArrayRef<uint64_t> Opcodes) -> DIExpression * {
+    SmallVector<uint64_t, 8> Ops(Opcodes.begin(), Opcodes.end());
+    return doSalvage(Ops);
+  };
+
+  if (auto *CI = dyn_cast<CastInst>(this)) {
+    // No-op casts are irrelevant for debug info.
+    if (CI->isNoopCast(DL))
+      return SrcDIExpr;
+
+    Type *Type = CI->getType();
+    // Casts other than Trunc, SExt, or ZExt to scalar types cannot be salvaged.
+    if (Type->isVectorTy() ||
+        !(isa<TruncInst>(this) || isa<SExtInst>(this) || isa<ZExtInst>(this)))
+      return nullptr;
+
+    Value *FromValue = CI->getOperand(0);
+    unsigned FromTypeBitSize = FromValue->getType()->getScalarSizeInBits();
+    unsigned ToTypeBitSize = Type->getScalarSizeInBits();
+
+    return applyOps(DIExpression::getExtOps(FromTypeBitSize, ToTypeBitSize,
+                                            isa<SExtInst>(this)));
+  }
+
+  if (auto *GEP = dyn_cast<GetElementPtrInst>(this)) {
+    unsigned BitWidth =
+        M.getDataLayout().getIndexSizeInBits(GEP->getPointerAddressSpace());
+    // Rewrite a constant GEP into a DIExpression.
+    APInt Offset(BitWidth, 0);
+    if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
+      return applyOffset(Offset.getSExtValue());
+    } else {
+      return nullptr;
+    }
+  } else if (auto *BI = dyn_cast<BinaryOperator>(this)) {
+    // Rewrite binary operations with constant integer operands.
+    auto *ConstInt = dyn_cast<ConstantInt>(getOperand(1));
+    if (!ConstInt || ConstInt->getBitWidth() > 64)
+      return nullptr;
+
+    uint64_t Val = ConstInt->getSExtValue();
+    switch (BI->getOpcode()) {
+    case Instruction::Add:
+      return applyOffset(Val);
+    case Instruction::Sub:
+      return applyOffset(-int64_t(Val));
+    case Instruction::Mul:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mul});
+    case Instruction::SDiv:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_div});
+    case Instruction::SRem:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mod});
+    case Instruction::Or:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_or});
+    case Instruction::And:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_and});
+    case Instruction::Xor:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_xor});
+    case Instruction::Shl:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shl});
+    case Instruction::LShr:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shr});
+    case Instruction::AShr:
+      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shra});
+    default:
+      // TODO: Salvage constants from each kind of binop we know about.
+      return nullptr;
+    }
+    // *Not* to do: we should not attempt to salvage load instructions,
+    // because the validity and lifetime of a dbg.value containing
+    // DW_OP_deref becomes difficult to analyze. See PR40628 for examples.
+  } else if ((M.getDwarfVersion() >= 5) && isa<AllocaInst>(this)) {
+    return SrcDIExpr;
+  }
+  return nullptr;
+}

llvm/lib/IR/Module.cpp

 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GVMaterializer.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalIFunc.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/ModuleSummaryIndex.h"
 #include "llvm/IR/SymbolTableListTraits.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/TypeFinder.h"
 #include "llvm/IR/Value.h"
 #include "llvm/IR/ValueSymbolTable.h"
if (ProfileSummary) {
         return;
       double Ratio = (double)BlockCount / NumCounts;
       ProfileSummary->setPartialProfileRatio(Ratio);
       setProfileSummary(ProfileSummary->getMD(getContext()),
                         ProfileSummary::PSK_Sample);
     }
   }
 }
+
+void Module::insertVarAddressMap(DbgVariableIntrinsic *DDI) {
+  if (DDI->getOperand(0) != nullptr)
+    VarAddrMap.insert(
+        std::pair<Value *, Value *>(DDI->getOperand(0), DDI->getOperand(1)));
+}
+
+Value *Module::findVarAddressMap(Value *Var) {
+  if (Var->isUsedByMetadata())
+    if (auto *L = LocalAsMetadata::getIfExists(Var))
+      if (auto *MDV = MetadataAsValue::getIfExists(Var->getContext(), L))
+        return VarAddrMap[MDV];
+
+  return nullptr;
+}

llvm/lib/IR/Value.cpp

void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
 
   replaceUsesWithIf(New, [BB](Use &U) {
     auto *I = dyn_cast<Instruction>(U.getUser());
     // Don't replace if it's an instruction in the BB basic block.
     return !I || I->getParent() != BB;
   });
 }
 
+void Value::findDbgUsers(SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers) {
+  // This function is hot. Check whether the value has any metadata to avoid a
+  // DenseMap lookup.
+  if (!isUsedByMetadata())
+    return;
+  if (auto *L = LocalAsMetadata::getIfExists(this))
+    if (auto *MDV = MetadataAsValue::getIfExists(getContext(), L))
+      for (User *U : MDV->users())
+        if (DbgVariableIntrinsic *DII = dyn_cast<DbgVariableIntrinsic>(U))
+          DbgUsers.push_back(DII);
+}
+
 namespace {
 // Various metrics for how much to strip off of pointers.
 enum PointerStripKind {
   PSK_ZeroIndices,
   PSK_ZeroIndicesAndAliases,
   PSK_ZeroIndicesSameRepresentation,
   PSK_ZeroIndicesAndInvariantGroups,
   PSK_InBoundsConstantIndices,

llvm/lib/Transforms/InstCombine/InstCombineInternal.h

public:
   /// Combiner aware instruction erasure.
   ///
   /// When dealing with an instruction that has side effects or produces a void
   /// value, we can't rely on DCE to delete the instruction. Instead, visit
   /// methods should return the value returned by this function.
   Instruction *eraseInstFromFunction(Instruction &I) override {
     LLVM_DEBUG(dbgs() << "IC: ERASE " << I << '\n');
     assert(I.use_empty() && "Cannot erase instruction that is used!");
-    salvageDebugInfo(I);
+    I.salvageDebugInfo();
 
     // Make sure that we reprocess all operands now that we reduced their
     // use counts.
     for (Use &Operand : I.operands())
       if (auto *Inst = dyn_cast<Instruction>(Operand))
         Worklist.add(Inst);
 
     Worklist.remove(&I);

llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

 bool InstCombinerImpl::SimplifyDemandedBits(Instruction *I, unsigned OpNo,
                                             const APInt &DemandedMask,
                                             KnownBits &Known, unsigned Depth) {
   Use &U = I->getOperandUse(OpNo);
   Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask, Known,
                                           Depth, I);
   if (!NewVal) return false;
   if (Instruction* OpInst = dyn_cast<Instruction>(U))
-    salvageDebugInfo(*OpInst);
+    OpInst->salvageDebugInfo();
 
   replaceUse(U, NewVal);
   return true;
 }
 
 /// This function attempts to replace V with a simpler value based on the
 /// demanded bits. When this function is called, it is known that only the bits
 /// set in DemandedMask of the result of V are ever used downstream.

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
   // but we believe in a permissible manner.
   SmallVector<WeakTrackingVH, 64> Users;
 
   // If we are removing an alloca with a dbg.declare, insert dbg.value calls
   // before each store.
   SmallVector<DbgVariableIntrinsic *, 8> DVIs;
   std::unique_ptr<DIBuilder> DIB;
   if (isa<AllocaInst>(MI)) {
-    findDbgUsers(DVIs, &MI);
+    MI.findDbgUsers(DVIs);
     DIB.reset(new DIBuilder(*MI.getModule(), /*AllowUnresolved=*/false));
   }
 
   if (isAllocSiteRemovable(&MI, Users, &TLI)) {
     for (unsigned i = 0, e = Users.size(); i != e; ++i) {
       // Lowering all @llvm.objectsize calls first because they may
       // use a bitcast/GEP of the alloca we are removing.
       if (!Users[i])
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
                                              C->isFalseWhenEqual()));
       } else if (auto *SI = dyn_cast<StoreInst>(I)) {
         for (auto *DVI : DVIs)
           if (DVI->isAddressOfVariable())
             ConvertDebugDeclareToDebugValue(DVI, SI, *DIB);
       } else {
         // Casts, GEP, or anything else: we're about to delete this instruction,
         // so it can not have any valid uses.
+        I->salvageDebugInfo();
         replaceInstUsesWith(*I, UndefValue::get(I->getType()));
       }
       eraseInstFromFunction(*I);
     }
 
     if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) {
       // Replace invoke with a NOP intrinsic to maintain the original CFG
       Module *M = II->getModule();
static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
   ++NumSunkInst;
 
   // Also sink all related debug uses from the source basic block. Otherwise we
   // get debug use before the def. Attempt to salvage debug uses first, to
   // maximise the range variables have location for. If we cannot salvage, then
   // mark the location undef: we know it was supposed to receive a new location
   // here, but that computation has been sunk.
   SmallVector<DbgVariableIntrinsic *, 2> DbgUsers;
-  findDbgUsers(DbgUsers, I);
+  I->findDbgUsers(DbgUsers);
 
   // Update the arguments of a dbg.declare instruction, so that it
   // does not point into a sunk instruction.
   auto updateDbgDeclare = [&I](DbgVariableIntrinsic *DII) {
     if (!isa<DbgDeclareInst>(DII))
       return false;
 
     if (isa<CastInst>(I))
if (User->getParent() != SrcBlock || updateDbgDeclare(User))
       continue;
 
     DIIClones.emplace_back(cast<DbgVariableIntrinsic>(User->clone()));
     LLVM_DEBUG(dbgs() << "CLONE: " << *DIIClones.back() << '\n');
   }
 
   // Perform salvaging without the clones, then sink the clones.
   if (!DIIClones.empty()) {
-    salvageDebugInfoForDbgValues(*I, DbgUsers);
+    I->salvageDebugInfoForDbgValues(DbgUsers);
     for (auto &DIIClone : DIIClones) {
       DIIClone->insertBefore(&*InsertPos);
       LLVM_DEBUG(dbgs() << "SINK: " << *DIIClone << '\n');
     }
   }
 
   return true;
 }
static bool prepareICWorklistFromFunction(Function &F, const DataLayout &DL,
   // some N^2 behavior in pathological cases.
   ICWorklist.reserve(InstrsForInstCombineWorklist.size());
   for (Instruction *Inst : reverse(InstrsForInstCombineWorklist)) {
     // DCE instruction if trivially dead. As we iterate in reverse program
     // order here, we will clean up whole chains of dead instructions.
     if (isInstructionTriviallyDead(Inst, TLI)) {
       ++NumDeadInst;
       LLVM_DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
-      salvageDebugInfo(*Inst);
+      Inst->salvageDebugInfo();
       Inst->eraseFromParent();
       MadeIRChange = true;
       continue;
     }
 
     ICWorklist.push(Inst);
   }
 

llvm/lib/Transforms/Scalar/BDCE.cpp

if (I.mayHaveSideEffects() && I.use_empty())
       continue;
 
     // Remove instructions that are dead, either because they were not reached
     // during analysis or have no demanded bits.
     if (DB.isInstructionDead(&I) ||
         (I.getType()->isIntOrIntVectorTy() &&
          DB.getDemandedBits(&I).isNullValue() &&
          wouldInstructionBeTriviallyDead(&I))) {
-      salvageDebugInfo(I);
+      I.salvageDebugInfo();
       Worklist.push_back(&I);
       I.dropAllReferences();
       Changed = true;
       continue;
     }
 
     // Convert SExt into ZExt if none of the extension bits is required
     if (SExtInst *SE = dyn_cast<SExtInst>(&I)) {

llvm/lib/Transforms/Scalar/DCE.cpp

 
 static bool DCEInstruction(Instruction *I,
                            SmallSetVector<Instruction *, 16> &WorkList,
                            const TargetLibraryInfo *TLI) {
   if (isInstructionTriviallyDead(I, TLI)) {
     if (!DebugCounter::shouldExecute(DCECounter))
       return false;
 
-    salvageDebugInfo(*I);
+    I->salvageDebugInfo();
     salvageKnowledge(I);
 
     // Null out all of the instruction's operands to see if any operand becomes
     // dead as we go.
     for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
       Value *OpV = I->getOperand(i);
       I->setOperand(i, nullptr);
 

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

do {
     Instruction *DeadInst = NowDeadInsts.pop_back_val();
     // Mark the DeadInst as dead in the list of throwable instructions.
     auto It = ThrowableInst.find(DeadInst);
     if (It != ThrowableInst.end())
       ThrowableInst[It->first] = false;
     ++NumFastOther;
 
     // Try to preserve debug information attached to the dead instruction.
-    salvageDebugInfo(*DeadInst);
+    DeadInst->salvageDebugInfo();
     salvageKnowledge(DeadInst);
 
     // This instruction is dead, zap it, in stages.  Start by removing it from
     // MemDep, which needs to know the operands and needs it to be in the
     // function.
     MD.removeInstruction(DeadInst);
 
     for (unsigned op = 0, e = DeadInst->getNumOperands(); op != e; ++op) {
void deleteDeadInstruction(Instruction *SI) {
     NowDeadInsts.push_back(SI);
     --NumFastOther;
 
     while (!NowDeadInsts.empty()) {
       Instruction *DeadInst = NowDeadInsts.pop_back_val();
       ++NumFastOther;
 
       // Try to preserve debug information attached to the dead instruction.
-      salvageDebugInfo(*DeadInst);
+      DeadInst->salvageDebugInfo();
       salvageKnowledge(DeadInst);
 
       // Remove the Instruction from MSSA.
       if (MemoryAccess *MA = MSSA.getMemoryAccess(DeadInst)) {
         if (MemoryDef *MD = dyn_cast<MemoryDef>(MA)) {
           SkipStores.insert(MD);
         }
         Updater.removeMemoryAccess(MA);

llvm/lib/Transforms/Scalar/EarlyCSE.cpp

for (Instruction &Inst : make_early_inc_range(BB->getInstList())) {
     if (isInstructionTriviallyDead(&Inst, &TLI)) {
       LLVM_DEBUG(dbgs() << "EarlyCSE DCE: " << Inst << '\n');
       if (!DebugCounter::shouldExecute(CSECounter)) {
         LLVM_DEBUG(dbgs() << "Skipping due to debug counter\n");
         continue;
       }
 
       salvageKnowledge(&Inst, &AC);
-      salvageDebugInfo(Inst);
+      Inst.salvageDebugInfo();
       removeMSSA(Inst);
       Inst.eraseFromParent();
       Changed = true;
       ++NumSimplify;
       continue;
     }
 
     // Skip assume intrinsics, they don't really have side effects (although

llvm/lib/Transforms/Scalar/GVN.cpp

for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
     bool AtStart = BI == BB->begin();
     if (!AtStart)
       --BI;
 
     for (auto *I : InstrsToErase) {
       assert(I->getParent() == BB && "Removing instruction from wrong block?");
       LLVM_DEBUG(dbgs() << "GVN removed: " << *I << '\n');
       salvageKnowledge(I, AC);
-      salvageDebugInfo(*I);
+      I->salvageDebugInfo();
       if (MD) MD->removeInstruction(I);
       if (MSSAU)
         MSSAU->removeMemoryAccess(I);
       LLVM_DEBUG(verifyRemoved(I));
       ICF->removeInstruction(I);
       I->eraseFromParent();
     }
     InstrsToErase.clear();

llvm/lib/Transforms/Scalar/LICM.cpp

for (DomTreeNode *DTN : reverse(Worklist)) {
     for (BasicBlock::iterator II = BB->end(); II != BB->begin();) {
       Instruction &I = *--II;
 
       // If the instruction is dead, we would try to sink it because it isn't
       // used in the loop, instead, just delete it.
       if (isInstructionTriviallyDead(&I, TLI)) {
         LLVM_DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n');
         salvageKnowledge(&I);
-        salvageDebugInfo(I);
+        I.salvageDebugInfo();
         ++II;
         eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
         Changed = true;
         continue;
       }
 
       // Check to see if we can sink this instruction to the exit blocks
       // of the loop.  We can do this if the all users of the instruction are
       // outside of the loop.  In this case, it doesn't even matter if the
       // operands of the instruction are loop invariant.
       //
       bool FreeInLoop = false;
       if (!I.mayHaveSideEffects() &&
           isNotUsedOrFreeInLoop(I, CurLoop, SafetyInfo, TTI, FreeInLoop) &&
           canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags,
                              ORE)) {
         if (sink(I, LI, DT, BFI, CurLoop, SafetyInfo, MSSAU, ORE)) {
           if (!FreeInLoop) {
             ++II;
-            salvageDebugInfo(I);
+            I.salvageDebugInfo();
             eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
           }
           Changed = true;
         }
       }
     }
   }
   if (MSSAU && VerifyMemorySSA)

llvm/lib/Transforms/Scalar/Reassociate.cpp

 // Insts so they will be removed as well.
 void ReassociatePass::RecursivelyEraseDeadInsts(Instruction *I,
                                                 OrderedSet &Insts) {
   assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
   SmallVector<Value *, 4> Ops(I->op_begin(), I->op_end());
   ValueRankMap.erase(I);
   Insts.remove(I);
   RedoInsts.remove(I);
-  llvm::salvageDebugInfo(*I);
+  I->salvageDebugInfo();
   I->eraseFromParent();
   for (auto Op : Ops)
     if (Instruction *OpInst = dyn_cast<Instruction>(Op))
       if (OpInst->use_empty())
         Insts.insert(OpInst);
 }
 
 /// Zap the given instruction, adding interesting operands to the work list.
 void ReassociatePass::EraseInst(Instruction *I) {
   assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
   LLVM_DEBUG(dbgs() << "Erasing dead inst: "; I->dump());
 
   SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
   // Erase the dead instruction.
   ValueRankMap.erase(I);
   RedoInsts.remove(I);
-  llvm::salvageDebugInfo(*I);
+  I->salvageDebugInfo();
   I->eraseFromParent();
   // Optimize its operands.
   SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
   for (unsigned i = 0, e = Ops.size(); i != e; ++i)
     if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
       // If this is a node in an expression tree, climb to the expression root
       // and add that since that's where optimization actually happens.
       unsigned Opcode = Op->getOpcode();

llvm/lib/Transforms/Utils/CodeExtractor.cpp

TI->setMetadata(
       MDBuilder(TI->getContext()).createBranchWeights(BranchWeights));
 }
 
 /// Erase debug info intrinsics which refer to values in \p F but aren't in
 /// \p F.
 static void eraseDebugIntrinsicsWithNonLocalRefs(Function &F) {
   for (Instruction &I : instructions(F)) {
     SmallVector<DbgVariableIntrinsic *, 4> DbgUsers;
-    findDbgUsers(DbgUsers, &I);
+    I.findDbgUsers(DbgUsers);
     for (DbgVariableIntrinsic *DVI : DbgUsers)
       if (DVI->getFunction() != &F)
         DVI->eraseFromParent();
   }
 }
 
 /// Fix up the debug info in the old and new functions by pointing line
 /// locations and debug intrinsics to the new subprogram scope, and by deleting

llvm/lib/Transforms/Utils/Local.cpp

while (!DeadInsts.empty()) {
     Instruction *I = cast_or_null<Instruction>(V);
     if (!I)
       continue;
     assert(isInstructionTriviallyDead(I, TLI) &&
            "Live instruction found in dead worklist!");
     assert(I->use_empty() && "Instructions with uses are not dead.");
 
     // Don't lose the debug info while deleting the instructions.
-    salvageDebugInfo(*I);
+    I->salvageDebugInfo();
 
     if (AboutToDeleteCallback)
       AboutToDeleteCallback(I);
 
     // Null out all of the instruction's operands to see if any operand becomes
     // dead as we go.
     for (Use &OpU : I->operands()) {
       Value *OpV = OpU.get();
if (MSSAU)
       MSSAU->removeMemoryAccess(I);
 
     I->eraseFromParent();
   }
 }
 
 bool llvm::replaceDbgUsesWithUndef(Instruction *I) {
   SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
-  findDbgUsers(DbgUsers, I);
+  I->findDbgUsers(DbgUsers);
   for (auto *DII : DbgUsers) {
     Value *Undef = UndefValue::get(I->getType());
     DII->setOperand(0, MetadataAsValue::get(DII->getContext(),
                                             ValueAsMetadata::get(Undef)));
   }
   return !DbgUsers.empty();
 }
 

 }
 
 static bool
 simplifyAndDCEInstruction(Instruction *I,
                           SmallSetVector<Instruction *, 16> &WorkList,
                           const DataLayout &DL,
                           const TargetLibraryInfo *TLI) {
   if (isInstructionTriviallyDead(I, TLI)) {
-    salvageDebugInfo(*I);
+    I->salvageDebugInfo();
 
     // Null out all of the instruction's operands to see if any operand becomes
     // dead as we go.
     for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
       Value *OpV = I->getOperand(i);
       I->setOperand(i, nullptr);
 
       if (!OpV->use_empty() || I == OpV)
if (!V->isUsedByMetadata())
     return;
   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);
 }
 
-void llvm::findDbgUsers(SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers,
-                        Value *V) {
-  // This function is hot. Check whether the value has any metadata to avoid a
-  // DenseMap lookup.
-  if (!V->isUsedByMetadata())
-    return;
-  if (auto *L = LocalAsMetadata::getIfExists(V))
-    if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
-      for (User *U : MDV->users())
-        if (DbgVariableIntrinsic *DII = dyn_cast<DbgVariableIntrinsic>(U))
-          DbgUsers.push_back(DII);
-}
-
 bool llvm::replaceDbgDeclare(Value *Address, Value *NewAddress,
                              DIBuilder &Builder, uint8_t DIExprFlags,
                              int Offset) {
   auto DbgAddrs = FindDbgAddrUses(Address);
   for (DbgVariableIntrinsic *DII : DbgAddrs) {
     DebugLoc Loc = DII->getDebugLoc();
     auto *DIVar = DII->getVariable();
     auto *DIExpr = DII->getExpression();
if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L))
       }
 }
 
 /// Wrap \p V in a ValueAsMetadata instance.
 static MetadataAsValue *wrapValueInMetadata(LLVMContext &C, Value *V) {
   return MetadataAsValue::get(C, ValueAsMetadata::get(V));
 }
 
-/// Where possible to salvage debug information for \p I do so
-/// and return True. If not possible mark undef and return False.
-void llvm::salvageDebugInfo(Instruction &I) {
-  SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
-  findDbgUsers(DbgUsers, &I);
-  salvageDebugInfoForDbgValues(I, DbgUsers);
-}
-
-void llvm::salvageDebugInfoForDbgValues(
-    Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers) {
-  auto &Ctx = I.getContext();
-  bool Salvaged = false;
-  auto wrapMD = [&](Value *V) { return wrapValueInMetadata(Ctx, V); };
-
-  for (auto *DII : DbgUsers) {
-    // Do not add DW_OP_stack_value for DbgDeclare and DbgAddr, because they
-    // are implicitly pointing out the value as a DWARF memory location
-    // description.
-    bool StackValue = isa<DbgValueInst>(DII);
-
-    DIExpression *DIExpr =
-        salvageDebugInfoImpl(I, DII->getExpression(), StackValue);
-
-    // salvageDebugInfoImpl should fail on examining the first element of
-    // DbgUsers, or none of them.
-    if (!DIExpr)
-      break;
-
-    DII->setOperand(0, wrapMD(I.getOperand(0)));
-    DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr));
-    LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
-    Salvaged = true;
-  }
-
-  if (Salvaged)
-    return;
-
-  for (auto *DII : DbgUsers) {
-    Value *Undef = UndefValue::get(I.getType());
-    DII->setOperand(0, MetadataAsValue::get(DII->getContext(),
-                                            ValueAsMetadata::get(Undef)));
-  }
-}
-
-DIExpression *llvm::salvageDebugInfoImpl(Instruction &I,
-                                         DIExpression *SrcDIExpr,
-                                         bool WithStackValue) {
-  auto &M = *I.getModule();
-  auto &DL = M.getDataLayout();
-
-  // Apply a vector of opcodes to the source DIExpression.
-  auto doSalvage = [&](SmallVectorImpl<uint64_t> &Ops) -> DIExpression * {
-    DIExpression *DIExpr = SrcDIExpr;
-    if (!Ops.empty()) {
-      DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, WithStackValue);
-    }
-    return DIExpr;
-  };
-
-  // Apply the given offset to the source DIExpression.
-  auto applyOffset = [&](uint64_t Offset) -> DIExpression * {
-    SmallVector<uint64_t, 8> Ops;
-    DIExpression::appendOffset(Ops, Offset);
-    return doSalvage(Ops);
-  };
-
-  // initializer-list helper for applying operators to the source DIExpression.
-  auto applyOps = [&](ArrayRef<uint64_t> Opcodes) -> DIExpression * {
-    SmallVector<uint64_t, 8> Ops(Opcodes.begin(), Opcodes.end());
-    return doSalvage(Ops);
-  };
-
-  if (auto *CI = dyn_cast<CastInst>(&I)) {
-    // No-op casts are irrelevant for debug info.
-    if (CI->isNoopCast(DL))
-      return SrcDIExpr;
-
-    Type *Type = CI->getType();
-    // Casts other than Trunc, SExt, or ZExt to scalar types cannot be salvaged.
-    if (Type->isVectorTy() ||
-        !(isa<TruncInst>(&I) || isa<SExtInst>(&I) || isa<ZExtInst>(&I)))
-      return nullptr;
-
-    Value *FromValue = CI->getOperand(0);
-    unsigned FromTypeBitSize = FromValue->getType()->getScalarSizeInBits();
-    unsigned ToTypeBitSize = Type->getScalarSizeInBits();
-
-    return applyOps(DIExpression::getExtOps(FromTypeBitSize, ToTypeBitSize,
-                                            isa<SExtInst>(&I)));
-  }
-
-  if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
-    unsigned BitWidth =
-        M.getDataLayout().getIndexSizeInBits(GEP->getPointerAddressSpace());
-    // Rewrite a constant GEP into a DIExpression.
-    APInt Offset(BitWidth, 0);
-    if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
-      return applyOffset(Offset.getSExtValue());
-    } else {
-      return nullptr;
-    }
-  } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
-    // Rewrite binary operations with constant integer operands.
-    auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1));
-    if (!ConstInt || ConstInt->getBitWidth() > 64)
-      return nullptr;
-
-    uint64_t Val = ConstInt->getSExtValue();
-    switch (BI->getOpcode()) {
-    case Instruction::Add:
-      return applyOffset(Val);
-    case Instruction::Sub:
-      return applyOffset(-int64_t(Val));
-    case Instruction::Mul:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mul});
-    case Instruction::SDiv:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_div});
-    case Instruction::SRem:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_mod});
-    case Instruction::Or:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_or});
-    case Instruction::And:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_and});
-    case Instruction::Xor:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_xor});
-    case Instruction::Shl:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shl});
-    case Instruction::LShr:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shr});
-    case Instruction::AShr:
-      return applyOps({dwarf::DW_OP_constu, Val, dwarf::DW_OP_shra});
-    default:
-      // TODO: Salvage constants from each kind of binop we know about.
-      return nullptr;
-    }
-    // *Not* to do: we should not attempt to salvage load instructions,
-    // because the validity and lifetime of a dbg.value containing
-    // DW_OP_deref becomes difficult to analyze. See PR40628 for examples.
-  }
-  return nullptr;
-}
-
 /// A replacement for a dbg.value expression.
 using DbgValReplacement = Optional<DIExpression *>;
 
 /// Point debug users of \p From to \p To using exprs given by \p RewriteExpr,
 /// possibly moving/undefing users to prevent use-before-def. Returns true if
 /// changes are made.
 static bool rewriteDebugUsers(
     Instruction &From, Value &To, Instruction &DomPoint, DominatorTree &DT,
     function_ref<DbgValReplacement(DbgVariableIntrinsic &DII)> RewriteExpr) {
   // Find debug users of From.
   SmallVector<DbgVariableIntrinsic *, 1> Users;
-  findDbgUsers(Users, &From);
+  From.findDbgUsers(Users);
   if (Users.empty())
     return false;
 
   // Prevent use-before-def of To.
   bool Changed = false;
   SmallPtrSet<DbgVariableIntrinsic *, 1> UndefOrSalvage;
   if (isa<Instruction>(&To)) {
     bool DomPointAfterFrom = From.getNextNonDebugInstruction() == &DomPoint;
for (auto *DII : Users) {
     DII->setOperand(0, wrapValueInMetadata(Ctx, &To));
     DII->setOperand(2, MetadataAsValue::get(Ctx, *DVR));
     LLVM_DEBUG(dbgs() << "REWRITE:  " << *DII << '\n');
     Changed = true;
   }
 
   if (!UndefOrSalvage.empty()) {
     // Try to salvage the remaining debug users.
-    salvageDebugInfo(From);
+    From.salvageDebugInfo();
     Changed = true;
   }
 
   return Changed;
 }
 
 /// Check if a bitcast between a value of type \p FromTy to type \p ToTy would
 /// losslessly preserve the bits and semantics of the value. This predicate is
void llvm::copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI,
   if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
     MDNode *NN = MDNode::get(OldLI.getContext(), None);
     NewLI.setMetadata(LLVMContext::MD_nonnull, NN);
   }
 }
 
 void llvm::dropDebugUsers(Instruction &I) {
   SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
-  findDbgUsers(DbgUsers, &I);
+  I.findDbgUsers(DbgUsers);
   for (auto *DII : DbgUsers)
     DII->eraseFromParent();
 }
 
 void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
                                     BasicBlock *BB) {
   // Since we are moving the instructions out of its basic block, we do not
   // retain their original debug locations (DILocations) and debug intrinsic

llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp

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;
       }
     }
 
-    findDbgUsers(DbgUsers, AI);
+    AI->findDbgUsers(DbgUsers);
   }
 };
 
 /// Data package used by RenamePass().
 struct RenamePassData {
   using ValVector = std::vector<Value *>;
   using LocationVector = std::vector<DebugLoc>;
 

llvm/test/DebugInfo/X86/implicit_pointer_temp_dyn_alloc.cc

+// RUN: clang %s -O2 -gdwarf-5 -S -emit-llvm -o %t.ll
+// RUN: FileCheck %s --input-file=%t.ll
+
+int main() {
+  int *i = new int(3);
+  int *j = new int(4);
+  // CHECK:  call void @llvm.dbg.value(metadata i32 3, metadata [[MD1:!.+]], metadata !DIExpression(DW_OP_LLVM_explicit_pointer))
+  // CHECK:  call void @llvm.dbg.value(metadata i32 4, metadata [[MD2:!.+]], metadata !DIExpression(DW_OP_LLVM_explicit_pointer))
+  delete i;
+  delete j;
+
+  return 0;
+}
+// CHECK: [[MD1]] = !DILocalVariable(name: "i"
+// CHECK: [[MD2]] = !DILocalVariable(name: "j"

llvm/unittests/IR/DebugInfoTest.cpp

)");
 
   // Find %b = add ...
   Instruction &I = *M->getFunction("f")->getEntryBlock().getFirstNonPHI();
 
   // Find the dbg.value using %b.
   SmallVector<DbgValueInst *, 1> DVIs;
   findDbgValues(DVIs, &I);
 
-  // Delete %b. The dbg.value should now point to undef.
+  // Delete %b. The dbg.value should now point to %a.
   I.eraseFromParent();
-  EXPECT_TRUE(isa<UndefValue>(DVIs[0]->getValue()));
+  EXPECT_FALSE(isa<UndefValue>(DVIs[0]->getValue()));
 }
 
 TEST(DIBuilder, CreateFortranArrayTypeWithAttributes) {
   LLVMContext Ctx;
   std::unique_ptr<Module> M(new Module("MyModule", Ctx));
   DIBuilder DIB(*M);
 
   DISubrange *Subrange = DIB.getOrCreateSubrange(1,1);

llvm/unittests/Transforms/Utils/LocalTest.cpp

TEST(Local, ReplaceAllDbgUsesWith) {
   // Simulate i32 <-> <2 x i16> conversion. This is unsupported.
   EXPECT_FALSE(replaceAllDbgUsesWith(E, A, A, DT));
   EXPECT_FALSE(replaceAllDbgUsesWith(A, E, E, DT));
 
   // Simulate i32* <-> i64* conversion.
   EXPECT_TRUE(replaceAllDbgUsesWith(D, C, C, DT));
 
   SmallVector<DbgVariableIntrinsic *, 2> CDbgVals;
-  findDbgUsers(CDbgVals, &C);
+  C.findDbgUsers(CDbgVals);
   EXPECT_EQ(2U, CDbgVals.size());
   EXPECT_TRUE(any_of(CDbgVals, [](DbgVariableIntrinsic *DII) {
     return isa<DbgAddrIntrinsic>(DII);
   }));
   EXPECT_TRUE(any_of(CDbgVals, [](DbgVariableIntrinsic *DII) {
     return isa<DbgDeclareInst>(DII);
   }));
 
   EXPECT_TRUE(replaceAllDbgUsesWith(C, D, D, DT));
 
   SmallVector<DbgVariableIntrinsic *, 2> DDbgVals;
-  findDbgUsers(DDbgVals, &D);
+  D.findDbgUsers(DDbgVals);
   EXPECT_EQ(2U, DDbgVals.size());
   EXPECT_TRUE(any_of(DDbgVals, [](DbgVariableIntrinsic *DII) {
     return isa<DbgAddrIntrinsic>(DII);
   }));
   EXPECT_TRUE(any_of(DDbgVals, [](DbgVariableIntrinsic *DII) {
     return isa<DbgDeclareInst>(DII);
   }));