[DebugInfo] Support for DW_OP_implicit_pointer (for InstComb optimization)

[alok]

Summary

This patch (9/N) stems from D69787

Summary:
  This modification should include most optimizations under the scope of DW_OP_implicit_pointer, though only InstComb optimization has been validated.

  It makes more sense to give a try to preserve debug info whenever an instruction is being erased. In place of doing salvaging before any call-site where Instruction::eraseFromParent is being called, this modification makes salvaging part of deletion method itself. To do this salvaging methods have been moved from file Transforms/Utils/Local.cpp to files llvm/lib/IR/Instruction.cpp and llvm/lib/IR/Value.cpp

Testing:
  - Added unit tests for validation of LLVM IR and object file thru llvm-dwarfdump
  - check-llvm, and an end-to-end test using gnu GDB to debug an optimized
     program (LLDB need to be enhanced to support).
  - check-debuginfo (the debug info integration tests)

[alok]

Updated to rebase due to changes in trunk and parent patches.

[alok]

Updated to rebase due to change in parent patch D70260.

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.
+  bool 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.
+  bool 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/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/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

 /// 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.addr intrinsics.
 TinyPtrVector<DbgVariableIntrinsic *> FindDbgAddrUses(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,
                        Instruction *InsertBefore, DIBuilder &Builder,
                        uint8_t DIExprFlags, int Offset);

 /// the instructions they replace.
 void replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
                               DIBuilder &Builder, int Offset = 0);
 
 /// Finds alloca where the value comes from.
 AllocaInst *findAllocaForValue(Value *V,
                                DenseMap<Value *, AllocaInst *> &AllocaForValue);
 
-/// 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.
-/// Returns true if any debug users were updated.
-bool salvageDebugInfo(Instruction &I);
-
 /// Salvage all debug users of the instruction \p I or mark it as undef if it
 /// cannot be salvaged.
 void salvageDebugInfoOrMarkUndef(Instruction &I);
 
-/// Implementation of salvageDebugInfo, applying only to instructions in
-/// \p Insns, rather than all debug users of \p I.
-bool 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);
-
 /// 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
 ///     \p To will be inserted after.

llvm/lib/CodeGen/CodeGenPrepare.cpp

for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
     // Replace a use of the cast with a use of the new cast.
     TheUse = InsertedCast;
     MadeChange = true;
     ++NumCastUses;
   }
 
   // If we removed all uses, nuke the cast.
   if (CI->use_empty()) {
-    salvageDebugInfo(*CI);
     CI->eraseFromParent();
     MadeChange = true;
   }
 
   return MadeChange;
 }
 
 /// If the specified cast instruction is a noop copy (e.g. it's casting from
for (Value::user_iterator UI = ShiftI->user_begin(), E = ShiftI->user_end();
     }
 
     // Replace a use of the shift with a use of the new shift.
     TheUse = InsertedShift;
   }
 
   // If we removed all uses, or there are none, nuke the shift.
   if (ShiftI->use_empty()) {
-    salvageDebugInfo(*ShiftI);
     ShiftI->eraseFromParent();
     MadeChange = true;
   }
 
   return MadeChange;
 }
 
 /// If counting leading or trailing zeros is an expensive operation and a zero

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/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/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);
 }

 void Instruction::setProfWeight(uint64_t W) {
   assert(isa<CallBase>(this) &&
          "Can only set weights for call like instructions");
   SmallVector<uint32_t, 1> Weights;
   Weights.push_back(W);
   MDBuilder MDB(getContext());
   setMetadata(LLVMContext::MD_prof, MDB.createBranchWeights(Weights));
 }
+
+bool 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 false;
+
+  // 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 false;
+
+  return salvageDebugInfoForDbgValues(DbgUsers);
+}
+
+bool Instruction::salvageDebugInfoForDbgValues(
+    ArrayRef<DbgVariableIntrinsic *> DbgUsers) {
+  auto &Ctx = getContext();
+  auto wrapMD = [&](Value *V) {
+    return MetadataAsValue::get(Ctx, ValueAsMetadata::get(V));
+  };
+  bool Changed = false;
+  Value *DebugDeclareAddress = nullptr;
+
+  if ((getModule()->getDwarfVersion() >= 5) && 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);
+  }
+
+  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 (isa<AllocaInst>(this) &&
+        (!DebugDeclareAddress || DII->isAddressOfVariable() ||
+         !DII->getExpression()->extractIfOffset(ExprOffset)))
+      continue;
+
+    if (isa<AllocaInst>(this)) {
+      // It will cause below transformation
+      //
+      // Before transformation
+      //
+      // %a = alloca [2 x i32], align 4
+      // call void @llvm.dbg.declare(metadata [2 x i32]* %arr, metadata !16,
+      // metadata !DIExpression()), !dbg !22
+      //
+      // call void @llvm.dbg.value(metadata [2 x i32]* %arr, metadata !20,
+      // metadata !DIExpression()), !dbg !24
+      //
+      // call void @llvm.dbg.value(metadata [2 x i32]* %arr, metadata !20,
+      // metadata !DIExpression(DW_OP_plus_uconst, 4, DW_OP_stack_value)),
+      // !dbg !24
+      //
+      // !16 = !DILocalVariable(name: "arr", scope: !12, file: !3, line: 5,
+      // type: !17) !20 = !DILocalVariable(name: "ptr", scope: !12, file: !3,
+      // line: 6, type: !21)
+      //
+      //
+      // After transformation
+      //
+      // %a = alloca [2 x i32], align 4
+      // call void @llvm.dbg.declare(metadata [2 x i32]* %arr, metadata !16,
+      // metadata !DIExpression()), !dbg !22
+      //
+      // call void @llvm.dbg.derefval(metadata !16, metadata !20, metadata
+      // !DIExpression(DW_OP_LLVM_implicit_pointer, DW_OP_LLVM_arg0, 0)), !dbg
+      // !24
+      //
+      // call void @llvm.dbg.derefval(metadata !16, metadata !20, metadata
+      //  !DIExpression(DW_OP_LLVM_implicit_pointer, DW_OP_LLVM_arg0, 4)), !dbg
+      //  !24
+      //
+      SmallVector<uint64_t, 8> Ops;
+      Ops.push_back(dwarf::DW_OP_LLVM_implicit_pointer);
+      Ops.push_back(dwarf::DW_OP_LLVM_arg0);
+      Ops.push_back(ExprOffset);
+      DIExpr = DIExpression::get(DIExpr->getContext(), Ops);
+      DIBuilder DIB(*getModule(), /*AllowUnresolved*/ false);
+      DIB.insertDbgDerefValueIntrinsic(DebugDeclareAddress,
+                            DII->getVariable(), DIExpr, 
+                            DII->getDebugLoc(), DII);
+      DII->eraseFromParent();
+    } else {
+      DII->setOperand(0, wrapMD(getOperand(0)));
+      DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr));
+      Changed = true;
+    }
+  }
+
+  return Changed;
+}
+
+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 =
+      [&](std::initializer_list<uint64_t> Opcodes) -> DIExpression * {
+    SmallVector<uint64_t, 8> Ops(Opcodes);
+    return doSalvage(Ops);
+  };
+
+  if (auto *CI = dyn_cast<CastInst>(this)) {
+    // No-op casts and zexts are irrelevant for debug info.
+    if (CI->isNoopCast(DL) || isa<ZExtInst>(this))
+      return SrcDIExpr;
+    return nullptr;
+  } else 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/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/InstructionCombining.cpp

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);
   for (auto *DII : reverse(DbgUsers)) {
     if (DII->getParent() == SrcBlock) {
       if (isa<DbgDeclareInst>(DII)) {
         // A dbg.declare instruction should not be cloned, since there can only be
         // one per variable fragment. It should be left in the original place since
         // sunk instruction is not an alloca(otherwise we could not be here).
         // But we need to update arguments of dbg.declare instruction, so that it
         // would not point into sunk instruction.
         if (!isa<CastInst>(I))
           continue; // dbg.declare points at something it shouldn't
 
         DII->setOperand(
             0, MetadataAsValue::get(I->getContext(),
                                     ValueAsMetadata::get(I->getOperand(0))));
         continue;
       }
 
       // dbg.value is in the same basic block as the sunk inst, see if we can
       // salvage it. Clone a new copy of the instruction: on success we need
       // both salvaged and unsalvaged copies.
       SmallVector<DbgVariableIntrinsic *, 1> TmpUser{
           cast<DbgVariableIntrinsic>(DII->clone())};
 
-      if (!salvageDebugInfoForDbgValues(*I, TmpUser)) {
+      if (!I->salvageDebugInfoForDbgValues(TmpUser)) {
         // We are unable to salvage: sink the cloned dbg.value, and mark the
         // original as undef, terminating any earlier variable location.
         LLVM_DEBUG(dbgs() << "SINK: " << *DII << '\n');
         TmpUser[0]->insertBefore(&*InsertPos);
         Value *Undef = UndefValue::get(I->getType());
         DII->setOperand(0, MetadataAsValue::get(DII->getContext(),
                                                 ValueAsMetadata::get(Undef)));
       } else {

llvm/lib/Transforms/Scalar/DCE.cpp

bool runOnFunction(Function &F) override {
 
     bool Changed = false;
     for (auto &BB : F) {
       for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) {
         Instruction *Inst = &*DI++;
         if (isInstructionTriviallyDead(Inst, TLI)) {
           if (!DebugCounter::shouldExecute(DCECounter))
             continue;
-          salvageDebugInfo(*Inst);
           Inst->eraseFromParent();
           Changed = true;
           ++DIEEliminated;
         }
       }
     }
     return Changed;
   }

 
 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();
 
     // 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)

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

deleteDeadInstruction(Instruction *I, BasicBlock::iterator *BBI,
   BasicBlock::iterator NewIter = *BBI;
 
   // Before we touch this instruction, remove it from memdep!
   do {
     Instruction *DeadInst = NowDeadInsts.pop_back_val();
     ++NumFastOther;
 
     // Try to preserve debug information attached to the dead instruction.
-    salvageDebugInfo(*DeadInst);
+    DeadInst->salvageDebugInfo();
 
     // 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) {
       Value *Op = DeadInst->getOperand(op);

llvm/lib/Transforms/Scalar/EarlyCSE.cpp

for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
 
     // Dead instructions should just be removed.
     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;
       }
-      if (!salvageDebugInfo(*Inst))
+      if (!Inst->salvageDebugInfo())
         replaceDbgUsesWithUndef(Inst);
       removeMSSA(Inst);
       Inst->eraseFromParent();
       Changed = true;
       ++NumSimplify;
       continue;
     }
 

llvm/lib/Transforms/Scalar/GVN.cpp

for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
     // Avoid iterator invalidation.
     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');
-      salvageDebugInfo(*I);
+      I->salvageDebugInfo();
       if (MD) MD->removeInstruction(I);
       LLVM_DEBUG(verifyRemoved(I));
       ICF->removeInstruction(I);
       I->eraseFromParent();
     }
     InstrsToErase.clear();
 
     if (AtStart)

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');
-        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

llvm/lib/Transforms/Scalar/SROA.cpp

bool SROA::runOnAlloca(AllocaInst &AI) {
   LLVM_DEBUG(AS.print(dbgs()));
   if (AS.isEscaped())
     return Changed;
 
   // Delete all the dead users of this alloca before splitting and rewriting it.
   for (Instruction *DeadUser : AS.getDeadUsers()) {
 
     // Try to preserve debug information attached to the instruction.
-    salvageDebugInfo(*DeadUser);
+    DeadUser->salvageDebugInfo();
 
     // Free up everything used by this instruction.
     for (Use &DeadOp : DeadUser->operands())
       clobberUse(DeadOp);
 
     // Now replace the uses of this instruction.
     DeadUser->replaceAllUsesWith(UndefValue::get(DeadUser->getType()));
 

 bool SROA::deleteDeadInstructions(
     SmallPtrSetImpl<AllocaInst *> &DeletedAllocas) {
   bool Changed = false;
   while (!DeadInsts.empty()) {
     Instruction *I = DeadInsts.pop_back_val();
     LLVM_DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n");
 
     // Try to preserve debug information attached to the dead instruction.
-    salvageDebugInfo(*I);
+    I->salvageDebugInfo();
     // If the instruction is an alloca, find the possible dbg.declare connected
     // to it, and remove it too. We must do this before calling RAUW or we will
     // not be able to find it.
     if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
       DeletedAllocas.insert(AI);
       for (DbgVariableIntrinsic *OldDII : FindDbgAddrUses(AI))
         OldDII->eraseFromParent();
     }

llvm/lib/Transforms/Utils/CodeExtractor.cpp

while (BlockIt != BB.end()) {
       ++BlockIt;
       if (isa<DbgInfoIntrinsic>(Inst))
         Inst->eraseFromParent();
     }
     // Remove debug info intrinsics which refer to values in the new function
     // from the old function.
     SmallVector<DbgVariableIntrinsic *, 4> DbgUsers;
     for (Instruction &I : BB)
-      findDbgUsers(DbgUsers, &I);
+      I.findDbgUsers(DbgUsers);
     for (DbgVariableIntrinsic *DVI : DbgUsers)
       DVI->eraseFromParent();
   }
 
   // Mark the new function `noreturn` if applicable. Terminators which resume
   // exception propagation are treated as returning instructions. This is to
   // avoid inserting traps after calls to outlined functions which unwind.
   bool doesNotReturn = none_of(*newFunction, [](const BasicBlock &BB) {

llvm/lib/Transforms/Utils/Local.cpp

void llvm::RecursivelyDeleteTriviallyDeadInstructions(
   // Process the dead instruction list until empty.
   while (!DeadInsts.empty()) {
     Instruction &I = *DeadInsts.pop_back_val();
     assert(I.use_empty() && "Instructions with uses are not dead.");
     assert(isInstructionTriviallyDead(&I, TLI) &&
            "Live instruction found in dead worklist!");
 
     // Don't lose the debug info while deleting the instructions.
-    salvageDebugInfo(I);
+    I.salvageDebugInfo();
 
     // 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();
       OpU.set(nullptr);
 
       if (!OpV->use_empty())
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 (llvm::any_of(AI->users(), [](User *U) -> bool {
           if (LoadInst *LI = dyn_cast<LoadInst>(U))
             return LI->isVolatile();
           if (StoreInst *SI = dyn_cast<StoreInst>(U))
             return SI->isVolatile();
           return false;
         }))
       continue;
 
+    // Try to preserve debug information attached to the instruction.
+    AI->salvageDebugInfo();
+
     for (auto &AIUse : AI->uses()) {
       User *U = AIUse.getUser();
       if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
         if (AIUse.getOperandNo() == 1)
           ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
       } else if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
         ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
       } else if (CallInst *CI = dyn_cast<CallInst>(U)) {
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,
                              Instruction *InsertBefore, 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));
 }
 
-bool llvm::salvageDebugInfo(Instruction &I) {
-  SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
-
-  // Return false if any of the operand is already deleted
-  for (unsigned i = 0; i < I.getNumOperands(); ++i)
-    if (!I.getOperand(i))
-      return false;
-
-  // Preserve the information we may need later when called function from
-  // current function is inlined. We need this information for
-  // DW_OP_LLVM_implicit_pointer.
-  if (auto DDI = dyn_cast<DbgVariableIntrinsic>(&I))
-    if (I.getModule()->getDwarfVersion() >= 5)
-      if (DDI->isAddressOfVariable())
-        I.getModule()->insertVarAddressMap(DDI);
-
-  findDbgUsers(DbgUsers, &I);
-  if (DbgUsers.empty())
-    return false;
-
-  return salvageDebugInfoForDbgValues(I, DbgUsers);
-}
-
 void llvm::salvageDebugInfoOrMarkUndef(Instruction &I) {
-  if (!salvageDebugInfo(I))
+  if (!I.salvageDebugInfo())
     replaceDbgUsesWithUndef(&I);
 }
 
-bool llvm::salvageDebugInfoForDbgValues(
-    Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers) {
-  auto &Ctx = I.getContext();
-  auto wrapMD = [&](Value *V) { return wrapValueInMetadata(Ctx, V); };
-  bool Changed = false;
-  Value *DebugDeclareAddress = nullptr;
-
-  if ((I.getModule()->getDwarfVersion() >= 5) && isa<AllocaInst>(I)) {
-    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 = I.getModule()->findVarAddressMap(&I);
-  }
-
-  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)
-      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 (isa<AllocaInst>(I) &&
-        (!DebugDeclareAddress || DII->isAddressOfVariable() ||
-         !DII->getExpression()->extractIfOffset(ExprOffset)))
-      continue;
-
-    if (isa<AllocaInst>(I)) {
-      // It will cause below transformation
-      //
-      // Before transformation
-      //
-      // %a = alloca [2 x i32], align 4
-      // call void @llvm.dbg.declare(metadata [2 x i32]* %arr, metadata !16,
-      // metadata !DIExpression()), !dbg !22
-      //
-      // call void @llvm.dbg.value(metadata [2 x i32]* %arr, metadata !20,
-      // metadata !DIExpression()), !dbg !24
-      //
-      // call void @llvm.dbg.value(metadata [2 x i32]* %arr, metadata !20,
-      // metadata !DIExpression(DW_OP_plus_uconst, 4, DW_OP_stack_value)),
-      // !dbg !24
-      //
-      // !16 = !DILocalVariable(name: "arr", scope: !12, file: !3, line: 5,
-      // type: !17) !20 = !DILocalVariable(name: "ptr", scope: !12, file: !3,
-      // line: 6, type: !21)
-      //
-      //
-      // After transformation
-      //
-      // %a = alloca [2 x i32], align 4
-      // call void @llvm.dbg.declare(metadata [2 x i32]* %arr, metadata !16,
-      // metadata !DIExpression()), !dbg !22
-      //
-      // call void @llvm.dbg.deref_value(metadata !16, metadata !20, metadata
-      // !DIExpression(DW_OP_LLVM_implicit_pointer, DW_OP_LLVM_arg0, 0)), !dbg
-      // !24
-      //
-      // call void @llvm.dbg.deref_value(metadata !16, metadata !20, metadata
-      //  !DIExpression(DW_OP_LLVM_implicit_pointer, DW_OP_LLVM_arg0, 4)), !dbg
-      //  !24
-      //
-      SmallVector<uint64_t, 8> Ops;
-      Ops.push_back(dwarf::DW_OP_LLVM_implicit_pointer);
-      Ops.push_back(dwarf::DW_OP_LLVM_arg0);
-      Ops.push_back(ExprOffset);
-      DIExpr = DIExpression::get(DIExpr->getContext(), Ops);
-      DIBuilder DIB(*I.getModule(), /*AllowUnresolved*/ false);
-      DIB.insertDbgDerefValueIntrinsic(DebugDeclareAddress,
-                            DII->getVariable(), DIExpr, 
-                            DII->getDebugLoc(), DII);
-      DII->eraseFromParent();
-    } else {
-      DII->setOperand(0, wrapMD(I.getOperand(0)));
-
-      DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr));
-      LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
-    }
-    Changed = true;
-  }
-
-  return Changed;
-}
-
-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 =
-      [&](std::initializer_list<uint64_t> Opcodes) -> DIExpression * {
-    SmallVector<uint64_t, 8> Ops(Opcodes);
-    return doSalvage(Ops);
-  };
-
-  if (auto *CI = dyn_cast<CastInst>(&I)) {
-    // No-op casts and zexts are irrelevant for debug info.
-    if (CI->isNoopCast(DL) || isa<ZExtInst>(&I))
-      return SrcDIExpr;
-    return nullptr;
-  } else 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.
-  } else if ((M.getDwarfVersion() >= 5) && isa<AllocaInst>(&I)) {
-    return SrcDIExpr;
-  }
-  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/deleting 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> DeleteOrSalvage;
   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 (!DeleteOrSalvage.empty()) {
     // Try to salvage the remaining debug users.
-    Changed |= salvageDebugInfo(From);
+    Changed |= From.salvageDebugInfo();
 
     // Delete the debug users which weren't salvaged.
     for (auto *DII : DeleteOrSalvage) {
       if (DII->getVariableLocation() == &From) {
         LLVM_DEBUG(dbgs() << "Erased UseBeforeDef:  " << *DII << '\n');
         DII->eraseFromParent();
         Changed = true;
       }
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;) {
     LBI.deleteValue(LI);
   }
 
   // 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.
 
   // Try to preserve debug information attached to the dead instruction.
-  salvageDebugInfo(*AI);
+  AI->salvageDebugInfo();
 
   // Record debuginfo for the store and remove the declaration's
   // debuginfo.
   for (DbgVariableIntrinsic *DII : Info.DbgDeclares) {
     DIBuilder DIB(*AI->getModule(), /*AllowUnresolved*/ false);
     ConvertDebugDeclareToDebugValue(DII, Info.OnlyStore, DIB);
     DII->eraseFromParent();
   }
if (I == StoresByIndex.begin()) {
       LI->replaceAllUsesWith(ReplVal);
     }
 
     LI->eraseFromParent();
     LBI.deleteValue(LI);
   }
 
   // Try to preserve debug information attached to the dead instruction.
-  salvageDebugInfo(*AI);
+  AI->salvageDebugInfo();
 
   // 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.
     for (DbgVariableIntrinsic *DII : Info.DbgDeclares) {
       DIBuilder DIB(*AI->getModule(), /*AllowUnresolved*/ false);
       ConvertDebugDeclareToDebugValue(DII, SI, DIB);

llvm/test/DebugInfo/dwarfdump-implicit_pointer_instcomb.c

+// RUN: clang %s -O2 -gdwarf-5 -o %t.o
+// RUN: llvm-dwarfdump  %t.o | FileCheck %s
+
+// CHECK-LABEL:  DW_AT_name    ("var")
+// CHECK-LABEL:  DW_TAG_variable
+// CHECK-NEXT:  DW_AT_location
+// CHECK-NEXT:  DW_OP_implicit_pointer [[DIE:0x.+]] +0
+
+// CHECK-LABEL:  DW_TAG_formal_parameter
+// CHECK-NEXT:  DW_AT_location
+// CHECK-NEXT:  DW_OP_implicit_pointer [[DIE]] +0
+// CHECK-NEXT:  "ptr"
+
+volatile int gvar = 7;
+
+int func(int *ptr) {
+  gvar = *ptr;
+  return *ptr + 5;
+}
+
+int main() {
+  int var = 4;
+  int *ptrVar = &var;
+
+  int res = func(ptrVar);
+
+  return res;
+}

llvm/test/DebugInfo/implicit_pointer_instcomb.c

+// RUN: clang %s -O2 -gdwarf-5 -S -emit-llvm -o %t.ll
+// RUN: FileCheck %s --input-file=%t.ll
+
+// CHECK:   !DIExpression(DW_OP_LLVM_implicit_pointer, DW_OP_LLVM_arg0, 0)
+// CHECK:   !DIExpression(DW_OP_LLVM_implicit_pointer, DW_OP_LLVM_arg0, 0)
+
+volatile int gvar = 7;
+
+int func(int *ptr) {
+  gvar = *ptr;
+  return *ptr + 5;
+}
+
+int main() {
+  int var = 4;
+  int *ptrVar = &var;
+
+  int res = func(ptrVar);
+
+  return res;
+}

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);
   }));