[DebugInfo] Shave even more users of DbgVariableIntrinsic from LLVM (#149136)

jmorse · web-flow · commit 2a1869b9815c · 2025-07-18T08:25:10.000+01:00
At this stage I'm just opportunistically deleting any code using
debug-intrinsic types, largely adjacent to calls to findDbgUsers. I'll
get to deleting that in probably one or more two commits.
diff --git a/llvm/include/llvm/IR/DebugInfo.h b/llvm/include/llvm/IR/DebugInfo.h
@@ -115,8 +115,7 @@ class DebugInfoFinder {
   LLVM_ABI void processVariable(DILocalVariable *DVI);
   /// Process debug info location.
   LLVM_ABI void processLocation(const Module &M, const DILocation *Loc);
-  /// Process a DbgRecord (e.g, treat a DbgVariableRecord like a
-  /// DbgVariableIntrinsic).
+  /// Process a DbgRecord.
   LLVM_ABI void processDbgRecord(const Module &M, const DbgRecord &DR);
 
   /// Process subprogram.
@@ -290,8 +289,6 @@ struct VarRecord {
   DILocalVariable *Var;
   DILocation *DL;
 
-  VarRecord(DbgVariableIntrinsic *DVI)
-      : Var(DVI->getVariable()), DL(getDebugValueLoc(DVI)) {}
   VarRecord(DbgVariableRecord *DVR)
       : Var(DVR->getVariable()), DL(getDebugValueLoc(DVR)) {}
   VarRecord(DILocalVariable *Var, DILocation *DL) : Var(Var), DL(DL) {}
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -66,7 +66,6 @@ namespace dwarf {
 enum Tag : uint16_t;
 }
 
-class DbgVariableIntrinsic;
 class DbgVariableRecord;
 
 LLVM_ABI extern cl::opt<bool> EnableFSDiscriminator;
@@ -4613,7 +4612,6 @@ class DebugVariable {
   LLVM_ABI static const FragmentInfo DefaultFragment;
 
 public:
-  LLVM_ABI DebugVariable(const DbgVariableIntrinsic *DII);
   LLVM_ABI DebugVariable(const DbgVariableRecord *DVR);
 
   DebugVariable(const DILocalVariable *Var,
@@ -4681,7 +4679,6 @@ template <> struct DenseMapInfo<DebugVariable> {
 /// information).
 class DebugVariableAggregate : public DebugVariable {
 public:
-  LLVM_ABI DebugVariableAggregate(const DbgVariableIntrinsic *DVI);
   DebugVariableAggregate(const DebugVariable &V)
       : DebugVariable(V.getVariable(), std::nullopt, V.getInlinedAt()) {}
 };
diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
@@ -2288,39 +2288,36 @@ bool AssignmentTrackingPass::runOnFunction(Function &F) {
   // Collect a map of {backing storage : dbg.declares} (currently "backing
   // storage" is limited to Allocas). We'll use this to find dbg.declares to
   // delete after running `trackAssignments`.
-  DenseMap<const AllocaInst *, SmallPtrSet<DbgDeclareInst *, 2>> DbgDeclares;
   DenseMap<const AllocaInst *, SmallPtrSet<DbgVariableRecord *, 2>> DVRDeclares;
   // Create another similar map of {storage : variables} that we'll pass to
   // trackAssignments.
   StorageToVarsMap Vars;
-  auto ProcessDeclare = [&](auto *Declare, auto &DeclareList) {
+  auto ProcessDeclare = [&](DbgVariableRecord &Declare) {
     // FIXME: trackAssignments doesn't let you specify any modifiers to the
     // variable (e.g. fragment) or location (e.g. offset), so we have to
     // leave dbg.declares with non-empty expressions in place.
-    if (Declare->getExpression()->getNumElements() != 0)
+    if (Declare.getExpression()->getNumElements() != 0)
       return;
-    if (!Declare->getAddress())
+    if (!Declare.getAddress())
       return;
     if (AllocaInst *Alloca =
-            dyn_cast<AllocaInst>(Declare->getAddress()->stripPointerCasts())) {
+            dyn_cast<AllocaInst>(Declare.getAddress()->stripPointerCasts())) {
       // FIXME: Skip VLAs for now (let these variables use dbg.declares).
       if (!Alloca->isStaticAlloca())
         return;
       // Similarly, skip scalable vectors (use dbg.declares instead).
       if (auto Sz = Alloca->getAllocationSize(*DL); Sz && Sz->isScalable())
         return;
-      DeclareList[Alloca].insert(Declare);
-      Vars[Alloca].insert(VarRecord(Declare));
+      DVRDeclares[Alloca].insert(&Declare);
+      Vars[Alloca].insert(VarRecord(&Declare));
     }
   };
   for (auto &BB : F) {
     for (auto &I : BB) {
       for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) {
         if (DVR.isDbgDeclare())
-          ProcessDeclare(&DVR, DVRDeclares);
+          ProcessDeclare(DVR);
       }
-      if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(&I))
-        ProcessDeclare(DDI, DbgDeclares);
     }
   }
 
@@ -2336,8 +2333,8 @@ bool AssignmentTrackingPass::runOnFunction(Function &F) {
   trackAssignments(F.begin(), F.end(), Vars, *DL);
 
   // Delete dbg.declares for variables now tracked with assignment tracking.
-  auto DeleteSubsumedDeclare = [&](const auto &Markers, auto &Declares) {
-    (void)Markers;
+  for (auto &[Insts, Declares] : DVRDeclares) {
+    auto Markers = at::getDVRAssignmentMarkers(Insts);
     for (auto *Declare : Declares) {
       // Assert that the alloca that Declare uses is now linked to a dbg.assign
       // describing the same variable (i.e. check that this dbg.declare has
@@ -2356,10 +2353,6 @@ bool AssignmentTrackingPass::runOnFunction(Function &F) {
       Changed = true;
     }
   };
-  for (auto &P : DbgDeclares)
-    DeleteSubsumedDeclare(at::getAssignmentMarkers(P.first), P.second);
-  for (auto &P : DVRDeclares)
-    DeleteSubsumedDeclare(at::getDVRAssignmentMarkers(P.first), P.second);
   return Changed;
 }
 
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -49,20 +49,11 @@ uint32_t DIType::getAlignInBits() const {
 const DIExpression::FragmentInfo DebugVariable::DefaultFragment = {
     std::numeric_limits<uint64_t>::max(), std::numeric_limits<uint64_t>::min()};
 
-DebugVariable::DebugVariable(const DbgVariableIntrinsic *DII)
-    : Variable(DII->getVariable()),
-      Fragment(DII->getExpression()->getFragmentInfo()),
-      InlinedAt(DII->getDebugLoc().getInlinedAt()) {}
-
 DebugVariable::DebugVariable(const DbgVariableRecord *DVR)
     : Variable(DVR->getVariable()),
       Fragment(DVR->getExpression()->getFragmentInfo()),
       InlinedAt(DVR->getDebugLoc().getInlinedAt()) {}
 
-DebugVariableAggregate::DebugVariableAggregate(const DbgVariableIntrinsic *DVI)
-    : DebugVariable(DVI->getVariable(), std::nullopt,
-                    DVI->getDebugLoc()->getInlinedAt()) {}
-
 DILocation::DILocation(LLVMContext &C, StorageType Storage, unsigned Line,
                        unsigned Column, uint64_t AtomGroup, uint8_t AtomRank,
                        ArrayRef<Metadata *> MDs, bool ImplicitCode)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -825,9 +825,6 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
   Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
 
   bool tryToSinkInstruction(Instruction *I, BasicBlock *DestBlock);
-  void tryToSinkInstructionDbgValues(
-      Instruction *I, BasicBlock::iterator InsertPos, BasicBlock *SrcBlock,
-      BasicBlock *DestBlock, SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers);
   void tryToSinkInstructionDbgVariableRecords(
       Instruction *I, BasicBlock::iterator InsertPos, BasicBlock *SrcBlock,
       BasicBlock *DestBlock, SmallVectorImpl<DbgVariableRecord *> &DPUsers);
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3575,6 +3575,7 @@ Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
   std::unique_ptr<DIBuilder> DIB;
   if (isa<AllocaInst>(MI)) {
     findDbgUsers(DVIs, &MI, &DVRs);
+    assert(DVIs.empty());
     DIB.reset(new DIBuilder(*MI.getModule(), /*AllowUnresolved=*/false));
   }
 
@@ -5253,8 +5254,7 @@ bool InstCombinerImpl::tryToSinkInstruction(Instruction *I,
   SmallVector<DbgVariableIntrinsic *, 2> DbgUsers;
   SmallVector<DbgVariableRecord *, 2> DbgVariableRecords;
   findDbgUsers(DbgUsers, I, &DbgVariableRecords);
-  if (!DbgUsers.empty())
-    tryToSinkInstructionDbgValues(I, InsertPos, SrcBlock, DestBlock, DbgUsers);
+  assert(DbgUsers.empty());
   if (!DbgVariableRecords.empty())
     tryToSinkInstructionDbgVariableRecords(I, InsertPos, SrcBlock, DestBlock,
                                            DbgVariableRecords);
@@ -5271,71 +5271,12 @@ bool InstCombinerImpl::tryToSinkInstruction(Instruction *I,
   return true;
 }
 
-void InstCombinerImpl::tryToSinkInstructionDbgValues(
-    Instruction *I, BasicBlock::iterator InsertPos, BasicBlock *SrcBlock,
-    BasicBlock *DestBlock, SmallVectorImpl<DbgVariableIntrinsic *> &DbgUsers) {
-  // For all debug values in the destination block, the sunk instruction
-  // will still be available, so they do not need to be dropped.
-  SmallVector<DbgVariableIntrinsic *, 2> DbgUsersToSalvage;
-  for (auto &DbgUser : DbgUsers)
-    if (DbgUser->getParent() != DestBlock)
-      DbgUsersToSalvage.push_back(DbgUser);
-
-  // Process the sinking DbgUsersToSalvage in reverse order, as we only want
-  // to clone the last appearing debug intrinsic for each given variable.
-  SmallVector<DbgVariableIntrinsic *, 2> DbgUsersToSink;
-  for (DbgVariableIntrinsic *DVI : DbgUsersToSalvage)
-    if (DVI->getParent() == SrcBlock)
-      DbgUsersToSink.push_back(DVI);
-  llvm::sort(DbgUsersToSink,
-             [](auto *A, auto *B) { return B->comesBefore(A); });
-
-  SmallVector<DbgVariableIntrinsic *, 2> DIIClones;
-  SmallSet<DebugVariable, 4> SunkVariables;
-  for (auto *User : DbgUsersToSink) {
-    // 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
-    // because the sunk instruction is not an alloca (otherwise we could not be
-    // here).
-    if (isa<DbgDeclareInst>(User))
-      continue;
-
-    DebugVariable DbgUserVariable =
-        DebugVariable(User->getVariable(), User->getExpression(),
-                      User->getDebugLoc()->getInlinedAt());
-
-    if (!SunkVariables.insert(DbgUserVariable).second)
-      continue;
-
-    // Leave dbg.assign intrinsics in their original positions and there should
-    // be no need to insert a clone.
-    if (isa<DbgAssignIntrinsic>(User))
-      continue;
-
-    DIIClones.emplace_back(cast<DbgVariableIntrinsic>(User->clone()));
-    if (isa<DbgDeclareInst>(User) && isa<CastInst>(I))
-      DIIClones.back()->replaceVariableLocationOp(I, I->getOperand(0));
-    LLVM_DEBUG(dbgs() << "CLONE: " << *DIIClones.back() << '\n');
-  }
-
-  // Perform salvaging without the clones, then sink the clones.
-  if (!DIIClones.empty()) {
-    salvageDebugInfoForDbgValues(*I, DbgUsersToSalvage, {});
-    // The clones are in reverse order of original appearance, reverse again to
-    // maintain the original order.
-    for (auto &DIIClone : llvm::reverse(DIIClones)) {
-      DIIClone->insertBefore(InsertPos);
-      LLVM_DEBUG(dbgs() << "SINK: " << *DIIClone << '\n');
-    }
-  }
-}
-
 void InstCombinerImpl::tryToSinkInstructionDbgVariableRecords(
     Instruction *I, BasicBlock::iterator InsertPos, BasicBlock *SrcBlock,
     BasicBlock *DestBlock,
     SmallVectorImpl<DbgVariableRecord *> &DbgVariableRecords) {
-  // Implementation of tryToSinkInstructionDbgValues, but for the
-  // DbgVariableRecord of variable assignments rather than dbg.values.
+  // For all debug values in the destination block, the sunk instruction
+  // will still be available, so they do not need to be dropped.
 
   // Fetch all DbgVariableRecords not already in the destination.
   SmallVector<DbgVariableRecord *, 2> DbgVariableRecordsToSalvage;
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -1489,6 +1489,7 @@ static bool checkAndReplaceCondition(
     SmallVector<DbgVariableIntrinsic *> DbgUsers;
     SmallVector<DbgVariableRecord *> DVRUsers;
     findDbgUsers(DbgUsers, Cmp, &DVRUsers);
+    assert(DbgUsers.empty());
 
     for (auto *DVR : DVRUsers) {
       auto *DTN = DT.getNode(DVR->getParent());
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -1222,9 +1222,7 @@ static void eraseDebugIntrinsicsWithNonLocalRefs(Function &F) {
     SmallVector<DbgVariableIntrinsic *, 4> DbgUsers;
     SmallVector<DbgVariableRecord *, 4> DbgVariableRecords;
     findDbgUsers(DbgUsers, &I, &DbgVariableRecords);
-    for (DbgVariableIntrinsic *DVI : DbgUsers)
-      if (DVI->getFunction() != &F)
-        DVI->eraseFromParent();
+    assert(DbgUsers.empty());
     for (DbgVariableRecord *DVR : DbgVariableRecords)
       if (DVR->getFunction() != &F)
         DVR->eraseFromParent();
@@ -1289,14 +1287,12 @@ static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
     SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
     SmallVector<DbgVariableRecord *, 1> DPUsers;
     findDbgUsers(DbgUsers, Input, &DPUsers);
+    assert(DbgUsers.empty());
     DIExpression *Expr = DIB.createExpression();
 
     // Iterate the debud users of the Input values. If they are in the extracted
     // function then update their location with the new value. If they are in
     // the parent function then create a similar debug record.
-    for (auto *DVI : DbgUsers)
-      UpdateOrInsertDebugRecord(DVI, Input, NewVal, Expr,
-                                isa<DbgDeclareInst>(DVI));
     for (auto *DVR : DPUsers)
       UpdateOrInsertDebugRecord(DVR, Input, NewVal, Expr, DVR->isDbgDeclare());
   }
diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1978,14 +1978,13 @@ static at::StorageToVarsMap collectEscapedLocals(const DataLayout &DL,
       continue;
 
     // Find all local variables associated with the backing storage.
-    auto CollectAssignsForStorage = [&](auto *DbgAssign) {
+    auto CollectAssignsForStorage = [&](DbgVariableRecord *DbgAssign) {
       // Skip variables from inlined functions - they are not local variables.
       if (DbgAssign->getDebugLoc().getInlinedAt())
         return;
       LLVM_DEBUG(errs() << " > DEF : " << *DbgAssign << "\n");
       EscapedLocals[Base].insert(at::VarRecord(DbgAssign));
     };
-    for_each(at::getAssignmentMarkers(Base), CollectAssignsForStorage);
     for_each(at::getDVRAssignmentMarkers(Base), CollectAssignsForStorage);
   }
   return EscapedLocals;
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
@@ -613,11 +613,10 @@ bool llvm::replaceDbgUsesWithUndef(Instruction *I) {
   SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
   SmallVector<DbgVariableRecord *, 1> DPUsers;
   findDbgUsers(DbgUsers, I, &DPUsers);
-  for (auto *DII : DbgUsers)
-    DII->setKillLocation();
+  assert(DbgUsers.empty());
   for (auto *DVR : DPUsers)
     DVR->setKillLocation();
-  return !DbgUsers.empty() || !DPUsers.empty();
+  return !DPUsers.empty();
 }
 
 /// areAllUsesEqual - Check whether the uses of a value are all the same.
@@ -2022,6 +2021,7 @@ void llvm::salvageDebugInfo(Instruction &I) {
   SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
   SmallVector<DbgVariableRecord *, 1> DPUsers;
   findDbgUsers(DbgUsers, &I, &DPUsers);
+  assert(DbgUsers.empty());
   salvageDebugInfoForDbgValues(I, DbgUsers, DPUsers);
 }
 
@@ -2070,66 +2070,9 @@ void llvm::salvageDebugInfoForDbgValues(
   const unsigned MaxExpressionSize = 128;
   bool Salvaged = false;
 
-  for (auto *DII : DbgUsers) {
-    if (auto *DAI = dyn_cast<DbgAssignIntrinsic>(DII)) {
-      if (DAI->getAddress() == &I) {
-        salvageDbgAssignAddress(DAI);
-        Salvaged = true;
-      }
-      if (DAI->getValue() != &I)
-        continue;
-    }
-
-    // Do not add DW_OP_stack_value for DbgDeclare, because they are implicitly
-    // pointing out the value as a DWARF memory location description.
-    bool StackValue = isa<DbgValueInst>(DII);
-    auto DIILocation = DII->location_ops();
-    assert(
-        is_contained(DIILocation, &I) &&
-        "DbgVariableIntrinsic must use salvaged instruction as its location");
-    SmallVector<Value *, 4> AdditionalValues;
-    // `I` may appear more than once in DII's location ops, and each use of `I`
-    // must be updated in the DIExpression and potentially have additional
-    // values added; thus we call salvageDebugInfoImpl for each `I` instance in
-    // DIILocation.
-    Value *Op0 = nullptr;
-    DIExpression *SalvagedExpr = DII->getExpression();
-    auto LocItr = find(DIILocation, &I);
-    while (SalvagedExpr && LocItr != DIILocation.end()) {
-      SmallVector<uint64_t, 16> Ops;
-      unsigned LocNo = std::distance(DIILocation.begin(), LocItr);
-      uint64_t CurrentLocOps = SalvagedExpr->getNumLocationOperands();
-      Op0 = salvageDebugInfoImpl(I, CurrentLocOps, Ops, AdditionalValues);
-      if (!Op0)
-        break;
-      SalvagedExpr =
-          DIExpression::appendOpsToArg(SalvagedExpr, Ops, LocNo, StackValue);
-      LocItr = std::find(++LocItr, DIILocation.end(), &I);
-    }
-    // salvageDebugInfoImpl should fail on examining the first element of
-    // DbgUsers, or none of them.
-    if (!Op0)
-      break;
+  // We should never see debug intrinsics nowadays.
+  assert(DbgUsers.empty());
 
-    SalvagedExpr = SalvagedExpr->foldConstantMath();
-    DII->replaceVariableLocationOp(&I, Op0);
-    bool IsValidSalvageExpr = SalvagedExpr->getNumElements() <= MaxExpressionSize;
-    if (AdditionalValues.empty() && IsValidSalvageExpr) {
-      DII->setExpression(SalvagedExpr);
-    } else if (isa<DbgValueInst>(DII) && IsValidSalvageExpr &&
-               DII->getNumVariableLocationOps() + AdditionalValues.size() <=
-                   MaxDebugArgs) {
-      DII->addVariableLocationOps(AdditionalValues, SalvagedExpr);
-    } else {
-      // Do not salvage using DIArgList for dbg.declare, as it is not currently
-      // supported in those instructions. Also do not salvage if the resulting
-      // DIArgList would contain an unreasonably large number of values.
-      DII->setKillLocation();
-    }
-    LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
-    Salvaged = true;
-  }
-  // Duplicate of above block for DbgVariableRecords.
   for (auto *DVR : DPUsers) {
     if (DVR->isDbgAssign()) {
       if (DVR->getAddress() == &I) {
@@ -2198,9 +2141,6 @@ void llvm::salvageDebugInfoForDbgValues(
   if (Salvaged)
     return;
 
-  for (auto *DII : DbgUsers)
-    DII->setKillLocation();
-
   for (auto *DVR : DPUsers)
     DVR->setKillLocation();
 }
@@ -3429,8 +3369,7 @@ void llvm::dropDebugUsers(Instruction &I) {
   SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
   SmallVector<DbgVariableRecord *, 1> DPUsers;
   findDbgUsers(DbgUsers, &I, &DPUsers);
-  for (auto *DII : DbgUsers)
-    DII->eraseFromParent();
+  assert(DbgUsers.empty());
   for (auto *DVR : DPUsers)
     DVR->eraseFromParent();
 }
diff --git a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
diff --git a/llvm/unittests/Transforms/Utils/DebugifyTest.cpp b/llvm/unittests/Transforms/Utils/DebugifyTest.cpp
diff --git a/llvm/unittests/Transforms/Utils/LocalTest.cpp b/llvm/unittests/Transforms/Utils/LocalTest.cpp
