Revert "Add option to generate additional debug info for expression dereferencing pointer to pointers. #94100"

[huangjd]

The option is causing the binary output to be different when compiled under -O0, because it introduce dbg.declare on pseudovariables. Going to change this implementation to use dbg.value instead.

[llvmbot]

@llvm/pr-subscribers-clang
@llvm/pr-subscribers-debuginfo

@llvm/pr-subscribers-clang-codegen

Author: William Junda Huang (huangjd)

Changes

The option is causing the binary output to be different when compiled under -O0, because it introduce dbg.declare on pseudovariables. Going to change this implementation to use dbg.value instead.

---

Full diff: https://github.com/llvm/llvm-project/pull/95174.diff

4 Files Affected:

• (modified) clang/lib/CodeGen/CGDebugInfo.cpp (-72)
• (modified) clang/lib/CodeGen/CGDebugInfo.h (-6)
• (modified) clang/lib/CodeGen/CGExprScalar.cpp (+1-20)
• (removed) clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp (-120)

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 11e2d549d8a45..99e12da0081af 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -5746,78 +5746,6 @@ void CGDebugInfo::EmitExternalVariable(llvm::GlobalVariable *Var,
   Var->addDebugInfo(GVE);
 }
 
-void CGDebugInfo::EmitPseudoVariable(CGBuilderTy &Builder,
-                                     llvm::Instruction *Value, QualType Ty) {
-  // Only when -g2 or above is specified, debug info for variables will be
-  // generated.
-  if (CGM.getCodeGenOpts().getDebugInfo() <=
-      llvm::codegenoptions::DebugLineTablesOnly)
-    return;
-
-  llvm::DebugLoc SaveDebugLoc = Builder.getCurrentDebugLocation();
-  if (!SaveDebugLoc.get())
-    return;
-
-  llvm::DIFile *Unit = SaveDebugLoc->getFile();
-  llvm::DIType *Type = getOrCreateType(Ty, Unit);
-
-  // Check if Value is already a declared variable and has debug info, in this
-  // case we have nothing to do. Clang emits declared variable as alloca, and
-  // it is loaded upon use, so we identify such pattern here.
-  if (llvm::LoadInst *Load = dyn_cast<llvm::LoadInst>(Value)) {
-    llvm::Value *Var = Load->getPointerOperand();
-    // There can be implicit type cast applied on a variable if it is an opaque
-    // ptr, in this case its debug info may not match the actual type of object
-    // being used as in the next instruction, so we will need to emit a pseudo
-    // variable for type-casted value.
-    auto DeclareTypeMatches = [&](auto *DbgDeclare) {
-      return DbgDeclare->getVariable()->getType() == Type;
-    };
-    if (any_of(llvm::findDbgDeclares(Var), DeclareTypeMatches) ||
-        any_of(llvm::findDVRDeclares(Var), DeclareTypeMatches))
-      return;
-  }
-
-  // Find the correct location to insert a sequence of instructions to
-  // materialize Value on the stack.
-  auto SaveInsertionPoint = Builder.saveIP();
-  if (llvm::InvokeInst *Invoke = dyn_cast<llvm::InvokeInst>(Value))
-    Builder.SetInsertPoint(Invoke->getNormalDest()->begin());
-  else if (llvm::Instruction *Next = Value->getIterator()->getNextNode())
-    Builder.SetInsertPoint(Next);
-  else
-    Builder.SetInsertPoint(Value->getParent());
-  llvm::DebugLoc DL = Value->getDebugLoc();
-  if (DL.get())
-    Builder.SetCurrentDebugLocation(DL);
-  else if (!Builder.getCurrentDebugLocation().get())
-    Builder.SetCurrentDebugLocation(SaveDebugLoc);
-
-  llvm::AllocaInst *PseudoVar = Builder.CreateAlloca(Value->getType());
-  Address PseudoVarAddr(PseudoVar, Value->getType(),
-                        CharUnits::fromQuantity(PseudoVar->getAlign()));
-  llvm::LoadInst *Load = Builder.CreateLoad(PseudoVarAddr);
-  Value->replaceAllUsesWith(Load);
-  Builder.SetInsertPoint(Load);
-  Builder.CreateStore(Value, PseudoVarAddr);
-
-  // Emit debug info for materialized Value.
-  unsigned Line = Builder.getCurrentDebugLocation().getLine();
-  unsigned Column = Builder.getCurrentDebugLocation().getCol();
-  llvm::DILocalVariable *D = DBuilder.createAutoVariable(
-      LexicalBlockStack.back(), "", nullptr, 0, Type, false,
-      llvm::DINode::FlagArtificial);
-  llvm::DILocation *DIL =
-      llvm::DILocation::get(CGM.getLLVMContext(), Line, Column,
-                            LexicalBlockStack.back(), CurInlinedAt);
-  SmallVector<uint64_t> Expr;
-  DBuilder.insertDeclare(PseudoVar, D, DBuilder.createExpression(Expr), DIL,
-                         Load);
-
-  Builder.restoreIP(SaveInsertionPoint);
-  Builder.SetCurrentDebugLocation(SaveDebugLoc);
-}
-
 void CGDebugInfo::EmitGlobalAlias(const llvm::GlobalValue *GV,
                                   const GlobalDecl GD) {
 
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index da466837aa3c3..8fe738be21568 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -530,12 +530,6 @@ class CGDebugInfo {
   /// Emit information about an external variable.
   void EmitExternalVariable(llvm::GlobalVariable *GV, const VarDecl *Decl);
 
-  /// Emit a pseudo variable and debug info for an intermediate value if it does
-  /// not correspond to a variable in the source code, so that a profiler can
-  /// track more accurate usage of certain instructions of interest.
-  void EmitPseudoVariable(CGBuilderTy &Builder, llvm::Instruction *Value,
-                          QualType Ty);
-
   /// Emit information about global variable alias.
   void EmitGlobalAlias(const llvm::GlobalValue *GV, const GlobalDecl Decl);
 
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 58f0a3113b4f8..1b144c178ce96 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -1937,26 +1937,7 @@ Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *E) {
     }
   }
 
-  llvm::Value *Result = EmitLoadOfLValue(E);
-
-  // If -fdebug-info-for-profiling is specified, emit a pseudo variable and its
-  // debug info for the pointer, even if there is no variable associated with
-  // the pointer's expression.
-  if (CGF.CGM.getCodeGenOpts().DebugInfoForProfiling && CGF.getDebugInfo()) {
-    if (llvm::LoadInst *Load = dyn_cast<llvm::LoadInst>(Result)) {
-      if (llvm::GetElementPtrInst *GEP =
-              dyn_cast<llvm::GetElementPtrInst>(Load->getPointerOperand())) {
-        if (llvm::Instruction *Pointer =
-                dyn_cast<llvm::Instruction>(GEP->getPointerOperand())) {
-          QualType Ty = E->getBase()->getType();
-          if (!E->isArrow())
-            Ty = CGF.getContext().getPointerType(Ty);
-          CGF.getDebugInfo()->EmitPseudoVariable(Builder, Pointer, Ty);
-        }
-      }
-    }
-  }
-  return Result;
+  return EmitLoadOfLValue(E);
 }
 
 Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
diff --git a/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp b/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
deleted file mode 100644
index baf791487771c..0000000000000
--- a/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
+++ /dev/null
@@ -1,120 +0,0 @@
-// Test debug info for intermediate value of a chained pointer deferencing
-// expression when the flag -fdebug-info-for-pointer-type is enabled.
-// RUN: %clang_cc1 -emit-llvm -triple x86_64-linux-gnu %s -fdebug-info-for-profiling -debug-info-kind=constructor -o - | FileCheck %s
-
-class A {
-public:
-  int i;
-  char c;
-  void *p;
-  int arr[3];
-};
-
-class B {
-public:
-  A* a;
-};
-
-class C {
-public:
-  B* b;
-  A* a;
-  A arr[10];
-};
-
-// CHECK-LABEL: define dso_local noundef i32 @{{.*}}func1{{.*}}(
-// CHECK:         [[A_ADDR:%.*]] = getelementptr inbounds %class.B, ptr {{%.*}}, i32 0, i32 0, !dbg [[DBG1:![0-9]+]]
-// CHECK-NEXT:    [[A:%.*]] = load ptr, ptr [[A_ADDR]], align {{.*}}, !dbg [[DBG1]]
-// CHECK-NEXT:    [[PSEUDO1:%.*]] = alloca ptr, align {{.*}}, !dbg [[DBG1]]
-// CHECK-NEXT:    store ptr [[A]], ptr [[PSEUDO1]], align {{.*}}, !dbg [[DBG1]]
-// CHECK-NEXT:    call void @llvm.dbg.declare(metadata ptr [[PSEUDO1]], metadata [[META1:![0-9]+]], metadata !DIExpression()), !dbg [[DBG1]]
-// CHECK-NEXT:    [[TMP1:%.*]] = load ptr, ptr [[PSEUDO1]], align {{.*}}, !dbg [[DBG1]]
-// CHECK-NEXT:    {{%.*}} = getelementptr inbounds %class.A, ptr [[TMP1]], i32 0, i32 0,
-int func1(B *b) {
-  return b->a->i;
-}
-
-// Should generate a pseudo variable when pointer is type-casted.
-// CHECK-LABEL: define dso_local noundef ptr @{{.*}}func2{{.*}}(
-// CHECK:         call void @llvm.dbg.declare(metadata ptr [[B_ADDR:%.*]], metadata [[META2:![0-9]+]], metadata !DIExpression())
-// CHECK-NEXT:    [[B:%.*]] = load ptr, ptr [[B_ADDR]],
-// CHECK-NEXT:    [[PSEUDO1:%.*]] = alloca ptr,
-// CHECK-NEXT:    store ptr [[B]], ptr [[PSEUDO1]],
-// CHECK-NEXT:    call void @llvm.dbg.declare(metadata ptr [[PSEUDO1]], metadata [[META3:![0-9]+]], metadata !DIExpression())
-// CHECK-NEXT:    [[TMP1:%.*]] = load ptr, ptr [[PSEUDO1]],
-// CHECK-NEXT:    {{%.*}} = getelementptr inbounds %class.B, ptr [[TMP1]], i32 0,
-A* func2(void *b) {
-  return ((B*)b)->a;
-}
-
-// Should not generate pseudo variable in this case.
-// CHECK-LABEL: define dso_local noundef i32 @{{.*}}func3{{.*}}(
-// CHECK:    call void @llvm.dbg.declare(metadata ptr [[B_ADDR:%.*]], metadata [[META4:![0-9]+]], metadata !DIExpression())
-// CHECK:    call void @llvm.dbg.declare(metadata ptr [[LOCAL1:%.*]], metadata [[META5:![0-9]+]], metadata !DIExpression())
-// CHECK-NOT: call void @llvm.dbg.declare(metadata ptr
-int func3(B *b) {
-  A *local1 = b->a;
-  return local1->i;
-}
-
-// CHECK-LABEL: define dso_local noundef signext i8 @{{.*}}func4{{.*}}(
-// CHECK:         [[A_ADDR:%.*]] = getelementptr inbounds %class.C, ptr {{%.*}}, i32 0, i32 1
-// CHECK-NEXT:    [[A:%.*]] = load ptr, ptr [[A_ADDR]],
-// CHECK-NEXT:    [[PSEUDO1:%.*]] = alloca ptr,
-// CHECK-NEXT:    store ptr [[A]], ptr [[PSEUDO1]],
-// CHECK-NEXT:    call void @llvm.dbg.declare(metadata ptr [[PSEUDO1]], metadata [[META6:![0-9]+]], metadata !DIExpression())
-// CHECK-NEXT:    [[TMP1:%.*]] = load ptr, ptr [[PSEUDO1]],
-// CHECK-NEXT:    {{%.*}} = getelementptr inbounds %class.A, ptr [[TMP1]], i32 0, i32 0,
-// CHECK:         [[CALL:%.*]] = call noundef ptr @{{.*}}foo{{.*}}(
-// CHECK-NEXT:    [[PSEUDO2:%.*]] = alloca ptr,
-// CHECK-NEXT:    store ptr [[CALL]], ptr [[PSEUDO2]]
-// CHECK-NEXT:    call void @llvm.dbg.declare(metadata ptr [[PSEUDO2]], metadata [[META6]], metadata !DIExpression())
-// CHECK-NEXT:    [[TMP2:%.*]] = load ptr, ptr [[PSEUDO2]]
-// CHECK-NEXT:    [[I1:%.*]] = getelementptr inbounds %class.A, ptr [[TMP2]], i32 0, i32 1
-char func4(C *c) {
-  extern A* foo(int x);
-  return foo(c->a->i)->c;
-}
-
-// CHECK-LABEL: define dso_local noundef signext i8 @{{.*}}func5{{.*}}(
-// CHECK:         call void @llvm.dbg.declare(metadata ptr {{%.*}}, metadata [[META7:![0-9]+]], metadata !DIExpression())
-// CHECK:         call void @llvm.dbg.declare(metadata ptr {{%.*}}, metadata [[META8:![0-9]+]], metadata !DIExpression())
-// CHECK:         [[A_ADDR:%.*]] = getelementptr inbounds %class.A, ptr {{%.*}}, i64 {{%.*}},
-// CHECK-NEXT:    [[PSEUDO1:%.*]] = alloca ptr,
-// CHECK-NEXT:    store ptr [[A_ADDR]], ptr [[PSEUDO1]],
-// CHECK-NEXT:    call void @llvm.dbg.declare(metadata ptr [[PSEUDO1]], metadata [[META9:![0-9]+]], metadata !DIExpression())
-// CHECK-NEXT:    [[TMP1:%.*]] = load ptr, ptr [[PSEUDO1]],
-// CHECK-NEXT:    {{%.*}} = getelementptr inbounds %class.A, ptr [[TMP1]], i32 0, i32 1,
-char func5(void *arr, int n) {
-  return ((A*)arr)[n].c;
-}
-
-// CHECK-LABEL: define dso_local noundef i32 @{{.*}}func6{{.*}}(
-// CHECK:         call void @llvm.dbg.declare(metadata ptr {{%.*}}, metadata [[META10:![0-9]+]], metadata !DIExpression())
-// CHECK:         call void @llvm.dbg.declare(metadata ptr {{%.*}}, metadata [[META11:![0-9]+]], metadata !DIExpression())
-int func6(B &b) {
-  return reinterpret_cast<A&>(b).i;
-}
-
-// CHECK-DAG: [[META_A:![0-9]+]] = distinct !DICompositeType(tag: DW_TAG_class_type, name: "A",
-// CHECK-DAG: [[META_AP:![0-9]+]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: [[META_A]],
-// CHECK-DAG: [[META_B:![0-9]+]] = distinct !DICompositeType(tag: DW_TAG_class_type, name: "B",
-// CHECK-DAG: [[META_BP:![0-9]+]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: [[META_B]],
-// CHECK-DAG: [[META_C:![0-9]+]] = distinct !DICompositeType(tag: DW_TAG_class_type, name: "C",
-// CHECK-DAG: [[META_CP:![0-9]+]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: [[META_C]],
-// CHECK-DAG: [[META_VP:![0-9]+]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null,
-// CHECK-DAG: [[META_I32:![0-9]+]] = !DIBasicType(name: "int", size: 32,
-// CHECK-DAG: [[META_BR:![0-9]+]] = !DIDerivedType(tag: DW_TAG_reference_type, baseType: [[META_B]],
-
-// CHECK-DAG: [[DBG1]] = !DILocation(line: 34, column: 13,
-// CHECK-DAG: [[META1]] = !DILocalVariable(scope: {{.*}}, type: [[META_AP]], flags: DIFlagArtificial)
-// CHECK-DAG: [[META2]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 46, type: [[META_VP]])
-// CHECK-DAG: [[META3]] = !DILocalVariable(scope: {{.*}}, type: [[META_BP]], flags: DIFlagArtificial)
-// CHECK-DAG: [[META4]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 55, type: [[META_BP]])
-// CHECK-DAG: [[META5]] = !DILocalVariable(name: "local1", scope: {{.*}}, file: {{.*}}, line: 56, type: [[META_AP]])
-// CHECK-DAG: [[META6]] = !DILocalVariable(scope: {{.*}}, type: [[META_AP]], flags: DIFlagArtificial)
-// CHECK-DAG: [[META7]] = !DILocalVariable(name: "arr", arg: 1, scope: {{.*}}, file: {{.*}}, line: 88, type: [[META_VP]])
-// CHECK-DAG: [[META8]] = !DILocalVariable(name: "n", arg: 2, scope: {{.*}}, file: {{.*}}, line: 88, type: [[META_I32]])
-// CHECK-DAG: [[META9]] = !DILocalVariable(scope: {{.*}}, type: [[META_AP]], flags: DIFlagArtificial)
-// CHECK-DAG: [[META10]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 95, type: [[META_BR]])
-// CHECK-DAG: [[META11]] = !DILocalVariable(scope: {{.*}}, type: [[META_AP]], flags: DIFlagArtificial)