Add option to generate additional debug info for expression dereferencing pointer to pointers. #81545

huangjd · 2024-02-12T22:35:11Z

Such expression does not correspond to a variable in the source code thus does not have a debug location. When the user collects perf data on the program, if the intermediate memory load instruction is sampled, it could not be attributed to any variable/class member, which causes the sampling results to be under-counted.
This patch adds an option -fdebug_info_for_pointer_type to generate a psuedo variable and its debug info for intermediate expression with pointer dereferencing, so that perf data collected on the instruction of that expression can be attributed to the correct class member.

This is a prototype so comments are needed.

…ter of pointers. Such expression does correspond to a variable in the source code thus does not have a debug location. However the user may want to collect sampling counter for memory accesses to analyze usage frequency of class members. By enabling -fdebug_info_for_pointer_type a psuedo variable and its debug info is generated in place whenever there's an intermediate expression with pointer access.

github-actions · 2024-02-12T22:39:26Z

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff 9261ab708e37c2d6499ac063045f816d25a5919c 8ba3e3cf3749ea1685fd6fe2d6dc44fc239ada1c -- clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp clang/lib/CodeGen/CGDebugInfo.cpp clang/lib/CodeGen/CGDebugInfo.h clang/lib/CodeGen/CGExprScalar.cpp

View the diff from clang-format here.

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 6c332b2ae9c..2ed7dbe2854 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -5706,9 +5706,9 @@ void CGDebugInfo::EmitPseudoVariable(CGBuilderTy &Builder,
   // 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::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);

snehasish · 2024-02-13T03:28:11Z

Any measurements of impact to compile time, memory etc on a reasonable size benchmark (e.g. clang)?

david-xl

Please add test cases. The clang user manual also needs update.

namhyung · 2024-03-06T18:00:27Z

clang/lib/CodeGen/CGDebugInfo.cpp

+  unsigned Line = getLineNumber(Loc);
+  unsigned Column = getColumnNumber(Loc);
+  llvm::DILocalVariable *D = DBuilder.createAutoVariable(
+      LexicalBlockStack.back(), Alloca->getName(), getOrCreateFile(Loc), Line,


Can it generate a variable without name? I think name is useless here and just bloats the binary size.

namhyung · 2024-03-06T18:05:48Z

Also I think it generates variables for destination of pointers, not the source. For example, if we have a->b->c, what we need is variables for a and b. Usually it would already have one for a, so it can skip generating it (unless there's a difference like due to type casts), and it'd be enough to just generate one for b.

requested by kernel dev.

llvmbot · 2024-03-15T03:46:43Z

@llvm/pr-subscribers-debuginfo

@llvm/pr-subscribers-llvm-ir

Author: William Junda Huang (huangjd)

Changes

Such expression does not correspond to a variable in the source code thus does not have a debug location. When the user collects perf data on the program, if the intermediate memory load instruction is sampled, it could not be attributed to any variable/class member, which causes the sampling results to be under-counted.
This patch adds an option -fdebug_info_for_pointer_type to generate a psuedo variable and its debug info for intermediate expression with pointer dereferencing, so that perf data collected on the instruction of that expression can be attributed to the correct class member.

This is a prototype so comments are needed.

Full diff: https://github.com/llvm/llvm-project/pull/81545.diff

8 Files Affected:

(modified) clang/include/clang/Basic/DebugOptions.def (+4)
(modified) clang/include/clang/Driver/Options.td (+4)
(modified) clang/lib/CodeGen/CGDebugInfo.cpp (+65)
(modified) clang/lib/CodeGen/CGDebugInfo.h (+6)
(modified) clang/lib/CodeGen/CGExprScalar.cpp (+20-1)
(modified) clang/lib/Driver/ToolChains/Clang.cpp (+3)
(added) clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp (+120)
(modified) llvm/include/llvm/IR/DIBuilder.h (+2)

diff --git a/clang/include/clang/Basic/DebugOptions.def b/clang/include/clang/Basic/DebugOptions.def
index 7cd3edf08a17ea..6dd09f46842077 100644
--- a/clang/include/clang/Basic/DebugOptions.def
+++ b/clang/include/clang/Basic/DebugOptions.def
@@ -129,6 +129,10 @@ DEBUGOPT(CodeViewCommandLine, 1, 0)
 /// Whether emit extra debug info for sample pgo profile collection.
 DEBUGOPT(DebugInfoForProfiling, 1, 0)
 
+/// Whether to generate pseudo variables and their debug info for intermediate
+/// pointer accesses.
+DEBUGOPT(DebugInfoForPointerType, 1, 0)
+
 /// Whether to emit .debug_gnu_pubnames section instead of .debug_pubnames.
 DEBUGOPT(DebugNameTable, 2, 0)
 
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 7f4fa33748faca..96b22d3f7640dd 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1675,6 +1675,10 @@ defm debug_info_for_profiling : BoolFOption<"debug-info-for-profiling",
   PosFlag<SetTrue, [], [ClangOption, CC1Option],
           "Emit extra debug info to make sample profile more accurate">,
   NegFlag<SetFalse>>;
+def fdebug_info_for_pointer_type : Flag<["-"], "fdebug-info-for-pointer-type">,
+  Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Generate pseudo variables and their debug info for intermediate pointer accesses">,
+  MarshallingInfoFlag<CodeGenOpts<"DebugInfoForPointerType">>;
 def fprofile_instr_generate : Flag<["-"], "fprofile-instr-generate">,
     Group<f_Group>, Visibility<[ClangOption, CLOption]>,
     HelpText<"Generate instrumented code to collect execution counts into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)">;
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 0f3f684d61dc94..f28e83a3b99ec2 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -5636,6 +5636,71 @@ 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::DIFile *Unit = Builder.getCurrentDebugLocation()->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();
+    if (llvm::Metadata *MDValue = llvm::ValueAsMetadata::getIfExists(Var)) {
+      if (llvm::Value *DbgValue = llvm::MetadataAsValue::getIfExists(
+              CGM.getLLVMContext(), MDValue)) {
+        for (llvm::User *U : DbgValue->users()) {
+          if (llvm::CallInst *DbgDeclare = dyn_cast<llvm::CallInst>(U)) {
+            if (DbgDeclare->getCalledFunction() == DBuilder.GetDeclareFn() &&
+                DbgDeclare->getArgOperand(0) == DbgValue) {
+              // 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.
+              llvm::DILocalVariable *MDNode = dyn_cast<llvm::DILocalVariable>(
+                  dyn_cast<llvm::MetadataAsValue>(DbgDeclare->getOperand(1))
+                      ->getMetadata());
+              if (MDNode->getType() == Type)
+                return;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  // Insert a sequence of instructions to materialize Value on the stack.
+  auto SaveInsertionPoint = Builder.saveIP();
+  Builder.SetInsertPoint(++(Value->getIterator()));
+  Builder.SetCurrentDebugLocation(Value->getDebugLoc());
+  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(), "pseudo_var", Unit, Line, Type);
+  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);
+}
+
 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 7b60e94555d060..2756ea1e7b4f1e 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -529,6 +529,12 @@ 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 181b15e9c7d0a7..cad79e77052842 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -1787,7 +1787,26 @@ Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *E) {
     }
   }
 
-  return EmitLoadOfLValue(E);
+  llvm::Value *Result = EmitLoadOfLValue(E);
+
+  // If -fdebug-info-for-pointer-type 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().DebugInfoForPointerType && 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;
 }
 
 Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index bcba7cbbdb58c2..7882c4f1225f1f 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4256,6 +4256,9 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
   // decision should be made in the driver as well though.
   llvm::DebuggerKind DebuggerTuning = TC.getDefaultDebuggerTuning();
 
+  if (Args.hasArg(options::OPT_fdebug_info_for_pointer_type))
+    CmdArgs.push_back("-fdebug-info-for-pointer-type");
+
   bool SplitDWARFInlining =
       Args.hasFlag(options::OPT_fsplit_dwarf_inlining,
                    options::OPT_fno_split_dwarf_inlining, false);
diff --git a/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp b/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
new file mode 100644
index 00000000000000..6758ef445d463a
--- /dev/null
+++ b/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
@@ -0,0 +1,120 @@
+// 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 %s -fdebug-info-for-pointer-type -debug-info-kind=constructor -S -emit-llvm -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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 34, type: [[META_AP]])
+// CHECK-DAG: [[META2]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 46, type: [[META_VP]])
+// CHECK-DAG: [[META3]] = !DILocalVariable(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 47, type: [[META_BP]])
+// 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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 76, type: [[META_AP]])
+// 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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 89, type: [[META_AP]])
+// CHECK-DAG: [[META10]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 95, type: [[META_BR]])
+// CHECK-DAG: [[META11]] = !DILocalVariable(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 96, type: [[META_AP]])
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
index edec161b397155..e420f73e152907 100644
--- a/llvm/include/llvm/IR/DIBuilder.h
+++ b/llvm/include/llvm/IR/DIBuilder.h
@@ -1024,6 +1024,8 @@ namespace llvm {
       N->replaceAllUsesWith(Replacement);
       return Replacement;
     }
+
+    Function *GetDeclareFn() { return DeclareFn; }
   };
 
   // Create wrappers for C Binding types (see CBindingWrapping.h).

llvmbot · 2024-03-15T03:46:43Z

@llvm/pr-subscribers-clang

Author: William Junda Huang (huangjd)

Changes

Such expression does not correspond to a variable in the source code thus does not have a debug location. When the user collects perf data on the program, if the intermediate memory load instruction is sampled, it could not be attributed to any variable/class member, which causes the sampling results to be under-counted.
This patch adds an option -fdebug_info_for_pointer_type to generate a psuedo variable and its debug info for intermediate expression with pointer dereferencing, so that perf data collected on the instruction of that expression can be attributed to the correct class member.

This is a prototype so comments are needed.

Full diff: https://github.com/llvm/llvm-project/pull/81545.diff

8 Files Affected:

(modified) clang/include/clang/Basic/DebugOptions.def (+4)
(modified) clang/include/clang/Driver/Options.td (+4)
(modified) clang/lib/CodeGen/CGDebugInfo.cpp (+65)
(modified) clang/lib/CodeGen/CGDebugInfo.h (+6)
(modified) clang/lib/CodeGen/CGExprScalar.cpp (+20-1)
(modified) clang/lib/Driver/ToolChains/Clang.cpp (+3)
(added) clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp (+120)
(modified) llvm/include/llvm/IR/DIBuilder.h (+2)

diff --git a/clang/include/clang/Basic/DebugOptions.def b/clang/include/clang/Basic/DebugOptions.def
index 7cd3edf08a17ea..6dd09f46842077 100644
--- a/clang/include/clang/Basic/DebugOptions.def
+++ b/clang/include/clang/Basic/DebugOptions.def
@@ -129,6 +129,10 @@ DEBUGOPT(CodeViewCommandLine, 1, 0)
 /// Whether emit extra debug info for sample pgo profile collection.
 DEBUGOPT(DebugInfoForProfiling, 1, 0)
 
+/// Whether to generate pseudo variables and their debug info for intermediate
+/// pointer accesses.
+DEBUGOPT(DebugInfoForPointerType, 1, 0)
+
 /// Whether to emit .debug_gnu_pubnames section instead of .debug_pubnames.
 DEBUGOPT(DebugNameTable, 2, 0)
 
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 7f4fa33748faca..96b22d3f7640dd 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1675,6 +1675,10 @@ defm debug_info_for_profiling : BoolFOption<"debug-info-for-profiling",
   PosFlag<SetTrue, [], [ClangOption, CC1Option],
           "Emit extra debug info to make sample profile more accurate">,
   NegFlag<SetFalse>>;
+def fdebug_info_for_pointer_type : Flag<["-"], "fdebug-info-for-pointer-type">,
+  Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Generate pseudo variables and their debug info for intermediate pointer accesses">,
+  MarshallingInfoFlag<CodeGenOpts<"DebugInfoForPointerType">>;
 def fprofile_instr_generate : Flag<["-"], "fprofile-instr-generate">,
     Group<f_Group>, Visibility<[ClangOption, CLOption]>,
     HelpText<"Generate instrumented code to collect execution counts into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)">;
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 0f3f684d61dc94..f28e83a3b99ec2 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -5636,6 +5636,71 @@ 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::DIFile *Unit = Builder.getCurrentDebugLocation()->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();
+    if (llvm::Metadata *MDValue = llvm::ValueAsMetadata::getIfExists(Var)) {
+      if (llvm::Value *DbgValue = llvm::MetadataAsValue::getIfExists(
+              CGM.getLLVMContext(), MDValue)) {
+        for (llvm::User *U : DbgValue->users()) {
+          if (llvm::CallInst *DbgDeclare = dyn_cast<llvm::CallInst>(U)) {
+            if (DbgDeclare->getCalledFunction() == DBuilder.GetDeclareFn() &&
+                DbgDeclare->getArgOperand(0) == DbgValue) {
+              // 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.
+              llvm::DILocalVariable *MDNode = dyn_cast<llvm::DILocalVariable>(
+                  dyn_cast<llvm::MetadataAsValue>(DbgDeclare->getOperand(1))
+                      ->getMetadata());
+              if (MDNode->getType() == Type)
+                return;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  // Insert a sequence of instructions to materialize Value on the stack.
+  auto SaveInsertionPoint = Builder.saveIP();
+  Builder.SetInsertPoint(++(Value->getIterator()));
+  Builder.SetCurrentDebugLocation(Value->getDebugLoc());
+  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(), "pseudo_var", Unit, Line, Type);
+  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);
+}
+
 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 7b60e94555d060..2756ea1e7b4f1e 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -529,6 +529,12 @@ 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 181b15e9c7d0a7..cad79e77052842 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -1787,7 +1787,26 @@ Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *E) {
     }
   }
 
-  return EmitLoadOfLValue(E);
+  llvm::Value *Result = EmitLoadOfLValue(E);
+
+  // If -fdebug-info-for-pointer-type 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().DebugInfoForPointerType && 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;
 }
 
 Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index bcba7cbbdb58c2..7882c4f1225f1f 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4256,6 +4256,9 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
   // decision should be made in the driver as well though.
   llvm::DebuggerKind DebuggerTuning = TC.getDefaultDebuggerTuning();
 
+  if (Args.hasArg(options::OPT_fdebug_info_for_pointer_type))
+    CmdArgs.push_back("-fdebug-info-for-pointer-type");
+
   bool SplitDWARFInlining =
       Args.hasFlag(options::OPT_fsplit_dwarf_inlining,
                    options::OPT_fno_split_dwarf_inlining, false);
diff --git a/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp b/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
new file mode 100644
index 00000000000000..6758ef445d463a
--- /dev/null
+++ b/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
@@ -0,0 +1,120 @@
+// 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 %s -fdebug-info-for-pointer-type -debug-info-kind=constructor -S -emit-llvm -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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 34, type: [[META_AP]])
+// CHECK-DAG: [[META2]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 46, type: [[META_VP]])
+// CHECK-DAG: [[META3]] = !DILocalVariable(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 47, type: [[META_BP]])
+// 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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 76, type: [[META_AP]])
+// 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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 89, type: [[META_AP]])
+// CHECK-DAG: [[META10]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 95, type: [[META_BR]])
+// CHECK-DAG: [[META11]] = !DILocalVariable(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 96, type: [[META_AP]])
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
index edec161b397155..e420f73e152907 100644
--- a/llvm/include/llvm/IR/DIBuilder.h
+++ b/llvm/include/llvm/IR/DIBuilder.h
@@ -1024,6 +1024,8 @@ namespace llvm {
       N->replaceAllUsesWith(Replacement);
       return Replacement;
     }
+
+    Function *GetDeclareFn() { return DeclareFn; }
   };
 
   // Create wrappers for C Binding types (see CBindingWrapping.h).

llvmbot · 2024-03-15T03:46:43Z

@llvm/pr-subscribers-clang-driver

Author: William Junda Huang (huangjd)

Changes

Such expression does not correspond to a variable in the source code thus does not have a debug location. When the user collects perf data on the program, if the intermediate memory load instruction is sampled, it could not be attributed to any variable/class member, which causes the sampling results to be under-counted.
This patch adds an option -fdebug_info_for_pointer_type to generate a psuedo variable and its debug info for intermediate expression with pointer dereferencing, so that perf data collected on the instruction of that expression can be attributed to the correct class member.

This is a prototype so comments are needed.

Full diff: https://github.com/llvm/llvm-project/pull/81545.diff

8 Files Affected:

(modified) clang/include/clang/Basic/DebugOptions.def (+4)
(modified) clang/include/clang/Driver/Options.td (+4)
(modified) clang/lib/CodeGen/CGDebugInfo.cpp (+65)
(modified) clang/lib/CodeGen/CGDebugInfo.h (+6)
(modified) clang/lib/CodeGen/CGExprScalar.cpp (+20-1)
(modified) clang/lib/Driver/ToolChains/Clang.cpp (+3)
(added) clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp (+120)
(modified) llvm/include/llvm/IR/DIBuilder.h (+2)

diff --git a/clang/include/clang/Basic/DebugOptions.def b/clang/include/clang/Basic/DebugOptions.def
index 7cd3edf08a17ea..6dd09f46842077 100644
--- a/clang/include/clang/Basic/DebugOptions.def
+++ b/clang/include/clang/Basic/DebugOptions.def
@@ -129,6 +129,10 @@ DEBUGOPT(CodeViewCommandLine, 1, 0)
 /// Whether emit extra debug info for sample pgo profile collection.
 DEBUGOPT(DebugInfoForProfiling, 1, 0)
 
+/// Whether to generate pseudo variables and their debug info for intermediate
+/// pointer accesses.
+DEBUGOPT(DebugInfoForPointerType, 1, 0)
+
 /// Whether to emit .debug_gnu_pubnames section instead of .debug_pubnames.
 DEBUGOPT(DebugNameTable, 2, 0)
 
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 7f4fa33748faca..96b22d3f7640dd 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1675,6 +1675,10 @@ defm debug_info_for_profiling : BoolFOption<"debug-info-for-profiling",
   PosFlag<SetTrue, [], [ClangOption, CC1Option],
           "Emit extra debug info to make sample profile more accurate">,
   NegFlag<SetFalse>>;
+def fdebug_info_for_pointer_type : Flag<["-"], "fdebug-info-for-pointer-type">,
+  Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Generate pseudo variables and their debug info for intermediate pointer accesses">,
+  MarshallingInfoFlag<CodeGenOpts<"DebugInfoForPointerType">>;
 def fprofile_instr_generate : Flag<["-"], "fprofile-instr-generate">,
     Group<f_Group>, Visibility<[ClangOption, CLOption]>,
     HelpText<"Generate instrumented code to collect execution counts into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)">;
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 0f3f684d61dc94..f28e83a3b99ec2 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -5636,6 +5636,71 @@ 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::DIFile *Unit = Builder.getCurrentDebugLocation()->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();
+    if (llvm::Metadata *MDValue = llvm::ValueAsMetadata::getIfExists(Var)) {
+      if (llvm::Value *DbgValue = llvm::MetadataAsValue::getIfExists(
+              CGM.getLLVMContext(), MDValue)) {
+        for (llvm::User *U : DbgValue->users()) {
+          if (llvm::CallInst *DbgDeclare = dyn_cast<llvm::CallInst>(U)) {
+            if (DbgDeclare->getCalledFunction() == DBuilder.GetDeclareFn() &&
+                DbgDeclare->getArgOperand(0) == DbgValue) {
+              // 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.
+              llvm::DILocalVariable *MDNode = dyn_cast<llvm::DILocalVariable>(
+                  dyn_cast<llvm::MetadataAsValue>(DbgDeclare->getOperand(1))
+                      ->getMetadata());
+              if (MDNode->getType() == Type)
+                return;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  // Insert a sequence of instructions to materialize Value on the stack.
+  auto SaveInsertionPoint = Builder.saveIP();
+  Builder.SetInsertPoint(++(Value->getIterator()));
+  Builder.SetCurrentDebugLocation(Value->getDebugLoc());
+  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(), "pseudo_var", Unit, Line, Type);
+  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);
+}
+
 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 7b60e94555d060..2756ea1e7b4f1e 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -529,6 +529,12 @@ 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 181b15e9c7d0a7..cad79e77052842 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -1787,7 +1787,26 @@ Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *E) {
     }
   }
 
-  return EmitLoadOfLValue(E);
+  llvm::Value *Result = EmitLoadOfLValue(E);
+
+  // If -fdebug-info-for-pointer-type 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().DebugInfoForPointerType && 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;
 }
 
 Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index bcba7cbbdb58c2..7882c4f1225f1f 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4256,6 +4256,9 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
   // decision should be made in the driver as well though.
   llvm::DebuggerKind DebuggerTuning = TC.getDefaultDebuggerTuning();
 
+  if (Args.hasArg(options::OPT_fdebug_info_for_pointer_type))
+    CmdArgs.push_back("-fdebug-info-for-pointer-type");
+
   bool SplitDWARFInlining =
       Args.hasFlag(options::OPT_fsplit_dwarf_inlining,
                    options::OPT_fno_split_dwarf_inlining, false);
diff --git a/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp b/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
new file mode 100644
index 00000000000000..6758ef445d463a
--- /dev/null
+++ b/clang/test/CodeGenCXX/debug-info-ptr-to-ptr.cpp
@@ -0,0 +1,120 @@
+// 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 %s -fdebug-info-for-pointer-type -debug-info-kind=constructor -S -emit-llvm -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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 34, type: [[META_AP]])
+// CHECK-DAG: [[META2]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 46, type: [[META_VP]])
+// CHECK-DAG: [[META3]] = !DILocalVariable(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 47, type: [[META_BP]])
+// 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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 76, type: [[META_AP]])
+// 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(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 89, type: [[META_AP]])
+// CHECK-DAG: [[META10]] = !DILocalVariable(name: "b", arg: 1, scope: {{.*}}, file: {{.*}}, line: 95, type: [[META_BR]])
+// CHECK-DAG: [[META11]] = !DILocalVariable(name: "pseudo_var", scope: {{.*}}, file: {{.*}}, line: 96, type: [[META_AP]])
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
index edec161b397155..e420f73e152907 100644
--- a/llvm/include/llvm/IR/DIBuilder.h
+++ b/llvm/include/llvm/IR/DIBuilder.h
@@ -1024,6 +1024,8 @@ namespace llvm {
       N->replaceAllUsesWith(Replacement);
       return Replacement;
     }
+
+    Function *GetDeclareFn() { return DeclareFn; }
   };
 
   // Create wrappers for C Binding types (see CBindingWrapping.h).

huangjd · 2024-04-02T00:07:37Z

I am making another diff (not to be submitted) to get statistics on how frequently these 2 cases are encountered

dwblaikie · 2024-04-02T15:45:48Z

As for impact, I believe @namhyung did some measurement for building the Linux kernel, and it does not have a significant impact.

That'd surprise me quite a bit - perhaps a self-host build of clang (ideally in Google's build config, that being the one you and I care about the most) - opt with fission? measuring the size of object and dwo files (linker action inputs, but ideally more fine-grained per-section size comparisons would be good) and the linked executable/dwp.

huangjd · 2024-04-03T02:30:18Z

diff.txt

Apply this patch to get statistics on how many pseudo variable is generated, which can be used as an impact estimation

clang/lib/CodeGen/CGExprScalar.cpp

clang/lib/CodeGen/CGDebugInfo.cpp

huangjd · 2024-05-28T19:11:20Z

Could I have a follow up on this? @dwblaikie

dwblaikie

Fair enough - let's give it a go.

joker-eph · 2024-05-29T23:15:50Z

There is a broken test in CI: https://lab.llvm.org/buildbot/#/builders/272/builds/17864

dwblaikie · 2024-05-29T23:37:53Z

There is a broken test in CI: https://lab.llvm.org/buildbot/#/builders/272/builds/17864

Fixed in ea1ecb5

…rs/230/builds/29066 Failure was introduced in #81545 On 64-bit targets for i32 return type, there will be extension in the function prototype.

chenzheng1030 · 2024-05-30T01:54:29Z

PPC buildbot fails at another place with above fix: https://lab.llvm.org/buildbot/#/builders/230/builds/29066

Commit 2b1d1c5 to fix the failure.

dyung · 2024-05-30T03:44:19Z

Hi, the test debug-info-ptr-to-ptr.cpp is still failing on a Mac bot. Can you take a look?

https://lab.llvm.org/buildbot/#/builders/280/builds/4515

…ereferencing pointer to pointers. (#81545)" This reverts commit aeccfee, and dependents: Revert "[NFC] Fix PPC buildbot failure https://lab.llvm.org/buildbot/#/builders/230/builds/29066" This reverts commit 2b1d1c5. Revert "Fix test - remove unnecessary/incorrect `-S`, in favor of `-emit-llvm`" This reverts commit ea1ecb5. The test is failing on MacOs and Windows

joker-eph · 2024-05-30T04:58:55Z

Reverted in 7d4a45d ; test is failing like this on Windows:

# RUN: at line 3
c:\ws\buildbot\premerge-monolithic-windows\build\bin\clang.exe -cc1 -internal-isystem C:\ws\buildbot\premerge-monolithic-windows\build\lib\clang\19\include -nostdsysteminc C:\ws\buildbot\premerge-monolithic-windows\llvm-project\clang\test\CodeGenCXX\debug-info-ptr-to-ptr.cpp -fdebug-info-for-profiling -debug-info-kind=constructor -emit-llvm -o - | c:\ws\buildbot\premerge-monolithic-windows\build\bin\filecheck.exe C:\ws\buildbot\premerge-monolithic-windows\llvm-project\clang\test\CodeGenCXX\debug-info-ptr-to-ptr.cpp
# executed command: 'c:\ws\buildbot\premerge-monolithic-windows\build\bin\clang.exe' -cc1 -internal-isystem 'C:\ws\buildbot\premerge-monolithic-windows\build\lib\clang\19\include' -nostdsysteminc 'C:\ws\buildbot\premerge-monolithic-windows\llvm-project\clang\test\CodeGenCXX\debug-info-ptr-to-ptr.cpp' -fdebug-info-for-profiling -debug-info-kind=constructor -emit-llvm -o -
# executed command: 'c:\ws\buildbot\premerge-monolithic-windows\build\bin\filecheck.exe' 'C:\ws\buildbot\premerge-monolithic-windows\llvm-project\clang\test\CodeGenCXX\debug-info-ptr-to-ptr.cpp'
# .---command stderr------------
# | C:\ws\buildbot\premerge-monolithic-windows\llvm-project\clang\test\CodeGenCXX\debug-info-ptr-to-ptr.cpp:60:17: error: CHECK-LABEL: expected string not found in input
# | // CHECK-LABEL: define dso_local noundef signext i8 @{{.*}}func4{{.*}}(
# |                 ^
# | <stdin>:48:54: note: scanning from here
# | define dso_local noundef i32 @"?func3@@YAHPEAVB@@@Z"(ptr noundef %b) #0 !dbg !45 {
# |                                                      ^
# | <stdin>:66:1: note: possible intended match here
# | define dso_local noundef i8 @"?func4@@YADPEAVC@@@Z"(ptr noundef %c) #0 !dbg !55 {
# | ^
# |

mizvekov · 2024-05-30T05:03:33Z

I think the fix for the breakage is to just pin the new test to a fixed triple like so -triple x86_64-linux-gnu.

huangjd · 2024-05-31T09:40:19Z

How do I reopen the PR after fixing the test case?

AaronBallman · 2024-05-31T11:15:55Z

How do I reopen the PR after fixing the test case?

AIUI, you cannot reopen a merged PR, you have to start a new PR and mention the old one to link the two together.

…cing pointer to pointers. (#94100) This is another attempt to land #81545, which was reverted. Fixed test case by adding a target triple so that clang generates the same IR for all platforms

huangjd requested review from AaronBallman, delcypher, adrian-prantl, david-xl and snehasish February 12, 2024 22:35

david-xl reviewed Feb 13, 2024

View reviewed changes

Code cleanup

95235b9

namhyung reviewed Mar 6, 2024

View reviewed changes

david-xl requested a review from dwblaikie March 6, 2024 18:05

huangjd added 4 commits March 13, 2024 18:07

Rewrite code to emit debug info for pointer instead of pointee, as

37d3c1b

requested by kernel dev.

More precise debug loc

75faf06

Correct debug type info for "a.b" expr

404bd99

Add test case

630137e

huangjd requested review from namhyung and david-xl March 15, 2024 03:45

huangjd self-assigned this Mar 15, 2024

huangjd marked this pull request as ready for review March 15, 2024 03:46

llvmbot added clang Clang issues not falling into any other category clang:driver 'clang' and 'clang++' user-facing binaries. Not 'clang-cl' clang:frontend Language frontend issues, e.g. anything involving "Sema" clang:codegen debuginfo llvm:ir labels Mar 15, 2024

Added more safeguards for invalid debug location from source

87e89d1

Changed pseudo variable declaration to be compliant with DWARF standard

4c2369d

dwblaikie reviewed Apr 22, 2024

View reviewed changes

clang/lib/CodeGen/CGExprScalar.cpp Outdated Show resolved Hide resolved

clang/lib/CodeGen/CGDebugInfo.cpp Show resolved Hide resolved

clang/lib/CodeGen/CGDebugInfo.cpp Outdated Show resolved Hide resolved

code cleanup

6c77216

huangjd requested a review from dwblaikie April 30, 2024 22:04

huangjd marked this pull request as draft May 7, 2024 19:27

huangjd marked this pull request as ready for review May 7, 2024 19:27

Removed line info for pseudo varaible because they are not needed

8ba3e3c

dwblaikie approved these changes May 29, 2024

View reviewed changes

huangjd merged commit aeccfee into llvm:main May 29, 2024
2 of 4 checks passed

huangjd deleted the debuginfoforpointertype branch May 29, 2024 22:10

huangjd restored the debuginfoforpointertype branch May 30, 2024 21:32

huangjd mentioned this pull request Jun 1, 2024

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

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Add option to generate additional debug info for expression dereferencing pointer to pointers. #81545

Add option to generate additional debug info for expression dereferencing pointer to pointers. #81545

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Add option to generate additional debug info for expression dereferencing pointer to pointers. #81545

Add option to generate additional debug info for expression dereferencing pointer to pointers. #81545

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