[DebugInfo] Generate debug information for labels. (Fix PR37395)

Generate DILabel metadata and call llvm.dbg.label after label
statement to associate the metadata with the label.

After fixing PR37395.

Differential Revision: https://reviews.llvm.org/D45045

Patch by Hsiangkai Wang.

llvm-svn: 337800

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -3729,6 +3729,32 @@ CGDebugInfo::EmitDeclareOfAutoVariable(const VarDecl *VD, llvm::Value *Storage,
   return EmitDeclare(VD, Storage, llvm::None, Builder);
 }
 
+void CGDebugInfo::EmitLabel(const LabelDecl *D, CGBuilderTy &Builder) {
+  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
+  assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
+
+  if (D->hasAttr<NoDebugAttr>())
+    return;
+
+  auto *Scope = cast<llvm::DIScope>(LexicalBlockStack.back());
+  llvm::DIFile *Unit = getOrCreateFile(D->getLocation());
+
+  // Get location information.
+  unsigned Line = getLineNumber(D->getLocation());
+  unsigned Column = getColumnNumber(D->getLocation());
+
+  StringRef Name = D->getName();
+
+  // Create the descriptor for the label.
+  auto *L =
+      DBuilder.createLabel(Scope, Name, Unit, Line, CGM.getLangOpts().Optimize);
+
+  // Insert an llvm.dbg.label into the current block.
+  DBuilder.insertLabel(L,
+                       llvm::DebugLoc::get(Line, Column, Scope, CurInlinedAt),
+                       Builder.GetInsertBlock());
+}
+
 llvm::DIType *CGDebugInfo::CreateSelfType(const QualType &QualTy,
                                           llvm::DIType *Ty) {
   llvm::DIType *CachedTy = getTypeOrNull(QualTy);

clang/lib/CodeGen/CGDebugInfo.h

@@ -399,6 +399,9 @@ public:
                                                    llvm::Value *AI,
                                                    CGBuilderTy &Builder);
 
+  /// Emit call to \c llvm.dbg.label for an label.
+  void EmitLabel(const LabelDecl *D, CGBuilderTy &Builder);
+
   /// Emit call to \c llvm.dbg.declare for an imported variable
   /// declaration in a block.
   void EmitDeclareOfBlockDeclRefVariable(

clang/lib/CodeGen/CGStmt.cpp

@@ -531,6 +531,16 @@ void CodeGenFunction::EmitLabel(const LabelDecl *D) {
   }
 
   EmitBlock(Dest.getBlock());
+
+  // Emit debug info for labels.
+  if (CGDebugInfo *DI = getDebugInfo()) {
+    if (CGM.getCodeGenOpts().getDebugInfo() >=
+        codegenoptions::LimitedDebugInfo) {
+      DI->setLocation(D->getLocation());
+      DI->EmitLabel(D, Builder);
+    }
+  }
+
   incrementProfileCounter(D->getStmt());
 }
 

clang/test/CodeGen/debug-label-inline.c

@@ -0,0 +1,28 @@
+// This test will test the correctness of generating DILabel and
+// llvm.dbg.label when the label is in inlined functions.
+//
+// RUN: %clang_cc1 -O2 %s -o - -emit-llvm -debug-info-kind=limited | FileCheck %s
+inline int f1(int a, int b) {
+  int sum;
+
+top:
+  sum = a + b;
+  return sum;
+}
+
+extern int ga, gb;
+
+int f2(void) {
+  int result;
+
+  result = f1(ga, gb);
+  // CHECK: call void @llvm.dbg.label(metadata [[LABEL_METADATA:!.*]]), !dbg [[LABEL_LOCATION:!.*]]
+
+  return result;
+}
+
+// CHECK: distinct !DISubprogram(name: "f1", {{.*}}, retainedNodes: [[ELEMENTS:!.*]])
+// CHECK: [[ELEMENTS]] = !{{{.*}}, [[LABEL_METADATA]]}
+// CHECK: [[LABEL_METADATA]] = !DILabel({{.*}}, name: "top", {{.*}}, line: 8)
+// CHECK: [[INLINEDAT:!.*]] = distinct !DILocation(line: 18,
+// CHECK: [[LABEL_LOCATION]] = !DILocation(line: 8, {{.*}}, inlinedAt: [[INLINEDAT]])

clang/test/CodeGen/debug-label.c

@@ -0,0 +1,16 @@
+// This test will test the correstness of generating DILabel and
+// llvm.dbg.label for labels.
+//
+// RUN: %clang_cc1 -emit-llvm %s -o - -emit-llvm -debug-info-kind=limited | FileCheck %s
+
+int f1(int a, int b) {
+  int sum;
+
+top:
+  // CHECK: call void @llvm.dbg.label(metadata [[LABEL_METADATA:!.*]]), !dbg [[LABEL_LOCATION:!.*]]
+  sum = a + b;
+  return sum;
+}
+
+// CHECK: [[LABEL_METADATA]] = !DILabel({{.*}}, name: "top", {{.*}}, line: 9)
+// CHECK: [[LABEL_LOCATION]] = !DILocation(line: 9,