Replace llvm::DIBuilder::DisableDebugLocations() with two RAII interfaces

inspired by CodegenFunction::LexicalScope.
- NoLocation temporarily turns off debug locations altogether.
  This is useful for emitting instructions that should be
  counted towards the function prologue.
- BuiltinLocation temporarily switches to an artificial debug location
  that has a valid scope, but no line information. This is useful when
  emitting compiler-generated helper functions that have no source
  location associated with them.

llvm-svn: 186552

clang/lib/CodeGen/CGBlocks.cpp

@@ -1164,9 +1164,8 @@ CodeGenFunction::GenerateBlockFunction(GlobalDecl GD,
     Alloca->setAlignment(Align);
     // Set the DebugLocation to empty, so the store is recognized as a
     // frame setup instruction by llvm::DwarfDebug::beginFunction().
-    Builder.DisableDebugLocations();
+    NoLocation NL(*this, Builder);
     Builder.CreateAlignedStore(BlockPointer, Alloca, Align);
-    Builder.EnableDebugLocations();
     BlockPointerDbgLoc = Alloca;
   }
 

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -51,6 +51,44 @@ CGDebugInfo::~CGDebugInfo() {
          "Region stack mismatch, stack not empty!");
 }
 
+
+NoLocation::NoLocation(CodeGenFunction &CGF, CGBuilderTy &B)
+  : DI(CGF.getDebugInfo()), Builder(B) {
+  if (DI) {
+    SavedLoc = DI->getLocation();
+    DI->CurLoc = SourceLocation();
+    Builder.SetCurrentDebugLocation(llvm::DebugLoc());
+  }
+}
+
+NoLocation::~NoLocation() {
+  if (DI) {
+    assert(Builder.getCurrentDebugLocation().isUnknown());
+    DI->CurLoc = SavedLoc;
+  }
+}
+
+BuiltinLocation::BuiltinLocation(CodeGenFunction &CGF, CGBuilderTy &B)
+  : DI(CGF.getDebugInfo()), Builder(B) {
+  if (DI) {
+    SavedLoc = DI->getLocation();
+    // Sync the Builder.
+    DI->EmitLocation(Builder, SavedLoc);
+    DI->CurLoc = SourceLocation();
+    // Construct a location that has a valid scope, but no line info.
+    llvm::MDNode *Scope = DI->LexicalBlockStack.empty() ?
+      DI->TheCU : DI->LexicalBlockStack.back();
+    Builder.SetCurrentDebugLocation(llvm::DebugLoc::get(0, 0, Scope));
+  }
+}
+
+BuiltinLocation::~BuiltinLocation() {
+  if (DI) {
+    assert(Builder.getCurrentDebugLocation().getLine() == 0);
+    DI->CurLoc = SavedLoc;
+  }
+}
+
 void CGDebugInfo::setLocation(SourceLocation Loc) {
   // If the new location isn't valid return.
   if (Loc.isInvalid()) return;
@@ -2449,7 +2487,6 @@ void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, QualType FnType,
 /// previous location will be reused.
 void CGDebugInfo::EmitLocation(CGBuilderTy &Builder, SourceLocation Loc,
                                bool ForceColumnInfo) {
-
   // Update our current location
   setLocation(Loc);
 

clang/lib/CodeGen/CGDebugInfo.h

@@ -47,6 +47,8 @@ namespace CodeGen {
 /// and is responsible for emitting to llvm globals or pass directly to
 /// the backend.
 class CGDebugInfo {
+  friend class NoLocation;
+  friend class BuiltinLocation;
   CodeGenModule &CGM;
   const CodeGenOptions::DebugInfoKind DebugKind;
   llvm::DIBuilder DBuilder;
@@ -387,6 +389,40 @@ private:
   /// \param Force  Assume DebugColumnInfo option is true.
   unsigned getColumnNumber(SourceLocation Loc, bool Force=false);
 };
+
+/// NoLocation - An RAII object that temporarily disables debug
+/// locations. This is useful for emitting instructions that should be
+/// counted towards the function prologue.
+class NoLocation {
+  SourceLocation SavedLoc;
+  CGDebugInfo *DI;
+  CGBuilderTy &Builder;
+public:
+  NoLocation(CodeGenFunction &CGF, CGBuilderTy &B);
+  /// ~NoLocation - Autorestore everything back to normal.
+  ~NoLocation();
+};
+
+/// BuiltinLocation - An RAII object that temporarily switches to an
+/// artificial debug location that has a valid scope, but no line
+/// information. This is useful when emitting compiler-generated
+/// helper functions that have no source location associated with
+/// them.
+///
+/// This is necessary because pasing an empty SourceLocation to
+/// CGDebugInfo::setLocation() will result in the last valid location
+/// being reused.
+class BuiltinLocation {
+  SourceLocation SavedLoc;
+  CGDebugInfo *DI;
+  CGBuilderTy &Builder;
+public:
+  BuiltinLocation(CodeGenFunction &CGF, CGBuilderTy &B);
+  /// ~BuildinLocation - Autorestore everything back to normal.
+  ~BuiltinLocation();
+};
+
+
 } // namespace CodeGen
 } // namespace clang