[DebugInfo] Enable debug information for C99 VLA types

Summary:
This patch enables debugging of C99 VLA types by generating more precise
LLVM Debug metadata, using the extended DISubrange 'count' field that
takes a DIVariable.
    
This should implement:
  Bug 30553: Debug info generated for arrays is not what GDB expects (not as good as GCC's)
https://bugs.llvm.org/show_bug.cgi?id=30553

Reviewers: echristo, aprantl, dexonsmith, clayborg, pcc, kristof.beyls, dblaikie

Reviewed By: aprantl

Subscribers: jholewinski, schweitz, davide, fhahn, JDevlieghere, cfe-commits

Differential Revision: https://reviews.llvm.org/D41698

llvm-svn: 323952

1 files changed, 24 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 75071a8e322..35ecf4dbee8 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2198,12 +2198,24 @@ public:
   /// This function can be called with a null (unreachable) insert point.
   void EmitVariablyModifiedType(QualType Ty);
 
-  /// getVLASize - Returns an LLVM value that corresponds to the size,
+  struct VlaSizePair {
+    llvm::Value *NumElts;
+    QualType Type;
+
+    VlaSizePair(llvm::Value *NE, QualType T) : NumElts(NE), Type(T) {}
+  };
+
+  /// Return the number of elements for a single dimension
+  /// for the given array type.
+  VlaSizePair getVLAElements1D(const VariableArrayType *vla);
+  VlaSizePair getVLAElements1D(QualType vla);
+
+  /// Returns an LLVM value that corresponds to the size,
   /// in non-variably-sized elements, of a variable length array type,
   /// plus that largest non-variably-sized element type.  Assumes that
   /// the type has already been emitted with EmitVariablyModifiedType.
-  std::pair<llvm::Value*,QualType> getVLASize(const VariableArrayType *vla);
-  std::pair<llvm::Value*,QualType> getVLASize(QualType vla);
+  VlaSizePair getVLASize(const VariableArrayType *vla);
+  VlaSizePair getVLASize(QualType vla);
 
   /// LoadCXXThis - Load the value of 'this'. This function is only valid while
   /// generating code for an C++ member function.
@@ -2511,6 +2523,15 @@ public:
   void emitAutoVarTypeCleanup(const AutoVarEmission &emission,
                               QualType::DestructionKind dtorKind);
 
+  /// Emits the alloca and debug information for the size expressions for each
+  /// dimension of an array. It registers the association of its (1-dimensional)
+  /// QualTypes and size expression's debug node, so that CGDebugInfo can
+  /// reference this node when creating the DISubrange object to describe the
+  /// array types.
+  void EmitAndRegisterVariableArrayDimensions(CGDebugInfo *DI,
+                                              const VarDecl &D,
+                                              bool EmitDebugInfo);
+
   void EmitStaticVarDecl(const VarDecl &D,
                          llvm::GlobalValue::LinkageTypes Linkage);