[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, 9 insertions, 13 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 668c572942f..2a0dd4a4104 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -1973,7 +1973,7 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
     // VLA types don't have constant size.
     if (const VariableArrayType *vla
           = CGF.getContext().getAsVariableArrayType(type)) {
-      llvm::Value *numElts = CGF.getVLASize(vla).first;
+      llvm::Value *numElts = CGF.getVLASize(vla).NumElts;
       if (!isInc) numElts = Builder.CreateNSWNeg(numElts, "vla.negsize");
       if (CGF.getLangOpts().isSignedOverflowDefined())
         value = Builder.CreateGEP(value, numElts, "vla.inc");
@@ -2271,16 +2271,13 @@ ScalarExprEmitter::VisitUnaryExprOrTypeTraitExpr(
         CGF.EmitIgnoredExpr(E->getArgumentExpr());
       }
 
-      QualType eltType;
-      llvm::Value *numElts;
-      std::tie(numElts, eltType) = CGF.getVLASize(VAT);
-
-      llvm::Value *size = numElts;
+      auto VlaSize = CGF.getVLASize(VAT);
+      llvm::Value *size = VlaSize.NumElts;
 
       // Scale the number of non-VLA elements by the non-VLA element size.
-      CharUnits eltSize = CGF.getContext().getTypeSizeInChars(eltType);
+      CharUnits eltSize = CGF.getContext().getTypeSizeInChars(VlaSize.Type);
       if (!eltSize.isOne())
-        size = CGF.Builder.CreateNUWMul(CGF.CGM.getSize(eltSize), numElts);
+        size = CGF.Builder.CreateNUWMul(CGF.CGM.getSize(eltSize), size);
 
       return size;
     }
@@ -2767,7 +2764,7 @@ static Value *emitPointerArithmetic(CodeGenFunction &CGF,
   if (const VariableArrayType *vla
         = CGF.getContext().getAsVariableArrayType(elementType)) {
     // The element count here is the total number of non-VLA elements.
-    llvm::Value *numElements = CGF.getVLASize(vla).first;
+    llvm::Value *numElements = CGF.getVLASize(vla).NumElts;
 
     // Effectively, the multiply by the VLA size is part of the GEP.
     // GEP indexes are signed, and scaling an index isn't permitted to
@@ -2962,10 +2959,9 @@ Value *ScalarExprEmitter::EmitSub(const BinOpInfo &op) {
   // For a variable-length array, this is going to be non-constant.
   if (const VariableArrayType *vla
         = CGF.getContext().getAsVariableArrayType(elementType)) {
-    llvm::Value *numElements;
-    std::tie(numElements, elementType) = CGF.getVLASize(vla);
-
-    divisor = numElements;
+    auto VlaSize = CGF.getVLASize(vla);
+    elementType = VlaSize.Type;
+    divisor = VlaSize.NumElts;
 
     // Scale the number of non-VLA elements by the non-VLA element size.
     CharUnits eltSize = CGF.getContext().getTypeSizeInChars(elementType);