1 files changed, 68 insertions, 14 deletions

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 04585a8afbb..6a2004828f9 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -955,6 +955,58 @@ void CodeGenFunction::EmitLifetimeEnd(llvm::Value *Size, llvm::Value *Addr) {
   C->setDoesNotThrow();
 }
 
+void CodeGenFunction::EmitAndRegisterVariableArrayDimensions(
+    CGDebugInfo *DI, const VarDecl &D, bool EmitDebugInfo) {
+  // For each dimension stores its QualType and corresponding
+  // size-expression Value.
+  SmallVector<CodeGenFunction::VlaSizePair, 4> Dimensions;
+
+  // Break down the array into individual dimensions.
+  QualType Type1D = D.getType();
+  while (getContext().getAsVariableArrayType(Type1D)) {
+    auto VlaSize = getVLAElements1D(Type1D);
+    if (auto *C = dyn_cast<llvm::ConstantInt>(VlaSize.NumElts))
+      Dimensions.emplace_back(C, Type1D.getUnqualifiedType());
+    else {
+      auto SizeExprAddr =
+          CreateDefaultAlignTempAlloca(VlaSize.NumElts->getType(), "vla_expr");
+      Builder.CreateStore(VlaSize.NumElts, SizeExprAddr);
+      Dimensions.emplace_back(SizeExprAddr.getPointer(),
+                              Type1D.getUnqualifiedType());
+    }
+    Type1D = VlaSize.Type;
+  }
+
+  if (!EmitDebugInfo)
+    return;
+
+  // Register each dimension's size-expression with a DILocalVariable,
+  // so that it can be used by CGDebugInfo when instantiating a DISubrange
+  // to describe this array.
+  for (auto &VlaSize : Dimensions) {
+    llvm::Metadata *MD;
+    if (auto *C = dyn_cast<llvm::ConstantInt>(VlaSize.NumElts))
+      MD = llvm::ConstantAsMetadata::get(C);
+    else {
+      // Create an artificial VarDecl to generate debug info for.
+      IdentifierInfo &NameIdent = getContext().Idents.getOwn(
+          cast<llvm::AllocaInst>(VlaSize.NumElts)->getName());
+      auto VlaExprTy = VlaSize.NumElts->getType()->getPointerElementType();
+      auto QT = getContext().getIntTypeForBitwidth(
+          VlaExprTy->getScalarSizeInBits(), false);
+      auto *ArtificialDecl = VarDecl::Create(
+          getContext(), const_cast<DeclContext *>(D.getDeclContext()),
+          D.getLocation(), D.getLocation(), &NameIdent, QT,
+          getContext().CreateTypeSourceInfo(QT), SC_Auto);
+
+      MD = DI->EmitDeclareOfAutoVariable(ArtificialDecl, VlaSize.NumElts,
+                                         Builder);
+    }
+    assert(MD && "No Size expression debug node created");
+    DI->registerVLASizeExpression(VlaSize.Type, MD);
+  }
+}
+
 /// EmitAutoVarAlloca - Emit the alloca and debug information for a
 /// local variable.  Does not emit initialization or destruction.
 CodeGenFunction::AutoVarEmission
@@ -975,6 +1027,10 @@ CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
   if (Ty->isVariablyModifiedType())
     EmitVariablyModifiedType(Ty);
 
+  auto *DI = getDebugInfo();
+  bool EmitDebugInfo = DI && CGM.getCodeGenOpts().getDebugInfo() >=
+                                 codegenoptions::LimitedDebugInfo;
+
   Address address = Address::invalid();
   if (Ty->isConstantSizeType()) {
     bool NRVO = getLangOpts().ElideConstructors &&
@@ -1108,28 +1164,26 @@ CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
       pushStackRestore(NormalCleanup, Stack);
     }
 
-    llvm::Value *elementCount;
-    QualType elementType;
-    std::tie(elementCount, elementType) = getVLASize(Ty);
-
-    llvm::Type *llvmTy = ConvertTypeForMem(elementType);
+    auto VlaSize = getVLASize(Ty);
+    llvm::Type *llvmTy = ConvertTypeForMem(VlaSize.Type);
 
     // Allocate memory for the array.
-    address = CreateTempAlloca(llvmTy, alignment, "vla", elementCount);
+    address = CreateTempAlloca(llvmTy, alignment, "vla", VlaSize.NumElts);
+
+    // If we have debug info enabled, properly describe the VLA dimensions for
+    // this type by registering the vla size expression for each of the
+    // dimensions.
+    EmitAndRegisterVariableArrayDimensions(DI, D, EmitDebugInfo);
   }
 
   setAddrOfLocalVar(&D, address);
   emission.Addr = address;
 
   // Emit debug info for local var declaration.
-  if (HaveInsertPoint())
-    if (CGDebugInfo *DI = getDebugInfo()) {
-      if (CGM.getCodeGenOpts().getDebugInfo() >=
-          codegenoptions::LimitedDebugInfo) {
-        DI->setLocation(D.getLocation());
-        DI->EmitDeclareOfAutoVariable(&D, address.getPointer(), Builder);
-      }
-    }
+  if (EmitDebugInfo && HaveInsertPoint()) {
+    DI->setLocation(D.getLocation());
+    (void)DI->EmitDeclareOfAutoVariable(&D, address.getPointer(), Builder);
+  }
 
   if (D.hasAttr<AnnotateAttr>())
     EmitVarAnnotations(&D, address.getPointer());