[DebugInfo] Enable debug information for C99 VLA types

[sdesmalen]

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

[aprantl]

It would be awesome if you could also add an end-to-end test to the debuginfo-tests repository so we can verify that this actually works in LLDB and GDB.

lib/CodeGen/CGDebugInfo.cpp

2360

perhaps write sizeNode/Count to a variable, so you don't have to duplicate the expression?

3483

Could this function be replaced by a default argument instead?

lib/CodeGen/CGDebugInfo.h

86

I'm expecting VLA's to not be very common, should we use a regular DenseMap instead?

317

This is performing the lookup twice. If you use .find() instead it will be more efficient. We also don't use accessor functions like this for any of the other caches. If you think that they help, perhaps make this more generic and useful for all caches?

397

do we need the qualifier on Optional?

lib/CodeGen/CGDecl.cpp

1175

Please move this code into a member function of CGDebugInfo.

1187

.

lib/CodeGen/CodeGenFunction.cpp

1984

return {VlaSize, Vla->getElementType()};

[sdesmalen]

Refactoring based on @aprantl's suggestions.

[sdesmalen]

lib/CodeGen/CGDebugInfo.cpp

2360

Unfortunately this is necessary because SizeNode and Count are different types, and therefore map to a different function signature of getOrCreateSubrange()

lib/CodeGen/CGDebugInfo.h

86

Is that not the argument to use a SmallDenseMap instead? The documentation for DenseMap says:
"Also, because DenseMap allocates space for a large number of key/value pairs (it starts with 64 by default), it will waste a lot of space if your keys or values are large."

There is no documentation for SmallDenseMap, but the name suggests it would be optimized for maps with only a few values?

317

Thanks, I've now removed the accessor function and replaced its uses with the SizeExprCache.find() method as you suggested.

lib/CodeGen/CGDecl.cpp

1175

I moved this to a separate method in CodeGenFunction instead, since it also has to create the actual store (next to creating the DebugInfo), which I don't think should be in CGDebugInfo. Let me know what you think.

lib/CodeGen/CodeGenFunction.cpp

1984

Thanks for the suggestion, that looks much better!

[aprantl]

lib/CodeGen/CGDebugInfo.h

86

I think you're right. This SmallDenseMap is not being allocated on the stack, so it is the right tradeoff here.

[sdesmalen]

Just a gentle reminder that this patch still needs to be accepted (the LLVM support for it has been merged).

[aprantl]

lib/CodeGen/CGDebugInfo.h

392

I think

llvm::DILocalVariable* EmitDeclareOfAutoVariable(const VarDecl *Decl, llvm::Value *AI,
                                 CGBuilderTy &Builder);

would be more natural.

471

same here. Why not just use a return value?

lib/CodeGen/CGDecl.cpp

958

LLVM coding style wants this comment to be on the member function declaration in the header file and only there. Also we don't repeat the function name in the comment any more.

984

s/'fake'/artificial/

990

I think it does, but can you assert me that this generates the same code with and without -g ?

lib/CodeGen/CodeGenFunction.h

2203

How about defining a struct with named members for improved readability? I think you can still use the return {a, b} syntax.

[sdesmalen]

• Changed return type of getVLASize() to a struct with named members.
• EmitDeclare and EmitDeclareOfAutoVariable now return a DILocalVariable* rather than it being returned in a pointer that was passed as default argument.

[sdesmalen]

lib/CodeGen/CGDebugInfo.h

471

Initially I thought it would make more sense for the EmitDeclare function to return the actual call instruction to llvm.dbg.declare, but I see that returning DILocalVariable* makes more sense and that this is in line with the other methods of this class.

lib/CodeGen/CGDecl.cpp

990

I'm not really sure what you mean with 'generates the same code', because without -g this function is not invoked? However, this function only affects debug information, not anything else related to the actual creation of the VLA. So without -g, no 'dbg.declare()' or corresponding DILocalVariables are generated for each subexpression of each dimension.

[aprantl]

lib/CodeGen/CGDecl.cpp

990

What I meant is that regardless of code being compile with or without -g, the .text section of the resulting binary is identical.

[sdesmalen]

lib/CodeGen/CGDecl.cpp

990

Actually, before I commit this patch, I just realize this is not the case. At least not with -O0 since it creates a stackobject to store the vla-size subexpression, which is referenced by the dbg.declare(). We can assume this store/alloca to be DCE'd at optimization levels higher than O0 so it should not have any impact, but strictly taken the .text section will not be the same with and without -g at -O0.

[aprantl]

The correct way to fix this is to generate the stack object unconditionally (it will get optimized away by mem2reg when optimizations are enabled) and only emit the dbg.declare when -g is present.

[sdesmalen]

• Now always emit an alloca for a VLA dimension expression (regardless of whether -g is passed).
• Fixed up some more tests since it now also triggers for all tests with variable length arrays that don't pass -g.
• Refactored EmitAndRegisterVariableArrayDimensions into two phases (one phase to create the alloca, another to create the llvm.dbg.declare call).

[aprantl]

lib/CodeGen/CGDecl.cpp

994

perhaps factor this out into a variable for readability?

[sdesmalen]

Thanks for your review @aprantl!

[CarlosAlbertoEnciso]

Hi @sdesmalen!

First of all my apologies for commenting after the issue has been closed, but I do not have an account to add a comment to the associated bugzilla.

I have found what it seems to be an issue with the current implementation.

For the given test case

int main() {
  int size = 2;

  int vla_expr[size];
  vla_expr[1] = 1;

  return 0;
}

and while debugging with LLDB, the following error is generated:

(lldb) n
Process 21014 stopped
* thread #1, name = 'bad.out', stop reason = step over
    frame #0: 0x0000000000400502 bad.out`main at vla_2.cpp:7
   4   	  int vla_expr[size];
   5   	  vla_expr[1] = 1;
   6   	
-> 7   	  return 0;
   8   	}

(lldb) p vla_expr
(unsigned long) $0 = 2

(lldb) p vla_expr[1]
error: subscripted value is not an array, pointer, or vector

(lldb)

Looking at the DWARF generated, there are 2 variables with the same name at the same scope

DW_TAG_subprogram "main"
  ...
  DW_TAG_variable "size"
  DW_TAG_variable "vla_expr"
  DW_TAG_variable "vla_expr"

I think there are 2 issues:

The compiler generated variable 'vla_expr'

• should be flagged as artificial (DW_AT_artificial)
• its name should start with double underscore to avoid conflicting with user-defined names.

Thanks,
Carlos

[CarlosAlbertoEnciso]

Hi @sdesmalen!

For the following test case

int main() {
  int size = 2;

  int var[size];
  var[1] = 1;

  return 0;
}

I compared the DWARF generated by GCC and it looks like

DW_TAG_variable "var"
  DW_AT_location ...
  DW_AT_type DW_FORM_ref4
    DW_TAG_array_type 
      DW_AT_type -> "int"
      DW_TAG_subrange_type 
        DW_AT_type -> "sizetype"
        DW_AT_upper_bound DW_FORM_exprloc [4] = { DW_OP_fbreg 0xffffffb8 DW_OP_deref }

GCC use DW_AT_upper_bound with an associated location expression to describe the VLA boundaries.

In order to reduce the side effects created by the artifical-variable as described in my previous comment and to keep the generated DWARF within a reasonable size, I would suggest the GCC aproach as a size optimization.

The DWARF description of the artificial-variable could be removed and its location expression used by the array's subrange_type, instead of the subrange_type making a reference to the artificial-variable.

lib/CodeGen/CGBlocks.cpp

for (const auto &CI : blockDecl->captures()) {
       const VarDecl *variable = CI.getVariable();
       DI->EmitLocation(Builder, variable->getLocation());
 
       if (CGM.getCodeGenOpts().getDebugInfo() >=
           codegenoptions::LimitedDebugInfo) {
         const CGBlockInfo::Capture &capture = blockInfo.getCapture(variable);
         if (capture.isConstant()) {
           auto addr = LocalDeclMap.find(variable)->second;
-          DI->EmitDeclareOfAutoVariable(variable, addr.getPointer(),
+          (void)DI->EmitDeclareOfAutoVariable(variable, addr.getPointer(),
                                               Builder);
           continue;
         }
 
         DI->EmitDeclareOfBlockDeclRefVariable(
             variable, BlockPointerDbgLoc, Builder, blockInfo,
             entry_ptr == entry->end() ? nullptr : &*entry_ptr);
       }
     }

lib/CodeGen/CGDebugInfo.h

#include "clang/Basic/OpenCLImageTypes.def"
   llvm::DIType *OCLNDRangeDITy = nullptr;
   llvm::DIType *OCLReserveIDDITy = nullptr;
 
   /// Cache of previously constructed Types.
   llvm::DenseMap<const void *, llvm::TrackingMDRef> TypeCache;
 
   llvm::SmallDenseMap<llvm::StringRef, llvm::StringRef> DebugPrefixMap;
 
+  /// Cache that maps VLA types to size expressions for that type,
+  /// represented by instantiated Metadata nodes.
+  llvm::SmallDenseMap<QualType, llvm::Metadata *> SizeExprCache;
+
   struct ObjCInterfaceCacheEntry {
     const ObjCInterfaceType *Type;
     llvm::DIType *Decl;
     llvm::DIFile *Unit;
     ObjCInterfaceCacheEntry(const ObjCInterfaceType *Type, llvm::DIType *Decl,
                             llvm::DIFile *Unit)
         : Type(Type), Decl(Decl), Unit(Unit) {}
   };
void AppendAddressSpaceXDeref(unsigned AddressSpace,
                                 SmallVectorImpl<int64_t> &Expr) const;
 
 public:
   CGDebugInfo(CodeGenModule &CGM);
   ~CGDebugInfo();
 
   void finalize();
 
+  /// Register VLA size expression debug node with the qualified type.
+  void registerVLASizeExpression(QualType Ty, llvm::Metadata *SizeExpr) {
+    SizeExprCache[Ty] = SizeExpr;
+  }
+
   /// Module debugging: Support for building PCMs.
   /// @{
   /// Set the main CU's DwoId field to \p Signature.
   void setDwoId(uint64_t Signature);
 
   /// When generating debug information for a clang module or
   /// precompiled header, this module map will be used to determine
   /// the module of origin of each Decl.
public:
   void EmitLexicalBlockStart(CGBuilderTy &Builder, SourceLocation Loc);
 
   /// Emit metadata to indicate the end of a new lexical block and pop
   /// the current block.
   void EmitLexicalBlockEnd(CGBuilderTy &Builder, SourceLocation Loc);
 
   /// Emit call to \c llvm.dbg.declare for an automatic variable
   /// declaration.
-  void EmitDeclareOfAutoVariable(const VarDecl *Decl, llvm::Value *AI,
+  /// Returns a pointer to the DILocalVariable associated with the
+  /// llvm.dbg.declare, or nullptr otherwise.
+  llvm::DILocalVariable *EmitDeclareOfAutoVariable(const VarDecl *Decl,
+                                                   llvm::Value *AI,
                                                    CGBuilderTy &Builder);
 
   /// Emit call to \c llvm.dbg.declare for an imported variable
   /// declaration in a block.
   void EmitDeclareOfBlockDeclRefVariable(const VarDecl *variable,
                                          llvm::Value *storage,
                                          CGBuilderTy &Builder,
                                          const CGBlockInfo &blockInfo,
                                          llvm::Instruction *InsertPoint = nullptr);
 
   /// Emit call to \c llvm.dbg.declare for an argument variable
public:
   llvm::DIMacro *CreateMacro(llvm::DIMacroFile *Parent, unsigned MType,
                              SourceLocation LineLoc, StringRef Name,
                              StringRef Value);
 
   /// Create debug info for a file referenced by an #include directive.
   llvm::DIMacroFile *CreateTempMacroFile(llvm::DIMacroFile *Parent,
                                          SourceLocation LineLoc,
                                          SourceLocation FileLoc);
+
 private:
   /// Emit call to llvm.dbg.declare for a variable declaration.
-  void EmitDeclare(const VarDecl *decl, llvm::Value *AI,
-                   llvm::Optional<unsigned> ArgNo, CGBuilderTy &Builder);
+  /// Returns a pointer to the DILocalVariable associated with the
+  /// llvm.dbg.declare, or nullptr otherwise.
+  llvm::DILocalVariable *EmitDeclare(const VarDecl *decl, llvm::Value *AI,
+                                     llvm::Optional<unsigned> ArgNo,
+                                     CGBuilderTy &Builder);
 
   /// Build up structure info for the byref.  See \a BuildByRefType.
   llvm::DIType *EmitTypeForVarWithBlocksAttr(const VarDecl *VD,
                                              uint64_t *OffSet);
 
   /// Get context info for the DeclContext of \p Decl.
   llvm::DIScope *getDeclContextDescriptor(const Decl *D);
   /// Get context info for a given DeclContext \p Decl.

lib/CodeGen/CGDebugInfo.cpp

llvm::DIType *CGDebugInfo::CreateTypeDefinition(const ObjCInterfaceType *Ty,
   LexicalBlockStack.pop_back();
   return RealDecl;
 }
 
 llvm::DIType *CGDebugInfo::CreateType(const VectorType *Ty,
                                       llvm::DIFile *Unit) {
   llvm::DIType *ElementTy = getOrCreateType(Ty->getElementType(), Unit);
   int64_t Count = Ty->getNumElements();
-  if (Count == 0)
-    // If number of elements are not known then this is an unbounded array.
-    // Use Count == -1 to express such arrays.
-    Count = -1;
 
-  llvm::Metadata *Subscript = DBuilder.getOrCreateSubrange(0, Count);
+  llvm::Metadata *Subscript;
+  QualType QTy(Ty, 0);
+  auto SizeExpr = SizeExprCache.find(QTy);
+  if (SizeExpr != SizeExprCache.end())
+    Subscript = DBuilder.getOrCreateSubrange(0, SizeExpr->getSecond());
+  else
+    Subscript = DBuilder.getOrCreateSubrange(0, Count ? Count : -1);
   llvm::DINodeArray SubscriptArray = DBuilder.getOrCreateArray(Subscript);
 
   uint64_t Size = CGM.getContext().getTypeSize(Ty);
   auto Align = getTypeAlignIfRequired(Ty, CGM.getContext());
 
   return DBuilder.createVectorType(Size, Align, ElementTy, SubscriptArray);
 }
 
while ((Ty = dyn_cast<ArrayType>(EltTy))) {
     else if (const auto *VAT = dyn_cast<VariableArrayType>(Ty)) {
       if (Expr *Size = VAT->getSizeExpr()) {
         llvm::APSInt V;
         if (Size->EvaluateAsInt(V, CGM.getContext()))
           Count = V.getExtValue();
       }
     }
 
-    // FIXME: Verify this is right for VLAs.
+    auto SizeNode = SizeExprCache.find(EltTy);
+    if (SizeNode != SizeExprCache.end())
+      Subscripts.push_back(
+          DBuilder.getOrCreateSubrange(0, SizeNode->getSecond()));
+    else
       Subscripts.push_back(DBuilder.getOrCreateSubrange(0, Count));
     EltTy = Ty->getElementType();
   }
 
   llvm::DINodeArray SubscriptArray = DBuilder.getOrCreateArray(Subscripts);
 
   return DBuilder.createArrayType(Size, Align, getOrCreateType(EltTy, Unit),
                                   SubscriptArray);
 }
llvm::DIType *CGDebugInfo::EmitTypeForVarWithBlocksAttr(const VarDecl *VD,
   llvm::DINodeArray Elements = DBuilder.getOrCreateArray(EltTys);
 
   llvm::DINode::DIFlags Flags = llvm::DINode::FlagBlockByrefStruct;
 
   return DBuilder.createStructType(Unit, "", Unit, 0, FieldOffset, 0, Flags,
                                    nullptr, Elements);
 }
 
-void CGDebugInfo::EmitDeclare(const VarDecl *VD, llvm::Value *Storage,
+llvm::DILocalVariable *CGDebugInfo::EmitDeclare(const VarDecl *VD,
+                                                llvm::Value *Storage,
                                                 llvm::Optional<unsigned> ArgNo,
                                                 CGBuilderTy &Builder) {
   assert(DebugKind >= codegenoptions::LimitedDebugInfo);
   assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
   if (VD->hasAttr<NoDebugAttr>())
-    return;
+    return nullptr;
 
   bool Unwritten =
       VD->isImplicit() || (isa<Decl>(VD->getDeclContext()) &&
                            cast<Decl>(VD->getDeclContext())->isImplicit());
   llvm::DIFile *Unit = nullptr;
   if (!Unwritten)
     Unit = getOrCreateFile(VD->getLocation());
   llvm::DIType *Ty;
   uint64_t XOffset = 0;
   if (VD->hasAttr<BlocksAttr>())
     Ty = EmitTypeForVarWithBlocksAttr(VD, &XOffset);
   else
     Ty = getOrCreateType(VD->getType(), Unit);
 
   // If there is no debug info for this type then do not emit debug info
   // for this variable.
   if (!Ty)
-    return;
+    return nullptr;
 
   // Get location information.
   unsigned Line = 0;
   unsigned Column = 0;
   if (!Unwritten) {
     Line = getLineNumber(VD->getLocation());
     Column = getColumnNumber(VD->getLocation());
   }
auto *D = ArgNo
                 : DBuilder.createAutoVariable(Scope, Name, Unit, Line, Ty,
                                               CGM.getLangOpts().Optimize, Flags,
                                               Align);
 
   // Insert an llvm.dbg.declare into the current block.
   DBuilder.insertDeclare(Storage, D, DBuilder.createExpression(Expr),
                          llvm::DebugLoc::get(Line, Column, Scope, CurInlinedAt),
                          Builder.GetInsertBlock());
+
+  return D;
 }
 
-void CGDebugInfo::EmitDeclareOfAutoVariable(const VarDecl *VD,
-                                            llvm::Value *Storage,
-                                            CGBuilderTy &Builder) {
+llvm::DILocalVariable *
+CGDebugInfo::EmitDeclareOfAutoVariable(const VarDecl *VD, llvm::Value *Storage,
   assert(DebugKind >= codegenoptions::LimitedDebugInfo);
-  EmitDeclare(VD, Storage, llvm::None, Builder);
+  return EmitDeclare(VD, Storage, llvm::None, Builder);
 }
 
 llvm::DIType *CGDebugInfo::CreateSelfType(const QualType &QualTy,
                                           llvm::DIType *Ty) {
   llvm::DIType *CachedTy = getTypeOrNull(QualTy);
   if (CachedTy)
     Ty = CachedTy;
   return DBuilder.createObjectPointerType(Ty);

lib/CodeGen/CGDecl.cpp

 
 void CodeGenFunction::EmitLifetimeEnd(llvm::Value *Size, llvm::Value *Addr) {
   Addr = Builder.CreateBitCast(Addr, AllocaInt8PtrTy);
   llvm::CallInst *C =
       Builder.CreateCall(CGM.getLLVMLifetimeEndFn(), {Size, 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 QT = getContext().getIntTypeForBitwidth(VlaSize.NumElts->getType()
+                                                       ->getPointerElementType()
+                                                       ->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
 CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
   QualType Ty = D.getType();
   assert(
       Ty.getAddressSpace() == LangAS::Default ||
       (Ty.getAddressSpace() == LangAS::opencl_private && getLangOpts().OpenCL));
 
   AutoVarEmission emission(D);
 
   bool isByRef = D.hasAttr<BlocksAttr>();
   emission.IsByRef = isByRef;
 
   CharUnits alignment = getContext().getDeclAlign(&D);
 
   // If the type is variably-modified, emit all the VLA sizes for it.
   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 &&
       D.isNRVOVariable();
 
     // If this value is an array or struct with a statically determinable
     // constant initializer, there are optimizations we can do.
     //
if (!DidCallStackSave) {
 
       DidCallStackSave = true;
 
       // Push a cleanup block and restore the stack there.
       // FIXME: in general circumstances, this should be an EH cleanup.
       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()) {
+    (void)DI->EmitDeclareOfAutoVariable(&D, address.getPointer(), Builder);
 
   if (D.hasAttr<AnnotateAttr>())
     EmitVarAnnotations(&D, address.getPointer());
 
   // Make sure we call @llvm.lifetime.end.
   if (emission.useLifetimeMarkers())
     EHStack.pushCleanup<CallLifetimeEnd>(NormalEHLifetimeMarker,
                                          emission.getAllocatedAddress(),

lib/CodeGen/CGExpr.cpp

static llvm::Value *getArrayIndexingBound(
   if (const auto *CE = dyn_cast<CastExpr>(Base)) {
     if (CE->getCastKind() == CK_ArrayToPointerDecay &&
         !isFlexibleArrayMemberExpr(CE->getSubExpr())) {
       IndexedType = CE->getSubExpr()->getType();
       const ArrayType *AT = IndexedType->castAsArrayTypeUnsafe();
       if (const auto *CAT = dyn_cast<ConstantArrayType>(AT))
         return CGF.Builder.getInt(CAT->getSize());
       else if (const auto *VAT = dyn_cast<VariableArrayType>(AT))
-        return CGF.getVLASize(VAT).first;
+        return CGF.getVLASize(VAT).NumElts;
       // Ignore pass_object_size here. It's not applicable on decayed pointers.
     }
   }
 
   QualType EltTy{Base->getType()->getPointeeOrArrayElementType(), 0};
   if (llvm::Value *POS = CGF.LoadPassedObjectSize(Base, EltTy)) {
     IndexedType = Base->getType();
     return POS;
if (const VariableArrayType *vla =
            getContext().getAsVariableArrayType(E->getType())) {
     // The base must be a pointer, which is not an aggregate.  Emit
     // it.  It needs to be emitted first in case it's what captures
     // the VLA bounds.
     Addr = EmitPointerWithAlignment(E->getBase(), &EltBaseInfo, &EltTBAAInfo);
     auto *Idx = EmitIdxAfterBase(/*Promote*/true);
 
     // The element count here is the total number of non-VLA elements.
-    llvm::Value *numElements = getVLASize(vla).first;
+    llvm::Value *numElements = 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
     // signed-overflow, so we use the same semantics for our explicit
     // multiply.  We suppress this if overflow is not undefined behavior.
     if (getLangOpts().isSignedOverflowDefined()) {
       Idx = Builder.CreateMul(Idx, numElements);
     } else {
LValue CodeGenFunction::EmitOMPArraySectionExpr(const OMPArraySectionExpr *E,
   if (auto *VLA = getContext().getAsVariableArrayType(ResultExprTy)) {
     // The base must be a pointer, which is not an aggregate.  Emit
     // it.  It needs to be emitted first in case it's what captures
     // the VLA bounds.
     Address Base =
         emitOMPArraySectionBase(*this, E->getBase(), BaseInfo, TBAAInfo,
                                 BaseTy, VLA->getElementType(), IsLowerBound);
     // The element count here is the total number of non-VLA elements.
-    llvm::Value *NumElements = getVLASize(VLA).first;
+    llvm::Value *NumElements = 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
     // signed-overflow, so we use the same semantics for our explicit
     // multiply.  We suppress this if overflow is not undefined behavior.
     if (getLangOpts().isSignedOverflowDefined())
       Idx = Builder.CreateMul(Idx, NumElements);
     else

lib/CodeGen/CGExprScalar.cpp

ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
 
   // Next most common: pointer increment.
   } else if (const PointerType *ptr = type->getAs<PointerType>()) {
     QualType type = ptr->getPointeeType();
 
     // 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");
       else
         value = CGF.EmitCheckedInBoundsGEP(
             value, numElts, /*SignedIndices=*/false, isSubtraction,
             E->getExprLoc(), "vla.inc");
 
if (const VariableArrayType *VAT =
         // sizeof(type) - make sure to emit the VLA size.
         CGF.EmitVariablyModifiedType(TypeToSize);
       } else {
         // C99 6.5.3.4p2: If the argument is an expression of type
         // VLA, it is evaluated.
         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;
     }
   } else if (E->getKind() == UETT_OpenMPRequiredSimdAlign) {
     auto Alignment =
         CGF.getContext()
             .toCharUnitsFromBits(CGF.getContext().getOpenMPDefaultSimdAlign(
                 E->getTypeOfArgument()->getPointeeType()))
if (!pointerType) {
     result = CGF.Builder.CreateGEP(result, index, "add.ptr");
     return CGF.Builder.CreateBitCast(result, pointer->getType());
   }
 
   QualType elementType = pointerType->getPointeeType();
   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
     // signed-overflow, so we use the same semantics for our explicit
     // multiply.  We suppress this if overflow is not undefined behavior.
     if (CGF.getLangOpts().isSignedOverflowDefined()) {
       index = CGF.Builder.CreateMul(index, numElements, "vla.index");
       pointer = CGF.Builder.CreateGEP(pointer, index, "add.ptr");
Value *ScalarExprEmitter::EmitSub(const BinOpInfo &op) {
   const BinaryOperator *expr = cast<BinaryOperator>(op.E);
   QualType elementType = expr->getLHS()->getType()->getPointeeType();
 
   llvm::Value *divisor = nullptr;
 
   // 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);
     if (!eltSize.isOne())
       divisor = CGF.Builder.CreateNUWMul(CGF.CGM.getSize(eltSize), divisor);
 
   // For everything elese, we can just compute it, safe in the
   // assumption that Sema won't let anything through that we can't

lib/CodeGen/CGOpenMPRuntime.cpp

for (unsigned I = 0, E = RHSExprs.size(); I < E; ++I, ++IPriv, ++Idx) {
     if ((*IPriv)->getType()->isVariablyModifiedType()) {
       // Store array size.
       ++Idx;
       Elem = CGF.Builder.CreateConstArrayGEP(ReductionList, Idx,
                                              CGF.getPointerSize());
       llvm::Value *Size = CGF.Builder.CreateIntCast(
           CGF.getVLASize(
                  CGF.getContext().getAsVariableArrayType((*IPriv)->getType()))
-              .first,
+              .NumElts,
           CGF.SizeTy, /*isSigned=*/false);
       CGF.Builder.CreateStore(CGF.Builder.CreateIntToPtr(Size, CGF.VoidPtrTy),
                               Elem);
     }
   }
 
   // 2. Emit reduce_func().
   auto *ReductionFn = emitReductionFunction(

lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp

for (unsigned I = 0, E = RHSExprs.size(); I < E; ++I, ++IPriv, ++Idx) {
     if ((*IPriv)->getType()->isVariablyModifiedType()) {
       // Store array size.
       ++Idx;
       Elem = CGF.Builder.CreateConstArrayGEP(ReductionList, Idx,
                                              CGF.getPointerSize());
       llvm::Value *Size = CGF.Builder.CreateIntCast(
           CGF.getVLASize(
                  CGF.getContext().getAsVariableArrayType((*IPriv)->getType()))
-              .first,
+              .NumElts,
           CGF.SizeTy, /*isSigned=*/false);
       CGF.Builder.CreateStore(CGF.Builder.CreateIntToPtr(Size, CGF.VoidPtrTy),
                               Elem);
     }
   }
 
   // 2. Emit reduce_func().
   auto *ReductionFn = emitReductionFunction(

lib/CodeGen/CGStmtOpenMP.cpp

 
 llvm::Value *CodeGenFunction::getTypeSize(QualType Ty) {
   auto &C = getContext();
   llvm::Value *Size = nullptr;
   auto SizeInChars = C.getTypeSizeInChars(Ty);
   if (SizeInChars.isZero()) {
     // getTypeSizeInChars() returns 0 for a VLA.
     while (auto *VAT = C.getAsVariableArrayType(Ty)) {
-      llvm::Value *ArraySize;
-      std::tie(ArraySize, Ty) = getVLASize(VAT);
-      Size = Size ? Builder.CreateNUWMul(Size, ArraySize) : ArraySize;
+      auto VlaSize = getVLASize(VAT);
+      Ty = VlaSize.Type;
+      Size = Size ? Builder.CreateNUWMul(Size, VlaSize.NumElts)
+                  : VlaSize.NumElts;
     }
     SizeInChars = C.getTypeSizeInChars(Ty);
     if (SizeInChars.isZero())
       return llvm::ConstantInt::get(SizeTy, /*V=*/0);
     Size = Builder.CreateNUWMul(Size, CGM.getSize(SizeInChars));
   } else
     Size = CGM.getSize(SizeInChars);
   return Size;

lib/CodeGen/CodeGenFunction.h

llvm::Value *emitArrayLength(const ArrayType *arrayType,
                                Address &addr);
 
   /// EmitVLASize - Capture all the sizes for the VLA expressions in
   /// the given variably-modified type and store them in the VLASizeMap.
   ///
   /// 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.
   llvm::Value *LoadCXXThis() {
     assert(CXXThisValue && "no 'this' value for this function");
     return CXXThisValue;
   }
   Address LoadCXXThisAddress();
public:
     }
   };
   AutoVarEmission EmitAutoVarAlloca(const VarDecl &var);
   void EmitAutoVarInit(const AutoVarEmission &emission);
   void EmitAutoVarCleanups(const AutoVarEmission &emission);
   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);
 
   class ParamValue {
     llvm::Value *Value;
     unsigned Alignment;
     ParamValue(llvm::Value *V, unsigned A) : Value(V), Alignment(A) {}
   public:

lib/CodeGen/CodeGenFunction.cpp

CodeGenFunction::EmitNullInitialization(Address DestPtr, QualType Ty) {
   const VariableArrayType *vla;
 
   // Don't bother emitting a zero-byte memset.
   if (size.isZero()) {
     // But note that getTypeInfo returns 0 for a VLA.
     if (const VariableArrayType *vlaType =
           dyn_cast_or_null<VariableArrayType>(
                                           getContext().getAsArrayType(Ty))) {
-      QualType eltType;
-      llvm::Value *numElts;
-      std::tie(numElts, eltType) = getVLASize(vlaType);
-
-      SizeVal = numElts;
-      CharUnits eltSize = getContext().getTypeSizeInChars(eltType);
+      auto VlaSize = getVLASize(vlaType);
+      SizeVal = VlaSize.NumElts;
+      CharUnits eltSize = getContext().getTypeSizeInChars(VlaSize.Type);
       if (!eltSize.isOne())
         SizeVal = Builder.CreateNUWMul(SizeVal, CGM.getSize(eltSize));
       vla = vlaType;
     } else {
       return;
     }
   } else {
     SizeVal = CGM.getSize(size);
llvm::Value *CodeGenFunction::emitArrayLength(const ArrayType *origArrayType,
                                               QualType &baseType,
                                               Address &addr) {
   const ArrayType *arrayType = origArrayType;
 
   // If it's a VLA, we have to load the stored size.  Note that
   // this is the size of the VLA in bytes, not its size in elements.
   llvm::Value *numVLAElements = nullptr;
   if (isa<VariableArrayType>(arrayType)) {
-    numVLAElements = getVLASize(cast<VariableArrayType>(arrayType)).first;
+    numVLAElements = getVLASize(cast<VariableArrayType>(arrayType)).NumElts;
 
     // Walk into all VLAs.  This doesn't require changes to addr,
     // which has type T* where T is the first non-VLA element type.
     do {
       QualType elementType = arrayType->getElementType();
       arrayType = getContext().getAsArrayType(elementType);
 
       // If we only have VLA components, 'addr' requires no adjustment.
llvm::Value *CodeGenFunction::emitArrayLength(const ArrayType *origArrayType,
 
   // If we had any VLA dimensions, factor them in.
   if (numVLAElements)
     numElements = Builder.CreateNUWMul(numVLAElements, numElements);
 
   return numElements;
 }
 
-std::pair<llvm::Value*, QualType>
-CodeGenFunction::getVLASize(QualType type) {
+CodeGenFunction::VlaSizePair CodeGenFunction::getVLASize(QualType type) {
   const VariableArrayType *vla = getContext().getAsVariableArrayType(type);
   assert(vla && "type was not a variable array type!");
   return getVLASize(vla);
 }
 
-std::pair<llvm::Value*, QualType>
+CodeGenFunction::VlaSizePair
 CodeGenFunction::getVLASize(const VariableArrayType *type) {
   // The number of elements so far; always size_t.
   llvm::Value *numElements = nullptr;
 
   QualType elementType;
   do {
     elementType = type->getElementType();
     llvm::Value *vlaSize = VLASizeMap[type->getSizeExpr()];
     assert(vlaSize && "no size for VLA!");
     assert(vlaSize->getType() == SizeTy);
 
     if (!numElements) {
       numElements = vlaSize;
     } else {
       // It's undefined behavior if this wraps around, so mark it that way.
       // FIXME: Teach -fsanitize=undefined to trap this.
       numElements = Builder.CreateNUWMul(numElements, vlaSize);
     }
   } while ((type = getContext().getAsVariableArrayType(elementType)));
 
-  return std::pair<llvm::Value*,QualType>(numElements, elementType);
+  return { numElements, elementType };
+}
+
+CodeGenFunction::VlaSizePair
+CodeGenFunction::getVLAElements1D(QualType type) {
+  const VariableArrayType *vla = getContext().getAsVariableArrayType(type);
+  assert(vla && "type was not a variable array type!");
+  return getVLAElements1D(vla);
+}
+
+CodeGenFunction::VlaSizePair
+CodeGenFunction::getVLAElements1D(const VariableArrayType *Vla) {
+  llvm::Value *VlaSize = VLASizeMap[Vla->getSizeExpr()];
+  assert(VlaSize && "no size for VLA!");
+  assert(VlaSize->getType() == SizeTy);
+  return { VlaSize, Vla->getElementType() };
 }
 
 void CodeGenFunction::EmitVariablyModifiedType(QualType type) {
   assert(type->isVariablyModifiedType() &&
          "Must pass variably modified type to EmitVLASizes!");
 
   EnsureInsertPoint();
 
   // We're going to walk down into the type and look for VLA
   // expressions.
   do {
     assert(type->isVariablyModifiedType());
 
     const Type *ty = type.getTypePtr();
     switch (ty->getTypeClass()) {
 
 #define TYPE(Class, Base)
 #define ABSTRACT_TYPE(Class, Base)
 #define NON_CANONICAL_TYPE(Class, Base)
 #define DEPENDENT_TYPE(Class, Base) case Type::Class:
 #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base)
 #include "clang/AST/TypeNodes.def"
       llvm_unreachable("unexpected dependent type!");

test/CodeGen/debug-info-vla.c

 // RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited -triple x86_64-apple-darwin %s -o - | FileCheck %s
 
 void testVLAwithSize(int s)
 {
-// CHECK: dbg.declare
-// CHECK: dbg.declare({{.*}}, metadata ![[VAR:.*]], metadata !DIExpression())
-// CHECK: ![[VAR]] = !DILocalVariable(name: "vla",{{.*}} line: [[@LINE+1]]
+// CHECK-DAG: dbg.declare({{.*}} %vla_expr, metadata ![[VLAEXPR:[0-9]+]]
+// CHECK-DAG: dbg.declare({{.*}} %vla, metadata ![[VAR:[0-9]+]]
+// CHECK-DAG: ![[VLAEXPR]] = !DILocalVariable(name: "vla_expr"
+// CHECK-DAG: ![[VAR]] = !DILocalVariable(name: "vla",{{.*}} line: [[@LINE+2]]
+// CHECK-DAG: !DISubrange(count: ![[VLAEXPR]])
   int vla[s];
   int i;
   for (i = 0; i < s; i++) {
     vla[i] = i*i;
   }
 }

test/CodeGenCXX/debug-info-vla.cpp

 // RUN: %clang -target x86_64-unknown-unknown -fverbose-asm -g -O0 -S -emit-llvm %s -o - -std=c++11 | FileCheck %s
 
 
 void f(int m) {
   int x[3][m];
 }
 
 int (*fp)(int[][*]) = nullptr;
 
 // CHECK: !DICompositeType(tag: DW_TAG_array_type,
 // CHECK-NOT:                               size:
 // CHECK-SAME:                              elements: [[ELEM_TYPE:![0-9]+]]
 // CHECK: [[ELEM_TYPE]] = !{[[NOCOUNT:.*]]}
 // CHECK: [[NOCOUNT]] = !DISubrange(count: -1)
 //
+// CHECK: [[VAR:![0-9]+]] = !DILocalVariable(name: "vla_expr"
 // CHECK: !DICompositeType(tag: DW_TAG_array_type,
 // CHECK-NOT:                               size:
 // CHECK-SAME:                              elements: [[ELEM_TYPE:![0-9]+]]
-// CHECK: [[ELEM_TYPE]] = !{[[THREE:.*]], [[NOCOUNT]]}
+// CHECK: [[ELEM_TYPE]] = !{[[THREE:.*]], [[VARRANGE:![0-9]+]]}
 // CHECK: [[THREE]] = !DISubrange(count: 3)
+// CHECK: [[VARRANGE]] = !DISubrange(count: [[VAR]])

test/CodeGenCXX/vla-consruct.cpp

void print(int n, int a, int b, int c, int d) {
   if (n == 2)
     throw(n);
 }
 
 void test(int n) {
   // CHECK: define void {{.*test.*}}(i32 [[n:%.+]]) #
   // CHECK: [[n_addr:%.+]] = alloca
   // CHECK-NEXT: [[saved_stack:%.+]] = alloca
+  // CHECK-NEXT: [[vla_expr:%.+]] = alloca i64, align 8
+  // CHECK-NEXT: [[vla_expr1:%.+]] = alloca i64, align 8
   // CHECK-NEXT: [[sizeof_S:%.+]] = alloca
   // CHECK-NEXT: [[sizeof_array_t_0_0:%.+]] = alloca
   // CHECK-NEXT: [[sizeof_array_t_0:%.+]] = alloca
   // CHECK-NEXT: [[sizeof_array_t:%.+]] = alloca
   // CHECK-NEXT: [[exn_slot:%.+]] = alloca i8*
   // CHECK-NEXT: [[ehselector_slot:%.+]] = alloca i32
   // CHECK-NEXT: store i32 [[n]], i32* [[n_addr]]
   // CHECK-NEXT: [[t0:%.+]] = load i32, i32* [[n_addr]]
   // CHECK-NEXT: [[t1:%.+]] = zext i32 [[t0]] to i64
   // CHECK-NEXT: [[t2:%.+]] = load i32, i32* [[n_addr]]
   // CHECK-NEXT: [[add:%.+]] = add nsw i32 [[t2]], 1
   // CHECK-NEXT: [[t3:%.+]] = zext i32 [[add]] to i64
   // CHECK-NEXT: [[t4:%.+]] = call i8* @llvm.stacksave()
   // CHECK-NEXT: store i8* [[t4]], i8** [[saved_stack]]
   // CHECK-NEXT: [[t5:%.+]] = mul nuw i64 [[t1]], [[t3]]
   // CHECK-NEXT: [[vla:%.+]] = alloca [[struct_S]], i64 [[t5]]
+  // CHECK-NEXT: store i64 [[t1]], i64* [[vla_expr]]
+  // CHECK-NEXT: store i64 [[t3]], i64* [[vla_expr1]]
   // CHECK-NEXT: [[t6:%.+]] = mul nuw i64 [[t1]], [[t3]]
   // CHECK-NEXT: [[isempty:%.+]] = icmp eq i64 [[t6]], 0
   // CHECK-NEXT: br i1 [[isempty]], label %[[arrayctor_cont:.+]], label %[[new_ctorloop:.+]]
 
   S array_t[n][n + 1];
 
   // CHECK: [[new_ctorloop]]
   // CHECK-NEXT: [[arrayctor_end:%.+]] = getelementptr inbounds [[struct_S]], [[struct_S]]* [[vla]], i64 [[t6]]

test/CodeGenObjC/arc.m

void test19() {
 
   // CHECK:      ret void
 }
 
 void test20(unsigned n) {
   // CHECK-LABEL: define void @test20
   // CHECK:      [[N:%.*]] = alloca i32, align 4
   // CHECK-NEXT: [[SAVED_STACK:%.*]] = alloca i8*
+  // CHECK-NEXT: [[VLA_EXPR:%.*]] = alloca i64, align 8
   // CHECK-NEXT: store i32 {{%.*}}, i32* [[N]], align 4
 
   id x[n];
 
   // Capture the VLA size.
   // CHECK-NEXT: [[T0:%.*]] = load i32, i32* [[N]], align 4
   // CHECK-NEXT: [[DIM:%.*]] = zext i32 [[T0]] to i64
 
   // Save the stack pointer.
   // CHECK-NEXT: [[T0:%.*]] = call i8* @llvm.stacksave()
   // CHECK-NEXT: store i8* [[T0]], i8** [[SAVED_STACK]]
 
   // Allocate the VLA.
   // CHECK-NEXT: [[VLA:%.*]] = alloca i8*, i64 [[DIM]], align 16
 
+  // Store the VLA #elements expression.
+  // CHECK-NEXT: store i64 %1, i64* [[VLA_EXPR]], align 8
+
   // Zero-initialize.
   // CHECK-NEXT: [[T0:%.*]] = bitcast i8** [[VLA]] to i8*
   // CHECK-NEXT: [[T1:%.*]] = mul nuw i64 [[DIM]], 8
   // CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 16 [[T0]], i8 0, i64 [[T1]], i1 false)
 
   // Destroy.
   // CHECK-NEXT: [[END:%.*]] = getelementptr inbounds i8*, i8** [[VLA]], i64 [[DIM]]
   // CHECK-NEXT: [[EMPTY:%.*]] = icmp eq i8** [[VLA]], [[END]]
void test20(unsigned n) {
   // CHECK-NEXT: call void @llvm.stackrestore(i8* [[T0]])
   // CHECK-NEXT: ret void
 }
 
 void test21(unsigned n) {
   // CHECK-LABEL: define void @test21
   // CHECK:      [[N:%.*]] = alloca i32, align 4
   // CHECK-NEXT: [[SAVED_STACK:%.*]] = alloca i8*
+  // CHECK-NEXT: [[VLA_EXPR:%.*]] = alloca i64, align 8
   // CHECK-NEXT: store i32 {{%.*}}, i32* [[N]], align 4
 
   id x[2][n][3];
 
   // Capture the VLA size.
   // CHECK-NEXT: [[T0:%.*]] = load i32, i32* [[N]], align 4
   // CHECK-NEXT: [[DIM:%.*]] = zext i32 [[T0]] to i64
 
   // CHECK-NEXT: [[T0:%.*]] = call i8* @llvm.stacksave()
   // CHECK-NEXT: store i8* [[T0]], i8** [[SAVED_STACK]]
 
 
   // Allocate the VLA.
   // CHECK-NEXT: [[T0:%.*]] = mul nuw i64 2, [[DIM]]
   // CHECK-NEXT: [[VLA:%.*]] = alloca [3 x i8*], i64 [[T0]], align 16
 
+  // Store the VLA #elements expression.
+  // CHECK-NEXT: store i64 %1, i64* [[VLA_EXPR]], align 8
+
   // Zero-initialize.
   // CHECK-NEXT: [[T0:%.*]] = bitcast [3 x i8*]* [[VLA]] to i8*
   // CHECK-NEXT: [[T1:%.*]] = mul nuw i64 2, [[DIM]]
   // CHECK-NEXT: [[T2:%.*]] = mul nuw i64 [[T1]], 24
   // CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 16 [[T0]], i8 0, i64 [[T2]], i1 false)
 
   // Destroy.
   // CHECK-NEXT: [[T0:%.*]] = mul nuw i64 2, [[DIM]]

test/OpenMP/target_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[IFELSE:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]

test/OpenMP/target_parallel_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[FAIL:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]

test/OpenMP/target_parallel_for_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[FAIL:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]

test/OpenMP/target_parallel_for_simd_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[FAIL:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]

test/OpenMP/target_simd_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[FAIL:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]

test/OpenMP/target_teams_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[FAIL:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]

test/OpenMP/target_teams_distribute_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[FAIL:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]

test/OpenMP/target_teams_distribute_simd_codegen.cpp

 //
 // CHECK: define {{.*}}[[FS1]]
 //
 // CHECK:          i8* @llvm.stacksave()
 // CHECK-64:       [[B_ADDR:%.+]] = bitcast i[[SZ]]* [[B_CADDR:%.+]] to i32*
 // CHECK-64:       store i32 %{{.+}}, i32* [[B_ADDR]],
 // CHECK-64:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_CADDR]],
 
+// CHECK-32:       store i32 %{{.+}}, i32* %vla_expr
 // CHECK-32:       store i32 %{{.+}}, i32* [[B_ADDR:%.+]],
 // CHECK-32:       [[B_CVAL:%.+]] = load i[[SZ]], i[[SZ]]* [[B_ADDR]],
 
 // CHECK:       [[IF:%.+]] = icmp sgt i32 {{[^,]+}}, 60
 // CHECK:       br i1 [[IF]], label %[[TRY:[^,]+]], label %[[FAIL:[^,]+]]
 // CHECK:       [[TRY]]
 // We capture 2 VLA sizes in this target region
 // CHECK:       [[CELEMSIZE2:%.+]] = mul nuw i[[SZ]] 2, [[VLA0:%.+]]