Allow EmitVAArg() to promote types and use this to fix some N32/N64 vararg issues for Mips.

Summary:
With this patch, passing a va_list to another function and reading 10 int's from
it works correctly on a big-endian target.

Based on a pair of patches by David Chisnall, one of which I've reworked
for the current trunk.

Reviewers: theraven, atanasyan

Reviewed By: theraven, atanasyan

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D6248

llvm-svn: 222339

1 files changed, 10 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 8807e828646..19d453d3caa 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -3296,18 +3296,26 @@ Value *ScalarExprEmitter::VisitChooseExpr(ChooseExpr *E) {
 
 Value *ScalarExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
   QualType Ty = VE->getType();
+
   if (Ty->isVariablyModifiedType())
     CGF.EmitVariablyModifiedType(Ty);
 
   llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
   llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
+  llvm::Type *ArgTy = ConvertType(VE->getType());
 
   // If EmitVAArg fails, we fall back to the LLVM instruction.
   if (!ArgPtr)
-    return Builder.CreateVAArg(ArgValue, ConvertType(VE->getType()));
+    return Builder.CreateVAArg(ArgValue, ArgTy);
 
   // FIXME Volatility.
-  return Builder.CreateLoad(ArgPtr);
+  llvm::Value *Val = Builder.CreateLoad(ArgPtr);
+
+  // If EmitVAArg promoted the type, we must truncate it.
+  if (ArgTy != Val->getType())
+    Val = Builder.CreateTrunc(Val, ArgTy);
+
+  return Val;
 }
 
 Value *ScalarExprEmitter::VisitBlockExpr(const BlockExpr *block) {