Create a fixed stack object for varargs that is as large as any register.

The size of this object isn't used for anything - technically it is of variable
size.

This avoids a false positive from the assert in
X86InstrInfo::loadRegFromStackSlot, and fixes PR7735.

llvm-svn: 109652

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index c0f5a403b9f..81e9750a408 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -1701,7 +1701,10 @@ X86TargetLowering::LowerFormalArguments(SDValue Chain,
   if (isVarArg) {
     if (Is64Bit || (CallConv != CallingConv::X86_FastCall &&
                     CallConv != CallingConv::X86_ThisCall)) {
-      FuncInfo->setVarArgsFrameIndex(MFI->CreateFixedObject(1, StackSize,true));
+      // The fixed varargs object is created large enough that we can load and
+      // store any register in it.
+      FuncInfo->setVarArgsFrameIndex(MFI->CreateFixedObject(32, StackSize,
+                                                            true));
     }
     if (Is64Bit) {
       unsigned TotalNumIntRegs = 0, TotalNumXMMRegs = 0;