Properly allocate win64 shadow reg area.
Patch by Jan Sjodin!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112875 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index e7a8d06..b3a5cff 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1616,6 +1616,11 @@
   SmallVector<CCValAssign, 16> ArgLocs;
   CCState CCInfo(CallConv, isVarArg, getTargetMachine(),
                  ArgLocs, *DAG.getContext());
+
+  // Allocate shadow area for Win64
+  if (IsWin64)
+   CCInfo.AllocateStack(32, 8);
+
   CCInfo.AnalyzeFormalArguments(Ins, CCAssignFnForNode(CallConv));
 
   unsigned LastVal = ~0U;
@@ -1842,8 +1847,7 @@
                                     DebugLoc dl, SelectionDAG &DAG,
                                     const CCValAssign &VA,
                                     ISD::ArgFlagsTy Flags) const {
-  const unsigned FirstStackArgOffset = (Subtarget->isTargetWin64() ? 32 : 0);
-  unsigned LocMemOffset = FirstStackArgOffset + VA.getLocMemOffset();
+  unsigned LocMemOffset = VA.getLocMemOffset();
   SDValue PtrOff = DAG.getIntPtrConstant(LocMemOffset);
   PtrOff = DAG.getNode(ISD::ADD, dl, getPointerTy(), StackPtr, PtrOff);
   if (Flags.isByVal()) {
@@ -1926,6 +1930,11 @@
   SmallVector<CCValAssign, 16> ArgLocs;
   CCState CCInfo(CallConv, isVarArg, getTargetMachine(),
                  ArgLocs, *DAG.getContext());
+
+  // Allocate shadow area for Win64
+  if (Subtarget->isTargetWin64())
+    CCInfo.AllocateStack(32, 8);
+
   CCInfo.AnalyzeCallOperands(Outs, CCAssignFnForNode(CallConv));
 
   // Get a count of how many bytes are to be pushed on the stack.