Revert win64 changes. They seem to be incomplete

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112885 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index b3a5cff..e7a8d06 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1616,11 +1616,6 @@
   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;
@@ -1847,7 +1842,8 @@
                                     DebugLoc dl, SelectionDAG &DAG,
                                     const CCValAssign &VA,
                                     ISD::ArgFlagsTy Flags) const {
-  unsigned LocMemOffset = VA.getLocMemOffset();
+  const unsigned FirstStackArgOffset = (Subtarget->isTargetWin64() ? 32 : 0);
+  unsigned LocMemOffset = FirstStackArgOffset + VA.getLocMemOffset();
   SDValue PtrOff = DAG.getIntPtrConstant(LocMemOffset);
   PtrOff = DAG.getNode(ISD::ADD, dl, getPointerTy(), StackPtr, PtrOff);
   if (Flags.isByVal()) {
@@ -1930,11 +1926,6 @@
   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.