Fix a couple issues with Win64 ABI

1) all registers were spilled as xmm, regardless of actual size
2) win64 abi doesn't do the varargs-size-in-%al thing

Still to look into:

xmm6-15 are marked as clobbered by call instructions on win64 even though they aren't.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109035 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index d10f4ec..64ca7c5 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1990,7 +1990,7 @@
     }
   }
 
-  if (Is64Bit && isVarArg) {
+  if (Is64Bit && isVarArg && !Subtarget->isTargetWin64()) {
     // From AMD64 ABI document:
     // For calls that may call functions that use varargs or stdargs
     // (prototype-less calls or calls to functions containing ellipsis (...) in
@@ -1999,7 +1999,6 @@
     // the number of registers, but must be an ubound on the number of SSE
     // registers used and is in the range 0 - 8 inclusive.
 
-    // FIXME: Verify this on Win64
     // Count the number of XMM registers allocated.
     static const unsigned XMMArgRegs[] = {
       X86::XMM0, X86::XMM1, X86::XMM2, X86::XMM3,