Small patch to restore home register stack space allocation for the Win64 case. Add test case. This code eventually needs to be tighter, since it's always allocating it, even in leaf routines.

llvm-svn: 116056

Author: d1r7y

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -1701,8 +1701,12 @@ X86TargetLowering::LowerFormalArguments(SDValue Chain,
         TotalNumXMMRegs = 0;
 
       if (IsWin64) {
+        const TargetFrameInfo &TFI = *getTargetMachine().getFrameInfo();
+        // Get to the caller-allocated home save location.  Add 8 to account
+        // for the return address.
+        int HomeOffset = TFI.getOffsetOfLocalArea() + 8;
         FuncInfo->setRegSaveFrameIndex(
-          MFI->CreateFixedObject(1, NumIntRegs * 8, false));
+          MFI->CreateFixedObject(1, NumIntRegs * 8 + HomeOffset, false));
         FuncInfo->setVarArgsFrameIndex(FuncInfo->getRegSaveFrameIndex());
       } else {
         // For X86-64, if there are vararg parameters that are passed via

llvm/test/CodeGen/X86/win64_params.ll

@@ -0,0 +1,11 @@
+; RUN: llc < %s -mtriple=x86_64-pc-win32 | FileCheck %s
+
+; Verify that the 5th and 6th parameters are coming from the correct location
+; on the stack.
+define i32 @f6(i32 %p1, i32 %p2, i32 %p3, i32 %p4, i32 %p5, i32 %p6) nounwind readnone optsize {
+entry:
+; CHECK: movl    80(%rsp), %eax
+; CHECK: addl    72(%rsp), %eax
+  %add = add nsw i32 %p6, %p5
+  ret i32 %add
+}