From 57708abb10223a1a57334549c23eb93e5bbf18e6 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron@aaronballman.com>
Date: Wed, 22 Feb 2012 03:04:40 +0000
Subject: [PATCH] Adding support for Microsoft's thiscall calling convention. 
 LLVM side of the patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151123 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86CallingConv.td           |  4 +-
 test/CodeGen/X86/thiscall-struct-return.ll | 47 ++++++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 test/CodeGen/X86/thiscall-struct-return.ll

diff --git a/lib/Target/X86/X86CallingConv.td b/lib/Target/X86/X86CallingConv.td
index 81d3796cc35..d148989e97f 100644
--- a/lib/Target/X86/X86CallingConv.td
+++ b/lib/Target/X86/X86CallingConv.td
@@ -331,8 +331,8 @@ def CC_X86_32_ThisCall : CallingConv<[
   // Promote i8/i16 arguments to i32.
   CCIfType<[i8, i16], CCPromoteToType<i32>>,
 
-  // The 'nest' parameter, if any, is passed in EAX.
-  CCIfNest<CCAssignToReg<[EAX]>>,
+  // Pass sret arguments indirectly through EAX
+  CCIfSRet<CCAssignToReg<[EAX]>>,
 
   // The first integer argument is passed in ECX
   CCIfType<[i32], CCAssignToReg<[ECX]>>,
diff --git a/test/CodeGen/X86/thiscall-struct-return.ll b/test/CodeGen/X86/thiscall-struct-return.ll
new file mode 100644
index 00000000000..a7be48355f6
--- /dev/null
+++ b/test/CodeGen/X86/thiscall-struct-return.ll
@@ -0,0 +1,47 @@
+; RUN: llc < %s -mtriple=i386-PC-Win32 | FileCheck %s
+
+%class.C = type { i8 }
+%struct.S = type { i32 }
+%struct.M = type { i32, i32 }
+
+declare void @_ZN1CC1Ev(%class.C* %this) unnamed_addr nounwind align 2
+declare x86_thiscallcc void @_ZNK1C5SmallEv(%struct.S* noalias sret %agg.result, %class.C* %this) nounwind align 2
+declare x86_thiscallcc void @_ZNK1C6MediumEv(%struct.M* noalias sret %agg.result, %class.C* %this) nounwind align 2
+
+define void @testv() nounwind {
+; CHECK: testv:
+; CHECK: leal
+; CHECK-NEXT: movl	%esi, (%esp)
+; CHECK-NEXT: calll _ZN1CC1Ev
+; CHECK: leal 8(%esp), %eax
+; CHECK-NEXT: movl %esi, %ecx
+; CHECK-NEXT: calll _ZNK1C5SmallEv
+entry:
+  %c = alloca %class.C, align 1
+  %tmp = alloca %struct.S, align 4
+  call void @_ZN1CC1Ev(%class.C* %c)
+  ; This call should put the return structure as a pointer
+  ; into EAX instead of returning directly in EAX.  The this
+  ; pointer should go into ECX
+  call x86_thiscallcc void @_ZNK1C5SmallEv(%struct.S* sret %tmp, %class.C* %c)
+  ret void
+}
+
+define void @test2v() nounwind {
+; CHECK: test2v:
+; CHECK: leal
+; CHECK-NEXT: movl	%esi, (%esp)
+; CHECK-NEXT: calll _ZN1CC1Ev
+; CHECK: leal 8(%esp), %eax
+; CHECK-NEXT: movl %esi, %ecx
+; CHECK-NEXT: calll _ZNK1C6MediumEv
+entry:
+  %c = alloca %class.C, align 1
+  %tmp = alloca %struct.M, align 4
+  call void @_ZN1CC1Ev(%class.C* %c)
+  ; This call should put the return structure as a pointer
+  ; into EAX instead of returning directly in EAX/EDX.  The this
+  ; pointer should go into ECX
+  call x86_thiscallcc void @_ZNK1C6MediumEv(%struct.M* sret %tmp, %class.C* %c)
+  ret void
+}