From 3e407efb8bfd5211e939822f15509aacb7b26ac6 Mon Sep 17 00:00:00 2001
From: Charles Davis <cdavis5x@gmail.com>
Date: Thu, 4 Jun 2015 22:50:05 +0000
Subject: [PATCH] [Target/X86] Don't use callee-saved registers in a Win64 tail
 call on non-Windows.

Summary:
A small bit that I missed when I updated the X86 backend to account for
the Win64 calling convention on non-Windows. Now we don't use dead
non-volatile registers when emitting a Win64 indirect tail call on
non-Windows.

Should fix PR23710.

Test Plan: Added test for the correct behavior based on the case I posted to PR23710.

Reviewers: rnk

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10258

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239111 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86RegisterInfo.cpp |  4 ++--
 test/CodeGen/X86/sibcall-win64.ll  | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 1f361631a0b..e9b6bfc3273 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -175,12 +175,12 @@ X86RegisterInfo::getPointerRegClass(const MachineFunction &MF,
       return &X86::GR64_NOSPRegClass;
     return &X86::GR32_NOSPRegClass;
   case 2: // Available for tailcall (not callee-saved GPRs).
-    if (IsWin64)
+    const Function *F = MF.getFunction();
+    if (IsWin64 || (F && F->getCallingConv() == CallingConv::X86_64_Win64))
       return &X86::GR64_TCW64RegClass;
     else if (Is64Bit)
       return &X86::GR64_TCRegClass;
 
-    const Function *F = MF.getFunction();
     bool hasHipeCC = (F ? F->getCallingConv() == CallingConv::HiPE : false);
     if (hasHipeCC)
       return &X86::GR32RegClass;
diff --git a/test/CodeGen/X86/sibcall-win64.ll b/test/CodeGen/X86/sibcall-win64.ll
index f7038726f9c..204e1f8b050 100644
--- a/test/CodeGen/X86/sibcall-win64.ll
+++ b/test/CodeGen/X86/sibcall-win64.ll
@@ -1,7 +1,11 @@
 ; RUN: llc < %s -mtriple=x86_64-pc-linux | FileCheck %s
 
 declare x86_64_win64cc void @win64_callee(i32)
+declare x86_64_win64cc void (i32)* @win64_indirect()
+declare x86_64_win64cc void @win64_other(i32)
 declare void @sysv_callee(i32)
+declare void (i32)* @sysv_indirect()
+declare void @sysv_other(i32)
 
 define void @sysv_caller(i32 %p1) {
 entry:
@@ -40,3 +44,23 @@ define x86_64_win64cc void @win64_matched(i32 %p1) {
 
 ; CHECK-LABEL: win64_matched:
 ; CHECK: jmp win64_callee # TAILCALL
+
+define x86_64_win64cc void @win64_indirect_caller(i32 %p1) {
+  %1 = call x86_64_win64cc void (i32)* @win64_indirect()
+  call x86_64_win64cc void @win64_other(i32 0)
+  tail call x86_64_win64cc void %1(i32 %p1)
+  ret void
+}
+
+; CHECK-LABEL: win64_indirect_caller:
+; CHECK: jmpq *%{{rax|rcx|rdx|r8|r9|r11}} # TAILCALL
+
+define void @sysv_indirect_caller(i32 %p1) {
+  %1 = call void (i32)* @sysv_indirect()
+  call void @sysv_other(i32 0)
+  tail call void %1(i32 %p1)
+  ret void
+}
+
+; CHECK-LABEL: sysv_indirect_caller:
+; CHECK: jmpq *%{{rax|rcx|rdx|rsi|rdi|r8|r9|r11}} # TAILCALL