[PATCH] [Target/X86] Don't use callee-saved registers in a Win64 tail call on non-Windows.

[Charles Davis]

Hi rnk,

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.

http://reviews.llvm.org/D10258

Files:
  lib/Target/X86/X86RegisterInfo.cpp
  test/CodeGen/X86/sibcall-win64.ll

Index: lib/Target/X86/X86RegisterInfo.cpp
===================================================================
--- lib/Target/X86/X86RegisterInfo.cpp
+++ lib/Target/X86/X86RegisterInfo.cpp
@@ -175,12 +175,12 @@
       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;
Index: test/CodeGen/X86/sibcall-win64.ll
===================================================================
--- test/CodeGen/X86/sibcall-win64.ll
+++ 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 @@
 
 ; 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

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