From 586ccac4ec4d023864e720dc36373809b9b88b09 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Tue, 18 Mar 2008 23:36:35 +0000
Subject: [PATCH] Fix a x86-64 isel lowering bug that's been around forever. A
 x86-64 varargs function implicitly reads X86::AL, don't clobber it!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48515 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 16 ++++++++++------
 test/CodeGen/X86/x86-64-varargs.ll | 11 +++++++++++
 2 files changed, 21 insertions(+), 6 deletions(-)
 create mode 100644 test/CodeGen/X86/x86-64-varargs.ll

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 8655eff4882..5a05abac898 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1746,18 +1746,22 @@ SDOperand X86TargetLowering::LowerCALL(SDOperand Op, SelectionDAG &DAG) {
   if (IsTailCall)
     Ops.push_back(DAG.getConstant(FPDiff, MVT::i32));
 
-  // Add an implicit use GOT pointer in EBX.
-  if (!IsTailCall && !Is64Bit &&
-      getTargetMachine().getRelocationModel() == Reloc::PIC_ &&
-      Subtarget->isPICStyleGOT())
-    Ops.push_back(DAG.getRegister(X86::EBX, getPointerTy()));
-
   // Add argument registers to the end of the list so that they are known live
   // into the call.
   for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i)
     Ops.push_back(DAG.getRegister(RegsToPass[i].first,
                                   RegsToPass[i].second.getValueType()));
   
+  // Add an implicit use GOT pointer in EBX.
+  if (!IsTailCall && !Is64Bit &&
+      getTargetMachine().getRelocationModel() == Reloc::PIC_ &&
+      Subtarget->isPICStyleGOT())
+    Ops.push_back(DAG.getRegister(X86::EBX, getPointerTy()));
+
+  // Add an implicit use of AL for x86 vararg functions.
+  if (Is64Bit && isVarArg)
+    Ops.push_back(DAG.getRegister(X86::AL, MVT::i8));
+
   if (InFlag.Val)
     Ops.push_back(InFlag);
 
diff --git a/test/CodeGen/X86/x86-64-varargs.ll b/test/CodeGen/X86/x86-64-varargs.ll
new file mode 100644
index 00000000000..2964dd3969f
--- /dev/null
+++ b/test/CodeGen/X86/x86-64-varargs.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | llc -mtriple=x86_64-apple-darwin -code-model=large -relocation-model=static | grep call | not grep rax
+
+@.str = internal constant [26 x i8] c"%d, %f, %d, %lld, %d, %f\0A\00"		; <[26 x i8]*> [#uses=1]
+
+declare i32 @printf(i8*, ...) nounwind 
+
+define i32 @main() nounwind  {
+entry:
+	%tmp10.i = tail call i32 (i8*, ...)* @printf( i8* getelementptr ([26 x i8]* @.str, i32 0, i64 0), i32 12, double 0x3FF3EB8520000000, i32 120, i64 123456677890, i32 -10, double 4.500000e+15 ) nounwind 		; <i32> [#uses=0]
+	ret i32 0
+}
-- 
2.34.1