From dcea16313dfb5ec101daf9483de22daa02e0d59b Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 4 Feb 2010 02:40:39 +0000
Subject: [PATCH] Indirect tail call has to go through a call preserved
 register since it's after callee register pops. X86 isel lowering is using
 EAX / R11 and it was somehow adding that to function live out. That prevented
 the real function return register from being added to the function live out
 list and bad things happen. This fixes 483.xalancbmk (with tail call opt).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95280 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 2b5ff3ca1a9..a44afb502c6 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1196,13 +1196,11 @@ X86TargetLowering::LowerReturn(SDValue Chain,
                  RVLocs, *DAG.getContext());
   CCInfo.AnalyzeReturn(Outs, RetCC_X86);
 
-  // If this is the first return lowered for this function, add the regs to the
-  // liveout set for the function.
-  if (DAG.getMachineFunction().getRegInfo().liveout_empty()) {
-    for (unsigned i = 0; i != RVLocs.size(); ++i)
-      if (RVLocs[i].isRegLoc())
-        DAG.getMachineFunction().getRegInfo().addLiveOut(RVLocs[i].getLocReg());
-  }
+  // Add the regs to the liveout set for the function.
+  MachineRegisterInfo &MRI = DAG.getMachineFunction().getRegInfo();
+  for (unsigned i = 0; i != RVLocs.size(); ++i)
+    if (RVLocs[i].isRegLoc() && !MRI.isLiveOut(RVLocs[i].getLocReg()))
+      MRI.addLiveOut(RVLocs[i].getLocReg());
 
   SDValue Flag;
 
@@ -1255,7 +1253,7 @@ X86TargetLowering::LowerReturn(SDValue Chain,
     X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
     unsigned Reg = FuncInfo->getSRetReturnReg();
     if (!Reg) {
-      Reg = MF.getRegInfo().createVirtualRegister(getRegClassFor(MVT::i64));
+      Reg = MRI.createVirtualRegister(getRegClassFor(MVT::i64));
       FuncInfo->setSRetReturnReg(Reg);
     }
     SDValue Val = DAG.getCopyFromReg(Chain, dl, Reg, getPointerTy());
@@ -1264,7 +1262,7 @@ X86TargetLowering::LowerReturn(SDValue Chain,
     Flag = Chain.getValue(1);
 
     // RAX now acts like a return value.
-    MF.getRegInfo().addLiveOut(X86::RAX);
+    MRI.addLiveOut(X86::RAX);
   }
 
   RetOps[0] = Chain;  // Update chain.
@@ -2097,14 +2095,15 @@ X86TargetLowering::LowerCall(SDValue Chain, SDValue Callee,
   }
 
   if (isTailCall && !WasGlobalOrExternal) {
-    unsigned Opc = Is64Bit ? X86::R11 : X86::EAX;
-
+    // Force the address into a (call preserved) caller-saved register since
+    // tailcall must happen after callee-saved registers are poped.
+    // FIXME: Give it a special register class that contains caller-saved
+    // register instead?
+    unsigned TCReg = Is64Bit ? X86::R11 : X86::EAX;
     Chain = DAG.getCopyToReg(Chain,  dl,
-                             DAG.getRegister(Opc, getPointerTy()),
+                             DAG.getRegister(TCReg, getPointerTy()),
                              Callee,InFlag);
-    Callee = DAG.getRegister(Opc, getPointerTy());
-    // Add register as live out.
-    MF.getRegInfo().addLiveOut(Opc);
+    Callee = DAG.getRegister(TCReg, getPointerTy());
   }
 
   // Returns a chain & a flag for retval copy to use.