From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 10 Sep 2007 20:48:53 +0000 (+0000)
Subject: It's not safe to rematerialize MOV32r0 etc. by simply cloning the original
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=b0869ed44d477b63c304eee762abb49d73b4fd68;p=oota-llvm.git

It's not safe to rematerialize MOV32r0 etc. by simply cloning the original
instruction. These are implemented with xor which will modify the conditional
code. They should be rematerialized as move instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41802 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 442b113c36c..774531e7a7b 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -265,9 +265,28 @@ void X86RegisterInfo::reMaterialize(MachineBasicBlock &MBB,
                                     MachineBasicBlock::iterator I,
                                     unsigned DestReg,
                                     const MachineInstr *Orig) const {
-  MachineInstr *MI = Orig->clone();
-  MI->getOperand(0).setReg(DestReg);
-  MBB.insert(I, MI);
+  // MOV32r0 etc. are implemented with xor which clobbers condition code.
+  // Re-materialize them as movri instructions to avoid side effects.
+  switch (Orig->getOpcode()) {
+  case X86::MOV8r0:
+    BuildMI(MBB, I, TII.get(X86::MOV8ri), DestReg).addImm(0);
+    break;
+  case X86::MOV16r0:
+    BuildMI(MBB, I, TII.get(X86::MOV16ri), DestReg).addImm(0);
+    break;
+  case X86::MOV32r0:
+    BuildMI(MBB, I, TII.get(X86::MOV32ri), DestReg).addImm(0);
+    break;
+  case X86::MOV64r0:
+    BuildMI(MBB, I, TII.get(X86::MOV64ri32), DestReg).addImm(0);
+    break;
+  default: {
+    MachineInstr *MI = Orig->clone();
+    MI->getOperand(0).setReg(DestReg);
+    MBB.insert(I, MI);
+    break;
+  }
+  }
 }
 
 static const MachineInstrBuilder &FuseInstrAddOperand(MachineInstrBuilder &MIB,