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.

llvm-svn: 41802

1 files changed, 22 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 442b113c36c..774531e7a7b 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/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,