If the insert_subreg source is <undef>, insert an implicit_def instead of a copy.
llvm-svn: 78141
diff --git a/llvm/lib/CodeGen/LowerSubregs.cpp b/llvm/lib/CodeGen/LowerSubregs.cpp
index 9c23a5a..e9e60a0 100644
--- a/llvm/lib/CodeGen/LowerSubregs.cpp
+++ b/llvm/lib/CodeGen/LowerSubregs.cpp
@@ -254,7 +254,13 @@
// Insert sub-register copy
const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
- TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
+ if (MI->getOperand(2).isUndef())
+ // If the source register being inserted is undef, then this becomes an
+ // implicit_def.
+ BuildMI(*MBB, MI, MI->getDebugLoc(),
+ TII.get(TargetInstrInfo::IMPLICIT_DEF), DstSubReg);
+ else
+ TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
MachineBasicBlock::iterator CopyMI = MI;
--CopyMI;
@@ -270,7 +276,7 @@
}
// Make sure the inserted register gets killed
- if (MI->getOperand(2).isKill())
+ if (MI->getOperand(2).isKill() && !MI->getOperand(2).isUndef())
TransferKillFlag(MI, InsReg, TRI);
}