}
if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
- MRI->setRegClass(DstReg, CP.getNewRC());
-
unsigned NewIdx = NewMI->getOperand(0).getSubReg();
- updateRegDefsUses(DstReg, DstReg, DstIdx);
- NewMI->getOperand(0).setSubReg(NewIdx);
+ const TargetRegisterClass *RCForInst;
+ if (NewIdx)
+ RCForInst = TRI->getMatchingSuperRegClass(MRI->getRegClass(DstReg), DefRC,
+ NewIdx);
+
+ if (MRI->constrainRegClass(DstReg, DefRC)) {
+ // The materialized instruction is quite capable of setting DstReg
+ // directly, but it may still have a now-trivial subregister index which
+ // we should clear.
+ NewMI->getOperand(0).setSubReg(0);
+ } else if (NewIdx && RCForInst) {
+ // The subreg index on NewMI is essential; we still have to make sure
+ // DstReg:idx is in a class that NewMI can use.
+ MRI->constrainRegClass(DstReg, RCForInst);
+ } else {
+ // DstReg is actually incompatible with NewMI, we have to move to a
+ // super-reg's class. This could come from a sequence like:
+ // GR32 = MOV32r0
+ // GR8 = COPY GR32:sub_8
+ MRI->setRegClass(DstReg, CP.getNewRC());
+ updateRegDefsUses(DstReg, DstReg, DstIdx);
+ NewMI->getOperand(0).setSubReg(
+ TRI->composeSubRegIndices(SrcIdx, DefMI->getOperand(0).getSubReg()));
+ }
} else if (NewMI->getOperand(0).getReg() != CopyDstReg) {
// The New instruction may be defining a sub-register of what's actually
// been asked for. If so it must implicitly define the whole thing.