================
@@ -1665,6 +1665,22 @@ void
TwoAddressInstructionImpl::processTiedPairs(MachineInstr *MI,
// by SubRegB is compatible with RegA with no subregister. So regardless of
// whether the dest oper writes a subreg, the source oper should not.
MO.setSubReg(0);
+
+ // Update uses of RegB to uses of RegA inside the bundle.
+ if (MI->isBundle()) {
+ for (MachineInstr *InnerMI = MI; InnerMI->isBundledWithSucc();) {
+ InnerMI = InnerMI->getNextNode();
+
+ for (MachineOperand &MO : InnerMI->all_uses()) {
+ if (MO.isReg() && MO.getReg() == RegB) {
+ assert(
+ MO.getSubReg() == 0 &&
+ "tied subregister uses in bundled instructions not supported");
+ MO.setReg(RegA);
----------------
nhaehnle wrote:
I played around with this but it got very confusing to me even in the
restricted use case that I described in the other comment. I'd prefer to just
keep this more restrictive for now, and if we find later on that supporting
subregisters is beneficial we relax it separately.
https://github.com/llvm/llvm-project/pull/166212
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