// Preserve semantics of sub-register operands.
if (MO.getSubReg()) {
// A virtual register kill refers to the whole register, so we may
- // have to add <imp-use,kill> operands for the super-register.
- if (MO.isUse()) {
- if (MO.isKill() && !MO.isUndef())
- SuperKills.push_back(PhysReg);
- } else if (MO.isDead())
- SuperDeads.push_back(PhysReg);
- else
- SuperDefs.push_back(PhysReg);
+ // have to add <imp-use,kill> operands for the super-register. A
+ // partial redef always kills and redefines the super-register.
+ if (MO.readsReg() && (MO.isDef() || MO.isKill()))
+ SuperKills.push_back(PhysReg);
+
+ if (MO.isDef()) {
+ // The <def,undef> flag only makes sense for sub-register defs, and
+ // we are substituting a full physreg. An <imp-use,kill> operand
+ // from the SuperKills list will represent the partial read of the
+ // super-register.
+ MO.setIsUndef(false);
+
+ // Also add implicit defs for the super-register.
+ if (MO.isDead())
+ SuperDeads.push_back(PhysReg);
+ else
+ SuperDefs.push_back(PhysReg);
+ }
// PhysReg operands cannot have subregister indexes.
PhysReg = TRI->getSubReg(PhysReg, MO.getSubReg());