if (ScratchWaveOffsetReg == TRI->reservedPrivateSegmentWaveByteOffsetReg(MF)) {
MachineRegisterInfo &MRI = MF.getRegInfo();
- // Skip the last 2 elements because the last one is reserved for VCC, and
- // this is the 2nd to last element already.
unsigned NumPreloaded = MFI->getNumPreloadedSGPRs();
- for (MCPhysReg Reg : getAllSGPRs().drop_back(6).slice(NumPreloaded)) {
+
+ // We need to drop register from the end of the list that we cannot use
+ // for the scratch wave offset.
+ // + 2 s102 and s103 do not exist on VI.
+ // + 2 for vcc
+ // + 2 for xnack_mask
+ // + 2 for flat_scratch
+ // + 4 for registers reserved for scratch resource register
+ // + 1 for register reserved for scratch wave offset. (By exluding this
+ // register from the list to consider, it means that when this
+ // register is being used for the scratch wave offset and there
+ // are no other free SGPRs, then the value will stay in this register.
+ // ----
+ // 13
+ for (MCPhysReg Reg : getAllSGPRs().drop_back(13).slice(NumPreloaded)) {
// Pick the first unallocated SGPR. Be careful not to pick an alias of the
// scratch descriptor, since we haven’t added its uses yet.
if (!MRI.isPhysRegUsed(Reg)) {