- unsigned LargeReg = isExtSubReg ? SrcReg : DstReg;
- unsigned SmallReg = isExtSubReg ? DstReg : SrcReg;
- unsigned LargeRegSize =
- li_->getInterval(LargeReg).getSize() / InstrSlots::NUM;
- unsigned SmallRegSize =
- li_->getInterval(SmallReg).getSize() / InstrSlots::NUM;
- const TargetRegisterClass *RC = mri_->getRegClass(SmallReg);
- unsigned Threshold = allocatableRCRegs_[RC].count();
- // Be conservative. If both sides are virtual registers, do not coalesce
- // if this will cause a high use density interval to target a smaller set
- // of registers.
- if (SmallRegSize > Threshold || LargeRegSize > Threshold) {
- LiveVariables::VarInfo &svi = lv_->getVarInfo(LargeReg);
- LiveVariables::VarInfo &dvi = lv_->getVarInfo(SmallReg);
- if ((float)dvi.NumUses / SmallRegSize <
- (float)svi.NumUses / LargeRegSize) {
- Again = true; // May be possible to coalesce later.
- return false;
+ unsigned OldSubIdx = isExtSubReg ? CopyMI->getOperand(0).getSubReg()
+ : CopyMI->getOperand(2).getSubReg();
+ if (OldSubIdx) {
+ if (OldSubIdx == SubIdx &&
+ !differingRegisterClasses(SrcReg, DstReg, SubRC))
+ // r1024<2> = EXTRACT_SUBREG r1025, 2. Then r1024 has already been
+ // coalesced to a larger register so the subreg indices cancel out.
+ // Also check if the other larger register is of the same register
+ // class as the would be resulting register.
+ SubIdx = 0;
+ else {
+ DOUT << "\t Sub-register indices mismatch.\n";
+ return false; // Not coalescable.
+ }
+ }
+ if (SubIdx) {
+ unsigned LargeReg = isExtSubReg ? SrcReg : DstReg;
+ unsigned SmallReg = isExtSubReg ? DstReg : SrcReg;
+ unsigned LargeRegSize =
+ li_->getInterval(LargeReg).getSize() / InstrSlots::NUM;
+ unsigned SmallRegSize =
+ li_->getInterval(SmallReg).getSize() / InstrSlots::NUM;
+ const TargetRegisterClass *RC = mri_->getRegClass(SmallReg);
+ unsigned Threshold = allocatableRCRegs_[RC].count();
+ // Be conservative. If both sides are virtual registers, do not coalesce
+ // if this will cause a high use density interval to target a smaller
+ // set of registers.
+ if (SmallRegSize > Threshold || LargeRegSize > Threshold) {
+ if ((float)std::distance(mri_->use_begin(SmallReg),
+ mri_->use_end()) / SmallRegSize <
+ (float)std::distance(mri_->use_begin(LargeReg),
+ mri_->use_end()) / LargeRegSize) {
+ Again = true; // May be possible to coalesce later.
+ return false;
+ }