STATISTIC(numSubJoins , "Number of subclass joins performed");
STATISTIC(numCommutes , "Number of instruction commuting performed");
STATISTIC(numExtends , "Number of copies extended");
+STATISTIC(NumReMats , "Number of instructions re-materialized");
STATISTIC(numPeep , "Number of identity moves eliminated after coalescing");
STATISTIC(numAborts , "Number of times interval joining aborted");
return true;
}
+/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
+/// computation, replace the copy by rematerialize the definition.
+bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
+ unsigned DstReg,
+ MachineInstr *CopyMI) {
+ unsigned CopyIdx = li_->getUseIndex(li_->getInstructionIndex(CopyMI));
+ LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
+ if (SrcLR == SrcInt.end()) // Should never happen!
+ return false;
+ VNInfo *ValNo = SrcLR->valno;
+ // If other defs can reach uses of this def, then it's not safe to perform
+ // the optimization.
+ if (ValNo->def == ~0U || ValNo->def == ~1U || ValNo->hasPHIKill)
+ return false;
+ MachineInstr *DefMI = li_->getInstructionFromIndex(ValNo->def);
+ const TargetInstrDesc &TID = DefMI->getDesc();
+ if (!TID.isAsCheapAsAMove())
+ return false;
+ bool SawStore = false;
+ if (!DefMI->isSafeToMove(tii_, SawStore))
+ return false;
+
+ unsigned DefIdx = li_->getDefIndex(CopyIdx);
+ const LiveRange *DLR= li_->getInterval(DstReg).getLiveRangeContaining(DefIdx);
+ DLR->valno->copy = NULL;
+
+ MachineBasicBlock::iterator MII = CopyMI;
+ MachineBasicBlock *MBB = CopyMI->getParent();
+ tii_->reMaterialize(*MBB, MII, DstReg, DefMI);
+ MachineInstr *NewMI = prior(MII);
+ // CopyMI may have implicit instructions, transfer them over to the newly
+ // rematerialized instruction. And update implicit def interval valnos.
+ for (unsigned i = CopyMI->getDesc().getNumOperands(),
+ e = CopyMI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = CopyMI->getOperand(i);
+ if (MO.isReg() && MO.isImplicit())
+ NewMI->addOperand(MO);
+ if (MO.isDef()) {
+ unsigned Reg = MO.getReg();
+ DLR = li_->getInterval(Reg).getLiveRangeContaining(DefIdx);
+ if (DLR && DLR->valno->copy == CopyMI)
+ DLR->valno->copy = NULL;
+ }
+ }
+
+ li_->ReplaceMachineInstrInMaps(CopyMI, NewMI);
+ CopyMI->eraseFromParent();
+ ReMatCopies.insert(CopyMI);
+ ++NumReMats;
+ return true;
+}
+
/// isBackEdgeCopy - Returns true if CopyMI is a back edge copy.
///
bool SimpleRegisterCoalescing::isBackEdgeCopy(MachineInstr *CopyMI,
unsigned UseDstReg = DstReg;
if (OldSubIdx)
UseDstReg = tri_->getSubReg(DstReg, OldSubIdx);
+
+ unsigned CopySrcReg, CopyDstReg;
+ if (tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg) &&
+ CopySrcReg != CopyDstReg &&
+ CopySrcReg == SrcReg && CopyDstReg != UseDstReg) {
+ // If the use is a copy and it won't be coalesced away, and its source
+ // is defined by a trivial computation, try to rematerialize it instead.
+ if (ReMaterializeTrivialDef(li_->getInterval(SrcReg), CopyDstReg,UseMI))
+ continue;
+ }
+
O.setReg(UseDstReg);
O.setSubReg(0);
} else {
MachineInstr *CopyMI = TheCopy.MI;
Again = false;
- if (JoinedCopies.count(CopyMI))
+ if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
return false; // Already done.
DOUT << li_->getInstructionIndex(CopyMI) << '\t' << *CopyMI;
if (!isEmpty && !JoinIntervals(DstInt, SrcInt, Swapped)) {
// Coalescing failed.
+
+ // If definition of source is defined by trivial computation, try
+ // rematerializing it.
+ if (!isExtSubReg && !isInsSubReg &&
+ ReMaterializeTrivialDef(SrcInt, DstInt.reg, CopyMI))
+ return true;
// If we can eliminate the copy without merging the live ranges, do so now.
if (!isExtSubReg && !isInsSubReg &&
if (TargetRegisterInfo::isVirtualRegister(DstReg))
RemoveUnnecessaryKills(DstReg, *ResDstInt);
- // SrcReg is guarateed to be the register whose live interval that is
- // being merged.
- li_->removeInterval(SrcReg);
if (isInsSubReg)
// Avoid:
// r1024 = op
RemoveDeadImpDef(DstReg, *ResDstInt);
UpdateRegDefsUses(SrcReg, DstReg, SubIdx);
+ // SrcReg is guarateed to be the register whose live interval that is
+ // being merged.
+ li_->removeInterval(SrcReg);
+
if (isEmpty) {
// Now the copy is being coalesced away, the val# previously defined
// by the copy is being defined by an IMPLICIT_DEF which defines a zero
void SimpleRegisterCoalescing::releaseMemory() {
JoinedCopies.clear();
+ ReMatCopies.clear();
}
static bool isZeroLengthInterval(LiveInterval *li) {