[llvm-commits] [llvm] r157132 - /llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
Jakob Stoklund Olesen
stoklund at 2pi.dk
Sat May 19 14:02:31 PDT 2012
Author: stoklund
Date: Sat May 19 16:02:31 2012
New Revision: 157132
URL: http://llvm.org/viewvc/llvm-project?rev=157132&view=rev
Log:
Remove the late DCE in RegisterCoalescer.
Dead code and joined copies are now eliminated on the fly, and there is
no need for a post pass.
This makes the coalescer work like other modern register allocator
passes: Code is changed on the fly, there is no pending list of changes
to be committed.
Modified:
llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
Modified: llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp?rev=157132&r1=157131&r2=157132&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp Sat May 19 16:02:31 2012
@@ -54,7 +54,6 @@
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(NumInflated , "Number of register classes inflated");
static cl::opt<bool>
@@ -81,14 +80,6 @@
AliasAnalysis *AA;
RegisterClassInfo RegClassInfo;
- /// JoinedCopies - Keep track of copies eliminated due to coalescing.
- ///
- SmallPtrSet<MachineInstr*, 32> JoinedCopies;
-
- /// ReMatDefs - Keep track of definition instructions which have
- /// been remat'ed.
- SmallPtrSet<MachineInstr*, 8> ReMatDefs;
-
/// WorkList - Copy instructions yet to be coalesced.
SmallVector<MachineInstr*, 8> WorkList;
@@ -167,14 +158,6 @@
/// subregister.
void updateRegDefsUses(unsigned SrcReg, unsigned DstReg, unsigned SubIdx);
- /// removeDeadDef - If a def of a live interval is now determined dead,
- /// remove the val# it defines. If the live interval becomes empty, remove
- /// it as well.
- bool removeDeadDef(LiveInterval &li, MachineInstr *DefMI);
-
- /// markAsJoined - Remember that CopyMI has already been joined.
- void markAsJoined(MachineInstr *CopyMI);
-
/// eliminateUndefCopy - Handle copies of undef values.
bool eliminateUndefCopy(MachineInstr *CopyMI, const CoalescerPair &CP);
@@ -384,18 +367,6 @@
MachineFunctionPass::getAnalysisUsage(AU);
}
-void RegisterCoalescer::markAsJoined(MachineInstr *CopyMI) {
- /// Joined copies are not deleted immediately, but kept in JoinedCopies.
- JoinedCopies.insert(CopyMI);
-
- /// Mark all register operands of CopyMI as <undef> so they won't affect dead
- /// code elimination.
- for (MachineInstr::mop_iterator I = CopyMI->operands_begin(),
- E = CopyMI->operands_end(); I != E; ++I)
- if (I->isReg())
- I->setIsUndef(true);
-}
-
void RegisterCoalescer::eliminateDeadDefs() {
SmallVector<LiveInterval*, 8> NewRegs;
LiveRangeEdit(0, NewRegs, *MF, *LIS, 0, this).eliminateDeadDefs(DeadDefs);
@@ -689,8 +660,6 @@
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR == IntA.end() || ULR->valno != AValNo)
continue;
- if (JoinedCopies.count(UseMI))
- return false;
// If this use is tied to a def, we can't rewrite the register.
if (UseMI->isRegTiedToDefOperand(UI.getOperandNo()))
return false;
@@ -733,8 +702,6 @@
MachineOperand &UseMO = UI.getOperand();
MachineInstr *UseMI = &*UI;
++UI;
- if (JoinedCopies.count(UseMI))
- continue;
if (UseMI->isDebugValue()) {
// FIXME These don't have an instruction index. Not clear we have enough
// info to decide whether to do this replacement or not. For now do it.
@@ -873,7 +840,6 @@
CopyMI->eraseFromParent();
ErasedInstrs.insert(CopyMI);
- ReMatDefs.insert(DefMI);
DEBUG(dbgs() << "Remat: " << *NewMI);
++NumReMats;
@@ -944,14 +910,13 @@
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg);
MachineInstr *UseMI = I.skipInstruction();) {
- bool AlreadyJoined = JoinedCopies.count(UseMI);
SmallVector<unsigned,8> Ops;
bool Reads, Writes;
tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
// If SrcReg wasn't read, it may still be the case that DstReg is live-in
// because SrcReg is a sub-register.
- if (!Reads && SubIdx && !AlreadyJoined)
+ if (!Reads && SubIdx)
Reads = DstInt.liveAt(LIS->getInstructionIndex(UseMI));
// Replace SrcReg with DstReg in all UseMI operands.
@@ -961,7 +926,7 @@
// Adjust <undef> flags in case of sub-register joins. We don't want to
// turn a full def into a read-modify-write sub-register def and vice
// versa.
- if (SubIdx && !AlreadyJoined && MO.isDef())
+ if (SubIdx && MO.isDef())
MO.setIsUndef(!Reads);
if (DstIsPhys)
@@ -970,10 +935,6 @@
MO.substVirtReg(DstReg, SubIdx, *TRI);
}
- // This instruction is a copy that will be removed.
- if (AlreadyJoined)
- continue;
-
DEBUG({
dbgs() << "\t\tupdated: ";
if (!UseMI->isDebugValue())
@@ -983,37 +944,6 @@
}
}
-/// removeIntervalIfEmpty - Check if the live interval of a physical register
-/// is empty, if so remove it and also remove the empty intervals of its
-/// sub-registers. Return true if live interval is removed.
-static bool removeIntervalIfEmpty(LiveInterval &li, LiveIntervals *LIS,
- const TargetRegisterInfo *TRI) {
- if (li.empty()) {
- if (TargetRegisterInfo::isPhysicalRegister(li.reg))
- for (const uint16_t* SR = TRI->getSubRegisters(li.reg); *SR; ++SR) {
- if (!LIS->hasInterval(*SR))
- continue;
- LiveInterval &sli = LIS->getInterval(*SR);
- if (sli.empty())
- LIS->removeInterval(*SR);
- }
- LIS->removeInterval(li.reg);
- return true;
- }
- return false;
-}
-
-/// removeDeadDef - If a def of a live interval is now determined dead, remove
-/// the val# it defines. If the live interval becomes empty, remove it as well.
-bool RegisterCoalescer::removeDeadDef(LiveInterval &li, MachineInstr *DefMI) {
- SlotIndex DefIdx = LIS->getInstructionIndex(DefMI).getRegSlot();
- LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx);
- if (DefIdx != MLR->valno->def)
- return false;
- li.removeValNo(MLR->valno);
- return removeIntervalIfEmpty(li, LIS, TRI);
-}
-
/// canJoinPhys - Return true if a copy involving a physreg should be joined.
bool RegisterCoalescer::canJoinPhys(CoalescerPair &CP) {
/// Always join simple intervals that are defined by a single copy from a
@@ -1040,9 +970,6 @@
bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
Again = false;
- if (JoinedCopies.count(CopyMI))
- return false; // Already done.
-
DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
CoalescerPair CP(*TII, *TRI);
@@ -1646,9 +1573,7 @@
}
void RegisterCoalescer::releaseMemory() {
- JoinedCopies.clear();
ErasedInstrs.clear();
- ReMatDefs.clear();
WorkList.clear();
DeadDefs.clear();
InflateRegs.clear();
@@ -1696,74 +1621,6 @@
for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
mii != mie; ) {
MachineInstr *MI = mii;
- if (JoinedCopies.count(MI)) {
- // Delete all coalesced copies.
- bool DoDelete = true;
- assert(MI->isCopyLike() && "Unrecognized copy instruction");
- unsigned SrcReg = MI->getOperand(MI->isSubregToReg() ? 2 : 1).getReg();
-
- if (TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
- MI->getNumOperands() > 2)
- // Do not delete extract_subreg, insert_subreg of physical
- // registers unless the definition is dead. e.g.
- // %DO<def> = INSERT_SUBREG %D0<undef>, %S0<kill>, 1
- // or else the scavenger may complain. LowerSubregs will
- // delete them later.
- DoDelete = false;
-
- if (MI->allDefsAreDead()) {
- if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
- LIS->hasInterval(SrcReg))
- LIS->shrinkToUses(&LIS->getInterval(SrcReg));
- DoDelete = true;
- }
- if (!DoDelete) {
- // We need the instruction to adjust liveness, so make it a KILL.
- if (MI->isSubregToReg()) {
- MI->RemoveOperand(3);
- MI->RemoveOperand(1);
- }
- MI->setDesc(TII->get(TargetOpcode::KILL));
- mii = llvm::next(mii);
- } else {
- LIS->RemoveMachineInstrFromMaps(MI);
- mii = mbbi->erase(mii);
- ++numPeep;
- }
- continue;
- }
-
- // Now check if this is a remat'ed def instruction which is now dead.
- if (ReMatDefs.count(MI)) {
- bool isDead = true;
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg())
- continue;
- unsigned Reg = MO.getReg();
- if (!Reg)
- continue;
- DeadDefs.push_back(Reg);
- if (MO.isDead())
- continue;
- if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
- !MRI->use_nodbg_empty(Reg)) {
- isDead = false;
- break;
- }
- }
- if (isDead) {
- while (!DeadDefs.empty()) {
- unsigned DeadDef = DeadDefs.back();
- DeadDefs.pop_back();
- removeDeadDef(LIS->getInterval(DeadDef), MI);
- }
- LIS->RemoveMachineInstrFromMaps(mii);
- mii = mbbi->erase(mii);
- continue;
- } else
- DeadDefs.clear();
- }
++mii;
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