DisableAdvCopyOpt("disable-adv-copy-opt", cl::Hidden, cl::init(false),
cl::desc("Disable advanced copy optimization"));
-// Limit the number of PHI instructions to process
-// in PeepholeOptimizer::getNextSource.
-static cl::opt<unsigned> RewritePHILimit(
- "rewrite-phi-limit", cl::Hidden, cl::init(10),
- cl::desc("Limit the length of PHI chains to lookup"));
-
STATISTIC(NumReuse, "Number of extension results reused");
STATISTIC(NumCmps, "Number of compares eliminated");
STATISTIC(NumImmFold, "Number of move immediate folded");
}
}
- /// \brief Track Def -> Use info used for rewriting copies.
- typedef SmallDenseMap<TargetInstrInfo::RegSubRegPair, ValueTrackerResult>
- RewriteMapTy;
-
private:
bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
bool optimizeCoalescableCopy(MachineInstr *MI);
bool optimizeUncoalescableCopy(MachineInstr *MI,
SmallPtrSetImpl<MachineInstr *> &LocalMIs);
- bool findNextSource(unsigned Reg, unsigned SubReg,
- RewriteMapTy &RewriteMap);
+ bool findNextSource(unsigned &Reg, unsigned &SubReg);
bool isMoveImmediate(MachineInstr *MI,
SmallSet<unsigned, 4> &ImmDefRegs,
DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
assert(Idx < getNumSources() && "SubReg source out of index");
return RegSrcs[Idx].SubReg;
}
-
- bool operator==(const ValueTrackerResult &Other) {
- if (Other.getInst() != getInst())
- return false;
-
- if (Other.getNumSources() != getNumSources())
- return false;
-
- for (int i = 0, e = Other.getNumSources(); i != e; ++i)
- if (Other.getSrcReg(i) != getSrcReg(i) ||
- Other.getSrcSubReg(i) != getSrcSubReg(i))
- return false;
- return true;
- }
};
/// \brief Helper class to track the possible sources of a value defined by
/// \brief Specialized version of getNextSource for SubregToReg
/// instructions.
ValueTrackerResult getNextSourceFromSubregToReg();
- /// \brief Specialized version of getNextSource for PHI instructions.
- ValueTrackerResult getNextSourceFromPHI();
public:
/// \brief Create a ValueTracker instance for the value defined by \p Reg.
/// \brief Try to find the next source that share the same register file
/// for the value defined by \p Reg and \p SubReg.
-/// When true is returned, the \p RewriteMap can be used by the client to
-/// retrieve all Def -> Use along the way up to the next source. Any found
-/// Use that is not itself a key for another entry, is the next source to
-/// use. During the search for the next source, multiple sources can be found
-/// given multiple incoming sources of a PHI instruction. In this case, we
-/// look in each PHI source for the next source; all found next sources must
-/// share the same register file as \p Reg and \p SubReg. The client should
-/// then be capable to rewrite all intermediate PHIs to get the next source.
+/// When true is returned, \p Reg and \p SubReg are updated with the
+/// register number and sub-register index of the new source.
/// \return False if no alternative sources are available. True otherwise.
-bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg,
- RewriteMapTy &RewriteMap) {
+bool PeepholeOptimizer::findNextSource(unsigned &Reg, unsigned &SubReg) {
// Do not try to find a new source for a physical register.
// So far we do not have any motivating example for doing that.
// Thus, instead of maintaining untested code, we will revisit that if
// that changes at some point.
if (TargetRegisterInfo::isPhysicalRegister(Reg))
return false;
- const TargetRegisterClass *DefRC = MRI->getRegClass(Reg);
-
- SmallVector<TargetInstrInfo::RegSubRegPair, 4> SrcToLook;
- TargetInstrInfo::RegSubRegPair CurSrcPair(Reg, SubReg);
- SrcToLook.push_back(CurSrcPair);
-
- unsigned PHICount = 0;
- while (!SrcToLook.empty() && PHICount < RewritePHILimit) {
- TargetInstrInfo::RegSubRegPair Pair = SrcToLook.pop_back_val();
- // As explained above, do not handle physical registers
- if (TargetRegisterInfo::isPhysicalRegister(Pair.Reg))
- return false;
-
- CurSrcPair = Pair;
- ValueTracker ValTracker(CurSrcPair.Reg, CurSrcPair.SubReg, *MRI,
- !DisableAdvCopyOpt, TII);
- ValueTrackerResult Res;
- bool ShouldRewrite = false;
-
- do {
- // Follow the chain of copies until we reach the top of the use-def chain
- // or find a more suitable source.
- Res = ValTracker.getNextSource();
- if (!Res.isValid())
- break;
-
- // Insert the Def -> Use entry for the recently found source.
- ValueTrackerResult CurSrcRes = RewriteMap.lookup(CurSrcPair);
- if (CurSrcRes.isValid()) {
- assert(CurSrcRes == Res && "ValueTrackerResult found must match");
- // An existent entry with multiple sources is a PHI cycle we must avoid.
- // Otherwise it's an entry with a valid next source we already found.
- if (CurSrcRes.getNumSources() > 1) {
- DEBUG(dbgs() << "findNextSource: found PHI cycle, aborting...\n");
- return false;
- }
- break;
- }
- RewriteMap.insert(std::make_pair(CurSrcPair, Res));
-
- // ValueTrackerResult usually have one source unless it's the result from
- // a PHI instruction. Add the found PHI edges to be looked up further.
- unsigned NumSrcs = Res.getNumSources();
- if (NumSrcs > 1) {
- PHICount++;
- for (unsigned i = 0; i < NumSrcs; ++i)
- SrcToLook.push_back(TargetInstrInfo::RegSubRegPair(
- Res.getSrcReg(i), Res.getSrcSubReg(i)));
- break;
- }
-
- CurSrcPair.Reg = Res.getSrcReg(0);
- CurSrcPair.SubReg = Res.getSrcSubReg(0);
- // Do not extend the live-ranges of physical registers as they add
- // constraints to the register allocator. Moreover, if we want to extend
- // the live-range of a physical register, unlike SSA virtual register,
- // we will have to check that they aren't redefine before the related use.
- if (TargetRegisterInfo::isPhysicalRegister(CurSrcPair.Reg))
- return false;
-
- const TargetRegisterClass *SrcRC = MRI->getRegClass(CurSrcPair.Reg);
- // If this source does not incur a cross register bank copy, use it.
- ShouldRewrite = shareSameRegisterFile(*TRI, DefRC, SubReg, SrcRC,
- CurSrcPair.SubReg);
- } while (!ShouldRewrite);
-
- // Continue looking for new sources...
- if (Res.isValid())
- continue;
+ const TargetRegisterClass *DefRC = MRI->getRegClass(Reg);
+ unsigned DefSubReg = SubReg;
+
+ unsigned Src;
+ unsigned SrcSubReg;
+ bool ShouldRewrite = false;
+
+ // Follow the chain of copies until we reach the top of the use-def chain
+ // or find a more suitable source.
+ ValueTracker ValTracker(Reg, DefSubReg, *MRI, !DisableAdvCopyOpt, TII);
+ do {
+ ValueTrackerResult Res = ValTracker.getNextSource();
+ if (!Res.isValid())
+ break;
+ Src = Res.getSrcReg(0);
+ SrcSubReg = Res.getSrcSubReg(0);
+
+ // Do not extend the live-ranges of physical registers as they add
+ // constraints to the register allocator.
+ // Moreover, if we want to extend the live-range of a physical register,
+ // unlike SSA virtual register, we will have to check that they are not
+ // redefine before the related use.
+ if (TargetRegisterInfo::isPhysicalRegister(Src))
+ break;
- // Do not continue searching for a new source if the there's at least
- // one use-def which cannot be rewritten.
- if (!ShouldRewrite)
- return false;
- }
+ const TargetRegisterClass *SrcRC = MRI->getRegClass(Src);
- if (PHICount >= RewritePHILimit) {
- DEBUG(dbgs() << "findNextSource: PHI limit reached\n");
- return false;
- }
+ // If this source does not incur a cross register bank copy, use it.
+ ShouldRewrite = shareSameRegisterFile(*TRI, DefRC, DefSubReg, SrcRC,
+ SrcSubReg);
+ } while (!ShouldRewrite);
// If we did not find a more suitable source, there is nothing to optimize.
- if (CurSrcPair.Reg == Reg)
+ if (!ShouldRewrite || Src == Reg)
return false;
+ Reg = Src;
+ SubReg = SrcSubReg;
return true;
}
-/// \brief Insert a PHI instruction with incoming edges \p SrcRegs that are
-/// guaranteed to have the same register class. This is necessary whenever we
-/// successfully traverse a PHI instruction and find suitable sources coming
-/// from its edges. By inserting a new PHI, we provide a rewritten PHI def
-/// suitable to be used in a new COPY instruction.
-MachineInstr *
-insertPHI(MachineRegisterInfo *MRI, const TargetInstrInfo *TII,
- const SmallVectorImpl<TargetInstrInfo::RegSubRegPair> &SrcRegs,
- MachineInstr *OrigPHI) {
- assert(!SrcRegs.empty() && "No sources to create a PHI instruction?");
-
- const TargetRegisterClass *NewRC = MRI->getRegClass(SrcRegs[0].Reg);
- unsigned NewVR = MRI->createVirtualRegister(NewRC);
- MachineBasicBlock *MBB = OrigPHI->getParent();
- MachineInstrBuilder MIB = BuildMI(*MBB, OrigPHI, OrigPHI->getDebugLoc(),
- TII->get(TargetOpcode::PHI), NewVR);
-
- unsigned MBBOpIdx = 2;
- for (auto RegPair : SrcRegs) {
- assert(NewRC == MRI->getRegClass(RegPair.Reg) &&
- "PHI sources must share the same register class");
-
- MIB.addReg(RegPair.Reg, 0, RegPair.SubReg);
- MIB.addMBB(OrigPHI->getOperand(MBBOpIdx).getMBB());
- // Since we're extended the lifetime of RegPair.Reg, clear the
- // kill flags to account for that and make RegPair.Reg reaches
- // the new PHI.
- MRI->clearKillFlags(RegPair.Reg);
- MBBOpIdx += 2;
- }
-
- return MIB;
-}
-
namespace {
/// \brief Helper class to rewrite the arguments of a copy-like instruction.
class CopyRewriter {
return true;
}
- /// \brief Given a \p Def.Reg and Def.SubReg pair, use \p RewriteMap to find
- /// the new source to use for rewrite. If \p HandleMultipleSources is true and
- /// multiple sources for a given \p Def are found along the way, we found a
- /// PHI instructions that needs to be rewritten.
- /// TODO: HandleMultipleSources should be removed once we test PHI handling
- /// with coalescable copies.
- TargetInstrInfo::RegSubRegPair
- getNewSource(MachineRegisterInfo *MRI, const TargetInstrInfo *TII,
- TargetInstrInfo::RegSubRegPair Def,
- PeepholeOptimizer::RewriteMapTy &RewriteMap,
- bool HandleMultipleSources = true) {
-
- TargetInstrInfo::RegSubRegPair LookupSrc(Def.Reg, Def.SubReg);
- do {
- ValueTrackerResult Res = RewriteMap.lookup(LookupSrc);
- // If there are no entries on the map, LookupSrc is the new source.
- if (!Res.isValid())
- return LookupSrc;
-
- // There's only one source for this definition, keep searching...
- unsigned NumSrcs = Res.getNumSources();
- if (NumSrcs == 1) {
- LookupSrc.Reg = Res.getSrcReg(0);
- LookupSrc.SubReg = Res.getSrcSubReg(0);
- continue;
- }
-
- // TODO: remove once multiple srcs w/ coaslescable copies are supported.
- if (!HandleMultipleSources)
- break;
-
- // Multiple sources, recurse into each source to find a new source
- // for it. Then, rewrite the PHI accordingly to its new edges.
- SmallVector<TargetInstrInfo::RegSubRegPair, 4> NewPHISrcs;
- for (unsigned i = 0; i < NumSrcs; ++i) {
- TargetInstrInfo::RegSubRegPair PHISrc(Res.getSrcReg(i),
- Res.getSrcSubReg(i));
- NewPHISrcs.push_back(
- getNewSource(MRI, TII, PHISrc, RewriteMap, HandleMultipleSources));
- }
-
- // Build the new PHI node and return its def register as the new source.
- MachineInstr *OrigPHI = const_cast<MachineInstr *>(Res.getInst());
- MachineInstr *NewPHI = insertPHI(MRI, TII, NewPHISrcs, OrigPHI);
- DEBUG(dbgs() << "-- getNewSource\n");
- DEBUG(dbgs() << " Replacing: " << *OrigPHI);
- DEBUG(dbgs() << " With: " << *NewPHI);
- const MachineOperand &MODef = NewPHI->getOperand(0);
- return TargetInstrInfo::RegSubRegPair(MODef.getReg(), MODef.getSubReg());
-
- } while (1);
-
- return TargetInstrInfo::RegSubRegPair(0, 0);
- }
-
- /// \brief Rewrite the source found through \p Def, by using the \p RewriteMap
- /// and create a new COPY instruction. More info about RewriteMap in
- /// PeepholeOptimizer::findNextSource. Right now this is only used to handle
- /// Uncoalescable copies, since they are copy like instructions that aren't
- /// recognized by the register allocator.
- virtual MachineInstr *
- RewriteSource(TargetInstrInfo::RegSubRegPair Def,
- PeepholeOptimizer::RewriteMapTy &RewriteMap) {
+ /// \brief Rewrite the current source with \p NewSrcReg and \p NewSecSubReg
+ /// by creating a new COPY instruction. \p DefReg and \p DefSubReg contain the
+ /// definition to be rewritten from the original copylike instruction.
+ /// \return The new COPY if the rewriting was possible, nullptr otherwise.
+ /// This is needed to handle Uncoalescable copies, since they are copy
+ /// like instructions that aren't recognized by the register allocator.
+ virtual MachineInstr *RewriteCurrentSource(unsigned DefReg,
+ unsigned DefSubReg,
+ unsigned NewSrcReg,
+ unsigned NewSrcSubReg) {
return nullptr;
}
};
return true;
}
- /// \brief Rewrite the source found through \p Def, by using the \p RewriteMap
- /// and create a new COPY instruction. More info about RewriteMap in
- /// PeepholeOptimizer::findNextSource. Right now this is only used to handle
- /// Uncoalescable copies, since they are copy like instructions that aren't
- /// recognized by the register allocator.
- MachineInstr *
- RewriteSource(TargetInstrInfo::RegSubRegPair Def,
- PeepholeOptimizer::RewriteMapTy &RewriteMap) override {
- assert(!TargetRegisterInfo::isPhysicalRegister(Def.Reg) &&
+ /// \brief Rewrite the current source with \p NewSrcReg and \p NewSrcSubReg
+ /// by creating a new COPY instruction. \p DefReg and \p DefSubReg contain the
+ /// definition to be rewritten from the original copylike instruction.
+ /// \return The new COPY if the rewriting was possible, nullptr otherwise.
+ MachineInstr *RewriteCurrentSource(unsigned DefReg, unsigned DefSubReg,
+ unsigned NewSrcReg,
+ unsigned NewSrcSubReg) override {
+ assert(!TargetRegisterInfo::isPhysicalRegister(DefReg) &&
"We do not rewrite physical registers");
- // Find the new source to use in the COPY rewrite.
- TargetInstrInfo::RegSubRegPair NewSrc =
- getNewSource(&MRI, &TII, Def, RewriteMap);
-
- // Insert the COPY.
- const TargetRegisterClass *DefRC = MRI.getRegClass(Def.Reg);
+ const TargetRegisterClass *DefRC = MRI.getRegClass(DefReg);
unsigned NewVR = MRI.createVirtualRegister(DefRC);
MachineInstr *NewCopy =
BuildMI(*CopyLike.getParent(), &CopyLike, CopyLike.getDebugLoc(),
TII.get(TargetOpcode::COPY), NewVR)
- .addReg(NewSrc.Reg, 0, NewSrc.SubReg);
+ .addReg(NewSrcReg, 0, NewSrcSubReg);
- NewCopy->getOperand(0).setSubReg(Def.SubReg);
- if (Def.SubReg)
+ NewCopy->getOperand(0).setSubReg(DefSubReg);
+ if (DefSubReg)
NewCopy->getOperand(0).setIsUndef();
- DEBUG(dbgs() << "-- RewriteSource\n");
- DEBUG(dbgs() << " Replacing: " << CopyLike);
- DEBUG(dbgs() << " With: " << *NewCopy);
- MRI.replaceRegWith(Def.Reg, NewVR);
+ MRI.replaceRegWith(DefReg, NewVR);
MRI.clearKillFlags(NewVR);
- // We extended the lifetime of NewSrc.Reg, clear the kill flags to
- // account for that.
- MRI.clearKillFlags(NewSrc.Reg);
-
return NewCopy;
}
};
unsigned SrcReg, SrcSubReg, TrackReg, TrackSubReg;
while (CpyRewriter->getNextRewritableSource(SrcReg, SrcSubReg, TrackReg,
TrackSubReg)) {
- // Keep track of PHI nodes and its incoming edges when looking for sources.
- RewriteMapTy RewriteMap;
+ unsigned NewSrc = TrackReg;
+ unsigned NewSubReg = TrackSubReg;
// Try to find a more suitable source. If we failed to do so, or get the
// actual source, move to the next source.
- if (!findNextSource(TrackReg, TrackSubReg, RewriteMap))
- continue;
-
- // Get the new source to rewrite. TODO: Only enable handling of multiple
- // sources (PHIs) once we have a motivating example and testcases for it.
- TargetInstrInfo::RegSubRegPair TrackPair(TrackReg, TrackSubReg);
- TargetInstrInfo::RegSubRegPair NewSrc = CpyRewriter->getNewSource(
- MRI, TII, TrackPair, RewriteMap, false /* multiple sources */);
- if (SrcReg == NewSrc.Reg || NewSrc.Reg == 0)
+ if (!findNextSource(NewSrc, NewSubReg) || SrcReg == NewSrc)
continue;
-
// Rewrite source.
- if (CpyRewriter->RewriteCurrentSource(NewSrc.Reg, NewSrc.SubReg)) {
+ if (CpyRewriter->RewriteCurrentSource(NewSrc, NewSubReg)) {
// We may have extended the live-range of NewSrc, account for that.
- MRI->clearKillFlags(NewSrc.Reg);
+ MRI->clearKillFlags(NewSrc);
Changed = true;
}
}
assert(MI && isUncoalescableCopy(*MI) && "Invalid argument");
// Check if we can rewrite all the values defined by this instruction.
- SmallVector<TargetInstrInfo::RegSubRegPair, 4> RewritePairs;
+ SmallVector<
+ std::pair<TargetInstrInfo::RegSubRegPair, TargetInstrInfo::RegSubRegPair>,
+ 4> RewritePairs;
// Get the right rewriter for the current copy.
std::unique_ptr<CopyRewriter> CpyRewriter(getCopyRewriter(*MI, *TII, *MRI));
// If none exists, bails out.
// Rewrite each rewritable source by generating new COPYs. This works
// differently from optimizeCoalescableCopy since it first makes sure that all
// definitions can be rewritten.
- RewriteMapTy RewriteMap;
- unsigned Reg, SubReg, CopyDefReg, CopyDefSubReg;
- while (CpyRewriter->getNextRewritableSource(Reg, SubReg, CopyDefReg,
- CopyDefSubReg)) {
+ unsigned SrcReg, SrcSubReg, TrackReg, TrackSubReg;
+ while (CpyRewriter->getNextRewritableSource(SrcReg, SrcSubReg, TrackReg,
+ TrackSubReg)) {
// If a physical register is here, this is probably for a good reason.
// Do not rewrite that.
- if (TargetRegisterInfo::isPhysicalRegister(CopyDefReg))
+ if (TargetRegisterInfo::isPhysicalRegister(TrackReg))
return false;
// If we do not know how to rewrite this definition, there is no point
// in trying to kill this instruction.
- TargetInstrInfo::RegSubRegPair Def(CopyDefReg, CopyDefSubReg);
- if (!findNextSource(Def.Reg, Def.SubReg, RewriteMap))
+ TargetInstrInfo::RegSubRegPair Def(TrackReg, TrackSubReg);
+ TargetInstrInfo::RegSubRegPair Src = Def;
+ if (!findNextSource(Src.Reg, Src.SubReg))
return false;
- RewritePairs.push_back(Def);
+ RewritePairs.push_back(std::make_pair(Def, Src));
}
// The change is possible for all defs, do it.
- for (const auto &Def : RewritePairs) {
+ for (const auto &PairDefSrc : RewritePairs) {
+ const auto &Def = PairDefSrc.first;
+ const auto &Src = PairDefSrc.second;
+
// Rewrite the "copy" in a way the register coalescer understands.
- MachineInstr *NewCopy = CpyRewriter->RewriteSource(Def, RewriteMap);
+ MachineInstr *NewCopy = CpyRewriter->RewriteCurrentSource(
+ Def.Reg, Def.SubReg, Src.Reg, Src.SubReg);
assert(NewCopy && "Should be able to always generate a new copy");
+
+ // We extended the lifetime of Src and clear the kill flags to
+ // account for that.
+ MRI->clearKillFlags(Src.Reg);
LocalMIs.insert(NewCopy);
}
-
// MI is now dead.
MI->eraseFromParent();
++NumUncoalescableCopies;
Def->getOperand(3).getImm());
}
-/// \brief Explore each PHI incoming operand and return its sources
-ValueTrackerResult ValueTracker::getNextSourceFromPHI() {
- assert(Def->isPHI() && "Invalid definition");
- ValueTrackerResult Res;
-
- // If we look for a different subreg, bails as we do not
- // support composing subreg yet.
- if (Def->getOperand(0).getSubReg() != DefSubReg)
- return ValueTrackerResult();
-
- // Return all register sources for PHI instructions.
- for (unsigned i = 1, e = Def->getNumOperands(); i < e; i += 2) {
- auto &MO = Def->getOperand(i);
- assert(MO.isReg() && "Invalid PHI instruction");
- Res.addSource(MO.getReg(), MO.getSubReg());
- }
-
- return Res;
-}
-
ValueTrackerResult ValueTracker::getNextSourceImpl() {
assert(Def && "This method needs a valid definition");
return getNextSourceFromExtractSubreg();
if (Def->isSubregToReg())
return getNextSourceFromSubregToReg();
- if (Def->isPHI())
- return getNextSourceFromPHI();
return ValueTrackerResult();
}
projects / oota-llvm.git / commitdiff