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Revert "[PeepholeOptimizer] Look through PHIs to find additional register sources"

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Reported to Broke some internal tests: PR24303

This reverts commit r243486.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243540 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bruno Cardoso Lopes 2015-07-29 17:46:47 +00:00
parent de85af6733
commit 4e3c7c262b
4 changed files with 83 additions and 398 deletions
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27
include/llvm/Target/TargetInstrInfo.h
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@ -1276,33 +1276,6 @@ private:
unsigned CallFrameSetupOpcode, CallFrameDestroyOpcode; unsigned CallFrameSetupOpcode, CallFrameDestroyOpcode;
}; };
/// \brief Provide DenseMapInfo for TargetInstrInfo::RegSubRegPair.
template<>
struct DenseMapInfo<TargetInstrInfo::RegSubRegPair> {
typedef DenseMapInfo<unsigned> RegInfo;
static inline TargetInstrInfo::RegSubRegPair getEmptyKey() {
return TargetInstrInfo::RegSubRegPair(RegInfo::getEmptyKey(),
RegInfo::getEmptyKey());
}
static inline TargetInstrInfo::RegSubRegPair getTombstoneKey() {
return TargetInstrInfo::RegSubRegPair(RegInfo::getTombstoneKey(),
RegInfo::getTombstoneKey());
}
/// \brief Reuse getHashValue implementation from
/// std::pair<unsigned, unsigned>.
static unsigned getHashValue(const TargetInstrInfo::RegSubRegPair &Val) {
std::pair<unsigned, unsigned> PairVal =
std::make_pair(Val.Reg, Val.SubReg);
return DenseMapInfo<std::pair<unsigned, unsigned>>::getHashValue(PairVal);
}
static bool isEqual(const TargetInstrInfo::RegSubRegPair &LHS,
const TargetInstrInfo::RegSubRegPair &RHS) {
return RegInfo::isEqual(LHS.Reg, RHS.Reg) &&
RegInfo::isEqual(LHS.SubReg, RHS.SubReg);
}
};
} // End llvm namespace } // End llvm namespace
#endif #endif

367
lib/CodeGen/PeepholeOptimizer.cpp
View File

@ -98,12 +98,6 @@ static cl::opt<bool>
DisableAdvCopyOpt("disable-adv-copy-opt", cl::Hidden, cl::init(false), DisableAdvCopyOpt("disable-adv-copy-opt", cl::Hidden, cl::init(false),
cl::desc("Disable advanced copy optimization")); 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(NumReuse, "Number of extension results reused");
STATISTIC(NumCmps, "Number of compares eliminated"); STATISTIC(NumCmps, "Number of compares eliminated");
STATISTIC(NumImmFold, "Number of move immediate folded"); STATISTIC(NumImmFold, "Number of move immediate folded");
@ -138,10 +132,6 @@ namespace {
} }
} }
/// \brief Track Def -> Use info used for rewriting copies.
typedef SmallDenseMap<TargetInstrInfo::RegSubRegPair, ValueTrackerResult>
RewriteMapTy;
private: private:
bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB); bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB, bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
@ -153,8 +143,7 @@ namespace {
bool optimizeCoalescableCopy(MachineInstr *MI); bool optimizeCoalescableCopy(MachineInstr *MI);
bool optimizeUncoalescableCopy(MachineInstr *MI, bool optimizeUncoalescableCopy(MachineInstr *MI,
SmallPtrSetImpl<MachineInstr *> &LocalMIs); SmallPtrSetImpl<MachineInstr *> &LocalMIs);
bool findNextSource(unsigned Reg, unsigned SubReg, bool findNextSource(unsigned &Reg, unsigned &SubReg);
RewriteMapTy &RewriteMap);
bool isMoveImmediate(MachineInstr *MI, bool isMoveImmediate(MachineInstr *MI,
SmallSet<unsigned, 4> &ImmDefRegs, SmallSet<unsigned, 4> &ImmDefRegs,
DenseMap<unsigned, MachineInstr*> &ImmDefMIs); DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
@ -231,20 +220,6 @@ namespace {
assert(Idx < getNumSources() && "SubReg source out of index"); assert(Idx < getNumSources() && "SubReg source out of index");
return RegSrcs[Idx].SubReg; 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 Helper class to track the possible sources of a value defined by
@ -306,8 +281,6 @@ namespace {
/// \brief Specialized version of getNextSource for SubregToReg /// \brief Specialized version of getNextSource for SubregToReg
/// instructions. /// instructions.
ValueTrackerResult getNextSourceFromSubregToReg(); ValueTrackerResult getNextSourceFromSubregToReg();
/// \brief Specialized version of getNextSource for PHI instructions.
ValueTrackerResult getNextSourceFromPHI();
public: public:
/// \brief Create a ValueTracker instance for the value defined by \p Reg. /// \brief Create a ValueTracker instance for the value defined by \p Reg.
@ -610,143 +583,58 @@ static bool shareSameRegisterFile(const TargetRegisterInfo &TRI,
/// \brief Try to find the next source that share the same register file /// \brief Try to find the next source that share the same register file
/// for the value defined by \p Reg and \p SubReg. /// for the value defined by \p Reg and \p SubReg.
/// When true is returned, the \p RewriteMap can be used by the client to /// When true is returned, \p Reg and \p SubReg are updated with the
/// retrieve all Def -> Use along the way up to the next source. Any found /// register number and sub-register index of the new source.
/// 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.
/// \return False if no alternative sources are available. True otherwise. /// \return False if no alternative sources are available. True otherwise.
bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg, bool PeepholeOptimizer::findNextSource(unsigned &Reg, unsigned &SubReg) {
RewriteMapTy &RewriteMap) {
// Do not try to find a new source for a physical register. // Do not try to find a new source for a physical register.
// So far we do not have any motivating example for doing that. // So far we do not have any motivating example for doing that.
// Thus, instead of maintaining untested code, we will revisit that if // Thus, instead of maintaining untested code, we will revisit that if
// that changes at some point. // that changes at some point.
if (TargetRegisterInfo::isPhysicalRegister(Reg)) if (TargetRegisterInfo::isPhysicalRegister(Reg))
return false; return false;
const TargetRegisterClass *DefRC = MRI->getRegClass(Reg);
SmallVector<TargetInstrInfo::RegSubRegPair, 4> SrcToLook; const TargetRegisterClass *DefRC = MRI->getRegClass(Reg);
TargetInstrInfo::RegSubRegPair CurSrcPair(Reg, SubReg); unsigned DefSubReg = SubReg;
SrcToLook.push_back(CurSrcPair);
unsigned Src;
unsigned SrcSubReg;
bool ShouldRewrite = false; bool ShouldRewrite = false;
unsigned PHILimit = RewritePHILimit; // Follow the chain of copies until we reach the top of the use-def chain
while (!SrcToLook.empty() && PHILimit) { // or find a more suitable source.
TargetInstrInfo::RegSubRegPair Pair = SrcToLook.pop_back_val(); ValueTracker ValTracker(Reg, DefSubReg, *MRI, !DisableAdvCopyOpt, TII);
// As explained above, do not handle physical registers do {
if (TargetRegisterInfo::isPhysicalRegister(Pair.Reg)) ValueTrackerResult Res = ValTracker.getNextSource();
return false; if (!Res.isValid())
break;
Src = Res.getSrcReg(0);
SrcSubReg = Res.getSrcSubReg(0);
CurSrcPair = Pair; // Do not extend the live-ranges of physical registers as they add
ValueTracker ValTracker(CurSrcPair.Reg, CurSrcPair.SubReg, *MRI, // constraints to the register allocator.
!DisableAdvCopyOpt, TII); // Moreover, if we want to extend the live-range of a physical register,
ValueTrackerResult Res; // unlike SSA virtual register, we will have to check that they are not
// redefine before the related use.
if (TargetRegisterInfo::isPhysicalRegister(Src))
break;
do { const TargetRegisterClass *SrcRC = MRI->getRegClass(Src);
// 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. // If this source does not incur a cross register bank copy, use it.
ValueTrackerResult CurSrcRes = RewriteMap.lookup(CurSrcPair); ShouldRewrite = shareSameRegisterFile(*TRI, DefRC, DefSubReg, SrcRC,
if (CurSrcRes.isValid()) { SrcSubReg);
assert(CurSrcRes == Res && "ValueTrackerResult found must match"); } while (!ShouldRewrite);
// 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) {
PHILimit--;
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;
if (!PHILimit) {
DEBUG(dbgs() << "findNextSource: PHI limit reached\n");
return false;
}
// 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;
}
// If we did not find a more suitable source, there is nothing to optimize. // If we did not find a more suitable source, there is nothing to optimize.
if (CurSrcPair.Reg == Reg) if (!ShouldRewrite || Src == Reg)
return false; return false;
Reg = Src;
SubReg = SrcSubReg;
return true; 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) {
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 { namespace {
/// \brief Helper class to rewrite the arguments of a copy-like instruction. /// \brief Helper class to rewrite the arguments of a copy-like instruction.
class CopyRewriter { class CopyRewriter {
@ -814,78 +702,22 @@ public:
virtual bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) { virtual bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) {
if (!CopyLike.isCopy() || CurrentSrcIdx != 1) if (!CopyLike.isCopy() || CurrentSrcIdx != 1)
return false; return false;
DEBUG(dbgs() << "-- RewriteCurrentSource\n");
DEBUG(dbgs() << " Replacing: " << CopyLike);
MachineOperand &MOSrc = CopyLike.getOperand(CurrentSrcIdx); MachineOperand &MOSrc = CopyLike.getOperand(CurrentSrcIdx);
MOSrc.setReg(NewReg); MOSrc.setReg(NewReg);
MOSrc.setSubReg(NewSubReg); MOSrc.setSubReg(NewSubReg);
DEBUG(dbgs() << " With: " << CopyLike);
return true; return true;
} }
/// \brief Given a \p Def.Reg and Def.SubReg pair, use \p RewriteMap to find /// \brief Rewrite the current source with \p NewSrcReg and \p NewSecSubReg
/// the new source to use for rewrite. If \p HandleMultipleSources is true and /// by creating a new COPY instruction. \p DefReg and \p DefSubReg contain the
/// multiple sources for a given \p Def are found along the way, we found a /// definition to be rewritten from the original copylike instruction.
/// PHI instructions that needs to be rewritten. /// \return The new COPY if the rewriting was possible, nullptr otherwise.
/// TODO: HandleMultipleSources should be removed once we test PHI handling /// This is needed to handle Uncoalescable copies, since they are copy
/// with coalescable copies. /// like instructions that aren't recognized by the register allocator.
TargetInstrInfo::RegSubRegPair virtual MachineInstr *RewriteCurrentSource(unsigned DefReg,
getNewSource(MachineRegisterInfo *MRI, const TargetInstrInfo *TII, unsigned DefSubReg,
TargetInstrInfo::RegSubRegPair Def, unsigned NewSrcReg,
PeepholeOptimizer::RewriteMapTy &RewriteMap, unsigned NewSrcSubReg) {
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) {
return nullptr; return nullptr;
} }
}; };
@ -933,44 +765,31 @@ public:
return true; return true;
} }
/// \brief Rewrite the source found through \p Def, by using the \p RewriteMap /// \brief Rewrite the current source with \p NewSrcReg and \p NewSrcSubReg
/// and create a new COPY instruction. More info about RewriteMap in /// by creating a new COPY instruction. \p DefReg and \p DefSubReg contain the
/// PeepholeOptimizer::findNextSource. Right now this is only used to handle /// definition to be rewritten from the original copylike instruction.
/// Uncoalescable copies, since they are copy like instructions that aren't /// \return The new COPY if the rewriting was possible, nullptr otherwise.
/// recognized by the register allocator. MachineInstr *RewriteCurrentSource(unsigned DefReg, unsigned DefSubReg,
MachineInstr * unsigned NewSrcReg,
RewriteSource(TargetInstrInfo::RegSubRegPair Def, unsigned NewSrcSubReg) override {
PeepholeOptimizer::RewriteMapTy &RewriteMap) override { assert(!TargetRegisterInfo::isPhysicalRegister(DefReg) &&
assert(!TargetRegisterInfo::isPhysicalRegister(Def.Reg) &&
"We do not rewrite physical registers"); "We do not rewrite physical registers");
// Find the new source to use in the COPY rewrite. const TargetRegisterClass *DefRC = MRI.getRegClass(DefReg);
TargetInstrInfo::RegSubRegPair NewSrc =
getNewSource(&MRI, &TII, Def, RewriteMap);
// Insert the COPY.
const TargetRegisterClass *DefRC = MRI.getRegClass(Def.Reg);
unsigned NewVR = MRI.createVirtualRegister(DefRC); unsigned NewVR = MRI.createVirtualRegister(DefRC);
MachineInstr *NewCopy = MachineInstr *NewCopy =
BuildMI(*CopyLike.getParent(), &CopyLike, CopyLike.getDebugLoc(), BuildMI(*CopyLike.getParent(), &CopyLike, CopyLike.getDebugLoc(),
TII.get(TargetOpcode::COPY), NewVR) TII.get(TargetOpcode::COPY), NewVR)
.addReg(NewSrc.Reg, 0, NewSrc.SubReg); .addReg(NewSrcReg, 0, NewSrcSubReg);
NewCopy->getOperand(0).setSubReg(Def.SubReg); NewCopy->getOperand(0).setSubReg(DefSubReg);
if (Def.SubReg) if (DefSubReg)
NewCopy->getOperand(0).setIsUndef(); NewCopy->getOperand(0).setIsUndef();
DEBUG(dbgs() << "-- RewriteSource\n"); MRI.replaceRegWith(DefReg, NewVR);
DEBUG(dbgs() << " Replacing: " << CopyLike);
DEBUG(dbgs() << " With: " << *NewCopy);
MRI.replaceRegWith(Def.Reg, NewVR);
MRI.clearKillFlags(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; return NewCopy;
} }
}; };
@ -1214,25 +1033,16 @@ bool PeepholeOptimizer::optimizeCoalescableCopy(MachineInstr *MI) {
unsigned SrcReg, SrcSubReg, TrackReg, TrackSubReg; unsigned SrcReg, SrcSubReg, TrackReg, TrackSubReg;
while (CpyRewriter->getNextRewritableSource(SrcReg, SrcSubReg, TrackReg, while (CpyRewriter->getNextRewritableSource(SrcReg, SrcSubReg, TrackReg,
TrackSubReg)) { TrackSubReg)) {
// Keep track of PHI nodes and its incoming edges when looking for sources. unsigned NewSrc = TrackReg;
RewriteMapTy RewriteMap; unsigned NewSubReg = TrackSubReg;
// Try to find a more suitable source. If we failed to do so, or get the // Try to find a more suitable source. If we failed to do so, or get the
// actual source, move to the next source. // actual source, move to the next source.
if (!findNextSource(TrackReg, TrackSubReg, RewriteMap)) if (!findNextSource(NewSrc, NewSubReg) || SrcReg == NewSrc)
continue; 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)
continue;
// Rewrite source. // 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. // We may have extended the live-range of NewSrc, account for that.
MRI->clearKillFlags(NewSrc.Reg); MRI->clearKillFlags(NewSrc);
Changed = true; Changed = true;
} }
} }
@ -1261,7 +1071,9 @@ bool PeepholeOptimizer::optimizeUncoalescableCopy(
assert(MI && isUncoalescableCopy(*MI) && "Invalid argument"); assert(MI && isUncoalescableCopy(*MI) && "Invalid argument");
// Check if we can rewrite all the values defined by this instruction. // 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. // Get the right rewriter for the current copy.
std::unique_ptr<CopyRewriter> CpyRewriter(getCopyRewriter(*MI, *TII, *MRI)); std::unique_ptr<CopyRewriter> CpyRewriter(getCopyRewriter(*MI, *TII, *MRI));
// If none exists, bails out. // If none exists, bails out.
@ -1271,32 +1083,39 @@ bool PeepholeOptimizer::optimizeUncoalescableCopy(
// Rewrite each rewritable source by generating new COPYs. This works // Rewrite each rewritable source by generating new COPYs. This works
// differently from optimizeCoalescableCopy since it first makes sure that all // differently from optimizeCoalescableCopy since it first makes sure that all
// definitions can be rewritten. // definitions can be rewritten.
RewriteMapTy RewriteMap; unsigned SrcReg, SrcSubReg, TrackReg, TrackSubReg;
unsigned Reg, SubReg, CopyDefReg, CopyDefSubReg; while (CpyRewriter->getNextRewritableSource(SrcReg, SrcSubReg, TrackReg,
while (CpyRewriter->getNextRewritableSource(Reg, SubReg, CopyDefReg, TrackSubReg)) {
CopyDefSubReg)) {
// If a physical register is here, this is probably for a good reason. // If a physical register is here, this is probably for a good reason.
// Do not rewrite that. // Do not rewrite that.
if (TargetRegisterInfo::isPhysicalRegister(CopyDefReg)) if (TargetRegisterInfo::isPhysicalRegister(TrackReg))
return false; return false;
// If we do not know how to rewrite this definition, there is no point // If we do not know how to rewrite this definition, there is no point
// in trying to kill this instruction. // in trying to kill this instruction.
TargetInstrInfo::RegSubRegPair Def(CopyDefReg, CopyDefSubReg); TargetInstrInfo::RegSubRegPair Def(TrackReg, TrackSubReg);
if (!findNextSource(Def.Reg, Def.SubReg, RewriteMap)) TargetInstrInfo::RegSubRegPair Src = Def;
if (!findNextSource(Src.Reg, Src.SubReg))
return false; return false;
RewritePairs.push_back(Def); RewritePairs.push_back(std::make_pair(Def, Src));
} }
// The change is possible for all defs, do it. // 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. // 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"); 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); LocalMIs.insert(NewCopy);
} }
// MI is now dead. // MI is now dead.
MI->eraseFromParent(); MI->eraseFromParent();
++NumUncoalescableCopies; ++NumUncoalescableCopies;
@ -1704,26 +1523,6 @@ ValueTrackerResult ValueTracker::getNextSourceFromSubregToReg() {
Def->getOperand(3).getImm()); 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() { ValueTrackerResult ValueTracker::getNextSourceImpl() {
assert(Def && "This method needs a valid definition"); assert(Def && "This method needs a valid definition");
@ -1746,8 +1545,6 @@ ValueTrackerResult ValueTracker::getNextSourceImpl() {
return getNextSourceFromExtractSubreg(); return getNextSourceFromExtractSubreg();
if (Def->isSubregToReg()) if (Def->isSubregToReg())
return getNextSourceFromSubregToReg(); return getNextSourceFromSubregToReg();
if (Def->isPHI())
return getNextSourceFromPHI();
return ValueTrackerResult(); return ValueTrackerResult();
} }

3
lib/Target/X86/X86InstrMMX.td
View File

@ -249,7 +249,6 @@ def MMX_MOVD64grr : MMXI<0x7E, MRMDestReg, (outs GR32:$dst), (ins VR64:$src),
(MMX_X86movd2w (x86mmx VR64:$src)))], (MMX_X86movd2w (x86mmx VR64:$src)))],
IIC_MMX_MOV_REG_MM>, Sched<[WriteMove]>; IIC_MMX_MOV_REG_MM>, Sched<[WriteMove]>;
let isBitcast = 1 in
def MMX_MOVD64to64rr : MMXRI<0x6E, MRMSrcReg, (outs VR64:$dst), (ins GR64:$src), def MMX_MOVD64to64rr : MMXRI<0x6E, MRMSrcReg, (outs VR64:$dst), (ins GR64:$src),
"movd\t{$src, $dst|$dst, $src}", "movd\t{$src, $dst|$dst, $src}",
[(set VR64:$dst, (bitconvert GR64:$src))], [(set VR64:$dst, (bitconvert GR64:$src))],
@ -263,7 +262,7 @@ def MMX_MOVD64to64rm : MMXRI<0x6E, MRMSrcMem, (outs VR64:$dst),
// These are 64 bit moves, but since the OS X assembler doesn't // These are 64 bit moves, but since the OS X assembler doesn't
// recognize a register-register movq, we write them as // recognize a register-register movq, we write them as
// movd. // movd.
let SchedRW = [WriteMove], isBitcast = 1 in { let SchedRW = [WriteMove] in {
def MMX_MOVD64from64rr : MMXRI<0x7E, MRMDestReg, def MMX_MOVD64from64rr : MMXRI<0x7E, MRMDestReg,
(outs GR64:$dst), (ins VR64:$src), (outs GR64:$dst), (ins VR64:$src),
"movd\t{$src, $dst|$dst, $src}", "movd\t{$src, $dst|$dst, $src}",

84
test/CodeGen/X86/mmx-coalescing.ll
View File

@ -1,84 +0,0 @@
; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=+mmx,+sse2 | FileCheck %s
%SA = type <{ %union.anon, i32, [4 x i8], i8*, i8*, i8*, i32, [4 x i8] }>
%union.anon = type { <1 x i64> }
; Check that extra movd (copy) instructions aren't generated.
define i32 @test(%SA* %pSA, i16* %A, i32 %B, i32 %C, i32 %D, i8* %E) {
entry:
; CHECK-LABEL: test
; CHECK: # BB#0:
; CHECK-NEXT: pshufw
; CHECK-NEXT: movd
; CHECK-NOT: movd
; CHECK-NEXT: testl
%shl = shl i32 1, %B
%shl1 = shl i32 %C, %B
%shl2 = shl i32 1, %D
%v = getelementptr inbounds %SA, %SA* %pSA, i64 0, i32 0, i32 0
%v0 = load <1 x i64>, <1 x i64>* %v, align 8
%SA0 = getelementptr inbounds %SA, %SA* %pSA, i64 0, i32 1
%v1 = load i32, i32* %SA0, align 4
%SA1 = getelementptr inbounds %SA, %SA* %pSA, i64 0, i32 3
%v2 = load i8*, i8** %SA1, align 8
%SA2 = getelementptr inbounds %SA, %SA* %pSA, i64 0, i32 4
%v3 = load i8*, i8** %SA2, align 8
%v4 = bitcast <1 x i64> %v0 to <4 x i16>
%v5 = bitcast <4 x i16> %v4 to x86_mmx
%v6 = tail call x86_mmx @llvm.x86.sse.pshuf.w(x86_mmx %v5, i8 -18)
%v7 = bitcast x86_mmx %v6 to <4 x i16>
%v8 = bitcast <4 x i16> %v7 to <1 x i64>
%v9 = extractelement <1 x i64> %v8, i32 0
%v10 = bitcast i64 %v9 to <2 x i32>
%v11 = extractelement <2 x i32> %v10, i32 0
%cmp = icmp eq i32 %v11, 0
br i1 %cmp, label %if.A, label %if.B
if.A:
; CHECK: %if.A
; CHECK-NEXT: movd
; CHECK-NEXT: psllq
%pa = phi <1 x i64> [ %v8, %entry ], [ %vx, %if.C ]
%v17 = extractelement <1 x i64> %pa, i32 0
%v18 = bitcast i64 %v17 to x86_mmx
%v19 = tail call x86_mmx @llvm.x86.mmx.pslli.q(x86_mmx %v18, i32 %B) #2
%v20 = bitcast x86_mmx %v19 to i64
%v21 = insertelement <1 x i64> undef, i64 %v20, i32 0
%cmp3 = icmp eq i64 %v20, 0
br i1 %cmp3, label %if.C, label %merge
if.B:
%v34 = bitcast <1 x i64> %v8 to <4 x i16>
%v35 = bitcast <4 x i16> %v34 to x86_mmx
%v36 = tail call x86_mmx @llvm.x86.sse.pshuf.w(x86_mmx %v35, i8 -18)
%v37 = bitcast x86_mmx %v36 to <4 x i16>
%v38 = bitcast <4 x i16> %v37 to <1 x i64>
br label %if.C
if.C:
%vx = phi <1 x i64> [ %v21, %if.A ], [ %v38, %if.B ]
%cvt = bitcast <1 x i64> %vx to <2 x i32>
%ex = extractelement <2 x i32> %cvt, i32 0
%cmp2 = icmp eq i32 %ex, 0
br i1 %cmp2, label %if.A, label %merge
merge:
; CHECK: %merge
; CHECK-NOT: movd
; CHECK-NEXT: pshufw
%vy = phi <1 x i64> [ %v21, %if.A ], [ %vx, %if.C ]
%v130 = bitcast <1 x i64> %vy to <4 x i16>
%v131 = bitcast <4 x i16> %v130 to x86_mmx
%v132 = tail call x86_mmx @llvm.x86.sse.pshuf.w(x86_mmx %v131, i8 -18)
%v133 = bitcast x86_mmx %v132 to <4 x i16>
%v134 = bitcast <4 x i16> %v133 to <1 x i64>
%v135 = extractelement <1 x i64> %v134, i32 0
%v136 = bitcast i64 %v135 to <2 x i32>
%v137 = extractelement <2 x i32> %v136, i32 0
ret i32 %v137
}
declare x86_mmx @llvm.x86.sse.pshuf.w(x86_mmx, i8)
declare x86_mmx @llvm.x86.mmx.pslli.q(x86_mmx, i32)