6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-06-24 08:24:33 +00:00
Code Issues Projects Releases Wiki Activity

Revert "Look through PHIs to find additional register sources"

Browse Source 
Likely broke compilation on ARM:

http://lab.llvm.org:8011/builders/clang-native-arm-lnt/builds/13054

This reverts commit 131ce4a838c081516cbfed039fc986b33e3979d6.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242310 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bruno Cardoso Lopes
2015-07-15 18:10:35 +00:00
parent 15afc3140e
commit ae1ebf6cf7
4 changed files with 83 additions and 378 deletions
Download Patch File Download Diff File Expand all files Collapse all files

347
lib/CodeGen/PeepholeOptimizer.cpp
View File

@ -98,12 +98,6 @@ static cl::opt<bool>
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");
@ -138,10 +132,6 @@ namespace {
}
}
/// \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,
@ -153,8 +143,7 @@ namespace {
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);
@ -231,20 +220,6 @@ namespace {
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
@ -306,8 +281,6 @@ namespace {
/// \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.
@ -610,133 +583,58 @@ static bool shareSameRegisterFile(const TargetRegisterInfo &TRI,
/// \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);
const TargetRegisterClass *DefRC = MRI->getRegClass(Reg);
unsigned DefSubReg = SubReg;
unsigned Src;
unsigned SrcSubReg;
bool ShouldRewrite = false;
unsigned PHILimit = RewritePHILimit;
while (!SrcToLook.empty() && PHILimit) {
TargetInstrInfo::RegSubRegPair Pair = SrcToLook.pop_back_val();
CurSrcPair = Pair;
ValueTracker ValTracker(CurSrcPair.Reg, CurSrcPair.SubReg, *MRI,
!DisableAdvCopyOpt, TII);
ValueTrackerResult Res;
// 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 {
// 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;
// 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;
// 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");
break;
}
RewriteMap.insert(std::make_pair(CurSrcPair, Res));
const TargetRegisterClass *SrcRC = MRI->getRegClass(Src);
// 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 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) {
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 {
@ -810,65 +708,16 @@ public:
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;
}
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);
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;
}
};
@ -916,41 +765,31 @@ public:
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();
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;
}
};
@ -1194,25 +1033,16 @@ bool PeepholeOptimizer::optimizeCoalescableCopy(MachineInstr *MI) {
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))
if (!findNextSource(NewSrc, NewSubReg) || SrcReg == NewSrc)
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)
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;
}
}
@ -1241,7 +1071,9 @@ bool PeepholeOptimizer::optimizeUncoalescableCopy(
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.
@ -1251,32 +1083,39 @@ bool PeepholeOptimizer::optimizeUncoalescableCopy(
// 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;
@ -1684,26 +1523,6 @@ ValueTrackerResult ValueTracker::getNextSourceFromSubregToReg() {
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");
@ -1726,8 +1545,6 @@ ValueTrackerResult ValueTracker::getNextSourceImpl() {
return getNextSourceFromExtractSubreg();
if (Def->isSubregToReg())
return getNextSourceFromSubregToReg();
if (Def->isPHI())
return getNextSourceFromPHI();
return ValueTrackerResult();
}