LoopRerollPass.cpp [plain text]
#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
using namespace llvm;
#define DEBUG_TYPE "loop-reroll"
STATISTIC(NumRerolledLoops, "Number of rerolled loops");
static cl::opt<unsigned>
MaxInc("max-reroll-increment", cl::init(2048), cl::Hidden,
cl::desc("The maximum increment for loop rerolling"));
namespace {
enum IterationLimits {
IL_MaxRerollIterations = 16,
IL_LoopIncIdx,
IL_End
};
class LoopReroll : public LoopPass {
public:
static char ID; LoopReroll() : LoopPass(ID) {
initializeLoopRerollPass(*PassRegistry::getPassRegistry());
}
bool runOnLoop(Loop *L, LPPassManager &LPM) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AliasAnalysis>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addPreserved<LoopInfoWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addRequired<ScalarEvolution>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
}
protected:
AliasAnalysis *AA;
LoopInfo *LI;
ScalarEvolution *SE;
TargetLibraryInfo *TLI;
DominatorTree *DT;
typedef SmallVector<Instruction *, 16> SmallInstructionVector;
typedef SmallSet<Instruction *, 16> SmallInstructionSet;
struct SimpleLoopReduction {
SimpleLoopReduction(Instruction *P, Loop *L)
: Valid(false), Instructions(1, P) {
assert(isa<PHINode>(P) && "First reduction instruction must be a PHI");
add(L);
}
bool valid() const {
return Valid;
}
Instruction *getPHI() const {
assert(Valid && "Using invalid reduction");
return Instructions.front();
}
Instruction *getReducedValue() const {
assert(Valid && "Using invalid reduction");
return Instructions.back();
}
Instruction *get(size_t i) const {
assert(Valid && "Using invalid reduction");
return Instructions[i+1];
}
Instruction *operator [] (size_t i) const { return get(i); }
size_t size() const {
assert(Valid && "Using invalid reduction");
return Instructions.size()-1;
}
typedef SmallInstructionVector::iterator iterator;
typedef SmallInstructionVector::const_iterator const_iterator;
iterator begin() {
assert(Valid && "Using invalid reduction");
return std::next(Instructions.begin());
}
const_iterator begin() const {
assert(Valid && "Using invalid reduction");
return std::next(Instructions.begin());
}
iterator end() { return Instructions.end(); }
const_iterator end() const { return Instructions.end(); }
protected:
bool Valid;
SmallInstructionVector Instructions;
void add(Loop *L);
};
struct ReductionTracker {
typedef SmallVector<SimpleLoopReduction, 16> SmallReductionVector;
void addSLR(SimpleLoopReduction &SLR) { PossibleReds.push_back(SLR); }
void restrictToScale(uint64_t Scale,
SmallInstructionSet &PossibleRedSet,
SmallInstructionSet &PossibleRedPHISet,
SmallInstructionSet &PossibleRedLastSet) {
PossibleRedIdx.clear();
PossibleRedIter.clear();
Reds.clear();
for (unsigned i = 0, e = PossibleReds.size(); i != e; ++i)
if (PossibleReds[i].size() % Scale == 0) {
PossibleRedLastSet.insert(PossibleReds[i].getReducedValue());
PossibleRedPHISet.insert(PossibleReds[i].getPHI());
PossibleRedSet.insert(PossibleReds[i].getPHI());
PossibleRedIdx[PossibleReds[i].getPHI()] = i;
for (Instruction *J : PossibleReds[i]) {
PossibleRedSet.insert(J);
PossibleRedIdx[J] = i;
}
}
}
bool isPairInSame(Instruction *J1, Instruction *J2) {
DenseMap<Instruction *, int>::iterator J1I = PossibleRedIdx.find(J1);
if (J1I != PossibleRedIdx.end()) {
DenseMap<Instruction *, int>::iterator J2I = PossibleRedIdx.find(J2);
if (J2I != PossibleRedIdx.end() && J1I->second == J2I->second)
return true;
}
return false;
}
void recordPair(Instruction *J1, Instruction *J2, unsigned i) {
if (PossibleRedIdx.count(J1)) {
assert(PossibleRedIdx.count(J2) &&
"Recording reduction vs. non-reduction instruction?");
PossibleRedIter[J1] = 0;
PossibleRedIter[J2] = i;
int Idx = PossibleRedIdx[J1];
assert(Idx == PossibleRedIdx[J2] &&
"Recording pair from different reductions?");
Reds.insert(Idx);
}
}
bool isSelectedPHI(Instruction *J) {
if (!isa<PHINode>(J))
return false;
for (DenseSet<int>::iterator RI = Reds.begin(), RIE = Reds.end();
RI != RIE; ++RI) {
int i = *RI;
if (cast<Instruction>(J) == PossibleReds[i].getPHI())
return true;
}
return false;
}
bool validateSelected();
void replaceSelected();
protected:
SmallReductionVector PossibleReds;
DenseMap<Instruction *, int> PossibleRedIdx;
DenseMap<Instruction *, int> PossibleRedIter;
DenseSet<int> Reds;
};
struct DAGRootTracker {
DAGRootTracker(LoopReroll *Parent, Loop *L, Instruction *IV,
ScalarEvolution *SE, AliasAnalysis *AA,
TargetLibraryInfo *TLI)
: Parent(Parent), L(L), SE(SE), AA(AA), TLI(TLI), IV(IV) {}
bool findRoots();
bool validate(ReductionTracker &Reductions);
void replace(const SCEV *IterCount);
protected:
typedef MapVector<Instruction*, SmallBitVector> UsesTy;
bool findScaleFromMul();
bool collectAllRoots();
bool collectUsedInstructions(SmallInstructionSet &PossibleRedSet);
void collectInLoopUserSet(const SmallInstructionVector &Roots,
const SmallInstructionSet &Exclude,
const SmallInstructionSet &Final,
DenseSet<Instruction *> &Users);
void collectInLoopUserSet(Instruction *Root,
const SmallInstructionSet &Exclude,
const SmallInstructionSet &Final,
DenseSet<Instruction *> &Users);
UsesTy::iterator nextInstr(int Val, UsesTy &In, UsesTy::iterator I);
LoopReroll *Parent;
Loop *L;
ScalarEvolution *SE;
AliasAnalysis *AA;
TargetLibraryInfo *TLI;
Instruction *IV;
uint64_t Inc;
uint64_t Scale;
Instruction *RealIV;
SmallInstructionVector Roots;
SmallInstructionVector LoopIncs;
UsesTy Uses;
};
void collectPossibleIVs(Loop *L, SmallInstructionVector &PossibleIVs);
void collectPossibleReductions(Loop *L,
ReductionTracker &Reductions);
bool reroll(Instruction *IV, Loop *L, BasicBlock *Header, const SCEV *IterCount,
ReductionTracker &Reductions);
};
}
char LoopReroll::ID = 0;
INITIALIZE_PASS_BEGIN(LoopReroll, "loop-reroll", "Reroll loops", false, false)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(LoopReroll, "loop-reroll", "Reroll loops", false, false)
Pass *llvm::createLoopRerollPass() {
return new LoopReroll;
}
static bool hasUsesOutsideLoop(Instruction *I, Loop *L) {
for (User *U : I->users()) {
if (!L->contains(cast<Instruction>(U)))
return true;
}
return false;
}
void LoopReroll::collectPossibleIVs(Loop *L,
SmallInstructionVector &PossibleIVs) {
BasicBlock *Header = L->getHeader();
for (BasicBlock::iterator I = Header->begin(),
IE = Header->getFirstInsertionPt(); I != IE; ++I) {
if (!isa<PHINode>(I))
continue;
if (!I->getType()->isIntegerTy())
continue;
if (const SCEVAddRecExpr *PHISCEV =
dyn_cast<SCEVAddRecExpr>(SE->getSCEV(I))) {
if (PHISCEV->getLoop() != L)
continue;
if (!PHISCEV->isAffine())
continue;
if (const SCEVConstant *IncSCEV =
dyn_cast<SCEVConstant>(PHISCEV->getStepRecurrence(*SE))) {
if (!IncSCEV->getValue()->getValue().isStrictlyPositive())
continue;
if (IncSCEV->getValue()->uge(MaxInc))
continue;
DEBUG(dbgs() << "LRR: Possible IV: " << *I << " = " <<
*PHISCEV << "\n");
PossibleIVs.push_back(I);
}
}
}
}
void LoopReroll::SimpleLoopReduction::add(Loop *L) {
assert(!Valid && "Cannot add to an already-valid chain");
Instruction *C = Instructions.front();
if (C->user_empty())
return;
do {
C = cast<Instruction>(*C->user_begin());
if (C->hasOneUse()) {
if (!C->isBinaryOp())
return;
if (!(isa<PHINode>(Instructions.back()) ||
C->isSameOperationAs(Instructions.back())))
return;
Instructions.push_back(C);
}
} while (C->hasOneUse());
if (Instructions.size() < 2 ||
!C->isSameOperationAs(Instructions.back()) ||
C->use_empty())
return;
for (User *U : C->users()) {
if (L->contains(cast<Instruction>(U)))
if (cast<Instruction>(U) != Instructions.front())
return;
}
Instructions.push_back(C);
Valid = true;
}
void LoopReroll::collectPossibleReductions(Loop *L,
ReductionTracker &Reductions) {
BasicBlock *Header = L->getHeader();
for (BasicBlock::iterator I = Header->begin(),
IE = Header->getFirstInsertionPt(); I != IE; ++I) {
if (!isa<PHINode>(I))
continue;
if (!I->getType()->isSingleValueType())
continue;
SimpleLoopReduction SLR(I, L);
if (!SLR.valid())
continue;
DEBUG(dbgs() << "LRR: Possible reduction: " << *I << " (with " <<
SLR.size() << " chained instructions)\n");
Reductions.addSLR(SLR);
}
}
void LoopReroll::DAGRootTracker::collectInLoopUserSet(
Instruction *Root, const SmallInstructionSet &Exclude,
const SmallInstructionSet &Final,
DenseSet<Instruction *> &Users) {
SmallInstructionVector Queue(1, Root);
while (!Queue.empty()) {
Instruction *I = Queue.pop_back_val();
if (!Users.insert(I).second)
continue;
if (!Final.count(I))
for (Use &U : I->uses()) {
Instruction *User = cast<Instruction>(U.getUser());
if (PHINode *PN = dyn_cast<PHINode>(User)) {
if (PN->getIncomingBlock(U) == L->getHeader())
continue;
}
if (L->contains(User) && !Exclude.count(User)) {
Queue.push_back(User);
}
}
for (User::op_iterator OI = I->op_begin(),
OIE = I->op_end(); OI != OIE; ++OI) {
if (Instruction *Op = dyn_cast<Instruction>(*OI))
if (Op->hasOneUse() && L->contains(Op) && !Exclude.count(Op) &&
!Final.count(Op))
Queue.push_back(Op);
}
}
}
void LoopReroll::DAGRootTracker::collectInLoopUserSet(
const SmallInstructionVector &Roots,
const SmallInstructionSet &Exclude,
const SmallInstructionSet &Final,
DenseSet<Instruction *> &Users) {
for (SmallInstructionVector::const_iterator I = Roots.begin(),
IE = Roots.end(); I != IE; ++I)
collectInLoopUserSet(*I, Exclude, Final, Users);
}
static bool isSimpleLoadStore(Instruction *I) {
if (LoadInst *LI = dyn_cast<LoadInst>(I))
return LI->isSimple();
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->isSimple();
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I))
return !MI->isVolatile();
return false;
}
bool LoopReroll::DAGRootTracker::findRoots() {
const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(IV));
Inc = cast<SCEVConstant>(RealIVSCEV->getOperand(1))->
getValue()->getZExtValue();
Scale = Inc;
RealIV = IV;
if (Inc == 1 && !findScaleFromMul())
return false;
if (!collectAllRoots())
return false;
if (Roots.size() > IL_MaxRerollIterations) {
DEBUG(dbgs() << "LRR: Aborting - too many iterations found. "
<< "#Found=" << Roots.size() << ", #Max=" << IL_MaxRerollIterations
<< "\n");
return false;
}
return true;
}
bool LoopReroll::DAGRootTracker::findScaleFromMul() {
if (RealIV->getNumUses() != 2)
return false;
const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(RealIV));
Instruction *User1 = cast<Instruction>(*RealIV->user_begin()),
*User2 = cast<Instruction>(*std::next(RealIV->user_begin()));
if (!SE->isSCEVable(User1->getType()) || !SE->isSCEVable(User2->getType()))
return false;
const SCEVAddRecExpr *User1SCEV =
dyn_cast<SCEVAddRecExpr>(SE->getSCEV(User1)),
*User2SCEV =
dyn_cast<SCEVAddRecExpr>(SE->getSCEV(User2));
if (!User1SCEV || !User1SCEV->isAffine() ||
!User2SCEV || !User2SCEV->isAffine())
return false;
if (User1SCEV == RealIVSCEV->getPostIncExpr(*SE)) {
std::swap(User1, User2);
std::swap(User1SCEV, User2SCEV);
}
if (User2SCEV != RealIVSCEV->getPostIncExpr(*SE))
return false;
assert(User2SCEV->getStepRecurrence(*SE)->isOne() &&
"Invalid non-unit step for multiplicative scaling");
LoopIncs.push_back(User2);
if (const SCEVConstant *MulScale =
dyn_cast<SCEVConstant>(User1SCEV->getStepRecurrence(*SE))) {
if (RealIVSCEV->getStart()->getType() != MulScale->getType())
return false;
if (SE->getMulExpr(RealIVSCEV->getStart(), MulScale) !=
User1SCEV->getStart())
return false;
ConstantInt *MulScaleCI = MulScale->getValue();
if (!MulScaleCI->uge(2) || MulScaleCI->uge(MaxInc))
return false;
Scale = MulScaleCI->getZExtValue();
IV = User1;
} else
return false;
DEBUG(dbgs() << "LRR: Found possible scaling " << *User1 << "\n");
assert(Scale <= MaxInc && "Scale is too large");
assert(Scale > 1 && "Scale must be at least 2");
return true;
}
bool LoopReroll::DAGRootTracker::collectAllRoots() {
Roots.resize(Scale-1);
for (User *U : IV->users()) {
Instruction *UI = cast<Instruction>(U);
if (!SE->isSCEVable(UI->getType()))
continue;
if (UI->getType() != IV->getType())
continue;
if (!L->contains(UI))
continue;
if (hasUsesOutsideLoop(UI, L))
continue;
if (const SCEVConstant *Diff = dyn_cast<SCEVConstant>(SE->getMinusSCEV(
SE->getSCEV(UI), SE->getSCEV(IV)))) {
uint64_t Idx = Diff->getValue()->getValue().getZExtValue();
if (Idx > 0 && Idx < Scale) {
if (Roots[Idx-1])
return false;
Roots[Idx-1] = UI;
} else if (Idx == Scale && Inc > 1) {
LoopIncs.push_back(UI);
}
}
}
for (unsigned i = 0; i < Scale-1; ++i) {
if (!Roots[i])
return false;
}
return true;
}
bool LoopReroll::DAGRootTracker::collectUsedInstructions(SmallInstructionSet &PossibleRedSet) {
for (auto &I : *L->getHeader()) {
Uses[&I].resize(IL_End);
}
SmallInstructionSet Exclude;
Exclude.insert(Roots.begin(), Roots.end());
Exclude.insert(LoopIncs.begin(), LoopIncs.end());
DenseSet<Instruction*> VBase;
collectInLoopUserSet(IV, Exclude, PossibleRedSet, VBase);
for (auto *I : VBase) {
Uses[I].set(0);
}
unsigned Idx = 1;
for (auto *Root : Roots) {
DenseSet<Instruction*> V;
collectInLoopUserSet(Root, Exclude, PossibleRedSet, V);
if (V.size() != VBase.size()) {
DEBUG(dbgs() << "LRR: Aborting - use sets are different sizes\n");
return false;
}
for (auto *I : V) {
Uses[I].set(Idx);
}
++Idx;
}
Exclude.clear();
Exclude.insert(Roots.begin(), Roots.end());
DenseSet<Instruction*> V;
collectInLoopUserSet(LoopIncs, Exclude, PossibleRedSet, V);
for (auto *I : V) {
Uses[I].set(IL_LoopIncIdx);
}
if (IV != RealIV)
Uses[RealIV].set(IL_LoopIncIdx);
return true;
}
LoopReroll::DAGRootTracker::UsesTy::iterator
LoopReroll::DAGRootTracker::nextInstr(int Val, UsesTy &In,
UsesTy::iterator I) {
while (I != In.end() && I->second.test(Val) == 0)
++I;
return I;
}
bool LoopReroll::DAGRootTracker::validate(ReductionTracker &Reductions) {
SmallInstructionSet PossibleRedSet;
SmallInstructionSet PossibleRedLastSet;
SmallInstructionSet PossibleRedPHISet;
Reductions.restrictToScale(Scale, PossibleRedSet,
PossibleRedPHISet, PossibleRedLastSet);
if (!collectUsedInstructions(PossibleRedSet))
return false;
for (auto *I : PossibleRedPHISet) {
Uses[I].set(IL_LoopIncIdx);
}
for (auto &KV : Uses) {
if (KV.second.count() != 1) {
DEBUG(dbgs() << "LRR: Aborting - instruction is not used in 1 iteration: "
<< *KV.first << " (#uses=" << KV.second.count() << ")\n");
return false;
}
}
DEBUG(
for (auto &KV : Uses) {
dbgs() << "LRR: " << KV.second.find_first() << "\t" << *KV.first << "\n";
}
);
for (unsigned Iter = 1; Iter < Scale; ++Iter) {
bool FutureSideEffects = false;
AliasSetTracker AST(*AA);
DenseMap<Value *, Value *> BaseMap;
auto BaseIt = nextInstr(0, Uses, Uses.begin());
auto RootIt = nextInstr(Iter, Uses, Uses.begin());
auto LastRootIt = Uses.begin();
while (BaseIt != Uses.end() && RootIt != Uses.end()) {
Instruction *BaseInst = BaseIt->first;
Instruction *RootInst = RootIt->first;
bool Continue = false;
if (BaseInst == RealIV || BaseInst == IV) {
BaseIt = nextInstr(0, Uses, ++BaseIt);
Continue = true;
}
if (std::find(Roots.begin(), Roots.end(), RootInst) != Roots.end()) {
LastRootIt = RootIt;
RootIt = nextInstr(Iter, Uses, ++RootIt);
Continue = true;
}
if (Continue) continue;
for (; LastRootIt != RootIt; ++LastRootIt) {
Instruction *I = LastRootIt->first;
if (LastRootIt->second.find_first() < (int)Iter)
continue;
if (I->mayWriteToMemory())
AST.add(I);
if (!isa<PHINode>(I) && !isSimpleLoadStore(I) &&
!isSafeToSpeculativelyExecute(I))
FutureSideEffects = true;
}
if (!BaseInst->isSameOperationAs(RootInst)) {
DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
" vs. " << *RootInst << "\n");
return false;
}
if (RootIt->second.count() > 1) {
DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
" vs. " << *RootInst << " (prev. case overlap)\n");
return false;
}
if (RootInst->mayReadFromMemory())
for (auto &K : AST) {
if (K.aliasesUnknownInst(RootInst, *AA)) {
DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
" vs. " << *RootInst << " (depends on future store)\n");
return false;
}
}
if (FutureSideEffects && ((!isSimpleLoadStore(BaseInst) &&
!isSafeToSpeculativelyExecute(BaseInst)) ||
(!isSimpleLoadStore(RootInst) &&
!isSafeToSpeculativelyExecute(RootInst)))) {
DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
" vs. " << *RootInst <<
" (side effects prevent reordering)\n");
return false;
}
bool InReduction = Reductions.isPairInSame(BaseInst, RootInst);
if (!(InReduction && BaseInst->isAssociative())) {
bool Swapped = false, SomeOpMatched = false;
for (unsigned j = 0; j < BaseInst->getNumOperands(); ++j) {
Value *Op2 = RootInst->getOperand(j);
if (InReduction)
if (Instruction *Op2I = dyn_cast<Instruction>(Op2))
if (Reductions.isPairInSame(RootInst, Op2I))
continue;
DenseMap<Value *, Value *>::iterator BMI = BaseMap.find(Op2);
if (BMI != BaseMap.end())
Op2 = BMI->second;
else if (Roots[Iter-1] == (Instruction*) Op2)
Op2 = IV;
if (BaseInst->getOperand(Swapped ? unsigned(!j) : j) != Op2) {
if (!Swapped && BaseInst->isCommutative() && !SomeOpMatched &&
BaseInst->getOperand(!j) == Op2) {
Swapped = true;
} else {
DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst
<< " vs. " << *RootInst << " (operand " << j << ")\n");
return false;
}
}
SomeOpMatched = true;
}
}
if ((!PossibleRedLastSet.count(BaseInst) &&
hasUsesOutsideLoop(BaseInst, L)) ||
(!PossibleRedLastSet.count(RootInst) &&
hasUsesOutsideLoop(RootInst, L))) {
DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
" vs. " << *RootInst << " (uses outside loop)\n");
return false;
}
Reductions.recordPair(BaseInst, RootInst, Iter);
BaseMap.insert(std::make_pair(RootInst, BaseInst));
LastRootIt = RootIt;
BaseIt = nextInstr(0, Uses, ++BaseIt);
RootIt = nextInstr(Iter, Uses, ++RootIt);
}
assert (BaseIt == Uses.end() && RootIt == Uses.end() &&
"Mismatched set sizes!");
}
DEBUG(dbgs() << "LRR: Matched all iteration increments for " <<
*RealIV << "\n");
return true;
}
void LoopReroll::DAGRootTracker::replace(const SCEV *IterCount) {
BasicBlock *Header = L->getHeader();
for (BasicBlock::reverse_iterator J = Header->rbegin();
J != Header->rend();) {
unsigned I = Uses[&*J].find_first();
if (I > 0 && I < IL_LoopIncIdx) {
Instruction *D = &*J;
DEBUG(dbgs() << "LRR: removing: " << *D << "\n");
D->eraseFromParent();
continue;
}
++J;
}
const DataLayout &DL = Header->getModule()->getDataLayout();
const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(RealIV));
const SCEV *Start = RealIVSCEV->getStart();
if (Inc == 1)
Start = SE->getMulExpr(Start,
SE->getConstant(Start->getType(), Scale));
const SCEVAddRecExpr *H =
cast<SCEVAddRecExpr>(SE->getAddRecExpr(Start,
SE->getConstant(RealIVSCEV->getType(), 1),
L, SCEV::FlagAnyWrap));
{ SCEVExpander Expander(*SE, DL, "reroll");
Value *NewIV = Expander.expandCodeFor(H, IV->getType(), Header->begin());
for (auto &KV : Uses) {
if (KV.second.find_first() == 0)
KV.first->replaceUsesOfWith(IV, NewIV);
}
if (BranchInst *BI = dyn_cast<BranchInst>(Header->getTerminator())) {
if (Uses[BI].find_first() == IL_LoopIncIdx) {
const SCEV *ICSCEV = RealIVSCEV->evaluateAtIteration(IterCount, *SE);
if (Inc == 1)
ICSCEV =
SE->getMulExpr(ICSCEV, SE->getConstant(ICSCEV->getType(), Scale));
const SCEV *ICMinus1SCEV =
SE->getMinusSCEV(ICSCEV, SE->getConstant(ICSCEV->getType(), 1));
Value *ICMinus1; if (isa<SCEVConstant>(ICMinus1SCEV)) {
ICMinus1 = Expander.expandCodeFor(ICMinus1SCEV, NewIV->getType(), BI);
} else {
BasicBlock *Preheader = L->getLoopPreheader();
if (!Preheader)
Preheader = InsertPreheaderForLoop(L, Parent);
ICMinus1 = Expander.expandCodeFor(ICMinus1SCEV, NewIV->getType(),
Preheader->getTerminator());
}
Value *Cond =
new ICmpInst(BI, CmpInst::ICMP_EQ, NewIV, ICMinus1, "exitcond");
BI->setCondition(Cond);
if (BI->getSuccessor(1) != Header)
BI->swapSuccessors();
}
}
}
SimplifyInstructionsInBlock(Header, TLI);
DeleteDeadPHIs(Header, TLI);
}
bool LoopReroll::ReductionTracker::validateSelected() {
for (DenseSet<int>::iterator RI = Reds.begin(), RIE = Reds.end();
RI != RIE; ++RI) {
int i = *RI;
int PrevIter = 0, BaseCount = 0, Count = 0;
for (Instruction *J : PossibleReds[i]) {
int Iter = PossibleRedIter[J];
if (Iter != PrevIter && Iter != PrevIter + 1 &&
!PossibleReds[i].getReducedValue()->isAssociative()) {
DEBUG(dbgs() << "LRR: Out-of-order non-associative reduction: " <<
J << "\n");
return false;
}
if (Iter != PrevIter) {
if (Count != BaseCount) {
DEBUG(dbgs() << "LRR: Iteration " << PrevIter <<
" reduction use count " << Count <<
" is not equal to the base use count " <<
BaseCount << "\n");
return false;
}
Count = 0;
}
++Count;
if (Iter == 0)
++BaseCount;
PrevIter = Iter;
}
}
return true;
}
void LoopReroll::ReductionTracker::replaceSelected() {
for (DenseSet<int>::iterator RI = Reds.begin(), RIE = Reds.end();
RI != RIE; ++RI) {
int i = *RI;
int j = 0;
for (int e = PossibleReds[i].size(); j != e; ++j)
if (PossibleRedIter[PossibleReds[i][j]] != 0) {
--j;
break;
}
SmallInstructionVector Users;
for (User *U : PossibleReds[i].getReducedValue()->users()) {
Users.push_back(cast<Instruction>(U));
}
for (SmallInstructionVector::iterator J = Users.begin(),
JE = Users.end(); J != JE; ++J)
(*J)->replaceUsesOfWith(PossibleReds[i].getReducedValue(),
PossibleReds[i][j]);
}
}
bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
const SCEV *IterCount,
ReductionTracker &Reductions) {
DAGRootTracker DAGRoots(this, L, IV, SE, AA, TLI);
if (!DAGRoots.findRoots())
return false;
DEBUG(dbgs() << "LRR: Found all root induction increments for: " <<
*IV << "\n");
if (!DAGRoots.validate(Reductions))
return false;
if (!Reductions.validateSelected())
return false;
Reductions.replaceSelected();
DAGRoots.replace(IterCount);
++NumRerolledLoops;
return true;
}
bool LoopReroll::runOnLoop(Loop *L, LPPassManager &LPM) {
if (skipOptnoneFunction(L))
return false;
AA = &getAnalysis<AliasAnalysis>();
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
SE = &getAnalysis<ScalarEvolution>();
TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
BasicBlock *Header = L->getHeader();
DEBUG(dbgs() << "LRR: F[" << Header->getParent()->getName() <<
"] Loop %" << Header->getName() << " (" <<
L->getNumBlocks() << " block(s))\n");
bool Changed = false;
if (L->getNumBlocks() > 1)
return Changed;
if (!SE->hasLoopInvariantBackedgeTakenCount(L))
return Changed;
const SCEV *LIBETC = SE->getBackedgeTakenCount(L);
const SCEV *IterCount =
SE->getAddExpr(LIBETC, SE->getConstant(LIBETC->getType(), 1));
DEBUG(dbgs() << "LRR: iteration count = " << *IterCount << "\n");
SmallInstructionVector PossibleIVs;
collectPossibleIVs(L, PossibleIVs);
if (PossibleIVs.empty()) {
DEBUG(dbgs() << "LRR: No possible IVs found\n");
return Changed;
}
ReductionTracker Reductions;
collectPossibleReductions(L, Reductions);
for (SmallInstructionVector::iterator I = PossibleIVs.begin(),
IE = PossibleIVs.end(); I != IE; ++I)
if (reroll(*I, L, Header, IterCount, Reductions)) {
Changed = true;
break;
}
return Changed;
}