Loop *L;
LoopInfo *LI;
ScalarEvolution *SE;
- const DataLayout *DL; // May be NULL
SmallVectorImpl<WeakVH> &DeadInsts;
bool Changed;
public:
- SimplifyIndvar(Loop *Loop, ScalarEvolution *SE, LPPassManager *LPM,
- SmallVectorImpl<WeakVH> &Dead, IVUsers *IVU = nullptr) :
- L(Loop),
- LI(LPM->getAnalysisIfAvailable<LoopInfo>()),
- SE(SE),
- DeadInsts(Dead),
- Changed(false) {
- DataLayoutPass *DLP = LPM->getAnalysisIfAvailable<DataLayoutPass>();
- DL = DLP ? &DLP->getDataLayout() : nullptr;
+ SimplifyIndvar(Loop *Loop, ScalarEvolution *SE, LoopInfo *LI,
+ SmallVectorImpl<WeakVH> &Dead, IVUsers *IVU = nullptr)
+ : L(Loop), LI(LI), SE(SE), DeadInsts(Dead), Changed(false) {
assert(LI && "IV simplification requires LoopInfo");
}
void eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand);
void eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
bool IsSigned);
+ bool strengthenOverflowingOperation(BinaryOperator *OBO, Value *IVOperand);
Instruction *splitOverflowIntrinsic(Instruction *IVUser,
const DominatorTree *DT);
return true;
}
+/// Annotate BO with nsw / nuw if it provably does not signed-overflow /
+/// unsigned-overflow. Returns true if anything changed, false otherwise.
+bool SimplifyIndvar::strengthenOverflowingOperation(BinaryOperator *BO,
+ Value *IVOperand) {
+
+ // Currently we only handle instructions of the form "add <indvar> <value>"
+ unsigned Op = BO->getOpcode();
+ if (Op != Instruction::Add)
+ return false;
+
+ // If BO is already both nuw and nsw then there is nothing left to do
+ if (BO->hasNoUnsignedWrap() && BO->hasNoSignedWrap())
+ return false;
+
+ IntegerType *IT = cast<IntegerType>(IVOperand->getType());
+ Value *OtherOperand = nullptr;
+ if (BO->getOperand(0) == IVOperand) {
+ OtherOperand = BO->getOperand(1);
+ } else {
+ assert(BO->getOperand(1) == IVOperand && "only other use!");
+ OtherOperand = BO->getOperand(0);
+ }
+
+ bool Changed = false;
+ const SCEV *OtherOpSCEV = SE->getSCEV(OtherOperand);
+ if (OtherOpSCEV == SE->getCouldNotCompute())
+ return false;
+
+ const SCEV *IVOpSCEV = SE->getSCEV(IVOperand);
+ const SCEV *ZeroSCEV = SE->getConstant(IVOpSCEV->getType(), 0);
+
+ if (!BO->hasNoSignedWrap()) {
+ // Upgrade the add to an "add nsw" if we can prove that it will never
+ // sign-overflow or sign-underflow.
+
+ const SCEV *SignedMax =
+ SE->getConstant(APInt::getSignedMaxValue(IT->getBitWidth()));
+ const SCEV *SignedMin =
+ SE->getConstant(APInt::getSignedMinValue(IT->getBitWidth()));
+
+ // The addition "IVOperand + OtherOp" does not sign-overflow if the result
+ // is sign-representable in 2's complement in the given bit-width.
+ //
+ // If OtherOp is SLT 0, then for an IVOperand in [SignedMin - OtherOp,
+ // SignedMax], "IVOperand + OtherOp" is in [SignedMin, SignedMax + OtherOp].
+ // Everything in [SignedMin, SignedMax + OtherOp] is representable since
+ // SignedMax + OtherOp is at least -1.
+ //
+ // If OtherOp is SGE 0, then for an IVOperand in [SignedMin, SignedMax -
+ // OtherOp], "IVOperand + OtherOp" is in [SignedMin + OtherOp, SignedMax].
+ // Everything in [SignedMin + OtherOp, SignedMax] is representable since
+ // SignedMin + OtherOp is at most -1.
+ //
+ // It follows that for all values of IVOperand in [SignedMin - smin(0,
+ // OtherOp), SignedMax - smax(0, OtherOp)] the result of the add is
+ // representable (i.e. there is no sign-overflow).
+
+ const SCEV *UpperDelta = SE->getSMaxExpr(ZeroSCEV, OtherOpSCEV);
+ const SCEV *UpperLimit = SE->getMinusSCEV(SignedMax, UpperDelta);
+
+ bool NeverSignedOverflows =
+ SE->isKnownPredicate(ICmpInst::ICMP_SLE, IVOpSCEV, UpperLimit);
+
+ if (NeverSignedOverflows) {
+ const SCEV *LowerDelta = SE->getSMinExpr(ZeroSCEV, OtherOpSCEV);
+ const SCEV *LowerLimit = SE->getMinusSCEV(SignedMin, LowerDelta);
+
+ bool NeverSignedUnderflows =
+ SE->isKnownPredicate(ICmpInst::ICMP_SGE, IVOpSCEV, LowerLimit);
+ if (NeverSignedUnderflows) {
+ BO->setHasNoSignedWrap(true);
+ Changed = true;
+ }
+ }
+ }
+
+ if (!BO->hasNoUnsignedWrap()) {
+ // Upgrade the add computing "IVOperand + OtherOp" to an "add nuw" if we can
+ // prove that it will never unsigned-overflow (i.e. the result will always
+ // be representable in the given bit-width).
+ //
+ // "IVOperand + OtherOp" is unsigned-representable in 2's complement iff it
+ // does not produce a carry. "IVOperand + OtherOp" produces no carry iff
+ // IVOperand ULE (UnsignedMax - OtherOp).
+
+ const SCEV *UnsignedMax =
+ SE->getConstant(APInt::getMaxValue(IT->getBitWidth()));
+ const SCEV *UpperLimit = SE->getMinusSCEV(UnsignedMax, OtherOpSCEV);
+
+ bool NeverUnsignedOverflows =
+ SE->isKnownPredicate(ICmpInst::ICMP_ULE, IVOpSCEV, UpperLimit);
+
+ if (NeverUnsignedOverflows) {
+ BO->setHasNoUnsignedWrap(true);
+ Changed = true;
+ }
+ }
+
+ return Changed;
+}
+
/// \brief Split sadd.with.overflow into add + sadd.with.overflow to allow
/// analysis and optimization.
///
pushIVUsers(IVOperand, Simplified, SimpleIVUsers);
continue;
}
+
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(UseOper.first)) {
+ if (isa<OverflowingBinaryOperator>(BO) &&
+ strengthenOverflowingOperation(BO, IVOperand)) {
+ // re-queue uses of the now modified binary operator and fall
+ // through to the checks that remain.
+ pushIVUsers(IVOperand, Simplified, SimpleIVUsers);
+ }
+ }
+
CastInst *Cast = dyn_cast<CastInst>(UseOper.first);
if (V && Cast) {
V->visitCast(Cast);
bool simplifyUsersOfIV(PHINode *CurrIV, ScalarEvolution *SE, LPPassManager *LPM,
SmallVectorImpl<WeakVH> &Dead, IVVisitor *V)
{
- LoopInfo *LI = &LPM->getAnalysis<LoopInfo>();
- SimplifyIndvar SIV(LI->getLoopFor(CurrIV->getParent()), SE, LPM, Dead);
+ LoopInfo *LI = &LPM->getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+ SimplifyIndvar SIV(LI->getLoopFor(CurrIV->getParent()), SE, LI, Dead);
SIV.simplifyUsers(CurrIV, V);
return SIV.hasChanged();
}
projects / oota-llvm.git / blobdiff