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fix a corner case in delinearization
handle special cases Step==1, Step==-1, GCD==1, and GCD==-1 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201868 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -7255,46 +7255,37 @@ SCEVAddRecExpr::delinearize(ScalarEvolution &SE,
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DEBUG(dbgs() << "(delinearize: " << *this << "\n");
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// Currently we fail to delinearize when the stride of this SCEV is 1. We
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// could decide to not fail in this case: we could just return 1 for the size
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// of the subscript, and this same SCEV for the access function.
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if (Step == One) {
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DEBUG(dbgs() << "failed to delinearize " << *this << "\n)\n");
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return this;
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}
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// When the stride of this SCEV is 1, do not compute the GCD: the size of this
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// subscript is 1, and this same SCEV for the access function.
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const SCEV *Remainder = Zero;
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const SCEV *GCD = One;
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// Find the GCD and Remainder of the Start and Step coefficients of this SCEV.
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const SCEV *Remainder = NULL;
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const SCEV *GCD = SCEVGCD::findGCD(SE, Start, Step, &Remainder);
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if (Step != One && !Step->isAllOnesValue())
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GCD = SCEVGCD::findGCD(SE, Start, Step, &Remainder);
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DEBUG(dbgs() << "GCD: " << *GCD << "\n");
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DEBUG(dbgs() << "Remainder: " << *Remainder << "\n");
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// Same remark as above: we currently fail the delinearization, although we
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// can very well handle this special case.
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if (GCD == One) {
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DEBUG(dbgs() << "failed to delinearize " << *this << "\n)\n");
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return this;
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}
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const SCEV *Quotient = Start;
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if (GCD != One && !GCD->isAllOnesValue())
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// As findGCD computed Remainder, GCD divides "Start - Remainder." The
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// Quotient is then this SCEV without Remainder, scaled down by the GCD. The
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// Quotient is what will be used in the next subscript delinearization.
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Quotient = SCEVDivision::divide(SE, SE.getMinusSCEV(Start, Remainder), GCD);
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// As findGCD computed Remainder, GCD divides "Start - Remainder." The
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// Quotient is then this SCEV without Remainder, scaled down by the GCD. The
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// Quotient is what will be used in the next subscript delinearization.
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const SCEV *Quotient =
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SCEVDivision::divide(SE, SE.getMinusSCEV(Start, Remainder), GCD);
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DEBUG(dbgs() << "Quotient: " << *Quotient << "\n");
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const SCEV *Rem;
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const SCEV *Rem = Quotient;
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if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Quotient))
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// Recursively call delinearize on the Quotient until there are no more
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// multiples that can be recognized.
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Rem = AR->delinearize(SE, Subscripts, Sizes);
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else
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Rem = Quotient;
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// Scale up the canonical induction variable IV by whatever remains from the
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// Step after division by the GCD: the GCD is the size of all the sub-array.
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if (Step != GCD) {
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if (Step != One && !Step->isAllOnesValue() && GCD != One &&
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!GCD->isAllOnesValue() && Step != GCD) {
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Step = SCEVDivision::divide(SE, Step, GCD);
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IV = SE.getMulExpr(IV, Step);
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}
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