[llvm] r201868 - fix a corner case in delinearization
Sebastian Pop
spop at codeaurora.org
Fri Feb 21 10:15:15 PST 2014
Author: spop
Date: Fri Feb 21 12:15:15 2014
New Revision: 201868
URL: http://llvm.org/viewvc/llvm-project?rev=201868&view=rev
Log:
fix a corner case in delinearization
handle special cases Step==1, Step==-1, GCD==1, and GCD==-1
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=201868&r1=201867&r2=201868&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Fri Feb 21 12:15:15 2014
@@ -7255,46 +7255,37 @@ SCEVAddRecExpr::delinearize(ScalarEvolut
DEBUG(dbgs() << "(delinearize: " << *this << "\n");
- // Currently we fail to delinearize when the stride of this SCEV is 1. We
- // could decide to not fail in this case: we could just return 1 for the size
- // of the subscript, and this same SCEV for the access function.
- if (Step == One) {
- DEBUG(dbgs() << "failed to delinearize " << *this << "\n)\n");
- return this;
- }
+ // When the stride of this SCEV is 1, do not compute the GCD: the size of this
+ // subscript is 1, and this same SCEV for the access function.
+ const SCEV *Remainder = Zero;
+ const SCEV *GCD = One;
// Find the GCD and Remainder of the Start and Step coefficients of this SCEV.
- const SCEV *Remainder = NULL;
- const SCEV *GCD = SCEVGCD::findGCD(SE, Start, Step, &Remainder);
+ if (Step != One && !Step->isAllOnesValue())
+ GCD = SCEVGCD::findGCD(SE, Start, Step, &Remainder);
DEBUG(dbgs() << "GCD: " << *GCD << "\n");
DEBUG(dbgs() << "Remainder: " << *Remainder << "\n");
- // Same remark as above: we currently fail the delinearization, although we
- // can very well handle this special case.
- if (GCD == One) {
- DEBUG(dbgs() << "failed to delinearize " << *this << "\n)\n");
- return this;
- }
+ const SCEV *Quotient = Start;
+ if (GCD != One && !GCD->isAllOnesValue())
+ // As findGCD computed Remainder, GCD divides "Start - Remainder." The
+ // Quotient is then this SCEV without Remainder, scaled down by the GCD. The
+ // Quotient is what will be used in the next subscript delinearization.
+ Quotient = SCEVDivision::divide(SE, SE.getMinusSCEV(Start, Remainder), GCD);
- // As findGCD computed Remainder, GCD divides "Start - Remainder." The
- // Quotient is then this SCEV without Remainder, scaled down by the GCD. The
- // Quotient is what will be used in the next subscript delinearization.
- const SCEV *Quotient =
- SCEVDivision::divide(SE, SE.getMinusSCEV(Start, Remainder), GCD);
DEBUG(dbgs() << "Quotient: " << *Quotient << "\n");
- const SCEV *Rem;
+ const SCEV *Rem = Quotient;
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Quotient))
// Recursively call delinearize on the Quotient until there are no more
// multiples that can be recognized.
Rem = AR->delinearize(SE, Subscripts, Sizes);
- else
- Rem = Quotient;
// Scale up the canonical induction variable IV by whatever remains from the
// Step after division by the GCD: the GCD is the size of all the sub-array.
- if (Step != GCD) {
+ if (Step != One && !Step->isAllOnesValue() && GCD != One &&
+ !GCD->isAllOnesValue() && Step != GCD) {
Step = SCEVDivision::divide(SE, Step, GCD);
IV = SE.getMulExpr(IV, Step);
}
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