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Rework scev-aa's basic computation so that it doesn't depend
on ScalarEvolution successfully folding and preserving range information for both A-B and B-A. Now, if it gets either one, it's sufficient. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107249 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -106,6 +106,12 @@ ScalarEvolutionAliasAnalysis::GetBaseValue(const SCEV *S) {
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AliasAnalysis::AliasResult
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AliasAnalysis::AliasResult
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ScalarEvolutionAliasAnalysis::alias(const Value *A, unsigned ASize,
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ScalarEvolutionAliasAnalysis::alias(const Value *A, unsigned ASize,
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const Value *B, unsigned BSize) {
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const Value *B, unsigned BSize) {
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// If either of the memory references is empty, it doesn't matter what the
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// pointer values are. This allows the code below to ignore this special
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// case.
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if (ASize == 0 || BSize == 0)
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return NoAlias;
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// This is ScalarEvolutionAliasAnalysis. Get the SCEVs!
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// This is ScalarEvolutionAliasAnalysis. Get the SCEVs!
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const SCEV *AS = SE->getSCEV(const_cast<Value *>(A));
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const SCEV *AS = SE->getSCEV(const_cast<Value *>(A));
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const SCEV *BS = SE->getSCEV(const_cast<Value *>(B));
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const SCEV *BS = SE->getSCEV(const_cast<Value *>(B));
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@ -118,14 +124,32 @@ ScalarEvolutionAliasAnalysis::alias(const Value *A, unsigned ASize,
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if (SE->getEffectiveSCEVType(AS->getType()) ==
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if (SE->getEffectiveSCEVType(AS->getType()) ==
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SE->getEffectiveSCEVType(BS->getType())) {
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SE->getEffectiveSCEVType(BS->getType())) {
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unsigned BitWidth = SE->getTypeSizeInBits(AS->getType());
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unsigned BitWidth = SE->getTypeSizeInBits(AS->getType());
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APInt AI(BitWidth, ASize);
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APInt ASizeInt(BitWidth, ASize);
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APInt BSizeInt(BitWidth, BSize);
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// Compute the difference between the two pointers.
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const SCEV *BA = SE->getMinusSCEV(BS, AS);
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const SCEV *BA = SE->getMinusSCEV(BS, AS);
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if (AI.ule(SE->getUnsignedRange(BA).getUnsignedMin())) {
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APInt BI(BitWidth, BSize);
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// Test whether the difference is known to be great enough that memory of
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const SCEV *AB = SE->getMinusSCEV(AS, BS);
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// the given sizes don't overlap. This assumes that ASizeInt and BSizeInt
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if (BI.ule(SE->getUnsignedRange(AB).getUnsignedMin()))
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// are non-zero, which is special-cased above.
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if (ASizeInt.ule(SE->getUnsignedRange(BA).getUnsignedMin()) &&
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(-BSizeInt).uge(SE->getUnsignedRange(BA).getUnsignedMax()))
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return NoAlias;
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// Folding the subtraction while preserving range information can be tricky
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// (because of INT_MIN, etc.); if the prior test failed, swap AS and BS
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// and try again to see if things fold better that way.
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// Compute the difference between the two pointers.
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const SCEV *AB = SE->getMinusSCEV(AS, BS);
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// Test whether the difference is known to be great enough that memory of
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// the given sizes don't overlap. This assumes that ASizeInt and BSizeInt
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// are non-zero, which is special-cased above.
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if (BSizeInt.ule(SE->getUnsignedRange(AB).getUnsignedMin()) &&
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(-ASizeInt).uge(SE->getUnsignedRange(AB).getUnsignedMax()))
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return NoAlias;
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return NoAlias;
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}
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}
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}
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// If ScalarEvolution can find an underlying object, form a new query.
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// If ScalarEvolution can find an underlying object, form a new query.
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