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| author | Dan Gohman <gohman@apple.com> | 2010-04-12 07:39:33 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2010-04-12 07:39:33 +0000 |
| commit | c89023362c11fa9e5d6448598e0600d16f79b972 (patch) | |
| tree | a56f5b51f98a152dfeb52d4d52f70911322e8278 /lib | |
| parent | 734ac3995b1b79695449ce8f092c893d3cbe9ecb (diff) | |
| download | external_llvm-c89023362c11fa9e5d6448598e0600d16f79b972.zip external_llvm-c89023362c11fa9e5d6448598e0600d16f79b972.tar.gz external_llvm-c89023362c11fa9e5d6448598e0600d16f79b972.tar.bz2 | |
Rewrite the overflow checking in the get{Signed,Unsigned}Range code for
AddRecs so that it checks for overflow in the computation that it is
performing, rather than just checking hasNo{Signed,Unsigned}Wrap, since
those flags are for a different computation. This fixes a bug that
impacts an upcoming change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101028 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 44 |
1 files changed, 34 insertions, 10 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index e3159a9..32fc9b6 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -2933,14 +2933,26 @@ ScalarEvolution::getUnsignedRange(const SCEV *S) { MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty); const SCEV *Start = AddRec->getStart(); - const SCEV *End = AddRec->evaluateAtIteration(MaxBECount, *this); + const SCEV *Step = AddRec->getStepRecurrence(*this); - // Check for overflow. - if (!AddRec->hasNoUnsignedWrap()) + ConstantRange StartRange = getUnsignedRange(Start); + ConstantRange StepRange = getSignedRange(Step); + ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount); + ConstantRange EndRange = + StartRange.add(MaxBECountRange.multiply(StepRange)); + + // Check for overflow. This must be done with ConstantRange arithmetic + // because we could be called from within the ScalarEvolution overflow + // checking code. + ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1); + ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1); + ConstantRange ExtMaxBECountRange = + MaxBECountRange.zextOrTrunc(BitWidth*2+1); + ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1); + if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) != + ExtEndRange) return ConservativeResult; - ConstantRange StartRange = getUnsignedRange(Start); - ConstantRange EndRange = getUnsignedRange(End); APInt Min = APIntOps::umin(StartRange.getUnsignedMin(), EndRange.getUnsignedMin()); APInt Max = APIntOps::umax(StartRange.getUnsignedMax(), @@ -3064,14 +3076,26 @@ ScalarEvolution::getSignedRange(const SCEV *S) { MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty); const SCEV *Start = AddRec->getStart(); - const SCEV *End = AddRec->evaluateAtIteration(MaxBECount, *this); + const SCEV *Step = AddRec->getStepRecurrence(*this); - // Check for overflow. - if (!AddRec->hasNoSignedWrap()) + ConstantRange StartRange = getSignedRange(Start); + ConstantRange StepRange = getSignedRange(Step); + ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount); + ConstantRange EndRange = + StartRange.add(MaxBECountRange.multiply(StepRange)); + + // Check for overflow. This must be done with ConstantRange arithmetic + // because we could be called from within the ScalarEvolution overflow + // checking code. + ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1); + ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1); + ConstantRange ExtMaxBECountRange = + MaxBECountRange.zextOrTrunc(BitWidth*2+1); + ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1); + if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) != + ExtEndRange) return ConservativeResult; - ConstantRange StartRange = getSignedRange(Start); - ConstantRange EndRange = getSignedRange(End); APInt Min = APIntOps::smin(StartRange.getSignedMin(), EndRange.getSignedMin()); APInt Max = APIntOps::smax(StartRange.getSignedMax(), |