From f9a0d593e9da6d7d16ae2f5b073eb6598bc35875 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Thu, 2 Aug 2018 13:46:20 +0000 Subject: [ValueTracking] fix maxnum miscompile for cannotBeOrderedLessThanZero (PR37776) This adds the NAN checks suggested in PR37776: https://bugs.llvm.org/show_bug.cgi?id=37776 If both operands to maxnum are NAN, that should get constant folded, so we don't have to handle that case. This is the same assumption as other FP ops in this function. Returning 'false' is always conservatively correct. Copying from the bug report: Currently, we have this for "when is cannotBeOrderedLessThanZero (mustBePositiveOrNaN) true for maxnum": L ------------------- | Pos | Neg | NaN | ------------------------ |Pos | x | x | x | ------------------------ R |Neg | x | | x | ------------------------ |NaN | x | x | x | ------------------------ The cases with (Neg & NaN) are wrong. We should have: L ------------------- | Pos | Neg | NaN | ------------------------ |Pos | x | x | x | ------------------------ R |Neg | x | | | ------------------------ |NaN | x | | x | ------------------------ Differential Revision: https://reviews.llvm.org/D50081 llvm-svn: 338716 --- llvm/lib/Analysis/ValueTracking.cpp | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'llvm/lib/Analysis/ValueTracking.cpp') diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 0ef3916..edd46c5 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -2817,10 +2817,13 @@ static bool cannotBeOrderedLessThanZeroImpl(const Value *V, default: break; case Intrinsic::maxnum: - return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly, - Depth + 1) || - cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly, - Depth + 1); + return (isKnownNeverNaN(I->getOperand(0)) && + cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, + SignBitOnly, Depth + 1)) || + (isKnownNeverNaN(I->getOperand(1)) && + cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, + SignBitOnly, Depth + 1)); + case Intrinsic::minnum: return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly, Depth + 1) && -- cgit v1.1