From 3a48b87c54b2eda1aa0798e87ffea735f28d5e8b Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Thu, 28 Jan 2010 17:22:42 +0000 Subject: Fix PR6165. The bug was that LHSKnownZero was being and'd with DemandedMask when it should have been and'd with LowBits. Fix that and while there beef up the logic in the case of a negative LHS. llvm-svn: 94745 --- .../Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 74a1b6803d4..ec1ed664961 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -681,10 +681,19 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, LHSKnownZero, LHSKnownOne, Depth+1)) return I; + // The low bits of LHS are unchanged by the srem. + KnownZero |= LHSKnownZero & LowBits; + KnownOne |= LHSKnownOne & LowBits; + + // If LHS is non-negative or has all low bits zero, then the upper bits + // are all zero. if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits)) - LHSKnownZero |= ~LowBits; + KnownZero |= ~LowBits; - KnownZero |= LHSKnownZero & DemandedMask; + // If LHS is negative and not all low bits are zero, then the upper bits + // are all one. + if (LHSKnownOne[BitWidth-1] && ((LHSKnownOne & LowBits) != 0)) + KnownOne |= ~LowBits; assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); } -- cgit v1.2.3