From 3327498095e5efb0adbc782f1b2990fb1d048a0d Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Fri, 29 Jan 2010 09:45:26 +0000 Subject: [PATCH] Change the SREM case to match the logic in the IR version ComputeMaskedBits. llvm-svn: 94805 --- .../lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 27 ++++++++++++------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 98c952acb756..4f26cdeaeb4f 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -1925,19 +1925,28 @@ void SelectionDAG::ComputeMaskedBits(SDValue Op, const APInt &Mask, } case ISD::SREM: if (ConstantSDNode *Rem = dyn_cast(Op.getOperand(1))) { - const APInt &RA = Rem->getAPIntValue(); - if (RA.isPowerOf2() || (-RA).isPowerOf2()) { - APInt LowBits = RA.isStrictlyPositive() ? (RA - 1) : ~RA; + const APInt &RA = Rem->getAPIntValue().abs(); + if (RA.isPowerOf2()) { + APInt LowBits = RA - 1; APInt Mask2 = LowBits | APInt::getSignBit(BitWidth); ComputeMaskedBits(Op.getOperand(0), Mask2,KnownZero2,KnownOne2,Depth+1); - // If the sign bit of the first operand is zero, the sign bit of - // the result is zero. If the first operand has no one bits below - // the second operand's single 1 bit, its sign will be zero. - if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits)) - KnownZero2 |= ~LowBits; + // The low bits of the first operand are unchanged by the srem. + KnownZero = KnownZero2 & LowBits; + KnownOne = KnownOne2 & LowBits; - KnownZero |= KnownZero2 & Mask; + // If the first operand is non-negative or has all low bits zero, then + // the upper bits are all zero. + if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits)) + KnownZero |= ~LowBits; + + // If the first operand is negative and not all low bits are zero, then + // the upper bits are all one. + if (KnownOne2[BitWidth-1] && ((KnownOne2 & LowBits) != 0)) + KnownOne |= ~LowBits; + + KnownZero &= Mask; + KnownOne &= Mask; assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?"); }