diff options
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp')
-rw-r--r-- | lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 94 |
1 files changed, 47 insertions, 47 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index a20f474cbf40..a2e757cb4273 100644 --- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -396,50 +396,50 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, /// If the high-bits of an ADD/SUB are not demanded, then we do not care /// about the high bits of the operands. unsigned NLZ = DemandedMask.countLeadingZeros(); - if (NLZ > 0) { - // Right fill the mask of bits for this ADD/SUB to demand the most - // significant bit and all those below it. - APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ)); - if (ShrinkDemandedConstant(I, 0, DemandedFromOps) || - SimplifyDemandedBits(I, 0, DemandedFromOps, LHSKnown, Depth + 1) || - ShrinkDemandedConstant(I, 1, DemandedFromOps) || - SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1)) { + // Right fill the mask of bits for this ADD/SUB to demand the most + // significant bit and all those below it. + APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ)); + if (ShrinkDemandedConstant(I, 0, DemandedFromOps) || + SimplifyDemandedBits(I, 0, DemandedFromOps, LHSKnown, Depth + 1) || + ShrinkDemandedConstant(I, 1, DemandedFromOps) || + SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1)) { + if (NLZ > 0) { // Disable the nsw and nuw flags here: We can no longer guarantee that // we won't wrap after simplification. Removing the nsw/nuw flags is // legal here because the top bit is not demanded. BinaryOperator &BinOP = *cast<BinaryOperator>(I); BinOP.setHasNoSignedWrap(false); BinOP.setHasNoUnsignedWrap(false); - return I; } - - // If we are known to be adding/subtracting zeros to every bit below - // the highest demanded bit, we just return the other side. - if (DemandedFromOps.isSubsetOf(RHSKnown.Zero)) - return I->getOperand(0); - // We can't do this with the LHS for subtraction, unless we are only - // demanding the LSB. - if ((I->getOpcode() == Instruction::Add || - DemandedFromOps.isOneValue()) && - DemandedFromOps.isSubsetOf(LHSKnown.Zero)) - return I->getOperand(1); + return I; } - // Otherwise just hand the add/sub off to computeKnownBits to fill in - // the known zeros and ones. - computeKnownBits(V, Known, Depth, CxtI); + // If we are known to be adding/subtracting zeros to every bit below + // the highest demanded bit, we just return the other side. + if (DemandedFromOps.isSubsetOf(RHSKnown.Zero)) + return I->getOperand(0); + // We can't do this with the LHS for subtraction, unless we are only + // demanding the LSB. + if ((I->getOpcode() == Instruction::Add || + DemandedFromOps.isOneValue()) && + DemandedFromOps.isSubsetOf(LHSKnown.Zero)) + return I->getOperand(1); + + // Otherwise just compute the known bits of the result. + bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap(); + Known = KnownBits::computeForAddSub(I->getOpcode() == Instruction::Add, + NSW, LHSKnown, RHSKnown); break; } case Instruction::Shl: { const APInt *SA; if (match(I->getOperand(1), m_APInt(SA))) { const APInt *ShrAmt; - if (match(I->getOperand(0), m_Shr(m_Value(), m_APInt(ShrAmt)))) { - Instruction *Shr = cast<Instruction>(I->getOperand(0)); - if (Value *R = simplifyShrShlDemandedBits( - Shr, *ShrAmt, I, *SA, DemandedMask, Known)) - return R; - } + if (match(I->getOperand(0), m_Shr(m_Value(), m_APInt(ShrAmt)))) + if (Instruction *Shr = dyn_cast<Instruction>(I->getOperand(0))) + if (Value *R = simplifyShrShlDemandedBits(Shr, *ShrAmt, I, *SA, + DemandedMask, Known)) + return R; uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1); APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt)); @@ -521,26 +521,25 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1)) return I; + unsigned SignBits = ComputeNumSignBits(I->getOperand(0), Depth + 1, CxtI); + assert(!Known.hasConflict() && "Bits known to be one AND zero?"); - // Compute the new bits that are at the top now. - APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt)); + // Compute the new bits that are at the top now plus sign bits. + APInt HighBits(APInt::getHighBitsSet( + BitWidth, std::min(SignBits + ShiftAmt - 1, BitWidth))); Known.Zero.lshrInPlace(ShiftAmt); Known.One.lshrInPlace(ShiftAmt); - // Handle the sign bits. - APInt SignMask(APInt::getSignMask(BitWidth)); - // Adjust to where it is now in the mask. - SignMask.lshrInPlace(ShiftAmt); - // If the input sign bit is known to be zero, or if none of the top bits // are demanded, turn this into an unsigned shift right. - if (BitWidth <= ShiftAmt || Known.Zero[BitWidth-ShiftAmt-1] || + assert(BitWidth > ShiftAmt && "Shift amount not saturated?"); + if (Known.Zero[BitWidth-ShiftAmt-1] || !DemandedMask.intersects(HighBits)) { BinaryOperator *LShr = BinaryOperator::CreateLShr(I->getOperand(0), I->getOperand(1)); LShr->setIsExact(cast<BinaryOperator>(I)->isExact()); return InsertNewInstWith(LShr, *I); - } else if (Known.One.intersects(SignMask)) { // New bits are known one. + } else if (Known.One[BitWidth-ShiftAmt-1]) { // New bits are known one. Known.One |= HighBits; } } @@ -993,22 +992,23 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts, break; } + // The element inserted overwrites whatever was there, so the input demanded + // set is simpler than the output set. + unsigned IdxNo = Idx->getZExtValue(); + APInt PreInsertDemandedElts = DemandedElts; + if (IdxNo < VWidth) + PreInsertDemandedElts.clearBit(IdxNo); + TmpV = SimplifyDemandedVectorElts(I->getOperand(0), PreInsertDemandedElts, + UndefElts, Depth + 1); + if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } + // If this is inserting an element that isn't demanded, remove this // insertelement. - unsigned IdxNo = Idx->getZExtValue(); if (IdxNo >= VWidth || !DemandedElts[IdxNo]) { Worklist.Add(I); return I->getOperand(0); } - // Otherwise, the element inserted overwrites whatever was there, so the - // input demanded set is simpler than the output set. - APInt DemandedElts2 = DemandedElts; - DemandedElts2.clearBit(IdxNo); - TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts2, - UndefElts, Depth + 1); - if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; } - // The inserted element is defined. UndefElts.clearBit(IdxNo); break; |