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For PR1271:
Remove a use of getLowBitsSet that caused the mask used for replacement of shl/lshr pairs with an AND instruction to be computed incorrectly. Its not clear exactly why this is the case. This solves the disappearing shifts problem, but it doesn't fix Regression/C/2003-05-21-UnionBitFields. It seems there is more going on. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35342 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -595,7 +595,7 @@ static ConstantInt *Multiply(ConstantInt *C1, ConstantInt *C2) {
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/// optimized based on the contradictory assumption that it is non-zero.
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/// Because instcombine aggressively folds operations with undef args anyway,
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/// this won't lose us code quality.
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static void ComputeMaskedBits(Value *V, const APInt& Mask, APInt& KnownZero,
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static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
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APInt& KnownOne, unsigned Depth = 0) {
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assert(V && "No Value?");
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assert(Depth <= 6 && "Limit Search Depth");
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@ -1200,7 +1200,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
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// Figure out what the input bits are. If the top bits of the and result
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// are not demanded, then the add doesn't demand them from its input
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// either.
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unsigned NLZ = DemandedMask.countLeadingZeros();
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uint32_t NLZ = DemandedMask.countLeadingZeros();
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// If there is a constant on the RHS, there are a variety of xformations
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// we can do.
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@ -1296,7 +1296,7 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
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if ((DemandedMask & APInt::getSignBit(BitWidth)) == 0) {
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// Right fill the mask of bits for this SUB to demand the most
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// significant bit and all those below it.
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uint32_t NLZ = DemandedMask.countLeadingZeros();
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unsigned NLZ = DemandedMask.countLeadingZeros();
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APInt DemandedFromOps(APInt::getAllOnesValue(BitWidth).lshr(NLZ));
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if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps,
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LHSKnownZero, LHSKnownOne, Depth+1))
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@ -4877,8 +4877,8 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
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if (LHSI->hasOneUse()) {
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// Otherwise strength reduce the shift into an and.
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unsigned ShAmtVal = (unsigned)ShAmt->getZExtValue();
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Constant *Mask = ConstantInt::get(APInt::getLowBitsSet(TypeBits,
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TypeBits - ShAmtVal));
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uint64_t Val = (1ULL << (TypeBits-ShAmtVal))-1;
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Constant *Mask = ConstantInt::get(CI->getType(), Val);
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Instruction *AndI =
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BinaryOperator::createAnd(LHSI->getOperand(0),
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@ -5809,7 +5809,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
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if (ShiftAmt1 == ShiftAmt2) {
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// If we have ((X >>? C) << C), turn this into X & (-1 << C).
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if (I.getOpcode() == Instruction::Shl) {
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APInt Mask(Ty->getMask().shl(ShiftAmt1));
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APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt1));
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return BinaryOperator::createAnd(X, ConstantInt::get(Mask));
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}
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// If we have ((X << C) >>u C), turn this into X & (-1 >>u C).
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@ -5847,9 +5847,8 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
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BinaryOperator::createShl(X, ConstantInt::get(Ty, ShiftDiff));
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InsertNewInstBefore(Shift, I);
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ConstantInt *Mask = ConstantInt::get(
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APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
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return BinaryOperator::createAnd(Shift, Mask);
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APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
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return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
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}
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// (X << C1) >>u C2 --> X >>u (C2-C1) & (-1 >> C2)
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@ -5859,7 +5858,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
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BinaryOperator::createLShr(X, ConstantInt::get(Ty, ShiftDiff));
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InsertNewInstBefore(Shift, I);
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APInt Mask(Ty->getMask().lshr(ShiftAmt2));
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APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
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return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
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}
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@ -5877,7 +5876,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
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ConstantInt::get(Ty, ShiftDiff));
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InsertNewInstBefore(Shift, I);
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APInt Mask(Ty->getMask().shl(ShiftAmt2));
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APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
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return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
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}
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@ -5888,7 +5887,7 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
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BinaryOperator::createShl(X, ConstantInt::get(Ty, ShiftDiff));
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InsertNewInstBefore(Shift, I);
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APInt Mask(Ty->getMask().lshr(ShiftAmt2));
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APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
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return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
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}
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