Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.690 -> 1.691 --- Log message: For PR1271: http://llvm.org/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. --- Diffs of the changes: (+11 -12) InstructionCombining.cpp | 23 +++++++++++------------ 1 files changed, 11 insertions(+), 12 deletions(-) Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.690 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.691 --- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.690 Sun Mar 25 15:43:09 2007 +++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Sun Mar 25 16:11:44 2007 @@ -595,7 +595,7 @@ /// optimized based on the contradictory assumption that it is non-zero. /// Because instcombine aggressively folds operations with undef args anyway, /// this won't lose us code quality. -static void ComputeMaskedBits(Value *V, const APInt& Mask, APInt& KnownZero, +static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero, APInt& KnownOne, unsigned Depth = 0) { assert(V && "No Value?"); assert(Depth <= 6 && "Limit Search Depth"); @@ -1200,7 +1200,7 @@ // Figure out what the input bits are. If the top bits of the and result // are not demanded, then the add doesn't demand them from its input // either. - unsigned NLZ = DemandedMask.countLeadingZeros(); + uint32_t NLZ = DemandedMask.countLeadingZeros(); // If there is a constant on the RHS, there are a variety of xformations // we can do. @@ -1296,7 +1296,7 @@ if ((DemandedMask & APInt::getSignBit(BitWidth)) == 0) { // Right fill the mask of bits for this SUB to demand the most // significant bit and all those below it. - uint32_t NLZ = DemandedMask.countLeadingZeros(); + unsigned NLZ = DemandedMask.countLeadingZeros(); APInt DemandedFromOps(APInt::getAllOnesValue(BitWidth).lshr(NLZ)); if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps, LHSKnownZero, LHSKnownOne, Depth+1)) @@ -4877,8 +4877,8 @@ if (LHSI->hasOneUse()) { // Otherwise strength reduce the shift into an and. unsigned ShAmtVal = (unsigned)ShAmt->getZExtValue(); - Constant *Mask = ConstantInt::get(APInt::getLowBitsSet(TypeBits, - TypeBits - ShAmtVal)); + uint64_t Val = (1ULL << (TypeBits-ShAmtVal))-1; + Constant *Mask = ConstantInt::get(CI->getType(), Val); Instruction *AndI = BinaryOperator::createAnd(LHSI->getOperand(0), @@ -5809,7 +5809,7 @@ if (ShiftAmt1 == ShiftAmt2) { // If we have ((X >>? C) << C), turn this into X & (-1 << C). if (I.getOpcode() == Instruction::Shl) { - APInt Mask(Ty->getMask().shl(ShiftAmt1)); + APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt1)); return BinaryOperator::createAnd(X, ConstantInt::get(Mask)); } // If we have ((X << C) >>u C), turn this into X & (-1 >>u C). @@ -5847,9 +5847,8 @@ BinaryOperator::createShl(X, ConstantInt::get(Ty, ShiftDiff)); InsertNewInstBefore(Shift, I); - ConstantInt *Mask = ConstantInt::get( - APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2)); - return BinaryOperator::createAnd(Shift, Mask); + APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2)); + return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask)); } // (X << C1) >>u C2 --> X >>u (C2-C1) & (-1 >> C2) @@ -5859,7 +5858,7 @@ BinaryOperator::createLShr(X, ConstantInt::get(Ty, ShiftDiff)); InsertNewInstBefore(Shift, I); - APInt Mask(Ty->getMask().lshr(ShiftAmt2)); + APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2)); return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask)); } @@ -5877,7 +5876,7 @@ ConstantInt::get(Ty, ShiftDiff)); InsertNewInstBefore(Shift, I); - APInt Mask(Ty->getMask().shl(ShiftAmt2)); + APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2)); return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask)); } @@ -5888,7 +5887,7 @@ BinaryOperator::createShl(X, ConstantInt::get(Ty, ShiftDiff)); InsertNewInstBefore(Shift, I); - APInt Mask(Ty->getMask().lshr(ShiftAmt2)); + APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2)); return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask)); } _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
