diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 1c39f050f50..29640e4b398 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -6304,8 +6304,7 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) { case Instruction::ZExt: { // We need to emit an AND to clear the high bits. assert(SrcBitSize < DestBitSize && "Not a zext?"); - Constant *C = ConstantInt::get(APInt::getAllOnesValue(SrcBitSize)); - C = ConstantExpr::getZExt(C, DestTy); + Constant *C = ConstantInt::get(APInt::getLowBitsSet(DestBitSize, SrcBitSize)); return BinaryOperator::createAnd(Res, C); } case Instruction::SExt: @@ -6487,8 +6486,7 @@ Instruction *InstCombiner::visitTrunc(CastInst &CI) { unsigned ShAmt = ShAmtV->getZExtValue(); // Get a mask for the bits shifting in. - APInt Mask(APInt::getAllOnesValue(SrcBitWidth).lshr( - SrcBitWidth-ShAmt).shl(DestBitWidth)); + APInt Mask(APInt::getLowBitsSet(SrcBitWidth, ShAmt).shl(DestBitWidth)); Value* SrcIOp0 = SrcI->getOperand(0); if (SrcI->hasOneUse() && MaskedValueIsZero(SrcIOp0, Mask)) { if (ShAmt >= DestBitWidth) // All zeros. @@ -6547,7 +6545,7 @@ Instruction *InstCombiner::visitZExt(CastInst &CI) { // If we're actually extending zero bits and the trunc is a no-op if (MidSize < DstSize && SrcSize == DstSize) { // Replace both of the casts with an And of the type mask. - APInt AndValue(APInt::getAllOnesValue(MidSize).zext(SrcSize)); + APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize)); Constant *AndConst = ConstantInt::get(AndValue); Instruction *And = BinaryOperator::createAnd(CSrc->getOperand(0), AndConst);