diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 35 |
1 files changed, 34 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp index 1b08b0e0557..81640f36a8e 100644 --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -3144,7 +3144,40 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) { II->getOperand(1)); } break; - + case Intrinsic::cttz: { + // If all bits below the first known one are known zero, + // this value is constant. + const IntegerType *IT = cast<IntegerType>(II->getOperand(1)->getType()); + uint32_t BitWidth = IT->getBitWidth(); + APInt KnownZero(BitWidth, 0); + APInt KnownOne(BitWidth, 0); + ComputeMaskedBits(II->getOperand(1), APInt::getAllOnesValue(BitWidth), + KnownZero, KnownOne); + unsigned TrailingZeros = KnownOne.countTrailingZeros(); + APInt Mask(APInt::getLowBitsSet(BitWidth, TrailingZeros)); + if ((Mask & KnownZero) == Mask) + return ReplaceInstUsesWith(CI, ConstantInt::get(IT, + APInt(BitWidth, TrailingZeros))); + + } + break; + case Intrinsic::ctlz: { + // If all bits above the first known one are known zero, + // this value is constant. + const IntegerType *IT = cast<IntegerType>(II->getOperand(1)->getType()); + uint32_t BitWidth = IT->getBitWidth(); + APInt KnownZero(BitWidth, 0); + APInt KnownOne(BitWidth, 0); + ComputeMaskedBits(II->getOperand(1), APInt::getAllOnesValue(BitWidth), + KnownZero, KnownOne); + unsigned LeadingZeros = KnownOne.countLeadingZeros(); + APInt Mask(APInt::getHighBitsSet(BitWidth, LeadingZeros)); + if ((Mask & KnownZero) == Mask) + return ReplaceInstUsesWith(CI, ConstantInt::get(IT, + APInt(BitWidth, LeadingZeros))); + + } + break; case Intrinsic::uadd_with_overflow: { Value *LHS = II->getOperand(1), *RHS = II->getOperand(2); const IntegerType *IT = cast<IntegerType>(II->getOperand(1)->getType()); |
