diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 57 |
1 files changed, 46 insertions, 11 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 3a5ad34aa77..42f1eded803 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -770,6 +770,12 @@ Value *InstCombiner::SimplifyMultipleUseDemandedBits(Instruction *I, computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth + 1, CxtI); + // If the client is only demanding bits that we know, return the known + // constant. + if ((DemandedMask & ((RHSKnownZero | LHSKnownZero)| + (RHSKnownOne & LHSKnownOne))) == DemandedMask) + return Constant::getIntegerValue(ITy, RHSKnownOne & LHSKnownOne); + // If all of the demanded bits are known 1 on one side, return the other. // These bits cannot contribute to the result of the 'and' in this // context. @@ -780,10 +786,10 @@ Value *InstCombiner::SimplifyMultipleUseDemandedBits(Instruction *I, (DemandedMask & ~RHSKnownZero)) return I->getOperand(1); - // If all of the demanded bits in the inputs are known zeros, return zero. - if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask) - return Constant::getNullValue(ITy); - + // Output known-1 bits are only known if set in both the LHS & RHS. + KnownOne = RHSKnownOne & LHSKnownOne; + // Output known-0 are known to be clear if zero in either the LHS | RHS. + KnownZero = RHSKnownZero | LHSKnownZero; break; case Instruction::Or: @@ -796,6 +802,12 @@ Value *InstCombiner::SimplifyMultipleUseDemandedBits(Instruction *I, computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth + 1, CxtI); + // If the client is only demanding bits that we know, return the known + // constant. + if ((DemandedMask & ((RHSKnownZero & LHSKnownZero)| + (RHSKnownOne | LHSKnownOne))) == DemandedMask) + return Constant::getIntegerValue(ITy, RHSKnownOne | LHSKnownOne); + // If all of the demanded bits are known zero on one side, return the // other. These bits cannot contribute to the result of the 'or' in this // context. @@ -815,9 +827,13 @@ Value *InstCombiner::SimplifyMultipleUseDemandedBits(Instruction *I, (DemandedMask & (~LHSKnownZero))) return I->getOperand(1); + // Output known-0 bits are only known if clear in both the LHS & RHS. + KnownZero = RHSKnownZero & LHSKnownZero; + // Output known-1 are known to be set if set in either the LHS | RHS. + KnownOne = RHSKnownOne | LHSKnownOne; break; - case Instruction::Xor: + case Instruction::Xor: { // We can simplify (X^Y) -> X or Y in the user's context if we know that // only bits from X or Y are demanded. @@ -826,6 +842,18 @@ Value *InstCombiner::SimplifyMultipleUseDemandedBits(Instruction *I, computeKnownBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth + 1, CxtI); + // Output known-0 bits are known if clear or set in both the LHS & RHS. + APInt IKnownZero = (RHSKnownZero & LHSKnownZero) | + (RHSKnownOne & LHSKnownOne); + // Output known-1 are known to be set if set in only one of the LHS, RHS. + APInt IKnownOne = (RHSKnownZero & LHSKnownOne) | + (RHSKnownOne & LHSKnownZero); + + // If the client is only demanding bits that we know, return the known + // constant. + if ((DemandedMask & (IKnownZero|IKnownOne)) == DemandedMask) + return Constant::getIntegerValue(ITy, IKnownOne); + // If all of the demanded bits are known zero on one side, return the // other. if ((DemandedMask & RHSKnownZero) == DemandedMask) @@ -833,16 +861,23 @@ Value *InstCombiner::SimplifyMultipleUseDemandedBits(Instruction *I, if ((DemandedMask & LHSKnownZero) == DemandedMask) return I->getOperand(1); + // Output known-0 bits are known if clear or set in both the LHS & RHS. + KnownZero = std::move(IKnownZero); + // Output known-1 are known to be set if set in only one of the LHS, RHS. + KnownOne = std::move(IKnownOne); break; } + default: + // Compute the KnownZero/KnownOne bits to simplify things downstream. + computeKnownBits(I, KnownZero, KnownOne, Depth, CxtI); - // Compute the KnownZero/KnownOne bits to simplify things downstream. - computeKnownBits(I, KnownZero, KnownOne, Depth, CxtI); + // If this user is only demanding bits that we know, return the known + // constant. + if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask) + return Constant::getIntegerValue(ITy, KnownOne); - // If this user is only demanding bits that we know, return the known - // constant. - if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask) - return Constant::getIntegerValue(ITy, KnownOne); + break; + } return nullptr; } |
