diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 18 |
1 files changed, 4 insertions, 14 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 10faf478676..2f6e411345f 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -277,20 +277,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, return InsertNewInstWith(And, *I); } - // If the RHS is a constant, see if we can change it. Don't alter a -1 - // constant because that's a canonical 'not' op, and that is better for - // combining, SCEV, and codegen. - const APInt *C; - if (match(I->getOperand(1), m_APInt(C)) && !C->isAllOnesValue()) { - if (DemandedMask.isSubsetOf(*C)) { - // Force bits to 1 to create a 'not' op. - I->setOperand(1, ConstantInt::getAllOnesValue(VTy)); - return I; - } - // If we can't turn this into a 'not', try to shrink the constant. - if (ShrinkDemandedConstant(I, 1, DemandedMask)) - return I; - } + // If the RHS is a constant, see if we can simplify it. + // FIXME: for XOR, we prefer to force bits to 1 if they will make a -1. + if (ShrinkDemandedConstant(I, 1, DemandedMask)) + return I; // If our LHS is an 'and' and if it has one use, and if any of the bits we // are flipping are known to be set, then the xor is just resetting those |
