diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 8bca658ce43..e36057907c1 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -2507,9 +2507,15 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) { if (Value *V = SimplifyBSwap(I, Builder)) return replaceInstUsesWith(I, V); - // A^B --> A|B iff A and B have no bits set in common. Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); - if (haveNoCommonBitsSet(Op0, Op1, DL, &AC, &I, &DT)) + + // Fold (X & M) ^ (Y & ~M) -> (X & M) | (Y & ~M) + // This it a special case in haveNoCommonBitsSet, but the commputeKnownBits + // calls in there are unnecessary as SimplifyDemandedInstructionBits should + // have already taken care of those cases. + Value *M; + if (match(&I, m_c_Xor(m_c_And(m_Not(m_Value(M)), m_Value()), + m_c_And(m_Deferred(M), m_Value())))) return BinaryOperator::CreateOr(Op0, Op1); // Apply DeMorgan's Law for 'nand' / 'nor' logic with an inverted operand. |
