llvm-project

8bea5110 - [X86] Fold AND(Y, XOR(X, SUB(0, X))) to ANDN(Y, BLSMSK(X)) (#128348)

[X86] Fold AND(Y, XOR(X, SUB(0, X))) to ANDN(Y, BLSMSK(X)) (#128348) XOR(X, SUB(0, X)) corresponds to a bitwise-negated BLSMSK instruction (i.e., x ^ (x - 1)). On its own, this transformation is probably not really profitable but when the XOR operation is an operand of an AND operation, we can use an ANDN instruction to reduce the number of emitted instructions by one. Fixes #103501.