diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp index 9ba0512a78b29b7a02c9e4e314c4bb4414f3805c..f3325096895ae3ceccfe72ed85a47768e0f40e66 100644 --- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp @@ -1725,6 +1725,15 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) { // and X, -1 == X if (AndRHS->isAllOnesValue()) return ReplaceInstUsesWith(I, Op0); + + // and (and X, c1), c2 -> and (x, c1&c2). Handle this case here, before + // calling MaskedValueIsZero, to avoid inefficient cases where we traipse + // through many levels of ands. + { + Value *X; ConstantInt *C1; + if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1)))) + return BinaryOperator::createAnd(X, ConstantExpr::getAnd(C1, AndRHS)); + } if (MaskedValueIsZero(Op0, AndRHS)) // LHS & RHS == 0 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));