https://gcc.gnu.org/g:bd848fa1d8968ffbbc783c70bdecd8b365085e95
commit r16-7300-gbd848fa1d8968ffbbc783c70bdecd8b365085e95 Author: Alexandre Oliva <[email protected]> Date: Wed Feb 4 23:48:55 2026 -0300 simplify-rtx: fix riscv redundant-bitmap-2.C The insn simplification expected by the test, to get a bset instruction, has been prevented since r15-9239, because we get rotates for bit clear and shifts for bit flip, and we don't know how to simplify those. Teach the rtl simplifier, at the spots where it had been extended to handle these logical simplifications, to also handle these less obvious negations. for gcc/ChangeLog * simplify-rtx.cc (negated_ops_p): New. (simplify_context::simplify_binary_operation_1): Use it. Diff: --- gcc/simplify-rtx.cc | 53 +++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 41 insertions(+), 12 deletions(-) diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc index 72c6bbb7d671..88aa95c81232 100644 --- a/gcc/simplify-rtx.cc +++ b/gcc/simplify-rtx.cc @@ -3074,6 +3074,39 @@ simplify_with_subreg_not (rtx_code binop, machine_mode mode, rtx op0, rtx op1) return simplify_gen_binary (binop, mode, op0, new_not); } +/* Return TRUE iff NOP is a negated form of OP, or vice-versa. */ +static bool +negated_ops_p (rtx nop, rtx op) +{ + /* Explicit negation. */ + if (GET_CODE (nop) == NOT + && rtx_equal_p (XEXP (nop, 0), op)) + return true; + if (GET_CODE (op) == NOT + && rtx_equal_p (XEXP (op, 0), nop)) + return true; + + /* (~C <r A) is a negated form of (C << A) if C == 1. */ + if (GET_CODE (op) == ASHIFT + && GET_CODE (nop) == ROTATE + && XEXP (op, 0) == CONST1_RTX (GET_MODE (op)) + && CONST_INT_P (XEXP (nop, 0)) + && INTVAL (XEXP (nop, 0)) == -2 + && rtx_equal_p (XEXP (op, 1), XEXP (nop, 1))) + return true; + if (GET_CODE (nop) == ASHIFT + && GET_CODE (op) == ROTATE + && XEXP (nop, 0) == CONST1_RTX (GET_MODE (op)) + && CONST_INT_P (XEXP (nop, 0)) + && INTVAL (XEXP (nop, 0)) == -2 + && rtx_equal_p (XEXP (op, 1), XEXP (nop, 1))) + return true; + + /* ??? Should we consider rotations of C and ~C by the same amount? */ + + return false; +} + /* Subroutine of simplify_binary_operation. Simplify a binary operation CODE with result mode MODE, operating on OP0 and OP1. If OP0 and/or OP1 are constant pool references, TRUEOP0 and TRUEOP1 represent the @@ -3861,8 +3894,7 @@ simplify_context::simplify_binary_operation_1 (rtx_code code, /* Convert (ior (and (not A) B) A) into A | B. */ if (GET_CODE (op0) == AND - && GET_CODE (XEXP (op0, 0)) == NOT - && rtx_equal_p (XEXP (XEXP (op0, 0), 0), op1)) + && negated_ops_p (XEXP (op0, 0), op1)) return simplify_gen_binary (IOR, mode, XEXP (op0, 1), op1); tem = simplify_with_subreg_not (code, mode, op0, op1); @@ -4133,8 +4165,7 @@ simplify_context::simplify_binary_operation_1 (rtx_code code, /* Convert (xor (and (not A) B) A) into A | B. */ if (GET_CODE (op0) == AND - && GET_CODE (XEXP (op0, 0)) == NOT - && rtx_equal_p (XEXP (XEXP (op0, 0), 0), op1)) + && negated_ops_p (XEXP (op0, 0), op1)) return simplify_gen_binary (IOR, mode, XEXP (op0, 1), op1); /* Convert (xor (and (rotate (~1) A) B) (ashift 1 A)) @@ -4413,21 +4444,19 @@ simplify_context::simplify_binary_operation_1 (rtx_code code, && rtx_equal_p (op1, XEXP (XEXP (op0, 1), 0))) return simplify_gen_binary (AND, mode, op1, XEXP (op0, 0)); - /* (and (ior/xor (X Y) (not Y)) -> X & ~Y */ + /* (and (ior/xor X Y) (not Y)) -> X & ~Y */ if ((GET_CODE (op0) == IOR || GET_CODE (op0) == XOR) - && GET_CODE (op1) == NOT - && rtx_equal_p (XEXP (op1, 0), XEXP (op0, 1))) + && negated_ops_p (op1, XEXP (op0, 1))) return simplify_gen_binary (AND, mode, XEXP (op0, 0), simplify_gen_unary (NOT, mode, - XEXP (op1, 0), + XEXP (op0, 1), mode)); - /* (and (ior/xor (Y X) (not Y)) -> X & ~Y */ + /* (and (ior/xor Y X) (not Y)) -> X & ~Y */ if ((GET_CODE (op0) == IOR || GET_CODE (op0) == XOR) - && GET_CODE (op1) == NOT - && rtx_equal_p (XEXP (op1, 0), XEXP (op0, 0))) + && negated_ops_p (op1, XEXP (op0, 0))) return simplify_gen_binary (AND, mode, XEXP (op0, 1), simplify_gen_unary (NOT, mode, - XEXP (op1, 0), + XEXP (op0, 0), mode)); /* Convert (and (ior A C) (ior B C)) into (ior (and A B) C). */
