Commit 2d497542 authored by Richard Henderson's avatar Richard Henderson Committed by Blue Swirl
Browse files

tcg-optimize: Fold sub r,0,x to neg r,x 



Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: default avatarRichard Henderson <rth@twiddle.net>
Signed-off-by: default avatarBlue Swirl <blauwirbel@gmail.com>
parent 4980ef9e

tcg/optimize.c

+33 −1
Original line number Diff line number Diff line
@@ -576,7 +576,8 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr, 
            break;

        }



        /* Simplify expressions for "shift/rot r, 0, a => movi r, 0" */

        /* Simplify expressions for "shift/rot r, 0, a => movi r, 0",

           and "sub r, 0, a => neg r, a" case.  */

        switch (op) {

        CASE_OP_32_64(shl):

        CASE_OP_32_64(shr):
@@ -592,6 +593,37 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr, 
                continue;

            }

            break;

        CASE_OP_32_64(sub):

            {

                TCGOpcode neg_op;

                bool have_neg;



                if (temps[args[2]].state == TCG_TEMP_CONST) {

                    /* Proceed with possible constant folding. */

                    break;

                }

                if (op == INDEX_op_sub_i32) {

                    neg_op = INDEX_op_neg_i32;

                    have_neg = TCG_TARGET_HAS_neg_i32;

                } else {

                    neg_op = INDEX_op_neg_i64;

                    have_neg = TCG_TARGET_HAS_neg_i64;

                }

                if (!have_neg) {

                    break;

                }

                if (temps[args[1]].state == TCG_TEMP_CONST

                    && temps[args[1]].val == 0) {

                    s->gen_opc_buf[op_index] = neg_op;

                    reset_temp(args[0]);

                    gen_args[0] = args[0];

                    gen_args[1] = args[2];

                    args += 3;

                    gen_args += 2;

                    continue;

                }

            }

            break;

        default:

            break;

        }