Re: [PATCH v5 54/60] target/riscv: integer extract instruction

[Richard Henderson]

On 3/12/20 7:58 AM, LIU Zhiwei wrote:
> +static bool trans_vext_x_v(DisasContext *s, arg_r *a)
> +{
> +    if (vext_check_isa_ill(s, RVV)) {
> +        TCGv_ptr src2;
> +        TCGv dest, src1;
> +        gen_helper_vext_x_v fns[4] = {
> +            gen_helper_vext_x_v_b, gen_helper_vext_x_v_h,
> +            gen_helper_vext_x_v_w, gen_helper_vext_x_v_d
> +        };
> +
> +        dest = tcg_temp_new();
> +        src1 = tcg_temp_new();
> +        src2 = tcg_temp_new_ptr();
> +
> +        gen_get_gpr(src1, a->rs1);
> +        tcg_gen_addi_ptr(src2, cpu_env, vreg_ofs(s, a->rs2));
> +
> +        fns[s->sew](dest, src2, src1, cpu_env);
> +        gen_set_gpr(a->rd, dest);
> +
> +        tcg_temp_free(dest);
> +        tcg_temp_free(src1);
> +        tcg_temp_free_ptr(src2);
> +        return true;
> +    }
> +    return false;
> +}

This entire operation can be performed inline easily.

static void extract_element(TCGv dest, TCGv_ptr base,
                            int ofs, int sew)
{
    switch (sew) {
    case MO_8:
        tcg_gen_ld8u_tl(dest, base, ofs);
        break;
    case MO_16:
        tcg_gen_ld16u_tl(dest, base, ofs);
        break;
    default:
        tcg_gen_ld32u_tl(dest, base, ofs);
        break;
#if TARGET_LONG_BITS == 64
    case MO_64:
        tcg_gen_ld_i64(dest, base, ofs);
        break;
#endif
    }
}

static bool trans_vext_x_v(DisasContext *s, arg_r *a)
{
...
    if (a->rs1 == 0) {
        /* Special case vmv.x.s rd, vs2. */
        do_extract(dest, cpu_env,
                   vreg_ofs(s, a->rs2), s->sew);
    } else {
        int vlen = s->vlen >> (3 + s->sew);
        TCGv_i32 ofs = tcg_temp_new_i32();
        TCGv_ptr  base = tcg_temp_new_ptr();
        TCGv t_vlen, t_zero;

        /* Mask the index to the length so that we do
           not produce an out-of-range load. */
        tcg_gen_trunc_tl_i32(ofs, cpu_gpr[a->rs1]);
        tcg_gen_andi_i32(ofs, ofs, vlen - 1);

        /* Convert the index to an offset.  */
        tcg_gen_shli_i32(ofs, ofs, s->sew);

        /* Convert the index to a pointer. */
        tcg_gen_extu_i32_ptr(base, ofs);
        tcg_gen_add_ptr(base, base, cpu_env);

        /* Perform the load. */
        do_extract(dest, base,
                   vreg_ofs(s, a->rs2), s->sew);
        tcg_temp_free_ptr(base);
        tcg_temp_free_i32(ofs);

        /* Flush out-of-range indexing to zero.  */
        t_vlen = tcg_const_tl(vlen);
        t_zero = tcg_const_tl(0);
        tcg_gen_movcond_tl(TCG_COND_LTU, dest, cpu_gpr[a->rs1],
                           t_vlen, dest, t_zero);
        tcg_temp_free(t_vlen);
        tcg_temp_free(t_zero);
    }


r~