Re: [PATCH v4 04/21] target/loongarch: Add fixed point arithmetic instruction translation

[Richard Henderson]

On 9/2/21 2:40 PM, Song Gao wrote:
> +static bool gen_r2_si12(DisasContext *ctx, arg_fmt_rdrjsi12 *a,
> +                        DisasExtend src_ext, DisasExtend dst_ext,
> +                        void (*func)(TCGv, TCGv, TCGv))
> +{
> +    ctx->dst_ext = dst_ext;
> +    TCGv dest = gpr_dst(ctx, a->rd);
> +    TCGv src1 = gpr_src(ctx, a->rj, src_ext);
> +    TCGv src2 = tcg_constant_tl(a->si12);

Prefer to put declarations before statements, as per old C90 still.

> +    func(dest, src1, src2);
> +
> +    if (ctx->dst_ext) {

Given that func does not receive ctx, why store dst_ext into ctx and then read it back? 
It seems like you should just use the parameter directly.

> +static bool gen_pc(DisasContext *ctx, arg_fmt_rdsi20 *a,
> +                   void (*func)(DisasContext *ctx, TCGv, target_long))
> +{
> +    TCGv dest = gpr_dst(ctx, a->rd);
> +
> +    func(ctx, dest, a->si20);
> +    return true;
> +}

Perhaps clearer with:

  target_long (*func)(target_long pc, target_long si20)

  target_long addr = func(ctx->base.pc_next, a->si20);
  TCGv dest = gpr_dst(ctx, a->rd);

  tcg_gen_movi_tl(dest, addr);
  return true;




> +static bool gen_mulh(DisasContext *ctx, arg_add_w *a,
> +                     void(*func)(TCGv_i32, TCGv_i32, TCGv_i32, TCGv_i32))
> +{
> +    TCGv dest = gpr_dst(ctx, a->rd);
> +    TCGv src1 = gpr_src(ctx, a->rj, EXT_NONE);
> +    TCGv src2 = gpr_src(ctx, a->rk, EXT_NONE);
> +    TCGv_i32 discard = tcg_temp_new_i32();
> +    TCGv_i32 t0 = tcg_temp_new_i32();
> +    TCGv_i32 t1 = tcg_temp_new_i32();
> +
> +    tcg_gen_trunc_tl_i32(t0, src1);
> +    tcg_gen_trunc_tl_i32(t1, src2);
> +    func(discard, t0, t0, t1);
> +    tcg_gen_ext_i32_tl(dest, t0);
> +
> +    tcg_temp_free_i32(discard);
> +    tcg_temp_free_i32(t0);
> +    tcg_temp_free_i32(t1);
> +    return true;
> +}

You should be able to use gen_r3 for these.

static void gen_mulh_w(TCGv dest, TCGv src1, TCGv src2)
{
    tcg_gen_mul_i64(dest, src1, src2);
    tcg_gen_sari_i64(dest, dest, 32);
}

static void gen_mulh_wu(TCGv dest, TCGv src1, TCGv src2)
{
    tcg_gen_mul_i64(dest, src1, src2);
    tcg_gen_sari_i64(dest, dest, 32);
}

static void gen_mulh_d(TCGv dest, TCGv src1, TCGv src2)
{
    TCGv discard = tcg_temp_new();
    tcg_gen_muls2_tl(discard, dest, src1, src2);
    tcg_temp_free(discard);
}

static void gen_mulh_du(TCGv dest, TCGv src1, TCGv src2)
{
    TCGv discard = tcg_temp_new();
    tcg_gen_mulu2_tl(discard, dest, src1, src2);
    tcg_temp_free(discard);
}

TRANS(mulh_w, gen_r3, EXT_SIGN, EXT_SIGN, EXT_NONE, gen_mulh_w)
TRANS(mulh_wu, gen_r3, EXT_ZERO, EXT_ZERO, EXT_NONE, gen_mulh_wu)
TRANS(mulh_d, gen_r3, EXT_NONE, EXT_NONE, EXT_NONE, gen_mulh_d)
TRANS(mulh_du, gen_r3, EXT_NONE, EXT_NONE, EXT_NONE, gen_mulh_du)

> +static bool gen_mulw_d(DisasContext *ctx, arg_add_w *a,
> +                     void(*func)(TCGv_i64, TCGv))
> +{
> +    TCGv dest = gpr_dst(ctx, a->rd);
> +    TCGv src1 = gpr_src(ctx, a->rj, EXT_NONE);
> +    TCGv src2 = gpr_src(ctx, a->rk, EXT_NONE);
> +
> +    func(src1, src1);
> +    func(src2, src2);
> +    tcg_gen_mul_i64(dest, src1, src2);
> +    return true;
> +}

The func parameter here serves the same purpose as DisasExtend, so again you 
can use gen_r3:

TRANS(mulw_d_w, gen_r3, EXT_SIGN, EXT_SIGN, EXT_NONE, tcg_gen_mul_tl)
TRANS(mulw_d_wu, gen_r3, EXT_ZERO, EXT_ZERO, EXT_NONE, tcg_gen_mul_tl)



> +
> +static bool gen_div_w(DisasContext *ctx, arg_fmt_rdrjrk *a,
> +                      DisasExtend src_ext, DisasExtend dst_ext,
> +                      void(*func)(TCGv, TCGv, TCGv))
> +{
> +    ctx->dst_ext = dst_ext;
> +    TCGv dest = gpr_dst(ctx, a->rd);
> +    TCGv src1 = gpr_src(ctx, a->rj, src_ext);
> +    TCGv src2 = gpr_src(ctx, a->rk, src_ext);
> +    TCGv t2 = tcg_temp_new();
> +    TCGv t3 = tcg_temp_new();
> +
> +    tcg_gen_setcondi_tl(TCG_COND_EQ, t2, src1, INT_MIN);
> +    tcg_gen_setcondi_tl(TCG_COND_EQ, t3, src2, -1);
> +    tcg_gen_and_tl(t2, t2, t3);
> +    tcg_gen_setcondi_tl(TCG_COND_EQ, t3, src2, 0);
> +    tcg_gen_or_tl(t2, t2, t3);
> +    tcg_gen_movi_tl(t3, 0);
> +    tcg_gen_movcond_tl(TCG_COND_NE, src2, t2, t3, t2, src2);

Bug, writing back to src2.

> +    func(dest, src1, src2);

You can split this out differently so that you can use gen_r3.

static TCGv prep_divisor_d(TCGv src1, TCGv src2)
{
    TCGv t0 = temp_new();
    TCGv t1 = tcg_temp_new();
    TCGv t2 = tcg_temp_new();
    TCGv zero = tcg_constant_tl(0);

    /*
     * If min / -1, set the divisor to 1.
     * This avoids potential host overflow trap and produces min.
     * If x / 0, set the divisor to 1.
     * This avoids potential host overflow trap;
     * the required result is undefined.
     */
    tcg_gen_setcondi_tl(TCG_COND_EQ, t0, src1, INT64_MIN);
    tcg_gen_setcondi_tl(TCG_COND_EQ, t1, src2, -1);
    tcg_gen_setcondi_tl(TCG_COND_EQ, t2, src2, 0);
    tcg_gen_and_tl(t0, t0, t1);
    tcg_gen_or_tl(t0, t0, t2);
    tcg_gen_movcond_tl(TCG_COND_NE, t0, t0, zero, t0, src2);

    tcg_temp_free(t1);
    tcg_temp_free(t2);
    return t0;
}

static TCGv prep_divisor_du(TCGv src2)
{
    TCGv t0 = temp_new();
    TCGv zero = tcg_constant_tl(0);
    TCGv one = tcg_constant_tl(1);

    /*
     * If x / 0, set the divisor to 1.
     * This avoids potential host overflow trap;
     * the required result is undefined.
     */
    tcg_gen_movcond_tl(TCG_COND_EQ, t0, src2, zero, one, src2);
    return t0;
}

static void gen_div_d(TCGv dest, TCGv src1, TCGv src2)
{
    src2 = prep_divisor_d(src1, src2);
    tcg_gen_div_tl(dest, src1, src2);
}

static void gen_rem_d(TCGv dest, TCGv src1, TCGv src2)
{
    src2 = prep_divisor_d(src1, src2);
    tcg_gen_rem_tl(dest, src1, src2);
}

static void gen_div_du(TCGv dest, TCGv src1, TCGv src2)
{
    src2 = prep_divisor_du(src2);
    tcg_gen_divu_tl(dest, src1, src2);
}

static void gen_rem_du(TCGv dest, TCGv src1, TCGv src2)
{
    src2 = prep_divisor_du(src2);
    tcg_gen_remu_tl(dest, src1, src2);
}

static void gen_div_w(TCGv dest, TCGv src1, TCGv src2)
{
    /* We need not check for integer overflow for div_w. */
    src2 = prep_divisor_du(src2);
    tcg_gen_div_tl(dest, src1, src2);
}

static void gen_rem_w(TCGv dest, TCGv src1, TCGv src2)
{
    /* We need not check for integer overflow for rem_w. */
    src2 = prep_divisor_du(src2);
    tcg_gen_rem_tl(dest, src1, src2);
}

TRANS(div_w, gen_r3, EXT_SIGN, EXT_SIGN, EXT_SIGN, gen_div_w)
TRANS(mod_w, gen_r3, EXT_SIGN, EXT_SIGN, EXT_SIGN, gen_rem_w)
TRANS(div_wu, gen_r3, EXT_ZERO, EXT_ZERO, EXT_SIGN, gen_div_du)
TRANS(mod_wu, gen_r3, EXT_ZERO, EXT_ZERO, EXT_SIGN, gen_div_du)
TRANS(div_d, gen_r3, EXT_NONE, EXT_NONE, EXT_NONE, gen_div_d)
TRANS(mod_d, gen_r3, EXT_NONE, EXT_NONE, EXT_NONE, gen_rem_d)
TRANS(div_du, gen_r3, EXT_NONE, EXT_NONE, EXT_NONE, gen_div_du)
TRANS(mod_du, gen_r3, EXT_NONE, EXT_NONE, EXT_NONE, gen_rem_du)

> --- a/target/loongarch/internals.h
> +++ b/target/loongarch/internals.h
> @@ -9,7 +9,6 @@
>   #ifndef LOONGARCH_INTERNALS_H
>   #define LOONGARCH_INTERNALS_H
>   
> -
>   void loongarch_translate_init(void);
>   
>   void loongarch_cpu_dump_state(CPUState *cpu, FILE *f, int flags);

Fold this back to a previous patch.

> -static inline bool use_goto_tb(DisasContext *ctx, target_ulong dest)
> -{
> -    return true;
> -}

Yes indeed, fold this patch to a previous patch.


r~