[v2] target/hppa: Fix unit carry conditions

Split do_unit_cond to do_unit_zero_cond to only handle conditions
versus zero.  These are the only ones that are legal for UXOR.
Simplify trans_uxor accordingly.

Rename do_unit to do_unit_addsub, since xor has been split.
Properly compute carry-out bits for add and subtract, mirroring
the code in do_add and do_sub.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---

v2: Cut and paste error between 64- and 32-bit paths.
    Shift 32-bit carry down 1 bit like 64-bit carry;
    tradeoff is shift vs needing a 64-bit constant for the mask.
    Don't use of TCG_COND_TST{NE,EQ}, as this will limit backports
    of the actual bug fix.  We can convert the port to test conditions
    en masse during the next devel cycle.
 
---
 target/hppa/translate.c | 218 +++++++++++++++++++++-------------------
 1 file changed, 113 insertions(+), 105 deletions(-)

On 3/25/24 20:02, Richard Henderson wrote:
> Split do_unit_cond to do_unit_zero_cond to only handle conditions
> versus zero.  These are the only ones that are legal for UXOR.
> Simplify trans_uxor accordingly.
>
> Rename do_unit to do_unit_addsub, since xor has been split.
> Properly compute carry-out bits for add and subtract, mirroring
> the code in do_add and do_sub.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

this patch does not break test #55 (uaddcm) any longer, and with the other
two patches test #58 (uaddcm & dcor) is OK as well.

So, for the whole series:
Reviewed-by: Helge Deller <deller@gmx.de>
Tested-by: Helge Deller <deller@gmx.de>

Thanks!
Helge



> ---
>
> v2: Cut and paste error between 64- and 32-bit paths.
>      Shift 32-bit carry down 1 bit like 64-bit carry;
>      tradeoff is shift vs needing a 64-bit constant for the mask.
>      Don't use of TCG_COND_TST{NE,EQ}, as this will limit backports
>      of the actual bug fix.  We can convert the port to test conditions
>      en masse during the next devel cycle.
>
> ---
>   target/hppa/translate.c | 218 +++++++++++++++++++++-------------------
>   1 file changed, 113 insertions(+), 105 deletions(-)
>
> diff --git a/target/hppa/translate.c b/target/hppa/translate.c
> index 3fc3e7754c..99c5c4cbca 100644
> --- a/target/hppa/translate.c
> +++ b/target/hppa/translate.c
> @@ -936,98 +936,44 @@ static DisasCond do_sed_cond(DisasContext *ctx, unsigned orig, bool d,
>       return do_log_cond(ctx, c * 2 + f, d, res);
>   }
>
> -/* Similar, but for unit conditions.  */
> -
> -static DisasCond do_unit_cond(unsigned cf, bool d, TCGv_i64 res,
> -                              TCGv_i64 in1, TCGv_i64 in2)
> +/* Similar, but for unit zero conditions.  */
> +static DisasCond do_unit_zero_cond(unsigned cf, bool d, TCGv_i64 res)
>   {
> -    DisasCond cond;
> -    TCGv_i64 tmp, cb = NULL;
> +    TCGv_i64 tmp;
>       uint64_t d_repl = d ? 0x0000000100000001ull : 1;
> -
> -    if (cf & 8) {
> -        /* Since we want to test lots of carry-out bits all at once, do not
> -         * do our normal thing and compute carry-in of bit B+1 since that
> -         * leaves us with carry bits spread across two words.
> -         */
> -        cb = tcg_temp_new_i64();
> -        tmp = tcg_temp_new_i64();
> -        tcg_gen_or_i64(cb, in1, in2);
> -        tcg_gen_and_i64(tmp, in1, in2);
> -        tcg_gen_andc_i64(cb, cb, res);
> -        tcg_gen_or_i64(cb, cb, tmp);
> -    }
> +    uint64_t ones = 0, sgns = 0;
>
>       switch (cf >> 1) {
> -    case 0: /* never / TR */
> -        cond = cond_make_f();
> -        break;
> -
>       case 1: /* SBW / NBW */
>           if (d) {
> -            tmp = tcg_temp_new_i64();
> -            tcg_gen_subi_i64(tmp, res, d_repl * 0x00000001u);
> -            tcg_gen_andc_i64(tmp, tmp, res);
> -            tcg_gen_andi_i64(tmp, tmp, d_repl * 0x80000000u);
> -            cond = cond_make_0(TCG_COND_NE, tmp);
> -        } else {
> -            /* undefined */
> -            cond = cond_make_f();
> +            ones = d_repl;
> +            sgns = d_repl << 31;
>           }
>           break;
> -
>       case 2: /* SBZ / NBZ */
> -        /* See hasless(v,1) from
> -         * https://graphics.stanford.edu/~seander/bithacks.html#ZeroInWord
> -         */
> -        tmp = tcg_temp_new_i64();
> -        tcg_gen_subi_i64(tmp, res, d_repl * 0x01010101u);
> -        tcg_gen_andc_i64(tmp, tmp, res);
> -        tcg_gen_andi_i64(tmp, tmp, d_repl * 0x80808080u);
> -        cond = cond_make_0(TCG_COND_NE, tmp);
> +        ones = d_repl * 0x01010101u;
> +        sgns = ones << 7;
>           break;
> -
>       case 3: /* SHZ / NHZ */
> -        tmp = tcg_temp_new_i64();
> -        tcg_gen_subi_i64(tmp, res, d_repl * 0x00010001u);
> -        tcg_gen_andc_i64(tmp, tmp, res);
> -        tcg_gen_andi_i64(tmp, tmp, d_repl * 0x80008000u);
> -        cond = cond_make_0(TCG_COND_NE, tmp);
> +        ones = d_repl * 0x00010001u;
> +        sgns = ones << 15;
>           break;
> -
> -    case 4: /* SDC / NDC */
> -        tcg_gen_andi_i64(cb, cb, d_repl * 0x88888888u);
> -        cond = cond_make_0(TCG_COND_NE, cb);
> -        break;
> -
> -    case 5: /* SWC / NWC */
> -        if (d) {
> -            tcg_gen_andi_i64(cb, cb, d_repl * 0x80000000u);
> -            cond = cond_make_0(TCG_COND_NE, cb);
> -        } else {
> -            /* undefined */
> -            cond = cond_make_f();
> -        }
> -        break;
> -
> -    case 6: /* SBC / NBC */
> -        tcg_gen_andi_i64(cb, cb, d_repl * 0x80808080u);
> -        cond = cond_make_0(TCG_COND_NE, cb);
> -        break;
> -
> -    case 7: /* SHC / NHC */
> -        tcg_gen_andi_i64(cb, cb, d_repl * 0x80008000u);
> -        cond = cond_make_0(TCG_COND_NE, cb);
> -        break;
> -
> -    default:
> -        g_assert_not_reached();
>       }
> -    if (cf & 1) {
> -        cond.c = tcg_invert_cond(cond.c);
> +    if (ones == 0) {
> +        /* Undefined, or 0/1 (never/always). */
> +        return cf & 1 ? cond_make_t() : cond_make_f();
>       }
>
> -    return cond;
> +    /*
> +     * See hasless(v,1) from
> +     * https://graphics.stanford.edu/~seander/bithacks.html#ZeroInWord
> +     */
> +    tmp = tcg_temp_new_i64();
> +    tcg_gen_subi_i64(tmp, res, ones);
> +    tcg_gen_andc_i64(tmp, tmp, res);
> +    tcg_gen_andi_i64(tmp, tmp, sgns);
> +
> +    return cond_make_0_tmp(cf & 1 ? TCG_COND_EQ : TCG_COND_NE, tmp);
>   }
>
>   static TCGv_i64 get_carry(DisasContext *ctx, bool d,
> @@ -1330,34 +1276,86 @@ static bool do_log_reg(DisasContext *ctx, arg_rrr_cf_d *a,
>       return nullify_end(ctx);
>   }
>
> -static void do_unit(DisasContext *ctx, unsigned rt, TCGv_i64 in1,
> -                    TCGv_i64 in2, unsigned cf, bool d, bool is_tc,
> -                    void (*fn)(TCGv_i64, TCGv_i64, TCGv_i64))
> +static void do_unit_addsub(DisasContext *ctx, unsigned rt, TCGv_i64 in1,
> +                           TCGv_i64 in2, unsigned cf, bool d,
> +                           bool is_tc, bool is_add)
>   {
> -    TCGv_i64 dest;
> +    TCGv_i64 dest = tcg_temp_new_i64();
> +    uint64_t test_cb = 0;
>       DisasCond cond;
>
> -    if (cf == 0) {
> -        dest = dest_gpr(ctx, rt);
> -        fn(dest, in1, in2);
> -        save_gpr(ctx, rt, dest);
> -        cond_free(&ctx->null_cond);
> -    } else {
> -        dest = tcg_temp_new_i64();
> -        fn(dest, in1, in2);
> -
> -        cond = do_unit_cond(cf, d, dest, in1, in2);
> -
> -        if (is_tc) {
> -            TCGv_i64 tmp = tcg_temp_new_i64();
> -            tcg_gen_setcond_i64(cond.c, tmp, cond.a0, cond.a1);
> -            gen_helper_tcond(tcg_env, tmp);
> +    /* Select which carry-out bits to test. */
> +    switch (cf >> 1) {
> +    case 4: /* NDC / SDC -- 4-bit carries */
> +        test_cb = dup_const(MO_8, 0x88);
> +        break;
> +    case 5: /* NWC / SWC -- 32-bit carries */
> +        if (d) {
> +            test_cb = dup_const(MO_32, INT32_MIN);
> +        } else {
> +            cf &= 1; /* undefined -- map to never/always */
>           }
> -        save_gpr(ctx, rt, dest);
> -
> -        cond_free(&ctx->null_cond);
> -        ctx->null_cond = cond;
> +        break;
> +    case 6: /* NBC / SBC -- 8-bit carries */
> +        test_cb = dup_const(MO_8, INT8_MIN);
> +        break;
> +    case 7: /* NHC / SHC -- 16-bit carries */
> +        test_cb = dup_const(MO_16, INT16_MIN);
> +        break;
>       }
> +    if (!d) {
> +        test_cb = (uint32_t)test_cb;
> +    }
> +
> +    if (!test_cb) {
> +        /* No need to compute carries if we don't need to test them. */
> +        if (is_add) {
> +            tcg_gen_add_i64(dest, in1, in2);
> +        } else {
> +            tcg_gen_sub_i64(dest, in1, in2);
> +        }
> +        cond = do_unit_zero_cond(cf, d, dest);
> +    } else {
> +        TCGv_i64 cb = tcg_temp_new_i64();
> +
> +        if (d) {
> +            TCGv_i64 cb_msb = tcg_temp_new_i64();
> +            if (is_add) {
> +                tcg_gen_add2_i64(dest, cb_msb, in1, ctx->zero, in2, ctx->zero);
> +                tcg_gen_xor_i64(cb, in1, in2);
> +            } else {
> +                /* See do_sub, !is_b. */
> +                TCGv_i64 one = tcg_constant_i64(1);
> +                tcg_gen_sub2_i64(dest, cb_msb, in1, one, in2, ctx->zero);
> +                tcg_gen_eqv_i64(cb, in1, in2);
> +            }
> +            tcg_gen_xor_i64(cb, cb, dest);
> +            tcg_gen_extract2_i64(cb, cb, cb_msb, 1);
> +        } else {
> +            if (is_add) {
> +                tcg_gen_add_i64(dest, in1, in2);
> +                tcg_gen_xor_i64(cb, in1, in2);
> +            } else {
> +                tcg_gen_sub_i64(dest, in1, in2);
> +                tcg_gen_eqv_i64(cb, in1, in2);
> +            }
> +            tcg_gen_xor_i64(cb, cb, dest);
> +            tcg_gen_shri_i64(cb, cb, 1);
> +        }
> +
> +        tcg_gen_andi_i64(cb, cb, test_cb);
> +        cond = cond_make_0_tmp(cf & 1 ? TCG_COND_EQ : TCG_COND_NE, cb);
> +    }
> +
> +    if (is_tc) {
> +        TCGv_i64 tmp = tcg_temp_new_i64();
> +        tcg_gen_setcond_i64(cond.c, tmp, cond.a0, cond.a1);
> +        gen_helper_tcond(tcg_env, tmp);
> +    }
> +    save_gpr(ctx, rt, dest);
> +
> +    cond_free(&ctx->null_cond);
> +    ctx->null_cond = cond;
>   }
>
>   #ifndef CONFIG_USER_ONLY
> @@ -2748,14 +2746,24 @@ static bool trans_cmpclr(DisasContext *ctx, arg_rrr_cf_d *a)
>
>   static bool trans_uxor(DisasContext *ctx, arg_rrr_cf_d *a)
>   {
> -    TCGv_i64 tcg_r1, tcg_r2;
> +    TCGv_i64 tcg_r1, tcg_r2, dest;
>
>       if (a->cf) {
>           nullify_over(ctx);
>       }
> +
>       tcg_r1 = load_gpr(ctx, a->r1);
>       tcg_r2 = load_gpr(ctx, a->r2);
> -    do_unit(ctx, a->t, tcg_r1, tcg_r2, a->cf, a->d, false, tcg_gen_xor_i64);
> +    dest = dest_gpr(ctx, a->t);
> +
> +    tcg_gen_xor_i64(dest, tcg_r1, tcg_r2);
> +    save_gpr(ctx, a->t, dest);
> +
> +    cond_free(&ctx->null_cond);
> +    if (a->cf) {
> +        ctx->null_cond = do_unit_zero_cond(a->cf, a->d, dest);
> +    }
> +
>       return nullify_end(ctx);
>   }
>
> @@ -2790,7 +2798,7 @@ static bool do_uaddcm(DisasContext *ctx, arg_rrr_cf_d *a, bool is_tc)
>       tcg_r2 = load_gpr(ctx, a->r2);
>       tmp = tcg_temp_new_i64();
>       tcg_gen_not_i64(tmp, tcg_r2);
> -    do_unit(ctx, a->t, tcg_r1, tmp, a->cf, a->d, is_tc, tcg_gen_add_i64);
> +    do_unit_addsub(ctx, a->t, tcg_r1, tmp, a->cf, a->d, is_tc, true);
>       return nullify_end(ctx);
>   }
>
> @@ -2817,8 +2825,8 @@ static bool do_dcor(DisasContext *ctx, arg_rr_cf_d *a, bool is_i)
>       }
>       tcg_gen_andi_i64(tmp, tmp, (uint64_t)0x1111111111111111ull);
>       tcg_gen_muli_i64(tmp, tmp, 6);
> -    do_unit(ctx, a->t, load_gpr(ctx, a->r), tmp, a->cf, a->d, false,
> -            is_i ? tcg_gen_add_i64 : tcg_gen_sub_i64);
> +    do_unit_addsub(ctx, a->t, load_gpr(ctx, a->r), tmp,
> +                   a->cf, a->d, false, is_i);
>       return nullify_end(ctx);
>   }
>