Re: [PATCH v2 6/8] target/ppc: Move div/mod fixed-point insns (64 bits operands) to decodetree.

[Nicholas Piggin]

On Tue Apr 23, 2024 at 4:32 PM AEST, Chinmay Rath wrote:
> Moving the below instructions to decodetree specification :
>
>       divd[u, e, eu][o][.]    : XO-form
>       mod{sd, ud}             : X-form
>
> With this patch, all the fixed-point arithmetic instructions have been
> moved to decodetree.
> The changes were verified by validating that the tcg ops generated by those
> instructions remain the same, which were captured using the '-d in_asm,op' 
> flag.
> Also, remaned do_divwe method in fixedpoint-impl.c.inc to do_dive because it 
> is
> now used to divide doubleword operands as well, and not just words.
>
> Signed-off-by: Chinmay Rath <rathc@linux.ibm.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

[...]

> +static bool do_divd(DisasContext *ctx, arg_XO *a, bool sign)
> +{
> +    gen_op_arith_divd(ctx, cpu_gpr[a->rt], cpu_gpr[a->ra], cpu_gpr[a->rb],
> +                      sign, a->oe, a->rc);
> +    return true;
> +}
> +
> +static bool do_modd(DisasContext *ctx, arg_X *a, bool sign)
> +{
> +    REQUIRE_INSNS_FLAGS2(ctx, ISA300);
> +    gen_op_arith_modd(ctx, cpu_gpr[a->rt], cpu_gpr[a->ra], cpu_gpr[a->rb],
> +                      sign);
> +    return true;
> +}
> +
> +TRANS64(DIVD, do_divd, true);
> +TRANS64(DIVDU, do_divd, false);
> +TRANS64(DIVDE, do_dive, gen_helper_DIVDE);
> +TRANS64(DIVDEU, do_dive, gen_helper_DIVDEU);
> +
> +TRANS64(MODSD, do_modd, true);
> +TRANS64(MODUD, do_modd, false);

Sigh. I'm having to fix a bunch of these for 32-bit builds. Just
doing the #ifdef TARGET_PPC64 ... #else qemu_build_not_reached();
thing.

Which is quite ugly and actually prevents using some of these
macros and requires open coding (e.g., because DIVDE helper is
not declared for 32-bit in this case).

Maybe we should move 64-bit only instructions into their own
.decode file and not build them for 32-bit, so we don't have
to add all these dummy translate functions for them.

For now I'll try to squash in the fixes.

Thanks,
Nick