Re: [PATCH v2 06/12] target/ppc: Add PPR32 SPR

[Richard Henderson]

On 5/20/24 18:30, Nicholas Piggin wrote:
> +void spr_write_ppr32(DisasContext *ctx, int sprn, int gprn)
> +{
> +    TCGv t0 = tcg_temp_new();
> +
> +    tcg_gen_shli_tl(t0, cpu_gpr[gprn], 32);
> +    gen_store_spr(SPR_PPR, t0);
> +    spr_store_dump_spr(SPR_PPR);
> +}

The documentation isn't clear on whether this zaps the low 32 bits. If the low bits of PPR 
are {reserved, must-be-zero, undefined} or suchlike, this is fine.

If not, then you need a deposit here, to preserve those bits, e.g.:

    gen_load_spr(t0, SPR_PPR);
    tcg_gen_deposit_tl(t0, t0, cpu_gpr[gprn], 32, 32);
    gen_store_spr(SPR_PPR, t0);

Anyway, it might be best to add a comment here re the above.


r~