Re: [Qemu-devel] [PATCH v5 36/76] target/mips: Add emulation of nanoMIPS 32-bit branch instructions

[Richard Henderson]

On 07/30/2018 12:12 PM, Aleksandar Markovic wrote:
> +/* Immediate Value Compact Branches */
> +static void gen_compute_imm_branch(DisasContext *ctx, uint32_t opc,
> +                                   int rt, int32_t imm, int32_t offset)
> +{
> +    TCGCond cond;
> +    int bcond_compute = 0;
> +    TCGv t0 = tcg_temp_new();
> +    TCGv t1 = tcg_temp_new();
> +
> +    if (ctx->hflags & MIPS_HFLAG_BMASK) {
> +#ifdef MIPS_DEBUG_DISAS
> +        LOG_DISAS("Branch in delay / forbidden slot at PC 0x" TARGET_FMT_lx
> +                  "\n", ctx->base.pc_next);
> +#endif
> +        generate_exception_end(ctx, EXCP_RI);
> +        goto out;
> +    }

What is this,

> +        ctx->hflags |= MIPS_HFLAG_FBNSLOT;

and this (and several other occurrences), given that forbidden slots have been
removed from the nanomips architecture?

I think perhaps all of your branching code, utilizing the existing expanders,
needs a re-think.


r~