Re: [PATCH 2/3] target/m68k: Implement TRAPcc

[Laurent Vivier]

Le 30/11/2021 à 11:37, Richard Henderson a écrit :
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/754
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   target/m68k/cpu.h       |  2 ++
>   target/m68k/cpu.c       |  1 +
>   target/m68k/translate.c | 21 +++++++++++++++++++++
>   3 files changed, 24 insertions(+)
>
> diff --git a/target/m68k/cpu.h b/target/m68k/cpu.h
> index a3423729ef..03f600f7e7 100644
> --- a/target/m68k/cpu.h
> +++ b/target/m68k/cpu.h
> @@ -527,6 +527,8 @@ enum m68k_features {
>       M68K_FEATURE_MOVEC,
>       /* Unaligned data accesses (680[2346]0) */
>       M68K_FEATURE_UNALIGNED_DATA,
> +    /* TRAPCC insn. (680[2346]0, and CPU32) */
> +    M68K_FEATURE_TRAPCC,
>   };
>   
>   static inline int m68k_feature(CPUM68KState *env, int feature)
> diff --git a/target/m68k/cpu.c b/target/m68k/cpu.c
> index c7aeb7da9c..5f778773d1 100644
> --- a/target/m68k/cpu.c
> +++ b/target/m68k/cpu.c
> @@ -162,6 +162,7 @@ static void m68020_cpu_initfn(Object *obj)
>       m68k_set_feature(env, M68K_FEATURE_CHK2);
>       m68k_set_feature(env, M68K_FEATURE_MSP);
>       m68k_set_feature(env, M68K_FEATURE_UNALIGNED_DATA);
> +    m68k_set_feature(env, M68K_FEATURE_TRAPCC);
>   }
>   
>   /*
> diff --git a/target/m68k/translate.c b/target/m68k/translate.c
> index 858ba761fc..cf29f35d91 100644
> --- a/target/m68k/translate.c
> +++ b/target/m68k/translate.c
> @@ -4879,6 +4879,26 @@ DISAS_INSN(trapv)
>       do_trapcc(s, 9); /* VS */
>   }
>   
> +DISAS_INSN(trapcc)
> +{
> +    /* Consume and discard the immediate operand. */
> +    switch (extract32(insn, 0, 3)) {
> +    case 2: /* trapcc.w */
> +        (void)read_im16(env, s);
> +        break;
> +    case 3: /* trapcc.l */
> +        (void)read_im32(env, s);
> +        break;

Do we need to actually read the memory to trigger a fault if needed or can we 
only increase the PC?

Normally these values are for the trap handler.

> +    case 4: /* trapcc (no operand) */
> +        break;
> +    default:
> +        /* Illegal insn */
> +        disas_undef(env, s, insn);
> +        return;
> +    }
> +    do_trapcc(s, extract32(insn, 8, 4));
> +}

Do we need to change something in m68k_interrupt_all()?

    if (!is_hw) {
        switch (cs->exception_index) {
        case EXCP_RTE:
            /* Return from an exception.  */
            m68k_rte(env);
            return;
        case EXCP_TRAP0 ...  EXCP_TRAP15:
            /* Move the PC after the trap instruction.  */
            retaddr += 2;
            break;
        }
    }

Thanks,
Laurent

> +
>   static void gen_load_fcr(DisasContext *s, TCGv res, int reg)
>   {
>       switch (reg) {
> @@ -6051,6 +6071,7 @@ void register_m68k_insns (CPUM68KState *env)
>       INSN(scc,       50c0, f0f8, CF_ISA_A); /* Scc.B Dx   */
>       INSN(scc,       50c0, f0c0, M68000);   /* Scc.B <EA> */
>       INSN(dbcc,      50c8, f0f8, M68000);
> +    INSN(trapcc,    50f8, f0f8, TRAPCC);
>       INSN(tpf,       51f8, fff8, CF_ISA_A);
>   
>       /* Branch instructions.  */