On 05/03/2011 05:59 PM, Max Filippov wrote:
> +static void gen_check_privilege(DisasContext *dc)
> +{
> + if (option_enabled(dc, XTENSA_OPTION_MMU)) {
> + TCGv_i32 tmp = tcg_temp_new_i32();
> + int label = gen_new_label();
> +
> + tcg_gen_andi_i32(tmp, cpu_SR[PS], PS_EXCM);
> + tcg_gen_brcondi_i32(TCG_COND_EQ, tmp, PS_EXCM, label);
> + tcg_gen_andi_i32(tmp, cpu_SR[PS], PS_RING);
> + tcg_gen_brcondi_i32(TCG_COND_GEU, tmp, 0, label);
> +
> + gen_exception_cause(dc, PRIVILEGED_CAUSE);
> +
> + gen_set_label(label);
> + tcg_temp_free(tmp);
> + }
> +}
This is a case where you almost certainly want to check this
condition inside QEMU and translate the opcode differently.
See cpu_get_tb_cpu_state, which sets bits in *flags. These
flags can then be checked in tb->flags while translating.
At which point you'd avoid all the conditionalization on
the value in PS here in check_privilege and merely issue
the exception_cause.
The ARM port is a good example for testing these sorts of bits.
r~
