Re: [Qemu-devel] [PATCH v6 07/17] target/m68k: add chk and chk2

[Richard Henderson <richard.henderson@linaro.org>]

On 01/02/2018 03:40 PM, Laurent Vivier wrote:
> +void HELPER(chk)(CPUM68KState *env, int32_t val, int32_t ub)
> +{
> +    if (val < 0 || val > ub) {
> +        CPUState *cs = CPU(m68k_env_get_cpu(env));
> +
> +        /* Recover PC and CC_OP for the beginning of the insn.  */
> +        cpu_restore_state(cs, GETPC());
> +
> +        /* Adjust PC and FLAGS to end of the insn.  */
> +        env->pc += 2;
> +        helper_flush_flags(env, env->cc_op);
> +        env->cc_n = val;
> +
> +        cs->exception_index = EXCP_CHK;
> +        cpu_loop_exit(cs);
> +    }
> +}
> +

I thought you said for 68040, N is always unset for val >= 0.
That would suggest

  helper_flush_flags(env, env->cc_op);
  env->cc_n = val;
  if (val < 0 || val > ub) {
    ...
  }

Did you examine the real hw change to the other flags?
Because they're officially undefined, which suggests

  env->cc_n = val;
  env->cc_op = CC_OP_LOGIC;

> +void HELPER(chk2)(CPUM68KState *env, int32_t val, int32_t lb, int32_t ub)
> +{
> +    helper_flush_flags(env, env->cc_op);
> +
> +    env->cc_z = val != lb && val != ub;
> +    env->cc_c = lb <= ub ? val < lb || val > ub : val > ub && val < lb;
> +
> +    if (env->cc_c) {
> +        CPUState *cs = CPU(m68k_env_get_cpu(env));
> +
> +        cpu_restore_state(cs, GETPC());
> +        env->cc_op = CC_OP_FLAGS;

A comment that we're reverting a change made during unwind would be helpful here.


r~