Re: [PATCH] target/arm: gdbstub: Guard M-profile code with CONFIG_TCG

[Fabiano Rosas <farosas@suse.de>]

Richard Henderson <richard.henderson@linaro.org> writes:

> On 7/4/23 17:44, Peter Maydell wrote:
>>> IIUC tcg_enabled(), this guard shouldn't be necessary; if CONFIG_TCG
>>> is not defined, tcg_enabled() evaluates to 0, and the compiler should
>>> elide the whole block.
>> 
>> IME it's a bit optimistic to assume that the compiler will always
>> do that, especially with no optimisation enabled.
>
> There's plenty of other places that we do.
> The compiler is usually pretty good with "if (0)".
>
> My question is if
>
>>       if (arm_feature(env, ARM_FEATURE_M) && tcg_enabled()) { 
>
> needs to be written
>
>      if (tcg_enabled()) {
>          if (arm_feature(..., M) {
>             ...
>          }
>      }

Yeah, that doesn't work either. I don't understand why in this
particular case the compiler seems unable to remove that code.

Can anyone else reproduce this or is it just happening on my setup?
Maybe something is broken on my side...