Re: [Qemu-devel] Arm emulation tweak

[Jamie Lokier <jamie@shareable.org>]

Nigel Horne wrote:
> This small patch reduces (on my machine) the call to new_tmp by 16 
> bytes, which may not sound much, but it's called so often that it makes 
> a nice speed up of Arm emulation:

>      if (GET_TCGV_I32(temps[num_temps]))
>        return temps[num_temps++];
> 
> !     tmp = tcg_temp_new_i32();
> !     temps[num_temps++] = tmp;
> !     return tmp;
>  }

becomes

>      if (GET_TCGV_I32(temps[num_temps]))
>        return temps[num_temps++];
> 
> !     return temps[num_temps++] = tcg_temp_new_i32();
>  }

That's pretty tragic if GCC fails to compile them to identical code,
assuming you had optimisation turned on.

Have you tried building with -Os, -O2 etc. to see if that makes a
difference?

Which GCC version are you using?

-- Jamie