bug#67005: 30.0.50; improve nadivce/comp/trampoline handling

[Andrea Corallo]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

[...]

>> Another suspectible spot is the following from function `Ffset':
>>
>>   if (!NILP (Vnative_comp_enable_subr_trampolines)
>>       && SUBRP (function)
>>       && !SUBR_NATIVE_COMPILEDP (function))
>>     CALLN (Ffuncall, Qcomp_subr_trampoline_install, symbol);
>
> Actually, I don't understand this code now that I re-(re-)*read it.
> Why do we negate the SUBR_NATIVE_COMPILEDP (function)?

"function" is the function we are redefining and we want to trigger the
trampoline thing only when that's a C primitive.  Those two conditions
are equivalent to 'subr-primitive-p'.

  Andrea