Re: master b467bb5 4/4: Minimize ‘equal’ calls in (delete x vector)

[Paul Eggert <eggert@cs.ucla.edu>]

On 8/15/20 1:21 PM, Pip Cet wrote:

> Looks correct, but establishes a rather questionable precedent of
> putting Lisp_Objects in SAFE_ALLOCA'd space. That's okay in this
> specific case, for a number of reasons, but it's bound to be copied by
> someone in circumstances where it's not :-)

It's not unprecedented, as there's one other instance of this, in 
font_sort_entities. Admittedly it's unusual; feel free to add a comment.
>> It does bug me a bit that GCC generates bad code for 'NILP (Fequal (...))' here.
>> I've been meaning to add a bool function equal (...) that would simplify the C
>> source a bit and presumably let GCC do better, but that can wait.
> 
> What's GCC doing, for you?

It's doing some weird thing involving cmp + adc. On second thought it's probably 
fine, as it is branch-free. Still, I always get confused when I write "!NILP 
(Fequal (a, b)' and too often I get it wrong. I'd rather write 'equal (a, b)'.