[GCC][PATCH v2][Aarch64] Exploiting BFXIL when OR-ing two AND-operations with appropriate bitmasks

[Kyrill Tkachov]

On 31/08/18 16:27, Sam Tebbs wrote:
> On 08/31/2018 11:59 AM, Kyrill Tkachov wrote:
>
> >
> > On 30/08/18 16:53, Sam Tebbs wrote:
> >>
> >>
> >> On 08/28/2018 11:53 PM, James Greenhalgh wrote:
> >> > Hm, I'm not very sure about the naming here; "left consecutive"
> >> isn't a
> >> > common phrase to denote the mask you're looking for (exact_log2
> >> (-i) != -1
> >> > if I'm reading right), and is misleading 0x0000ffff is 'left
> >> consecutive'
> >> > too, just with zeroes rather than ones.
> >> >
> >> I think you're right about it not being the best naming. Do you have any
> >> suggestions for a better name?
> >
> > Naming things is hard... :(
> >
> > How about aarch64_hi_bits_all_ones_p ?
> >
> > Kyrill
>
> That sounds good! Although I'm confused about what the 'p' means.
>

It stands for "predicate" meaning a boolean function with no side-effects.
It's the preferred way to name these kinds of functions in GCC (though I can't seem to find the documentation mandate for it).
IIRC it's a remnant from the LISP days. You'll find a lot of *_p functions in GCC.

Kyrill