[PATCH 3/4 v3][PR 67328] Added bool conversion for wide_ints

[Richard Sandiford]

Yuri Gribov <tetra2005@gmail.com> writes:
> On Tue, May 30, 2017 at 7:35 AM, Richard Sandiford
> <richard.sandiford@linaro.org> wrote:
>> Yuri Gribov <tetra2005@gmail.com> writes:
>>> From 330209f721a598ec393dcb5d62de3457ee282153 Mon Sep 17 00:00:00 2001
>>> From: Yury Gribov <tetra2005@gmail.com>
>>> Date: Fri, 26 May 2017 07:53:10 +0100
>>> Subject: [PATCH 3/4] Added bool conversion for wide_ints.
>>>
>>> gcc/
>>> 2017-05-26  Yury Gribov  <tetra2005@gmail.com>
>>>
>>>       * wide-int.cc (wi::zero_p_large): New method.
>>>       * wide-int.h (wi::zero_p): New method.
>>
>> Do you still need this bit?  It looks like it isn't used by the other
>> parts of the series.
>>
>> The idea was that wi::eq_p (x, 0) (or just x == 0, if x is a
>> wide-int-based type) is supposed to be as fast as a dedicated zero check.
>> It'd be OK to have a helper function anyway, but it should probably be
>> defined using wi::eq_p.
>>
>> The zero_p_large fallback can never return true, since a zero of
>> any precision will have a length of 1.
>
> Thanks Richard, I'll update the patch. The bool check is used in
> successive patch (4/4), in
>      widest_int mask = wi::to_widest (@2);
>      bool mask_all_ones_p = !(mask & (mask + 1));

Ah, OK.  That's equivalent to mask == -1 (or wi::eq_p (@2, -1), to avoid
the temporary).  I think it'd be better to use one of those instead.
There's an argument that if ! is defined, it should return an integer
of the same precision as the argument.

Thanks,
Richard