Re: [PATCH] Abstract out calculation of max HWIs per wide int.

[Aldy Hernandez <aldyh@redhat.com>]

On 4/17/23 20:47, Andrew Pinski wrote:
> On Mon, Apr 17, 2023 at 11:44 AM Aldy Hernandez via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>>
>> I'm about to add one more use of the same snippet of code, for a total
>> of 4 identical calculations in the code base.
>>
>> This seems safe enough even before the release, since this file hardly
>> changes and I'm pretty much the only one who's touched it this year.
>>
>> OK for trunk?
>>
>> gcc/ChangeLog:
>>
>>          * wide-int.h (WIDE_INT_MAX_HWIS): New.
>>          (class fixed_wide_int_storage): Use it.
>>          (trailing_wide_ints <N>::set_precision): Use it.
>>          (trailing_wide_ints <N>::extra_size): Use it.
>> ---
>>   gcc/wide-int.h | 12 +++++++-----
>>   1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/gcc/wide-int.h b/gcc/wide-int.h
>> index a450a744c9f..6be343c0eb5 100644
>> --- a/gcc/wide-int.h
>> +++ b/gcc/wide-int.h
>> @@ -264,6 +264,10 @@ along with GCC; see the file COPYING3.  If not see
>>   /* The number of HWIs needed to store an offset_int.  */
>>   #define OFFSET_INT_ELTS (ADDR_MAX_PRECISION / HOST_BITS_PER_WIDE_INT)
>>
>> +/* The max number of HWIs needed to store a wide_int of PRECISION.  */
>> +#define WIDE_INT_MAX_HWIS(PRECISION) \
>> +  ((PRECISION + HOST_BITS_PER_WIDE_INT - 1) / HOST_BITS_PER_WIDE_INT)
> 
> Does it make sense to use an constexpr inline function instead of a
> define here since GCC is written in C++11 after all?
> That is:
> constexpr inline unsigned WIDE_INT_MAX_HWIS(unsigned precision)
> {
>    return ((precision + HOST_BITS_PER_WIDE_INT - 1) / HOST_BITS_PER_WIDE_INT);
> }

I am following the current style in wide-int.h, both in naming as well 
as macros, but I have no strong opinions.

I'm happy to do whatever y'all agree is best.
Aldy