From: Florian Weimer <fweimer@redhat.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>,
GCC Development <gcc@gcc.gnu.org>
Subject: Re: [RFC] Adding a new attribute to function param to mark it as constant
Date: Wed, 04 Aug 2021 19:08:08 +0200 [thread overview]
Message-ID: <8735rp6suf.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <20210804161645.GI1583@gate.crashing.org> (Segher Boessenkool's message of "Wed, 4 Aug 2021 11:16:45 -0500")
* Segher Boessenkool:
> On Wed, Aug 04, 2021 at 03:27:00PM +0100, Richard Earnshaw wrote:
>> On 04/08/2021 14:40, Segher Boessenkool wrote:
>> >On Wed, Aug 04, 2021 at 02:00:42PM +0100, Richard Earnshaw wrote:
>> >>We don't want to have to resort to macros. Not least because at some
>> >>point we want to replace the content of arm_neon.h with a single #pragma
>> >>directive to remove all the parsing of the header that's needed. What's
>> >>more, if we had a suitable pragma we'd stand a fighting chance of being
>> >>able to extend support to other languages as well that don't use the
>> >>pre-processor, such as Fortran or Ada (not that that is on the cards
>> >>right now).
>> >
>> >So how do you want to handle constants-that-are-not-yet-constant, say
>> >before inlining? And how do you want to deal with those possibly not
>> >ever becoming constant, perhaps because you used a too low "n" in -On
>> >(but there are very many random other causes)? And, what *is* a
>> >constant, anyway? This is even more fuzzy if you consider those
>> >other languages as well.
>> >
>> >(Does skipping parsing of some trivial header save so much time? Huh!)
>>
>> Trivial? arm_neon.h is currently 20k lines of source. What's more, it
>> has to support inline functions that might not be available when the
>> header is parsed, but might become available if the user subsequently
>> compiles a function with different attributes enabled. It is very
>> definitely *NOT* trivial.
>
> Ha yes :-) I just assumed without looking that it would be like other
> architectures' intrinsics headers. Whoops.
But isn't it?
$ echo '#include <x86intrin.h>' | gcc -E - | wc -l
41045
Thanks,
Florian
next prev parent reply other threads:[~2021-08-04 17:08 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 10:53 Prathamesh Kulkarni
2021-07-23 17:59 ` Andrew Pinski
2021-07-26 9:04 ` Prathamesh Kulkarni
2021-07-27 8:19 ` Richard Biener
2021-08-03 10:11 ` Prathamesh Kulkarni
2021-08-03 10:13 ` Prathamesh Kulkarni
2021-08-03 17:44 ` Martin Sebor
2021-08-04 9:46 ` Richard Earnshaw
2021-08-06 0:06 ` Martin Sebor
2021-08-06 10:51 ` Richard Earnshaw
2021-08-06 20:39 ` Martin Sebor
2021-08-12 8:32 ` Prathamesh Kulkarni
2021-08-13 17:14 ` Martin Sebor
2021-08-18 6:52 ` Prathamesh Kulkarni
2021-08-18 14:40 ` Martin Sebor
2021-08-19 8:10 ` Prathamesh Kulkarni
2021-08-03 21:55 ` Segher Boessenkool
2021-08-04 9:50 ` Prathamesh Kulkarni
2021-08-04 10:17 ` Segher Boessenkool
2021-08-04 11:50 ` Prathamesh Kulkarni
2021-08-04 12:46 ` Segher Boessenkool
2021-08-04 13:00 ` Richard Earnshaw
2021-08-04 13:40 ` Segher Boessenkool
2021-08-04 14:27 ` Richard Earnshaw
2021-08-04 16:16 ` Segher Boessenkool
2021-08-04 17:08 ` Florian Weimer [this message]
2021-08-04 17:59 ` Segher Boessenkool
2021-08-05 9:32 ` Richard Earnshaw
2021-08-05 9:01 ` Prathamesh Kulkarni
2021-08-05 15:06 ` Segher Boessenkool
2021-08-06 20:10 Martin Uecker
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