From: Jakub Jelinek <jakub@redhat.com>
To: "Martin Liška" <mliska@suse.cz>
Cc: gcc-patches@gcc.gnu.org, Uros Bizjak <ubizjak@gmail.com>
Subject: Re: [PATCH] i386: fix assert (__builtin_cpu_supports ("x86-64") >= 0)
Date: Fri, 9 Dec 2022 10:31:16 +0100 [thread overview]
Message-ID: <Y5MAZLyb5FWuPOmt@tucnak> (raw)
In-Reply-To: <38137444-4255-6e0d-db37-f635748363db@suse.cz>
On Fri, Dec 09, 2022 at 10:18:34AM +0100, Martin Liška wrote:
> I'm going to push the revision.
>
> What exactly do you mean by random? I just know there are differences in between
> x86 and ppc:
>
> int __builtin_cpu_supports(const char *feature)
> This function returns a positive integer if the run-time CPU supports feature and returns 0 otherwise.
>
> This function returns a value of 1 if the run-time CPU supports the HWCAP feature feature and returns 0 otherwise.
Because x86-64-v2 etc. isn't a HWCAP feature, but rather an architecture
(or set of canned HWCAP features). So __builtin_cpu_is for those,
or especially for __builtin_cpu_is ("x86-64") would make more sense.
Though I see that many of the valid -march= values actually aren't supported
by __builtin_cpu_is either, whether it is pentium, nocona, lakemont etc.
but does support say some vendors (intel, amd).
Jakub
prev parent reply other threads:[~2022-12-09 9:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-25 12:57 Martin Liška
2022-12-02 9:46 ` Martin Liška
2022-12-02 9:54 ` Uros Bizjak
2022-12-07 10:30 ` Martin Liška
2022-12-07 11:27 ` Jakub Jelinek
2022-12-09 9:18 ` Martin Liška
2022-12-09 9:31 ` Jakub Jelinek [this message]
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