From: Sriraman Tallam <tmsriram@google.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Richard Guenther <richard.guenther@gmail.com>,
Jan Hubicka <jh@suse.cz>, Uros Bizjak <ubizjak@gmail.com>,
reply@codereview.appspotmail.com, gcc-patches@gcc.gnu.org,
David Li <davidxl@google.com>
Subject: Re: User directed Function Multiversioning via Function Overloading (issue5752064)
Date: Mon, 07 May 2012 16:58:00 -0000 [thread overview]
Message-ID: <CAAs8HmwXAbwYbEaxvwA7KZx=454outzb-Cx4iifzZY9gB3Zx3w@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOp_zzhPqYdzbJqRmLcDmcRo+fLS-RyDB6wB8K-uj8nu4Q@mail.gmail.com>
On Wed, May 2, 2012 at 11:04 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, May 2, 2012 at 10:44 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>>>>>
>>>>> 1. Since AVX > SSE4 > SSSE3 > SSE3 > SSE2 > SSE, with
>>>>> foo for AVX and SSE3, on AVX processors, which foo will be
>>>>> selected?
>>>>
>>>> foo for AVX will get called since that appears ahead.
>>>>
>>>> The dispatching is done in the same order in which the functions are
>>>> specified. If, potentially, two foo versions can be dispatched for an
>>>> architecture, the first foo will get called. There is no way right
>>>> now to specify the order in which the dispatching should be done.
>>>
>>> This is very fragile. We know ISAs and processors. The source
>>> order should be irrelevant.
>>
>> I am not sure it is always possible keep this dispatching unambiguous
>> to the user. It might be better to let the user specify a priority for
>> each version to control the order of dispatching.
>>
>> Still, one way to implement what you said is to assign a significance
>> number to each ISA, where the number of sse4 > sse, for instance.
>> Then, the dispatching can be done in the descending order of
>> significance. What do you think?
>
> This sounds reasonable. You should also take processor into
> account when doing this.
>
>> I thought about this earlier and I was thinking along the lines of
>> letting the user specify a priority for each version, when there is
>> ambiguity.
>>
>>>
>>>>
>>>>> 2. I don't see any tests for __builtin_cpu_supports ("XXX")
>>>>> nor __builtin_cpu_is ("XXX"). I think you need tests for
>>>>> them.
>>>>
>>>> This is already there as part of the previous CPU detection patch that
>>>> was submitted. Please see gcc.target/i386/builtin_target.c. Did you
>>>> want something else?
>>>
>>> gcc.target/i386/builtin_target.c doesn't test if __builtin_cpu_supports ("XXX")
>>> and __builtin_cpu_is ("XXX") are implemented correctly.
>>
>> Oh, you mean like doing a CPUID again in the test case itself and checking, ok.
>>
>
> Yes. BTW, I think you should also add FMA support to
> config/i386/i386-cpuinfo.c.
I am preparing a patch for this. I will send it your way soon enough.
Thanks,
-Sri.
>
> Thanks.
>
> --
> H.J.
next prev parent reply other threads:[~2012-05-07 16:58 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-07 0:47 Sriraman Tallam
2012-03-07 14:05 ` Richard Guenther
2012-03-07 19:08 ` Sriraman Tallam
2012-03-08 21:37 ` Xinliang David Li
2012-03-08 21:00 ` Xinliang David Li
2012-03-09 20:04 ` Sriraman Tallam
2012-04-27 5:09 ` Sriraman Tallam
2012-04-27 13:39 ` H.J. Lu
2012-04-27 14:35 ` Sriraman Tallam
2012-04-27 14:39 ` H.J. Lu
2012-04-27 14:53 ` Sriraman Tallam
2012-04-27 15:36 ` H.J. Lu
2012-04-27 15:45 ` Sriraman Tallam
2012-05-01 23:51 ` Sriraman Tallam
2012-05-02 0:09 ` H.J. Lu
2012-05-02 2:45 ` Sriraman Tallam
2012-05-02 13:42 ` H.J. Lu
2012-05-02 15:08 ` Sriraman Tallam
2012-05-02 16:06 ` H.J. Lu
2012-05-02 17:44 ` Sriraman Tallam
2012-05-02 18:04 ` H.J. Lu
2012-05-07 16:58 ` Sriraman Tallam [this message]
2012-05-09 19:01 ` Sriraman Tallam
2012-05-10 17:55 ` H.J. Lu
2012-05-12 2:04 ` Sriraman Tallam
2012-05-12 13:38 ` H.J. Lu
2012-05-14 18:29 ` Sriraman Tallam
2012-05-26 0:07 ` H.J. Lu
2012-05-26 0:16 ` Sriraman Tallam
2012-05-26 0:27 ` H.J. Lu
2012-05-26 1:54 ` Sriraman Tallam
[not found] ` <CAMe9rOowm9K7r1xnRdRjW5Y4Ay+WxgSsBLTgGvq24z=i42AS+g@mail.gmail.com>
[not found] ` <CAAs8HmzeQigcLQyfkC02u=6gCTLkjLLa_jYmp+b1HEtpMCrYWw@mail.gmail.com>
2012-05-26 5:06 ` H.J. Lu
2012-05-26 22:35 ` Sriraman Tallam
2012-05-26 23:56 ` H.J. Lu
2012-05-27 0:24 ` Sriraman Tallam
2012-05-27 2:06 ` H.J. Lu
2012-05-27 2:23 ` Sriraman Tallam
2012-05-27 2:31 ` H.J. Lu
2012-05-27 19:02 ` Ian Lance Taylor
2012-06-04 19:01 ` Sriraman Tallam
2012-06-04 21:36 ` H.J. Lu
2012-06-04 22:29 ` Sriraman Tallam
2012-06-05 13:56 ` H.J. Lu
2012-06-14 20:35 ` Sriraman Tallam
2012-06-20 1:10 ` Sriraman Tallam
2012-07-06 9:14 ` Richard Guenther
2012-07-06 17:38 ` Sriraman Tallam
2012-07-07 6:06 ` Jason Merrill
2012-07-07 18:38 ` Xinliang David Li
2012-07-08 11:21 ` Jason Merrill
2012-07-09 21:27 ` Xinliang David Li
2012-07-10 9:46 ` Jason Merrill
2012-07-10 16:09 ` Xinliang David Li
[not found] ` <CAAs8HmxHF38ktt6syjWp-MpjiX+6NcXh7_8Xn6iKnAiF2vRymQ@mail.gmail.com>
2012-07-19 20:40 ` Jason Merrill
2012-07-30 19:16 ` Sriraman Tallam
2012-08-25 0:34 ` Sriraman Tallam
2012-09-18 16:29 ` Sriraman Tallam
2012-10-05 17:07 ` Xinliang David Li
2012-10-05 17:44 ` Jason Merrill
2012-10-05 18:14 ` Jason Merrill
2012-10-05 21:58 ` Sriraman Tallam
2012-10-05 22:50 ` Jason Merrill
2012-10-05 23:45 ` Sriraman Tallam
2012-10-05 18:32 ` Jason Merrill
2012-10-11 0:13 ` Sriraman Tallam
2012-10-12 22:41 ` Sriraman Tallam
2012-10-19 15:23 ` Diego Novillo
2012-10-20 4:29 ` Sriraman Tallam
2012-10-23 21:21 ` Sriraman Tallam
2012-10-26 16:53 ` Jan Hubicka
2012-10-28 4:31 ` Sriraman Tallam
2012-10-29 13:05 ` Jan Hubicka
2012-10-29 17:56 ` Sriraman Tallam
2012-10-30 19:18 ` Jason Merrill
2012-10-31 0:58 ` Sriraman Tallam
[not found] ` <CAAs8Hmw09giv-5_v0irhByTjTJV=kD58rCAD2SAz7M8zrwjBOA@mail.gmail.com>
2012-10-31 14:27 ` Jason Merrill
2012-11-02 2:53 ` Sriraman Tallam
2012-11-06 2:38 ` Sriraman Tallam
2012-11-06 15:52 ` Jason Merrill
2012-11-06 18:17 ` Sriraman Tallam
2012-11-10 1:33 ` Sriraman Tallam
2012-11-12 5:04 ` Jason Merrill
2012-11-13 1:11 ` Sriraman Tallam
2012-11-13 2:39 ` Jason Merrill
2012-11-13 21:57 ` Sriraman Tallam
2012-11-17 22:23 ` H.J. Lu
2012-11-06 22:15 ` Gerald Pfeifer
2012-10-26 14:11 ` Diego Novillo
2012-10-26 16:54 Xinliang David Li
2012-10-26 17:28 ` Sriraman Tallam
2012-11-06 22:17 Dominique Dhumieres
2012-11-07 1:16 ` Gerald Pfeifer
2012-11-07 8:53 ` Dominique Dhumieres
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