From: Martin Sebor <msebor@gmail.com>
To: Jason Merrill <jason@redhat.com>,
Jonathan Wakely <jwakely@redhat.com>,
Richard Biener <richard.guenther@gmail.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PING][PATCH] define auto_vec copy ctor and assignment (PR 90904)
Date: Thu, 5 Aug 2021 20:07:21 -0600 [thread overview]
Message-ID: <b93280f8-b673-f6b4-8652-468c61c925e8@gmail.com> (raw)
In-Reply-To: <3c6631e9-d95c-dbf6-e50e-cee99f8652d7@redhat.com>
On 7/30/21 9:06 AM, Jason Merrill wrote:
> On 7/27/21 2:56 PM, Martin Sebor wrote:
>> Ping: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575690.html
>>
>> Are there any other suggestions or comments or is the latest revision
>> okay to commit?
>
> OK.
I had to make a few more adjustments to fix up code that's snuck
in since I last tested the patch. I committed r12-2776 after
retesting on x86_64-linux.
With the cleanup out of the way I'll resubmit the copy ctor patch
next.
Martin
>
>> On 7/20/21 12:34 PM, Martin Sebor wrote:
>>> On 7/14/21 10:23 AM, Jason Merrill wrote:
>>>> On 7/14/21 10:46 AM, Martin Sebor wrote:
>>>>> On 7/13/21 9:39 PM, Jason Merrill wrote:
>>>>>> On 7/13/21 4:02 PM, Martin Sebor wrote:
>>>>>>> On 7/13/21 12:37 PM, Jason Merrill wrote:
>>>>>>>> On 7/13/21 10:08 AM, Jonathan Wakely wrote:
>>>>>>>>> On Mon, 12 Jul 2021 at 12:02, Richard Biener wrote:
>>>>>>>>>> Somebody with more C++ knowledge than me needs to approve the
>>>>>>>>>> vec.h changes - I don't feel competent to assess all effects
>>>>>>>>>> of the change.
>>>>>>>>>
>>>>>>>>> They look OK to me except for:
>>>>>>>>>
>>>>>>>>> -extern vnull vNULL;
>>>>>>>>> +static constexpr vnull vNULL{ };
>>>>>>>>>
>>>>>>>>> Making vNULL have static linkage can make it an ODR violation
>>>>>>>>> to use
>>>>>>>>> vNULL in templates and inline functions, because different
>>>>>>>>> instantiations will refer to a different "vNULL" in each
>>>>>>>>> translation
>>>>>>>>> unit.
>>>>>>>>
>>>>>>>> The ODR says this is OK because it's a literal constant with the
>>>>>>>> same value (6.2/12.2.1).
>>>>>>>>
>>>>>>>> But it would be better without the explicit 'static'; then in
>>>>>>>> C++17 it's implicitly inline instead of static.
>>>>>>>
>>>>>>> I'll remove the static.
>>>>>>>
>>>>>>>>
>>>>>>>> But then, do we really want to keep vNULL at all? It's a weird
>>>>>>>> blurring of the object/pointer boundary that is also dependent
>>>>>>>> on vec being a thin wrapper around a pointer. In almost all
>>>>>>>> cases it can be replaced with {}; one exception is ==
>>>>>>>> comparison, where it seems to be testing that the embedded
>>>>>>>> pointer is null, which is a weird thing to want to test.
>>>>>>>
>>>>>>> The one use case I know of for vNULL where I can't think of
>>>>>>> an equally good substitute is in passing a vec as an argument by
>>>>>>> value. The only way to do that that I can think of is to name
>>>>>>> the full vec type (i.e., the specialization) which is more typing
>>>>>>> and less generic than vNULL. I don't use vNULL myself so I wouldn't
>>>>>>> miss this trick if it were to be removed but others might feel
>>>>>>> differently.
>>>>>>
>>>>>> In C++11, it can be replaced by {} in that context as well.
>>>>>
>>>>> Cool. I thought I'd tried { } here but I guess not.
>>>>>
>>>>>>
>>>>>>> If not, I'm all for getting rid of vNULL but with over 350 uses
>>>>>>> of it left, unless there's some clever trick to make the removal
>>>>>>> (mostly) effortless and seamless, I'd much rather do it
>>>>>>> independently
>>>>>>> of this initial change. I also don't know if I can commit to making
>>>>>>> all this cleanup.
>>>>>>
>>>>>> I already have a patch to replace all but one use of vNULL, but
>>>>>> I'll hold off with it until after your patch.
>>>>>
>>>>> So what's the next step? The patch only removes a few uses of vNULL
>>>>> but doesn't add any. Is it good to go as is (without the static and
>>>>> with the additional const changes Richard suggested)? This patch is
>>>>> attached to my reply to Richard:
>>>>> https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575199.html
>>>>
>>>> As Richard wrote:
>>>>
>>>>> The pieces where you change vec<> passing to const vec<>& and the few
>>>>> where you change vec<> * to const vec<> * are OK - this should make
>>>>> the
>>>>> rest a smaller piece to review.
>>>>
>>>> Please go ahead and apply those changes and send a new patch with
>>>> the remainder of the changes.
>>>
>>> I have just pushed r12-2418:
>>> https://gcc.gnu.org/pipermail/gcc-cvs/2021-July/350886.html
>>>
>>>>
>>>> A few other comments:
>>>>
>>>>> - omp_declare_simd_clauses);
>>>>> + *omp_declare_simd_clauses);
>>>>
>>>> Instead of doing this indirection in all of the callers, let's
>>>> change c_finish_omp_declare_simd to take a pointer as well, and do
>>>> the indirection in initializing a reference variable at the top of
>>>> the function.
>>>
>>> Okay.
>>>
>>>>
>>>>> + sched_init_luids (bbs.to_vec ());
>>>>> + haifa_init_h_i_d (bbs.to_vec ());
>>>>
>>>> Why are these to_vec changes needed when you are also changing the
>>>> functions to take const&?
>>>
>>> Calling to_vec() here isn't necessary so I've removed it.
>>>
>>>>
>>>>> - vec<tree> checks = LOOP_VINFO_CHECK_NONZERO (loop_vinfo);
>>>>> + vec<tree> checks = LOOP_VINFO_CHECK_NONZERO (loop_vinfo).to_vec ();
>>>>
>>>> Why not use a reference here and in other similar spots?
>>>
>>> Sure, that works too.
>>>
>>> Attached is what's left of the original changes now that r12-2418
>>> has been applied.
>>>
>>> Martin
>>
>
next prev parent reply other threads:[~2021-08-06 2:07 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-26 23:30 [PATCH] " Martin Sebor
2021-04-27 7:58 ` Richard Biener
2021-04-27 13:58 ` Martin Sebor
2021-04-27 14:04 ` Richard Biener
2021-04-27 15:52 ` Martin Sebor
2021-05-03 21:50 ` [PING][PATCH] " Martin Sebor
2021-05-11 20:02 ` [PING 2][PATCH] " Martin Sebor
2021-05-27 19:33 ` [PING 3][PATCH] " Martin Sebor
2021-05-27 20:53 ` [PATCH] " Jason Merrill
2021-06-01 19:56 ` Martin Sebor
2021-06-01 21:38 ` Jason Merrill
2021-06-25 20:51 ` Martin Sebor
2021-06-25 22:11 ` Jason Merrill
2021-06-25 22:36 ` Martin Sebor
2021-06-28 8:07 ` Richard Biener
2021-06-28 18:07 ` Martin Sebor
2021-06-29 10:58 ` Richard Biener
2021-06-29 11:34 ` Martin Jambor
2021-06-30 1:46 ` Martin Sebor
2021-06-30 8:48 ` Richard Biener
2021-06-30 9:29 ` Martin Jambor
2021-07-06 15:06 ` [PING][PATCH] " Martin Sebor
2021-07-07 7:28 ` Richard Biener
2021-07-07 14:37 ` Martin Sebor
2021-07-12 11:02 ` Richard Biener
2021-07-13 14:08 ` Jonathan Wakely
2021-07-13 18:37 ` Jason Merrill
2021-07-13 20:02 ` Martin Sebor
2021-07-14 3:39 ` Jason Merrill
2021-07-14 10:47 ` Jonathan Wakely
2021-07-14 14:46 ` Martin Sebor
2021-07-14 16:23 ` Jason Merrill
2021-07-20 18:34 ` Martin Sebor
2021-07-20 20:08 ` Jason Merrill
2021-07-20 21:52 ` Martin Sebor
2021-07-27 18:56 ` Martin Sebor
2021-07-30 15:06 ` Jason Merrill
2021-08-06 2:07 ` Martin Sebor [this message]
2021-08-06 7:52 ` Christophe Lyon
2021-08-06 12:17 ` Christophe Lyon
2021-07-14 14:44 ` Martin Sebor
2021-06-29 14:43 ` [PATCH] " Jason Merrill
2021-06-29 17:18 ` Martin Sebor
2021-06-30 8:40 ` Richard Biener
2021-06-30 9:00 ` Richard Sandiford
2021-06-30 12:01 ` Richard Biener
2021-06-28 8:05 ` Richard Biener
2021-06-29 12:30 ` Trevor Saunders
2021-06-02 6:55 ` Richard Biener
2021-06-02 16:04 ` Martin Sebor
2021-06-03 8:29 ` Trevor Saunders
2021-06-07 8:51 ` Richard Biener
2021-06-07 10:33 ` Trevor Saunders
2021-06-07 13:33 ` Richard Biener
2021-06-07 20:34 ` Martin Sebor
2021-06-08 3:26 ` Trevor Saunders
2021-06-08 7:19 ` Richard Biener
2021-06-07 22:17 ` Martin Sebor
2021-06-08 2:41 ` Trevor Saunders
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