From: "Martin Liška" <mliska@suse.cz>
To: Jeff Law <law@redhat.com>, Michael Matz <matz@suse.de>
Cc: Jan Hubicka <hubicka@ucw.cz>,
gcc-patches@gcc.gnu.org,
Richard Biener <richard.guenther@gmail.com>
Subject: Re: [PATCH] Come up with -flto=auto option.
Date: Wed, 24 Jul 2019 06:59:00 -0000 [thread overview]
Message-ID: <f25419b4-5031-553f-6917-09adcfc85d95@suse.cz> (raw)
In-Reply-To: <b40e3a33-cd90-faf3-9ad4-8be084b4f16f@redhat.com>
On 7/24/19 12:32 AM, Jeff Law wrote:
> On 7/23/19 8:23 AM, Martin Liška wrote:
>> On 7/23/19 3:57 PM, Jeff Law wrote:
>>> On 7/23/19 7:50 AM, Michael Matz wrote:
>>>> Hi,
>>>>
>>>> On Tue, 23 Jul 2019, Jeff Law wrote:
>>>>
>>>>>> great you found time to make this. It should become the default for
>>>>>> -flto IMO.
>>>>> I was going to hack it into the rpm configury bits since we have access
>>>>> to the # cores there. But an auto-selector within GCC is even better.
>>>>>
>>>>> BTW, isn't this all going to wreck havoc with reproducible builds since
>>>>> partitioning can affect code generation? That's one of our open
>>>>> questions...
>>>>
>>>> See Richi for this, but the reason for -flto=auto (or just -flto, or
>>>> whatever the endresult will be) is _also_ reproducible builds, because
>>>> some packages like to encode the compile flags into their binaries and
>>>> hence would change depending on build host just because of "-flto=32" vs.
>>>> "-flto=64" even when the code remains exactly the same.
>>> Makes sense.
>>>
>>> What did you end up doing with old autoconf scripts that aren't LTO
>>> safe? Many of the older style tests to see if a function exists are
>>> broken by LTO. I've seen more issues with this than anything in the LTO
>>> space so far.
>>
>> Well, I've seen some of these failures, but only a few.
> Many appear to be silent, possibly not really affecting anything (like
> all the packages that test for doprnt, but really don't care about it in
> the end). But there were enough real failures that I put in auditing
> to detect any cases where we get different config.h files with LTO vs
> non-LTO and that is tripping often enough to have my concerns about how
> much work it's going to be to get everything fixed.
I see.
>
>
> But still, overall we're moving forward. Next step is to get everything
> classified into buckets and start iterating. Presumably you'd be open
> to a google doc of some kind where we can coordinate any such efforts?
Sure, I'm open. In the meantime, I've got a META issue that I use for tracking
of LTO-related issues in openSUSE:
https://bugzilla.opensuse.org/show_bug.cgi?id=1133084
Martin
>
> jeff
>
> ps. I'm on PTO July 25 to Aug 5, so not much is going to happen in the
> next couple weeks :-)
>
next prev parent reply other threads:[~2019-07-24 6:47 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 8:55 Martin Liška
2019-07-23 9:29 ` Jan Hubicka
2019-07-23 10:34 ` [PATCH] Deduce automatically number of cores for -flto option Martin Liška
2019-07-24 15:47 ` Jeff Law
2019-07-29 13:37 ` Martin Liška
2019-07-30 13:47 ` Martin Liška
2019-07-31 1:23 ` Jakub Jelinek
2019-07-31 7:24 ` Martin Liška
2019-07-31 7:40 ` Jakub Jelinek
2019-07-31 7:49 ` Jan Hubicka
2019-07-31 7:50 ` Martin Liška
2019-07-31 7:54 ` Martin Liška
2019-07-31 8:08 ` Jakub Jelinek
2019-07-31 8:21 ` Jan Hubicka
2019-07-31 8:37 ` Martin Liška
2019-07-31 9:12 ` Jakub Jelinek
2019-07-31 9:15 ` Jan Hubicka
2019-07-31 9:17 ` Jakub Jelinek
2019-07-31 9:22 ` Jan Hubicka
2019-07-31 10:02 ` Martin Liška
2019-07-31 12:02 ` Jan Hubicka
2019-07-31 15:42 ` Martin Liška
2019-08-01 13:19 ` Jakub Jelinek
2019-08-01 14:34 ` [PATCH] Properly detect working jobserver in gcc driver Martin Liška
2019-08-01 14:41 ` Jakub Jelinek
2019-08-02 6:30 ` Martin Liška
2019-08-02 7:45 ` Jakub Jelinek
2019-08-02 8:47 ` Martin Liška
2019-08-02 8:50 ` Jakub Jelinek
2019-08-02 9:04 ` Richard Biener
2019-08-02 9:08 ` Jan Hubicka
2019-08-02 9:15 ` Jan Hubicka
2019-08-02 9:19 ` Martin Liška
2019-08-02 9:55 ` Richard Biener
2019-08-05 6:41 ` Martin Liška
2019-08-09 8:14 ` Martin Liška
2019-08-09 8:22 ` Richard Biener
2019-08-09 12:51 ` Martin Liška
2019-08-09 13:56 ` Martin Liška
2019-08-12 15:18 ` Jeff Law
2019-07-23 13:13 ` [PATCH] Come up with -flto=auto option Jeff Law
2019-07-23 13:22 ` Richard Biener
2019-07-23 13:57 ` Michael Matz
2019-07-23 14:00 ` Jeff Law
2019-07-23 14:27 ` Martin Liška
2019-07-23 22:56 ` Jeff Law
2019-07-24 6:59 ` Martin Liška [this message]
2019-07-24 15:16 ` Jeff Law
2019-07-23 22:32 ` Allan Sandfeld Jensen
2019-07-24 6:47 ` Martin Liška
2019-07-24 7:12 ` Allan Sandfeld Jensen
2019-07-24 7:15 ` Martin Liška
2019-07-24 11:09 ` Nathan Sidwell
2019-07-24 15:46 ` Jeff Law
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