Davide Italiano via llvm-dev
2017-Oct-03 19:13 UTC
[llvm-dev] New Pass Manager with flto[=thin] not enabled (??)
On Tue, Oct 3, 2017 at 12:08 PM, Davide Italiano <davide at freebsd.org> wrote:> On Tue, Oct 3, 2017 at 11:57 AM, Graham Yiu via llvm-dev > <llvm-dev at lists.llvm.org> wrote: >> Hello, >> >> I recently noticed that the new pass manager was not enabled at regular/thin >> LTO link step even if '-fexperimental-new-pass-manager' was specified in the >> compile step and link step commands. Upon closer inspection, it seems >> there's so real way to invoke the new pass manager path ('runNewPMPasses' in >> lib/LTO/LTOBackend.cpp) during link step. >> > > `-fexperimental-new-pass-manager` is a compile time flag and has no > effect on the link step IIRC. > You may want to teach the driver to pass the correct flag to the LTO > plugin in gold or to lld. > > -- > DavideFor lld in particular, currently there's only the ability to specifiy a custom pass pipeline when passing `--lto-newpm-passes` to the linker. This is because, historically, when I added this flag, the pass manager work was still in progress and the `-O2/LTO` pipeline wasn't fleshed entirely (missing passes & functionality). You can probably add the option to lld now, if you can't/don't know how to do it, I may take a look this weekend. Thanks, -- Davide "There are no solved problems; there are only problems that are more or less solved" -- Henri Poincare
Graham Yiu via llvm-dev
2017-Oct-03 19:38 UTC
[llvm-dev] New Pass Manager with flto[=thin] not enabled (??)
Hi David,
Hi David,
So I should note that we're only interested in the gold linker with
LTO/thinLTO. It didn't occur to me at the time that we also need to
account for lld.
I noticed the current way of passing options to gold plugin is slightly
hacky, in that there are handful of options we define and pass to gold
specifically like -O<#> or -mcpu=[arch]. This seems like it'll be a
maintenance nightmare in the future.
Also, are there ways to embed options into bitcode files from the compile
step?
Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077 C2-707/8200/Markham
Email: gyiu at ca.ibm.com
From: Davide Italiano <davide at freebsd.org>
To: Graham Yiu <gyiu at ca.ibm.com>
Cc: llvm-dev <llvm-dev at lists.llvm.org>
Date: 10/03/2017 03:14 PM
Subject: Re: [llvm-dev] New Pass Manager with flto[=thin] not enabled
(??)
Sent by: davide.italiano at gmail.com
On Tue, Oct 3, 2017 at 12:08 PM, Davide Italiano <davide at freebsd.org>
wrote:> On Tue, Oct 3, 2017 at 11:57 AM, Graham Yiu via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> Hello,
>>
>> I recently noticed that the new pass manager was not enabled at
regular/thin>> LTO link step even if '-fexperimental-new-pass-manager' was
specified in
the>> compile step and link step commands. Upon closer inspection, it seems
>> there's so real way to invoke the new pass manager path
('runNewPMPasses' in>> lib/LTO/LTOBackend.cpp) during link step.
>>
>
> `-fexperimental-new-pass-manager` is a compile time flag and has no
> effect on the link step IIRC.
> You may want to teach the driver to pass the correct flag to the LTO
> plugin in gold or to lld.
>
> --
> Davide
For lld in particular, currently there's only the ability to specifiy
a custom pass pipeline when passing `--lto-newpm-passes` to the
linker. This is because, historically, when I added this flag, the
pass manager work was still in progress and the `-O2/LTO` pipeline
wasn't fleshed entirely (missing passes & functionality).
You can probably add the option to lld now, if you can't/don't know
how to do it, I may take a look this weekend.
Thanks,
--
Davide
"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare
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Teresa Johnson via llvm-dev
2017-Oct-03 20:29 UTC
[llvm-dev] New Pass Manager with flto[=thin] not enabled (??)
Hi Graham, This looks like an oversight. Agree that the way of passing options through to the linkers is not great as it requires adding plumbing through the driver. But I think that is the best option for now. It would entail adding a gold-plugin option that would be set from the clang driver and using that to set Conf.UseNewPM. Do you want to send this patch? Thanks, Teresa On Tue, Oct 3, 2017 at 12:38 PM, Graham Yiu via llvm-dev < llvm-dev at lists.llvm.org> wrote:> Hi David, > > Hi David, > > So I should note that we're only interested in the gold linker with > LTO/thinLTO. It didn't occur to me at the time that we also need to account > for lld. > > I noticed the current way of passing options to gold plugin is slightly > hacky, in that there are handful of options we define and pass to gold > specifically like -O<#> or -mcpu=[arch]. This seems like it'll be a > maintenance nightmare in the future. > > Also, are there ways to embed options into bitcode files from the compile > step? > > Graham Yiu > LLVM Compiler Development > IBM Toronto Software Lab > Office: (905) 413-4077 C2-707/8200/Markham > Email: gyiu at ca.ibm.com > > [image: Inactive hide details for Davide Italiano ---10/03/2017 03:14:18 > PM---On Tue, Oct 3, 2017 at 12:08 PM, Davide Italiano <davide@]Davide > Italiano ---10/03/2017 03:14:18 PM---On Tue, Oct 3, 2017 at 12:08 PM, > Davide Italiano <davide at freebsd.org> wrote: > On Tue, Oct 3, 2017 a > > From: Davide Italiano <davide at freebsd.org> > To: Graham Yiu <gyiu at ca.ibm.com> > Cc: llvm-dev <llvm-dev at lists.llvm.org> > Date: 10/03/2017 03:14 PM > Subject: Re: [llvm-dev] New Pass Manager with flto[=thin] not enabled (??) > Sent by: davide.italiano at gmail.com > ------------------------------ > > > > On Tue, Oct 3, 2017 at 12:08 PM, Davide Italiano <davide at freebsd.org> > wrote: > > On Tue, Oct 3, 2017 at 11:57 AM, Graham Yiu via llvm-dev > > <llvm-dev at lists.llvm.org> wrote: > >> Hello, > >> > >> I recently noticed that the new pass manager was not enabled at > regular/thin > >> LTO link step even if '-fexperimental-new-pass-manager' was specified > in the > >> compile step and link step commands. Upon closer inspection, it seems > >> there's so real way to invoke the new pass manager path > ('runNewPMPasses' in > >> lib/LTO/LTOBackend.cpp) during link step. > >> > > > > `-fexperimental-new-pass-manager` is a compile time flag and has no > > effect on the link step IIRC. > > You may want to teach the driver to pass the correct flag to the LTO > > plugin in gold or to lld. > > > > -- > > Davide > > For lld in particular, currently there's only the ability to specifiy > a custom pass pipeline when passing `--lto-newpm-passes` to the > linker. This is because, historically, when I added this flag, the > pass manager work was still in progress and the `-O2/LTO` pipeline > wasn't fleshed entirely (missing passes & functionality). > You can probably add the option to lld now, if you can't/don't know > how to do it, I may take a look this weekend. > > Thanks, > > -- > Davide > > "There are no solved problems; there are only problems that are more > or less solved" -- Henri Poincare > > > > > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > >-- Teresa Johnson | Software Engineer | tejohnson at google.com | 408-460-2413 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171003/0dee1283/attachment.html> -------------- next part -------------- A non-text attachment was scrubbed... Name: graycol.gif Type: image/gif Size: 105 bytes Desc: not available URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171003/0dee1283/attachment.gif>