[PATCH] D22677: [ThinLTO/gold] Support for getting list of included objects from gold

Fri Jul 22 12:08:23 PDT 2016

Define a lit.local.cfg and add checks there. For instance:
projects/compiler-rt/test/profile/Linux/lit.local.cfg

David

On Fri, Jul 22, 2016 at 12:04 PM, Teresa Johnson <tejohnson at google.com>
wrote:

>
>
> On Fri, Jul 22, 2016 at 11:46 AM, Xinliang David Li <davidxl at google.com>
> wrote:
>
>> Can we have a subdir in the test that requires latest version of gold --
>> so that more tests can be added?
>>
>
> AFAICT there is no way to require a specific version of gold via Lit
> currently, but I think I see how such a requirement could be added (there
> is something similar for the python version, in utils/lit/tests/lit.cfg,
> although I don't see it being used anywhere). Let me try to do that.
>
> Teresa
>
>
>>
>> David
>>
>> On Fri, Jul 22, 2016 at 11:41 AM, Teresa Johnson <tejohnson at google.com>
>> wrote:
>>
>>> tejohnson added inline comments.
>>>
>>> ================
>>> Comment at: test/tools/gold/X86/thinlto_emit_linked_objects.ll:18
>>> @@ +17,3 @@
>>> +; RUN:    %t.o \
>>> +; RUN:    --start-lib %t2.o --end-lib
>>> +
>>> ----------------
>>> tejohnson wrote:
>>> > mehdi_amini wrote:
>>> > > tejohnson wrote:
>>> > > > tejohnson wrote:
>>> > > > > tejohnson wrote:
>>> > > > > > mehdi_amini wrote:
>>> > > > > > > tejohnson wrote:
>>> > > > > > > > tejohnson wrote:
>>> > > > > > > > > davidxl wrote:
>>> > > > > > > > > > tejohnson wrote:
>>> > > > > > > > > > > davidxl wrote:
>>> > > > > > > > > > > > tejohnson wrote:
>>> > > > > > > > > > > > > davidxl wrote:
>>> > > > > > > > > > > > > > Perhaps add test case about real archive case
>>> as well.
>>> > > > > > > > > > > > > For a distributed build the build system needs
>>> to extract the constituent objects (otherwise the combined index paths will
>>> not point to an object file)
>>> > > > > > > > > > > > I think this feature is more about two step link
>>> (not about a particular distributed build system). It is possible that some
>>> other distributed build system uses archive, right?
>>> > > > > > > > > > > Using archives directly with a distributed build
>>> won't work - the combined index module paths need to point to an object
>>> file for the distributed backends to import from. The build system needs to
>>> extract the objects (e.g. into a temp dir) and pass those.
>>> > > > > > > > > > >
>>> > > > > > > > > > > Note that archives passed to a non-distributed build
>>> work fine because we load the modules from the offset within the archive
>>> passed to the plugin from gold and serve those to the importer.
>>> > > > > > > > > > how about thin archive?
>>> > > > > > > > > Gold does not seem to like thin archives (regardless of
>>> LTO vs ThinLTO). I get an error (from gold, not the plugin) like:
>>> > > > > > > > >
>>> > > > > > > > > error: foo.a: no archive symbol table (run ranlib)
>>> > > > > > > > >
>>> > > > > > > > > (even when I run ranlib)
>>> > > > > > > > Note this issue is specific to bitcode files in the
>>> archive - gold with regular native objects in a thin archive works just
>>> fine. Looks like ranlib doesn't work on an archive of bitcode files, and
>>> that seems to be needed with a thin archive.
>>> > > > > > > Do you mean "ranlib doesn't work on a *thin* archive of
>>> bitcode files"?
>>> > > > > > > Otherwise how do you build LLVM itself with LTO?
>>> > > > > > According to http://llvm.org/docs/GoldPlugin.html it isn't
>>> supported for archives of bitcode files at all, but apparently isn't needed
>>> for a whole (non-thin) archive:
>>> > > > > >
>>> > > > > > "export RANLIB=/bin/true #ranlib is not needed, and doesn't
>>> support .bc files in .a"
>>> > > > > So I can't get gold to work with a (non-thin) archive created by
>>> ar, it gives the same error. Maybe it needs to take the -plugin option? In
>>> any case, a non-thin archive created via llvm-ar is accepted and works
>>> fine. I don't see an llvm-ar option to create a thin archive though?
>>> > > > Aha - llvm-ar does support thin archives, it's just that the T
>>> option is not documented in the help. =)
>>> > > >
>>> > > > With that, it does work for llvm-ar thin archives! Will add
>>> another case to the new test that does the same for thin archives before
>>> submitting.
>>> > > > According to http://llvm.org/docs/GoldPlugin.html it isn't
>>> supported for archives of bitcode files at all.
>>> > >
>>> > > Documentation patch?
>>> > Reading through that page some more, it gives instructions earlier on
>>> getting the plugin to work with ar:
>>> > "ar and nm also accept the -plugin option and it’s possible to to
>>> install LLVMgold.so to /usr/lib/bfd-plugins for a seamless setup. If you
>>> built your own gold, be sure to install the ar and nm-new you built to
>>> /usr/bin."
>>> >
>>> > So I think it is ok. I just took the latter comment out of context.
>>> >
>>> > However, I will send a patch to document the llvm-ar T modifier
>>> > With that, it does work for llvm-ar thin archives! Will add another
>>> case to the new test that does the same for thin archives before submitting.
>>>
>>> And, removed in r276453 due to bot failure - looks like gold v1.11 does
>>> not like the thin archive (gold v1.12 is fine though!).
>>>
>>>
>>> Repository:
>>>   rL LLVM
>>>
>>> https://reviews.llvm.org/D22677
>>>
>>>
>>>
>>>
>>
>
>
> --
> 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-commits/attachments/20160722/c5a5e6db/attachment.html>