[llvm-dev] (Thin)LTO llvm build

Mehdi Amini via llvm-dev llvm-dev at lists.llvm.org
Fri Sep 16 16:59:40 PDT 2016

> On Sep 16, 2016, at 4:46 PM, Carsten Mattner <carstenmattner at gmail.com> wrote:
> On Sat, Sep 17, 2016 at 12:48 AM, Teresa Johnson <tejohnson at google.com <mailto:tejohnson at google.com>> wrote:
>> On Fri, Sep 16, 2016 at 2:54 PM, Carsten Mattner via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>> On Fri, Sep 16, 2016 at 11:28 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:
>>>> You probably missed -DLLVM_BINUTILS_INCDIR.
>>>> See: http://llvm.org/docs/GoldPlugin.html
>>> plugin-api.h is in /usr/include, so I'd expect it to be found, but I
>>> can explicitly set BINUTILS_INCDIR and re-bootstrap with gcc 6.2.1.
>>> I have ld.gold, but I'm not sure if /usr/bin/ld uses it, though I'd expect
>>> it to since it's been in for a couple releases now.
>>> $ ld -v
>>> GNU ld (GNU Binutils) 2.27
>>> $ ld.bfd -v
>>> GNU ld (GNU Binutils) 2.27
>>> $ ld.gold -v
>>> GNU gold (GNU Binutils 2.27) 1.12
>> Looks like your default ld is GNU ld.bfd not ld.gold. You can either change your
>> /usr/bin/ld (which probably is a link to /usr/bin/ld.bfd) to point instead to
>> /usr/bin/ld.gold, or if you prefer, set your PATH before the stage1 compile to a
>> location that has ld linked to ld.gold.
> I can look into and check why Arch Linux has it configured like that.
> In the meantime, Mehdi's suggestion to explicitly pass BINUTILS_INCDIR
> restored the previous configure behavior, and the new llvm build has
> lib/LLVMgold.so. Thanks to both of you for pointing out the missing cmake
> flag.
> I've checked the configure step and it didn't fail as it did before, but before
> I try to build in ThinLTO mode: since the configure step checks for the gold
> plugin, is it safe to assume that I don't have to change the default system
> ld to gold and ThinLTO will work, or is that a build requirement for
> bootstrapping llvm in ThinLTO mode?

Try to build llvm-tblgen, you’ll know quite quickly :)


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