llvm dev - Sep 2016 - (Thin)LTO llvm build

> On Sep 16, 2016, at 2:27 PM, Mehdi Amini via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
>> 
>> On Sep 16, 2016, at 2:18 PM, Carsten Mattner <carstenmattner at
gmail.com> wrote:
>> 
>> On Fri, Sep 16, 2016 at 10:54 PM, Mehdi Amini <mehdi.amini at
apple.com> wrote:
>> 
>>> Can you look for the specific errors in the CMake log and error
files?
>>> 
>>> CMake is very good at not presenting the real issue…
>>> Here it is trying to build very simple programs to check features
>>> availability. Like:
>>> 
>>>  #include <strings.h>
>>>  int main() { ffs(0); return 0; }
>> 
>> In CMakeError.log there are errors like:
>> 
>> CheckIncludeFile.c:1:10: fatal error: 'malloc/malloc.h' file
not found
>> #include <malloc/malloc.h>
>> 
>> ...
>> 
>> CheckIncludeFile.c:1:10: fatal error: 'ndir.h' file not found
>> #include <ndir.h>
>> 
>> ...
>> 
>> CheckIncludeFile.c:1:10: fatal error: 'sys/ndir.h' file not
found
>> #include <sys/ndir.h>
>> 
>> ...
>> 
>> fatal error: 'intrin.h' file not found
>> 
>> These seem like tests that are expected to fail.
>> 
>> ...
>> 
>> The interesting test
>> 
>> int main() { __builtin_ffs(0); return 0; }
>> 
>> fails like this:
>> 
>> /usr/bin/ld[...]llvm/bin/../lib/LLVMgold.so:
>> cannot open shared object file: No such file[…]
> 
> 
> I assume that "/usr/bin/ld[...]llvm/bin” is the path where clang is
installed right?
> It seems that when you built the stage1 clang, it didn’t find Gold
installed, and then didn’t build the plugin.
> So you need to go back to the first build (not the ThinLTO one, the one
with the system compiler), and make sure that CMake finds gold.
You probably missed -DLLVM_BINUTILS_INCDIR.

See: http://llvm.org/docs/GoldPlugin.html

— 
Mehdi

> 
> 
>> 
>> I have two questions here:
>> 
>> Is there anything I might have missed when configuring the gcc-built
>> llvm install for it to be incomplete in the linker department? I mean,
>> the system linker is used (not lld) and that via CC=clang is looking
>> for the gold linker plugin, which seems to be missing. Probably
>> something got lost in my transition from autoconf to cmake?
>> 
>> Anything else to pass to cmake so that it, in addition to llvm-ar and
>> llvm-ranlib, also used lld? Or isn't that a requirement for
building
>> with ThinLTO?
> 
> No requirement for lld.
> 
> 
> — 
> Mehdi
> 
> 
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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

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.

Teresa

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-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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