1480005 - Automatically use llvm-ar, llvm-ranlib and llvm-nm when building with llvm-based LTO

Status: RESOLVED FIXED

(Firefox Build System :: General, enhancement)

Comment 1

[Mike Hommey [:glandium]]

It'd be nice to have longer term, but I'll just hack up mozconfigs for my needs for now.

Fixing this properly will require moving the detection to moz.configure, and detect and handle llvm toolchains generically (e.g. looking for llvm-$tool-$version where $version matches that of clang-$version, if the compiler is not the short "clang").

Comment 4

[Simon Giesecke [:sg] [he/him]]

What exactly must be added to the mozconfig to work around this?

Comment 5

[Mike Hommey [:glandium]]

AR=llvm-ar
RANLIB=llvm-ranlib
NM=llvm-nm

You may need the full paths, and you may need to export the variables.

Comment 6

[Mike Hommey [:glandium]]

Attachment: Bug 1480005 - Always use llvm-lib when targetting Windows.

The linker is always lld-link, as we don't support MSVC anymore, so the
fallback to "lib" is never used.

Comment 7

[Mike Hommey [:glandium]]

Attachment: Bug 1480005 - Look for llvm-ar for AR when compiling with clang.

And stop setting AR to llvm-ar in mozconfigs.

Comment 8

[Mike Hommey [:glandium]]

Attachment: Bug 1480005 - Remove check for RANLIB.

It hasn't been used since bug 569597 and bug 1295937.

Comment 9

[Mike Hommey [:glandium]]

Attachment: Bug 1480005 - Move NM to python configure.

There is only one place where it's used:
config/check_vanilla_allocations.py, which is only executed from
js/src/build/Makefile.in on the condition that the build is targeting
Linux and not LTO. But the LTO test is actually outdated, because we
don't build with -flto, but -flto=thin, so the exclusion doesn't
work anymore.

There is however no AC_CHECK_PROG, and we currently rely on NM to be
given, or fall back to "nm", which works in most cases, except LTO with
clang. It works on CI because in LTO builds we explicitly set NM to
llvm-nm (which can output symbols from LLVM bitcode objects), but we
could also do that automatically.

So we add a full detection of nm/llvm-nm to python configure, and limit
it to Linux, since we only ever use it there.

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/feeb84104920
Always use llvm-lib when targetting Windows. r=firefox-build-system-reviewers,dmajor
https://hg.mozilla.org/integration/autoland/rev/3f9924127a79
Look for llvm-ar for AR when compiling with clang. r=firefox-build-system-reviewers,nalexander
https://hg.mozilla.org/integration/autoland/rev/300c5c7f61b7
Remove check for RANLIB. r=firefox-build-system-reviewers,nalexander
https://hg.mozilla.org/integration/autoland/rev/061ad2d4f4e3
Move NM to python configure. r=firefox-build-system-reviewers,nalexander

Comment 11

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/feeb84104920
https://hg.mozilla.org/mozilla-central/rev/3f9924127a79
https://hg.mozilla.org/mozilla-central/rev/300c5c7f61b7
https://hg.mozilla.org/mozilla-central/rev/061ad2d4f4e3