[Bug target/81763] Issues with BMI on 32bit x86 apps on GCC 7.1+

["amonakov at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81763

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

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                 CC|                            |amonakov at gcc dot gnu.org

--- Comment #8 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
Mike, you can start by preparing two build trees, one with faulty mesa compiled
with -march=native, the other with working-fine mesa compiled with
-march=native -mno-bmi. You should be able to collect:

- .o files from each tree, and
- link commands from build logs

and be able to re-link mesa libraries by hand and verify they still exhibit the
same behavior (one fails, the other doesn't).

>From there you can proceed by building "hybrid" libraries by taking a set of
good .o files and a complementary set of bad .o files. This will allow you to
find a single .o file that makes the library behave wrongly. More explanation
and a helper script for bisecting is available at
https://gcc.gnu.org/wiki/Analysing_Large_Testcases

At that point please share your status (once you're down to one file there's no
generic recipe, you'd have to get creative).