[Bug target/56866] gcc 4.7.x/gcc-4.8.x with '-O3 -march=bdver2' misscompiles glibc-2.17/crypt/sha512.c

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56866

--- Comment #12 from Marc Glisse <glisse at gcc dot gnu.org> 2013-04-17 21:49:15 UTC ---
(In reply to comment #11)
> If fixing broken gcc's XOP/FMA/FMA4-extensions on AMD-CPUs depends on my
> ability to extract a stand-alone-test from glibc-testsuite then I'm
> realy sorry for not having the necessary skills (as already stated).

Skills can be learned, and the best way is through practice. Ideally someone
with the right combination of knowledge, hardware and free time would look at
it, and you seem to be the closest currently ;-)

> Why not simply using the failing test-cases from gcc-testsuite
> which are all standalone and depends on XOP:

Good idea. I suggest you pick a simple one:

> +FAIL: gcc.target/i386/sse2-mul-1.c execution test

it looks like a list of several tests in a row. If you can first replace the
aborts with printf to determine the first one that fails, then remove
everything after that point, you have already narrowed the issue quite a bit.
Then you can try to simplify what remains. Ideally, you would get a program
small enough that posting the dumps would show the obvious issue. Do make sure
while reducing the program that it still works correctly without the bdver2
option.