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From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/95558] Invalid IPA optimizations based on weak definition
Date: Sat, 06 Jun 2020 08:01:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95558

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amonakov at gcc dot gnu.or=
g,
                   |                            |marxin at gcc dot gnu.org
          Component|middle-end                  |ipa
           Keywords|                            |wrong-code

--- Comment #1 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
All functions are incorrectly discovered to be pure, and then the loop that
only makes calls to non-weak pure functions is eliminated.

Minimal testcase for the root issue, wrong warning with -O2
-Wsuggest-attribute=3Dpure:

static void dummy(){}

void weak() __attribute__((weak,alias("dummy")));

int foo()
{
    weak();
    return 0;
}=