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From: "jamborm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/107640] New: IPA-CP drops known values passed by reference
 when the reference is to a global variable
Date: Fri, 11 Nov 2022 16:05:02 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: ipa
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jamborm at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107640

            Bug ID: 107640
           Summary: IPA-CP drops known values passed by reference when the
                    reference is to a global variable
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

Combining IPA-CP of (scalar) parameter values and of values passed by refer=
ence
(aggregate values) does not work in the same function parameter, we drop the
aggregate values on the floor.

The following aborts when compiled with -O2 -DFAIL

struct S
{
  int a, b, c;
};

volatile int gi;

void __attribute__((noipa))
consume_s (struct S *p)
{
  gi =3D p->a;
}

static void __attribute__((noinline))
foo (struct S *p)
{
  if (!__builtin_constant_p (p->b))
    __builtin_abort ();
  consume_s (p);
}

static struct S __attribute((used)) gs;

int main (int argc, char *argv[])
{
  struct S *p;

#ifdef FAIL
  p =3D &gs;
#else
  struct S s;
  p =3D &s;
#endif

  p->a =3D 10;
  p->b =3D 20;
  foo (p);
  return 0;
}=