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From: "konstantin.vladimirov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/114703] New: Missed devirtualization in rather simple case
Date: Fri, 12 Apr 2024 13:57:25 +0000
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X-Bugzilla-Component: ipa
X-Bugzilla-Version: 13.2.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114703

            Bug ID: 114703
           Summary: Missed devirtualization in rather simple case
           Product: gcc
           Version: 13.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: konstantin.vladimirov at gmail dot com
  Target Milestone: ---

See code here:

https://godbolt.org/z/T9Ma7qe3E

struct A {
  virtual int foo() { return 1; }
};

struct B : A {
  int foo() override { return 2; }
  virtual int foo(int i) { return i + 1; }
};

int use(int, int, int);

int main() {
  B *p =3D new B;
#if 0
  A* q =3D p;
#else
  A* q =3D new B;
#endif=20=20
  int result1 =3D p->foo(1);
  int result2 =3D p->foo();
  int result3 =3D q->foo();
  use(result1, result2, result3);
}

clang devirtualizes just fine, gcc lacks this one.

Interesting that if you flip preprocessor switch, everything works with gcc
either.=