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From: "socketpair at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/111577] New: -Os gives significantly bigger code than -O0
Date: Mon, 25 Sep 2023 00:33:36 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111577

            Bug ID: 111577
           Summary: -Os gives significantly bigger code than -O0
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: socketpair at gmail dot com
  Target Milestone: ---

Yes, I saw #35806, #41175 and others.

See https://godbolt.org/z/Pnh89Y3Yb

```
#include <string>

using namespace std;

int main(int argc, char* argv[]) {
    if (argv[0] =3D=3D nullptr || argv[1] =3D=3D nullptr) return 0;

    string zxc(argv[0]);
    string qwe(argv[1]);
    string asd(argv[2]);

    zxc =3D qwe + asd;

    return zxc.size();
}
```

-Os -std=3Dc++2b -march=3Dskylake -m64 (615 bytes)

compare size with the smae, but with options:

-O0 -std=3Dc++2b -march=3Dskylake -m64 (409 bytes)

-O0 - is much LESS (!) in bytes. I think it's a bug.=