[Bug c++/114290] New: GCC output incorrect output with -O2

[Bug c++/114290] New: GCC output incorrect output with -O2

[jlame646 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114290

            Bug ID: 114290
           Summary: GCC output incorrect output with -O2
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jlame646 at gmail dot com
  Target Milestone: ---

The following program gives wrong output `0` with `-O2` for input `2`. When
`f(1,1)` is commented out(or removed) it produces correct output.
https://godbolt.org/z/3rxah7Grx

```
#include <cstdio>
#include <iostream>
struct Node {
    int x;
};
Node f(int A, int B) {
    if (A < 0) return {0};
    return {A / B + (A % B != 0)};
}
Node g(int C, int D) {
    if (C > 0) return {0};
    return {C / D + (C % D != 0)};
}
int main() {
    int n;

    std::cin >> n;
    f(1, 1); //commenting this line fixes the issue
    Node t = g(-1, n);

    std::cout << t.x;
} 
```

[Bug ipa/114290] GCC output incorrect output with -O2

[i at rvalue dot moe]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114290

rvalue <i at rvalue dot moe> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |i at rvalue dot moe

--- Comment #1 from rvalue <i at rvalue dot moe> ---
I've done some bisect and found the problematic commit was
9f2cfe108f75de49a331ba27f01d509e2c8c1c70 and the problematic patch was
https://gcc.gnu.org/pipermail/gcc-patches/2019-June/524662.html

Tested on target x86_64-unknown-linux-gnu

[Bug ipa/114290] [11/12/13/14 regression] GCC output incorrect output with -O2 since r9-7460-g9f2cfe108f75de

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114290

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sjames at gcc dot gnu.org
            Summary|GCC output incorrect output |[11/12/13/14 regression]
                   |with -O2                    |GCC output incorrect output
                   |                            |with -O2 since
                   |                            |r9-7460-g9f2cfe108f75de
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=90982

--- Comment #2 from Sam James <sjames at gcc dot gnu.org> ---
r9-7460-g9f2cfe108f75de

[Bug ipa/114290] [11/12/13/14 regression] GCC output incorrect output with -O2 since r9-7460-g9f2cfe108f75de

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114290

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu.org

--- Comment #3 from Sam James <sjames at gcc dot gnu.org> ---
(In reply to Sam James from comment #2)
> r9-7460-g9f2cfe108f75de

... i.e. r10-1350-gbaf8d2ecd702d4.

[Bug ipa/114290] [11/12/13/14 regression] GCC output incorrect output with -O2 since r9-7460-g9f2cfe108f75de

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114290

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
   Target Milestone|---                         |11.5

[Bug ipa/114290] [11/12/13/14 regression] GCC output incorrect output with -O2 since r9-7460-g9f2cfe108f75de

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114290

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Yes this is a dup of bug 113907.

What is happening is fnsplit happens and splits off from both f and g:

    return {A / B + (A % B != 0)};
and
    return {C / D + (C % D != 0)};

into a new 2 functions and the range information is still there for A/B (C/D).

Which is fine.
And then ICF comes along and sees this 2 new functions are the same (which they
are) but since the range information is there still from one version of the
function (which in this case the bad one), the wrong result happens.

This is all described in PR 113907 too.

*** This bug has been marked as a duplicate of bug 113907 ***