[Bug c/112986] New: s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[Bug c/112986] New: s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[22s302h0659 at sonline20 dot sen.go.kr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

            Bug ID: 112986
           Summary: s390x gcc O2, O3: Incorrect logic operation in <
                    comparison with the same values
           Product: gcc
           Version: 11.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 22s302h0659 at sonline20 dot sen.go.kr
  Target Milestone: ---

# Environment

- Compiler: s390x-linux-gnu-gcc (64bit)
- Version: gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)
- Platform: Windows 11_5.15.90.1-microsoft-standard-WSL2
- Build Optimization Options: O0, O1, O2, O3

I installed the s390x-linux-gnu toolchain using the 'apt' package manager in
Ubuntu and utilized s390x-linux-gnu-gcc (version 11.4.0) from it.

# build script & excution script

```c
s390x-linux-gnu-gcc -o bug0 bug.c -O0 -fsanitize=undefined 
s390x-linux-gnu-gcc -o bug1 bug.c -O1 -fsanitize=undefined 
s390x-linux-gnu-gcc -o bug2 bug.c -O2 -fsanitize=undefined 
s390x-linux-gnu-gcc -o bug3 bug.c -O3 -fsanitize=undefined 
```

```c
qemu-s390x-static -L /usr/s390x-linux-gnu/ ./bug0
qemu-s390x-static -L /usr/s390x-linux-gnu/ ./bug1
qemu-s390x-static -L /usr/s390x-linux-gnu/ ./bug2
qemu-s390x-static -L /usr/s390x-linux-gnu/ ./bug3
```

This is the build script and the execution script.

# Source Code

```c
#include <stdio.h>

unsigned int g_2 = 1;
signed short g_70 = 1;

int main (int argc, char* argv[])
{
    printf("bug = %d\n", ((signed long long)g_2 < g_70));
    return 0;
}
```

In the s390x architecture, the '<' comparison operation for the same values
returns an incorrect logical value.

# output

```c
Expected output
O0: 0
O1: 0
O2: 0
O3: 0

Actual output
O0: 0
O1: 0
O2: 1
O3: 1
```

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
How was gcc configured (gcc -v should print that)?  Mainly, what -march= and
-mtune= does it default to and is it PIE by default or not?
I certainly don't see anything in the -O1 vs. -O2 assembly difference that
would result in a different result.

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[krebbel at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

Andreas Krebbel <krebbel at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-12-13
                 CC|                            |iii at linux dot ibm.com

--- Comment #2 from Andreas Krebbel <krebbel at gcc dot gnu.org> ---
I can confirm the failure when running the binaries with qemu.

However, the binaries run as expected on real hardware. So it might rather be a
qemu issue.

@Ilya:Ubuntu 22.04 is using qemu 6.2.0. Is this perhaps something you have
fixed already?

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[krebbel at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

--- Comment #3 from Andreas Krebbel <krebbel at gcc dot gnu.org> ---
*** Bug 112996 has been marked as a duplicate of this bug. ***

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[iii at linux dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

--- Comment #4 from Ilya Leoshkevich <iii at linux dot ibm.com> ---
Hi,

Nina fixed this in v8.0.0
(https://gitlab.com/qemu-project/qemu/-/commit/54fce97cfcaf5463ee5f325bc1f1d4adc2772f38).
The fix was backported to v7.2.2
(https://gitlab.com/qemu-project/qemu/-/commit/17b032c6598ea756889f25e8d3e4cd9f2036669b),
but not to v6.

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[22s302h0659 at sonline20 dot sen.go.kr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

--- Comment #5 from 김대영 <22s302h0659 at sonline20 dot sen.go.kr> ---
Thank you for your response. Naturally, I anticipated that the issue might be
with the s390x architecture cross-compiler. However, unexpectedly, I was
unaware that qemu was generating incorrect instructions during the binary
execution process

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[krebbel at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

Andreas Krebbel <krebbel at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #6 from Andreas Krebbel <krebbel at gcc dot gnu.org> ---
No problem. Thanks for testing s390x!
I've requested the qemu fix to be included into Ubuntu 22.04. Closing the BZ
now.

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[krebbel at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

Andreas Krebbel <krebbel at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |shinwogud12 at gmail dot com

--- Comment #7 from Andreas Krebbel <krebbel at gcc dot gnu.org> ---
*** Bug 112665 has been marked as a duplicate of this bug. ***

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

--- Comment #8 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
*** Bug 112998 has been marked as a duplicate of this bug. ***

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

--- Comment #9 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
*** Bug 112329 has been marked as a duplicate of this bug. ***

[Bug target/112986] s390x gcc O2, O3: Incorrect logic operation in < comparison with the same values

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112986

--- Comment #10 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
*** Bug 112112 has been marked as a duplicate of this bug. ***