[Bug c/107257] New: Wrong code at -O2 on x86

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* [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu
@ 2022-10-14  8:32 shaohua.li at inf dot ethz.ch
  2022-10-14  9:27 ` [Bug c/107257] " rguenth at gcc dot gnu.org
                   ` (9 more replies)
  0 siblings, 10 replies; 11+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2022-10-14  8:32 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

            Bug ID: 107257
           Summary: Wrong code at -O2 on x86_64-linux-gnu
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
  Target Milestone: ---

% gcc-tk -v
Using built-in specs.
COLLECT_GCC=gcc-tk
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-9f0d4adabe2035886a1aa8d2ca990a90de000613/libexec/gcc/x86_64-pc-linux-gnu/13.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --disable-bootstrap
--enable-languages=c,c++
--prefix=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-9f0d4adabe2035886a1aa8d2ca990a90de000613
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.0.0 20221013 (experimental) (GCC)
%
% gcc-tk -w -O0 a.c && ./a.out
2
% gcc-tk -w -O2 a.c && ./a.out
0
%
% cat a.c
l;
m;
static signed char n();
s() { n(); }
signed char n(u) {
  for (; u <= 2; u++) {
    l = 2;
    for (; l ; l--) {
      m = 2;
      for (; m; m--)
        if (u)
          break;
    }
  }
}
main() {
  s(2);
  printf("%d\n", m);
}
%

Compiler explorer: https://godbolt.org/z/z5Mhxaz9E

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug c/107257] Wrong code at -O2 on x86_64-linux-gnu
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
@ 2022-10-14  9:27 ` rguenth at gcc dot gnu.org
  2022-10-14 10:00 ` marxin at gcc dot gnu.org
                   ` (8 subsequent siblings)
  9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-10-14  9:27 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
      Known to fail|                            |10.4.0
   Last reconfirmed|                            |2022-10-14
           Keywords|                            |needs-bisection
     Ever confirmed|0                           |1

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug c/107257] Wrong code at -O2 on x86_64-linux-gnu
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
  2022-10-14  9:27 ` [Bug c/107257] " rguenth at gcc dot gnu.org
@ 2022-10-14 10:00 ` marxin at gcc dot gnu.org
  2022-10-14 10:03 ` marxin at gcc dot gnu.org
                   ` (7 subsequent siblings)
  9 siblings, 0 replies; 11+ messages in thread
From: marxin at gcc dot gnu.org @ 2022-10-14 10:00 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Martin Liška <marxin at gcc dot gnu.org> changed:

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

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
A few notes about reduction: please don't over-reduce the testcase (by removing
of the variable and function types). Moreover, if possible, please use C-Vise
that does not rename identifiers by default.

Anyway, thanks for the test-case!

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug c/107257] Wrong code at -O2 on x86_64-linux-gnu
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
  2022-10-14  9:27 ` [Bug c/107257] " rguenth at gcc dot gnu.org
  2022-10-14 10:00 ` marxin at gcc dot gnu.org
@ 2022-10-14 10:03 ` marxin at gcc dot gnu.org
  2022-10-14 12:52 ` rguenth at gcc dot gnu.org
                   ` (6 subsequent siblings)
  9 siblings, 0 replies; 11+ messages in thread
From: marxin at gcc dot gnu.org @ 2022-10-14 10:03 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
...
> static signed char n();
> s() { n(); }

This seems fishy as you are calling 'n' w/o an argument.

> signed char n(u) {
>   for (; u <= 2; u++) {
...

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug c/107257] Wrong code at -O2 on x86_64-linux-gnu
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
                   ` (2 preceding siblings ...)
  2022-10-14 10:03 ` marxin at gcc dot gnu.org
@ 2022-10-14 12:52 ` rguenth at gcc dot gnu.org
  2022-10-17 10:27 ` shaohua.li at inf dot ethz.ch
                   ` (5 subsequent siblings)
  9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-10-14 12:52 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Richard Biener <rguenth at gcc dot gnu.org> changed:

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

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Indeed, the bogus expectation is eventually that s(2) gets the argument
register set up for the call to n(), but obviously that's misguided.

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug c/107257] Wrong code at -O2 on x86_64-linux-gnu
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
                   ` (3 preceding siblings ...)
  2022-10-14 12:52 ` rguenth at gcc dot gnu.org
@ 2022-10-17 10:27 ` shaohua.li at inf dot ethz.ch
  2022-10-17 11:05 ` [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47 marxin at gcc dot gnu.org
                   ` (4 subsequent siblings)
  9 siblings, 0 replies; 11+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2022-10-17 10:27 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Li Shaohua <shaohua.li at inf dot ethz.ch> changed:

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

--- Comment #4 from Li Shaohua <shaohua.li at inf dot ethz.ch> ---
Hi,
 Sorry for my previous over-reduced test case. Here is a well-formed reduction:
```
void printf();
int a, b, c;
int d[3];
int e(int f, int g, int k, int l, int m, int n) {
  int h = 4 * f + 2 * (g + l + n) + k + m, j = h >> 4;
  return j;
}
void o(int f) {
  int i = 0;
  for (; i < 3; i++)
    d[i] = 4279432140;
  for (; - 72 + f - -72 <= 2; f++) {
    a = 2;
    for (; a >= 0; a--) {
      b = 2;
      for (; b >= 0; b--) {
        int p = !(d[b] > 0 != e(10, 29, 42, 74, 89, -68) + f - 15);
        if (p)
          break;
      }
      if (f)
        break;
    }
  }
}
void q() {
  int i = 0;
  o(0);
  if (c)
    for (; i < 1;)
      for (; i < 1; i++)
        ;
}
int main() {
  q();
  printf("%d\n", b);
}


```

Compiler explorer: https://godbolt.org/z/bjjW5q17r

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
                   ` (4 preceding siblings ...)
  2022-10-17 10:27 ` shaohua.li at inf dot ethz.ch
@ 2022-10-17 11:05 ` marxin at gcc dot gnu.org
  2022-10-17 11:09 ` rguenth at gcc dot gnu.org
                   ` (3 subsequent siblings)
  9 siblings, 0 replies; 11+ messages in thread
From: marxin at gcc dot gnu.org @ 2022-10-17 11:05 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|needs-bisection             |
          Component|c                           |target
               Host|                            |x86_64-linux-gnu
            Summary|Wrong code at -O2 on        |[13 Regression] Wrong code
                   |x86_64-linux-gnu            |at -O2 on x86_64-linux-gnu
                   |                            |since
                   |                            |r13-857-gf1652e3343b1ec47
   Target Milestone|---                         |13.0
           Priority|P3                          |P1
                 CC|                            |sayle at gcc dot gnu.org

--- Comment #5 from Martin Liška <marxin at gcc dot gnu.org> ---
Thanks, a bit modified:

cat pr107257.c
int a, b, c;
int d[3];
int e(int f, int g, int k, int l, int m, int n) {
  int h = 4 * f + 2 * (g + l + n) + k + m, j = h >> 4;
  return j;
}
void o(int f) {
  int i = 0;
  for (; i < 3; i++)
    d[i] = 4279432140;
  for (; - 72 + f - -72 <= 2; f++) {
    a = 2;
    for (; a >= 0; a--) {
      b = 2;
      for (; b >= 0; b--) {
        int p = !(d[b] > 0 != e(10, 29, 42, 74, 89, -68) + f - 15);
        if (p)
          break;
      }
      if (f)
        break;
    }
  }
}
void q() {
  int i = 0;
  o(0);
  if (c)
    for (; i < 1;)
      for (; i < 1; i++)
        ;
}
int main() {
  q();
  __builtin_printf("%d\n", b);
  if (b != -1)
    __builtin_abort ();
}

Started with r13-857-gf1652e3343b1ec47.

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
                   ` (5 preceding siblings ...)
  2022-10-17 11:05 ` [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47 marxin at gcc dot gnu.org
@ 2022-10-17 11:09 ` rguenth at gcc dot gnu.org
  2022-10-20 17:25 ` pinskia at gcc dot gnu.org
                   ` (2 subsequent siblings)
  9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-10-17 11:09 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
With -fno-tree-slp-vectorize the failure goes away.  diff in optimized:

 __attribute__((noipa, noinline, noclone, no_icf))
 void q ()
 {
-  <bb 2> [local count: 1073742492]:
-  MEM <unsigned long> [(int *)&d] = 18380021091030725580;
+  int b_lsm.15;
+  int f;
+  _Bool _5;
+
+  <bb 2> [local count: 1073741824]:
+  MEM <vector(2) int> [(int *)&d] = { -15535156, -15535156 };
   d[2] = -15535156;
+
+  <bb 3> [local count: 8687551919]:
+  # f_30 = PHI <f_25(5), 0(2)>
+  if (f_30 == 0)
+    goto <bb 5>; [1.43%]
+  else
+    goto <bb 4>; [98.57%]
+
+  <bb 4> [local count: 4698759900]:
+  if (f_30 != 2)
+    goto <bb 5>; [79.66%]
+  else
+    goto <bb 6>; [20.34%]
+
+  <bb 5> [local count: 7731921808]:
+  # f_25 = PHI <2(4), 1(3)>
+  goto <bb 3>; [100.00%]
+
+  <bb 6> [local count: 1073742492]:
   a = 2;
-  b = -1;
+  _5 = f_30 == 0;
+  b_lsm.15_33 = _5 ? 2 : -1;
+  b = b_lsm.15_33;
   return;

 }

both variants look OK so instead RTL expansion looks fishy(?)

;; b = b_lsm.15_33;

(insn 28 26 29 (parallel [
            (set (reg:CCC 17 flags)
                (ne:CCC (reg/v:SI 83 [ f ])
                    (const_int 0 [0])))
            (set (reg:SI 89)
                (neg:SI (reg/v:SI 83 [ f ])))
        ]) -1
     (nil))

(insn 29 28 30 (parallel [
            (set (reg:SI 90)
                (neg:SI (ltu:SI (reg:CCC 17 flags)
                        (const_int 0 [0]))))
            (clobber (reg:CC 17 flags))
        ]) -1
     (nil))

(insn 30 29 31 (parallel [
            (set (reg:SI 90)
                (ior:SI (reg:SI 90)
                    (const_int 2 [0x2])))
            (clobber (reg:CC 17 flags))
        ]) -1
     (nil))

(insn 31 30 32 (set (reg:SI 88 [ b_lsm.15 ])
        (reg:SI 90)) -1
     (nil))

(insn 32 31 0 (set (mem/c:SI (symbol_ref:DI ("b") [flags 0x2]  <var_decl
0x7ffff6526d80 b>) [1 b+0 S4 A32])
        (reg:SI 88 [ b_lsm.15 ])) -1
     (nil))

and we eventually optimize this to

q:
.LFB2:
        .cfi_startproc
        movq    .LC0(%rip), %rax
        movl    $-15535156, d+8(%rip)
        movl    $2, a(%rip)
        movq    %rax, d(%rip)
        movl    $2, b(%rip)
        ret

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
                   ` (6 preceding siblings ...)
  2022-10-17 11:09 ` rguenth at gcc dot gnu.org
@ 2022-10-20 17:25 ` pinskia at gcc dot gnu.org
  2023-07-27  8:01 ` shaohua.li at inf dot ethz.ch
  2023-07-27 14:47 ` shaohua.li at inf dot ethz.ch
  9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-10-20 17:25 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

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

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

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---

            (set (reg:CCC 17 flags)
                (ne:CCC (reg/v:SI 83 [ f ])
                    (const_int 0 [0])))

Yes this is broken ...

Which means this is a dup of bug 107172.

*** This bug has been marked as a duplicate of bug 107172 ***

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
                   ` (7 preceding siblings ...)
  2022-10-20 17:25 ` pinskia at gcc dot gnu.org
@ 2023-07-27  8:01 ` shaohua.li at inf dot ethz.ch
  2023-07-27 14:47 ` shaohua.li at inf dot ethz.ch
  9 siblings, 0 replies; 11+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2023-07-27  8:01 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Shaohua Li <shaohua.li at inf dot ethz.ch> changed:

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

--- Comment #8 from Shaohua Li <shaohua.li at inf dot ethz.ch> ---
This bug is not a dup of https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107172,
which has been fixed but the trunk is still faulty on this test case.

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47
  2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
                   ` (8 preceding siblings ...)
  2023-07-27  8:01 ` shaohua.li at inf dot ethz.ch
@ 2023-07-27 14:47 ` shaohua.li at inf dot ethz.ch
  9 siblings, 0 replies; 11+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2023-07-27 14:47 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107257

Shaohua Li <shaohua.li at inf dot ethz.ch> changed:

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

--- Comment #9 from Shaohua Li <shaohua.li at inf dot ethz.ch> ---
Sorry, this is indeed a dup.

*** This bug has been marked as a duplicate of bug 107172 ***

^ permalink raw reply	[flat|nested] 11+ messages in thread

end of thread, other threads:[~2023-07-27 14:47 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-10-14  8:32 [Bug c/107257] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
2022-10-14  9:27 ` [Bug c/107257] " rguenth at gcc dot gnu.org
2022-10-14 10:00 ` marxin at gcc dot gnu.org
2022-10-14 10:03 ` marxin at gcc dot gnu.org
2022-10-14 12:52 ` rguenth at gcc dot gnu.org
2022-10-17 10:27 ` shaohua.li at inf dot ethz.ch
2022-10-17 11:05 ` [Bug target/107257] [13 Regression] Wrong code at -O2 on x86_64-linux-gnu since r13-857-gf1652e3343b1ec47 marxin at gcc dot gnu.org
2022-10-17 11:09 ` rguenth at gcc dot gnu.org
2022-10-20 17:25 ` pinskia at gcc dot gnu.org
2023-07-27  8:01 ` shaohua.li at inf dot ethz.ch
2023-07-27 14:47 ` shaohua.li at inf dot ethz.ch

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