[Bug tree-optimization/95248] New: GCC produces incorrect code with -O3 for loops

[Bug tree-optimization/95248] New: GCC produces incorrect code with -O3 for loops

[vsevolod.livinskij at frtk dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95248

            Bug ID: 95248
           Summary: GCC produces incorrect code with -O3 for loops
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vsevolod.livinskij at frtk dot ru
  Target Milestone: ---

GCC produces incorrect code with -O3 for loops

Error:
>$ gcc -O0 driver.cpp func.cpp && ./a.out
1
>$ gcc -O3 driver.cpp func.cpp && ./a.out
0

Reproducer:
>$ cat driver.cpp
#include <stdio.h>

int var_2 = -2013646301;
int var_3 = -1126567434;
unsigned int var_12 = 1;
unsigned int var_19;
unsigned int arr_25 [24] [21] [15] [17] [15] ;

void test();

int main() {
    test();
    printf("%u\n", var_19);
}

>$ cat func.cpp
extern int var_2;
extern int var_3;
extern unsigned int var_12;
extern unsigned int var_19;
extern unsigned int arr_25 [24] [21] [15] [17] [15] ;

void test() {
  for (int a = 0; a < 3; a = 42)
    for (int b = 0; b < 20; b++)
      for (int c = 0; c < 4; c = 4)
        for (int d = 0; d < 6; d += 4)
          for (int e = 0; e < 4; e += 2) {
            arr_25[a][b][c][d][e] = var_2 || var_3;
            var_19 = var_12;
          }
}

GCC version:
gcc version 11.0.0 (ed63c387aa0bc1846082524455a6ff1fcec40f9d)

[Bug tree-optimization/95248] [11 Regression] GCC produces incorrect code with -O3 for loops since r11-272-gb6ff3ddecfa93d53

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95248

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marxin at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org
      Known to fail|                            |11.0
            Summary|GCC produces incorrect code |[11 Regression] GCC
                   |with -O3 for loops          |produces incorrect code
                   |                            |with -O3 for loops since
                   |                            |r11-272-gb6ff3ddecfa93d53
     Ever confirmed|0                           |1
      Known to work|                            |10.1.0
   Last reconfirmed|                            |2020-05-21
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Confirmed, started with r11-272-gb6ff3ddecfa93d53.

[Bug tree-optimization/95248] [11 Regression] GCC produces incorrect code with -O3 for loops since r11-272-gb6ff3ddecfa93d53

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95248

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
   Target Milestone|---                         |11.0
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine.

[Bug tree-optimization/95248] [11 Regression] GCC produces incorrect code with -O3 for loops since r11-272-gb6ff3ddecfa93d53

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95248

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:b6ed2e2bca54d1d290f553549d28b0c60a0f240f

commit r11-563-gb6ed2e2bca54d1d290f553549d28b0c60a0f240f
Author: Richard Biener <rguenther@suse.de>
Date:   Fri May 22 08:48:04 2020 +0200

    tree-optimization/95248 - fix oversight in SM rewrite

    This fixes a leftover early out in determining the sequence of stores
    to materialize.

    2020-05-22  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/95248
            * tree-ssa-loop-im.c (sm_seq_valid_bb): Remove bogus early out.

            * gcc.dg/torture/pr95248.c: New testcase.

[Bug tree-optimization/95248] [11 Regression] GCC produces incorrect code with -O3 for loops since r11-272-gb6ff3ddecfa93d53

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95248

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.