[Bug tree-optimization/104281] New: wrong code at -O3

[Bug tree-optimization/104281] New: wrong code at -O3

[zhendong.su at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104281

            Bug ID: 104281
           Summary: wrong code at -O3
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhendong.su at inf dot ethz.ch
  Target Milestone: ---

It is a recent regression and likely related to PR 104280 and PR 104279, but it
only reproduces at -O3. 

[537] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/12.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--prefix=/local/suz-local/software/local/gcc-trunk --enable-languages=c,c++
--disable-werror --enable-multilib --with-system-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.1 20220129 (experimental) [master r12-6930-gf6f2d6cfec1] (GCC) 
[538] % 
[538] % gcctk -O2 small.c; ./a.out
[539] % 
[539] % gcctk -O3 small.c
[540] % timeout -s 9 5 ./a.out
Killed
[541] % 
[541] % cat small.c
unsigned a = 1;
int b, c = 2;
long d;
int main() {
  while (1) {
    int m = a;
  L:
    a = ~(-(m || b & d));
    b = ((1 ^ a) / c);
    if (b)
      goto L;
    break;
  }
  return 0;
}

[Bug tree-optimization/104281] wrong code at -O3

[zhendong.su at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104281

--- Comment #1 from Zhendong Su <zhendong.su at inf dot ethz.ch> ---
Compiler Explorer: https://godbolt.org/z/ovnrnEGj6

[Bug tree-optimization/104281] [12 Regression] wrong code at -O3

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104281

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0
            Version|unknown                     |12.0

[Bug tree-optimization/104281] [12 Regression] wrong code at -O3

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104281

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:a1544878966020d1f7a640b35d1f7a5f0e055624

commit r12-6931-ga1544878966020d1f7a640b35d1f7a5f0e055624
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Jan 29 17:54:43 2022 +0100

    match.pd: Fix up 1 / X for unsigned X optimization [PR104280]

    On Fri, Jan 28, 2022 at 11:38:23AM -0700, Jeff Law wrote:
    > Thanks.  Given the original submission and most of the review work was
done
    > prior to stage3 closing, I went ahead and installed this on the trunk.

    Unfortunately this breaks quite a lot of things.
    The main problem is that GIMPLE allows EQ_EXPR etc. only with BOOLEAN_TYPE
    or with TYPE_PRECISION == 1 integral type (or vector boolean).
    Violating this causes verification failures in tree-cfg.cc in some cases,
    in other cases wrong-code issues because before it is verified we e.g.
    transform
    1U / x
    into
    x == 1U
    and later into
    x (because we assume that == type must be one of the above cases and
    when it is the same type as the type of the first operand, for boolean-ish
    cases it should be equivalent).

    Fixed by changing that
    (eq @1 { build_one_cst (type); })
    into
    (convert (eq:boolean_type_node @1 { build_one_cst (type); }))
    Note, I'm not 100% sure if :boolean_type_node is required in that case,
    I see some spots in match.pd that look exactly like this, while there is
    e.g. (convert (le ...)) that supposedly does the right thing too.
    The signed integer 1/X case doesn't need changes changes, for
    (cond (le ...) ...)
    le gets correctly boolean_type_node and cond should use type.
    I've also reformatted it, some lines were too long, match.pd uses
    indentation by 1 column instead of 2 etc.

    2022-01-29  Jakub Jelinek  <jakub@redhat.com>
                Andrew Pinski  <apinski@marvell.com>

            PR tree-optimization/104279
            PR tree-optimization/104280
            PR tree-optimization/104281
            * match.pd (1 / X -> X == 1 for unsigned X): Build eq with
            boolean_type_node and convert to type.  Formatting fixes.

            * gcc.dg/torture/pr104279.c: New test.
            * gcc.dg/torture/pr104280.c: New test.
            * gcc.dg/torture/pr104281.c: New test.

[Bug tree-optimization/104281] [12 Regression] wrong code at -O3

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104281

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.