[Bug debug/94329] New: gcc-9: error: use_only.f90: ‘-fcompare-debug’ failure (length)

[Bug debug/94329] New: gcc-9: error: use_only.f90: ‘-fcompare-debug’ failure (length)

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

            Bug ID: 94329
           Summary: gcc-9: error: use_only.f90: ‘-fcompare-debug’ failure
                    (length)
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---

Fails since GCC 4.9.0:

$ cat use_only.f90
SUBROUTINE r_to_s1b ( s, hinv )
REAL hinv(:,:)     
DO I=1,3
DO J=1,3
S = hinv(i,j)
END DO
END DO
END

$ gcc -Werror -fcompare-debug -O1 -fno-tree-loop-optimize -fwrapv -c
use_only.f90
gcc: error: use_only.f90: ‘-fcompare-debug’ failure (length)

[Bug debug/94329] gcc-9: error: use_only.f90: ‘-fcompare-debug’ failure (length)

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
   Last reconfirmed|                            |2020-03-25
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

[Bug debug/94329] [8/9/10 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|gcc-9: error: use_only.f90: |[8/9/10 Regression] error:
                   |‘-fcompare-debug’ failure   |use_only.f90:
                   |(length)                    |‘-fcompare-debug’ failure
                   |                            |(length)
   Target Milestone|---                         |8.5

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with my r0-126015-g5e40da4f64effc4104fd5d787c37da9cd04c06fe
Will have a look.

[Bug tree-optimization/94329] [8/9/10 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
          Component|debug                       |tree-optimization

[Bug tree-optimization/94329] [8/9/10 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

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

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

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 48131
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48131&action=edit
gcc10-pr94329.patch

Untested fix.

[Bug tree-optimization/94329] [8/9/10 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

--- Comment #3 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:679becf175c5d7f6b323cd3af0a09c6039b4123d

commit r10-7437-g679becf175c5d7f6b323cd3af0a09c6039b4123d
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Mar 28 10:21:52 2020 +0100

    reassoc: Fix -fcompare-debug bug in reassociate_bb [PR94329]

    The following testcase FAILs with -fcompare-debug, because reassociate_bb
    mishandles the case when the last stmt in a bb has zero uses.  In that case
    reassoc_remove_stmt (like gsi_remove) moves the iterator to the next stmt,
    i.e. gsi_end_p is true, which means the code sets the iterator back to
    gsi_last_bb.  The problem is that the for loop does gsi_prev on that before
    handling the next statement, which means the former penultimate stmt, now
    last one, is not processed by reassociate_bb.
    Now, with -g, if there is at least one debug stmt at the end of the bb,
    reassoc_remove_stmt moves the iterator to that following debug stmt and we
    just do gsi_prev and continue with the former penultimate non-debug stmt,
    now last non-debug stmt.

    The following patch fixes that by not doing the gsi_prev in this case;
there
    are too many continue; cases, so I didn't want to copy over the gsi_prev to
    all of them, so this patch uses a bool for that instead.  The second
    gsi_end_p check isn't needed anymore, because when we don't do the
    undesirable gsi_prev after gsi = gsi_last_bb, the loop !gsi_end_p (gsi)
    condition will catch the removal of the very last stmt from a bb.

    2020-03-28  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/94329
            * tree-ssa-reassoc.c (reassociate_bb): When calling
reassoc_remove_stmt
            on the last stmt in a bb, make sure gsi_prev isn't done immediately
            after gsi_last_bb.

            * gfortran.dg/pr94329.f90: New test.

[Bug tree-optimization/94329] [8/9 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[8/9/10 Regression] error:  |[8/9 Regression] error:
                   |use_only.f90:               |use_only.f90:
                   |‘-fcompare-debug’ failure   |‘-fcompare-debug’ failure
                   |(length)                    |(length)

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed on the trunk so far.

[Bug tree-optimization/94329] [8/9 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:aa9c08ef97f4df1ebb1fc8d72f2e7f9f8c1045c2

commit r9-8472-gaa9c08ef97f4df1ebb1fc8d72f2e7f9f8c1045c2
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Mar 28 10:21:52 2020 +0100

    reassoc: Fix -fcompare-debug bug in reassociate_bb [PR94329]

    The following testcase FAILs with -fcompare-debug, because reassociate_bb
    mishandles the case when the last stmt in a bb has zero uses.  In that case
    reassoc_remove_stmt (like gsi_remove) moves the iterator to the next stmt,
    i.e. gsi_end_p is true, which means the code sets the iterator back to
    gsi_last_bb.  The problem is that the for loop does gsi_prev on that before
    handling the next statement, which means the former penultimate stmt, now
    last one, is not processed by reassociate_bb.
    Now, with -g, if there is at least one debug stmt at the end of the bb,
    reassoc_remove_stmt moves the iterator to that following debug stmt and we
    just do gsi_prev and continue with the former penultimate non-debug stmt,
    now last non-debug stmt.

    The following patch fixes that by not doing the gsi_prev in this case;
there
    are too many continue; cases, so I didn't want to copy over the gsi_prev to
    all of them, so this patch uses a bool for that instead.  The second
    gsi_end_p check isn't needed anymore, because when we don't do the
    undesirable gsi_prev after gsi = gsi_last_bb, the loop !gsi_end_p (gsi)
    condition will catch the removal of the very last stmt from a bb.

    2020-03-28  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/94329
            * tree-ssa-reassoc.c (reassociate_bb): When calling
reassoc_remove_stmt
            on the last stmt in a bb, make sure gsi_prev isn't done immediately
            after gsi_last_bb.

            * gfortran.dg/pr94329.f90: New test.

[Bug tree-optimization/94329] [8 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[8/9 Regression] error:     |[8 Regression] error:
                   |use_only.f90:               |use_only.f90:
                   |‘-fcompare-debug’ failure   |‘-fcompare-debug’ failure
                   |(length)                    |(length)

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 9.4+ too.

[Bug tree-optimization/94329] [8 Regression] error: use_only.f90: ‘-fcompare-debug’ failure (length)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94329

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

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

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 8.5 in r8-10476-gc53f6b6c38fd3c61257c9f311ca9dc21135223b4.