[Bug tree-optimization/96349] New: [10/11 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[Bug tree-optimization/96349] New: [10/11 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

            Bug ID: 96349
           Summary: [10/11 Regression] ICE: SSA corruption (Unable to
                    coalesce ssa_names 2 and 3 which are marked as MUST
                    COALESCE.) [in fail_abnormal_edge_coalesce]
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc-11.0.0-alpha20200726 snapshot (g:39ddfef9a5c24acf6412236f52f6716c8e0ebc9e)
ICEs when compiling the following testcase w/ -O3:

void __attribute__ ((returns_twice))
gr (void);

void
ib (void);

void
zg (void);

void
yw (int uz)
{
  gr ();

  for (;;)
    if (uz != 0)
      {
        uz = 0;
        ib ();
      }
    else
      zg ();
}

% gcc-11.0.0 -O3 -c kl7mlgao.c

Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.
uz_2(ab) and  uz_3(ab)
during RTL pass: expand
kl7mlgao.c: In function 'yw':
kl7mlgao.c:11:1: internal compiler error: SSA corruption
   11 | yw (int uz)
      | ^~
0xedadfa fail_abnormal_edge_coalesce
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200726/work/gcc-11-20200726/gcc/tree-ssa-coalesce.c:1003
0xedadfa coalesce_partitions
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200726/work/gcc-11-20200726/gcc/tree-ssa-coalesce.c:1425
0xedadfa coalesce_ssa_name(_var_map*)
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200726/work/gcc-11-20200726/gcc/tree-ssa-coalesce.c:1755
0xe78937 remove_ssa_form
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200726/work/gcc-11-20200726/gcc/tree-outof-ssa.c:1065
0xe78937 rewrite_out_of_ssa(ssaexpand*)
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200726/work/gcc-11-20200726/gcc/tree-outof-ssa.c:1323
0x912f80 execute
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200726/work/gcc-11-20200726/gcc/cfgexpand.c:6377

[Bug tree-optimization/96349] [10/11 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
   Target Milestone|---                         |10.3
   Last reconfirmed|                            |2020-07-28
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed, I'll take a look.

[Bug tree-optimization/96349] [10/11 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fxue at os dot amperecomputing.com
                   |                            |, matz at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
-fno-split-loops fixes it.

t.c:16:8: optimized: loop split on semi-invariant condition at false branch

so it's the new splitting code, still going to give it a quick shot at a fix.

[Bug tree-optimization/96349] [10/11 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

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

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

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r10-4447-g095f78c62157124a, but it's just an inroduction of a
param that exposed it.

[Bug tree-optimization/96349] [10/11 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

--- Comment #4 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:2b2f3867c09c8977268b8ffbd646ac242188b335

commit r11-2402-g2b2f3867c09c8977268b8ffbd646ac242188b335
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Jul 28 09:45:52 2020 +0200

    tree-optimization/96349 - avoid abnormal coalescing issues in loop split

    This avoids splitting a loop when the entry value of a loop PHI is
    involved with abnormal coalescing.

    2020-07-28  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/96349
            * tree-ssa-loop-split.c (stmt_semi_invariant_p_1): When the
            condition runs into a loop PHI with an abnormal entry value give
up.

            * gcc.dg/torture/pr96349.c: New testcase.

[Bug tree-optimization/96349] [10 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
            Summary|[10/11 Regression] ICE: SSA |[10 Regression] ICE: SSA
                   |corruption (Unable to       |corruption (Unable to
                   |coalesce ssa_names 2 and 3  |coalesce ssa_names 2 and 3
                   |which are marked as MUST    |which are marked as MUST
                   |COALESCE.) [in              |COALESCE.) [in
                   |fail_abnormal_edge_coalesce |fail_abnormal_edge_coalesce
                   |]                           |]
      Known to work|                            |11.0

[Bug tree-optimization/96349] [10 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:d1f9b13fd45f9c7ca6c5dd31245705388645f306

commit r10-8744-gd1f9b13fd45f9c7ca6c5dd31245705388645f306
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Jul 28 09:45:52 2020 +0200

    tree-optimization/96349 - avoid abnormal coalescing issues in loop split

    This avoids splitting a loop when the entry value of a loop PHI is
    involved with abnormal coalescing.

    2020-07-28  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/96349
            * tree-ssa-loop-split.c (stmt_semi_invariant_p_1): When the
            condition runs into a loop PHI with an abnormal entry value give
up.

            * gcc.dg/torture/pr96349.c: New testcase.

    (cherry picked from commit 2b2f3867c09c8977268b8ffbd646ac242188b335)

[Bug tree-optimization/96349] [10 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 3 which are marked as MUST COALESCE.) [in fail_abnormal_edge_coalesce]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96349

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
      Known to fail|                            |10.2.0
      Known to work|                            |10.2.1
         Resolution|---                         |FIXED

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.