[Bug tree-optimization/109721] New: [14 Regression] predcom-2 fails after recent changes

[Bug tree-optimization/109721] New: [14 Regression] predcom-2 fails after recent changes

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109721

            Bug ID: 109721
           Summary: [14 Regression] predcom-2 fails after recent changes
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: law at gcc dot gnu.org
  Target Milestone: ---

arc-elf target.

FAIL: gcc.dg/tree-ssa/predcom-2.c scan-tree-dump-times pcom "Unrolling 2
times." 2

Bisection points to:

f385252b2336a4a57a30fddf82e558c73bcc85cc is the first bad commit
commit f385252b2336a4a57a30fddf82e558c73bcc85cc
Author: Richard Biener <rguenther@suse.de>
Date:   Tue May 2 10:34:48 2023 +0200

    tree-optimization/109672 - properly check emulated plus during vect

    The following refactors the check for emulated vector support for
    the cases of plus, minus and negate.  In the PR we end up with
    a SImode plus, supported by the target but emulated and in this
    context fail to verify we are dealing with exactly word_mode.

            PR tree-optimization/109672
            * tree-vect-stmts.cc (vectorizable_operation): For plus,
            minus and negate always check the vector mode is word mode.

It should be visible with a cross-compiler.  No need for a full toolchain
stack.

[Bug tree-optimization/109721] [14 Regression] predcom-2 started to fail on arc-elf after r14-391

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109721

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[14 Regression] predcom-2   |[14 Regression] predcom-2
                   |fails after recent changes  |started to fail on arc-elf
                   |                            |after r14-391
           Keywords|                            |testsuite-fail
   Target Milestone|---                         |14.0

[Bug tree-optimization/109721] [14 Regression] predcom-2 started to fail on arc-elf after r14-391

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109721

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The testcase might need now -fno-tree-vectorizer .

[Bug tree-optimization/109721] [14 Regression] predcom-2 started to fail on arc-elf after r14-391

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109721

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-05-04
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
There's dependences so I doubt anything is vectorized here.  I'll check.

[Bug tree-optimization/109721] [14 Regression] predcom-2 started to fail on arc-elf after r14-391

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109721

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Huh, we indeed vectorize count_averages ().  But I have no idea how the
offending rev should have changed this ...

Ah.  Before we had

gcc.dg/tree-ssa/predcom-2.c:27:55: missed:   not vectorized: relevant stmt not
supported: _9 = _8 & 65535;

but now we let this slip through with

gcc.dg/tree-ssa/predcom-2.c:26:17: note: 
  proceeding using word mode.

but we do not actually use word_mode.  Later veclower decomposes the
bitwise vector and:

-  vect__9.38_33 = vect__8.37_31 & { 65535, 65535 };
+  _26 = BIT_FIELD_REF <vect__8.37_31, 32, 0>;
+  _19 = _26 & 65535;
+  _23 = BIT_FIELD_REF <vect__8.37_31, 32, 32>;
+  _10 = _23 & 65535;
+  vect__9.38_33 = {_19, _10};


Btw, when writing the patch I noticed we let SImode AND through when
target_support_p even though it isn't word_mode and I didn't want to
change that but had to catch the case where SImode PLUS is supported
(well, obviously...) but emulated vectors rely on it being word_mode.

I'm going to amend this more.

But maybe this arch is also missing bit operation vector support for
some unknown reason.

[Bug tree-optimization/109721] [14 Regression] predcom-2 started to fail on arc-elf after r14-391

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109721

--- 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:82cfd93ae81a5687bf2a1b12d964c630e95517a7

commit r14-474-g82cfd93ae81a5687bf2a1b12d964c630e95517a7
Author: Richard Biener <rguenther@suse.de>
Date:   Thu May 4 10:06:47 2023 +0200

    tree-optimization/109721 - emulated vectors

    When fixing PR109672 I noticed we let SImode AND through when
    target_support_p even though it isn't word_mode and I didn't want to
    change that but had to catch the case where SImode PLUS is supported
    but emulated vectors rely on it being word_mode.  The following
    makes sure to preserve the word_mode check when !target_support_p
    to avoid excessive lowering later even for bit operations.

            PR tree-optimization/109721
            * tree-vect-stmts.cc (vectorizable_operation): Make sure
            to test word_mode for all !target_support_p operations.

[Bug tree-optimization/109721] [14 Regression] predcom-2 started to fail on arc-elf after r14-391

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109721

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

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

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Should be fixed.