[Bug other/115282] New: 15 regression] gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c fails after r15-812-gc71886f2ca2e46

[Bug other/115282] New: 15 regression] gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c fails after r15-812-gc71886f2ca2e46

[seurer at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115282

            Bug ID: 115282
           Summary: 15 regression]
                    gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c fails
                    after r15-812-gc71886f2ca2e46
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: seurer at gcc dot gnu.org
  Target Milestone: ---

g:c71886f2ca2e46ce1449c7064d6f1b447d02fcba, r15-812-gc71886f2ca2e46

I am seeing this on BE only.

make  -k check-gcc RUNTESTFLAGS="--target_board=unix'{-m32,-m64}'
ppc-costmodel-vect.exp=gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c"

FAIL: gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c scan-tree-dump-times vect
"vectorizing stmts using SLP" 3
FAIL: gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c scan-tree-dump-times vect
"vectorizing stmts using SLP" 3


commit c71886f2ca2e46ce1449c7064d6f1b447d02fcba (HEAD)
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Sep 29 13:13:16 2023 +0200

    Avoid splitting store dataref groups during SLP discovery

[Bug target/115282] [15 regression] gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c fails after r15-812-gc71886f2ca2e46

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115282

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |15.0
           Keywords|                            |testsuite-fail
          Component|other                       |target
            Summary|15 regression]              |[15 regression]
                   |gcc.dg/vect/costmodel/ppc/c |gcc.dg/vect/costmodel/ppc/c
                   |ostmodel-slp-12.c fails     |ostmodel-slp-12.c fails
                   |after                       |after
                   |r15-812-gc71886f2ca2e46     |r15-812-gc71886f2ca2e46

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
I don't see a good reason why, but I don't have a BE cross around to check
myself.  Does BE vect maybe not have unsigned integer vector multiplication
support?

[Bug target/115282] [15 regression] gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c fails after r15-812-gc71886f2ca2e46

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115282

Kewen Lin <linkw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-05-31
             Status|UNCONFIRMED                 |NEW
                 CC|                            |linkw at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #2 from Kewen Lin <linkw at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> I don't see a good reason why, but I don't have a BE cross around to check
> myself.  Does BE vect maybe not have unsigned integer vector multiplication
> support?

BE should have int vector mult too, I noticed it's guarded with TARGET_ALTIVEC.

The first loop (line 17) causes the difference, previously it did the splitting
like: 

test.c:16:17: note:   Splitting SLP group at stmt 6
test.c:16:17: note:   Split group into 6 and 2

but now it won't and then seems to fail due to that:

test.c:16:17: note:   ==> examining statement: _14 = in[_13];
test.c:16:17: missed:   permutation requires at least three vectors _2 =
in[_1];
test.c:16:17: missed:   unsupported load permutation
test.c:25:14: missed:   not vectorized: relevant stmt not supported: _14 =
in[_13];
test.c:16:17: note:   Cannot vectorize all-constant op node 0x140dd450
test.c:16:17: note:   removing SLP instance operations starting from: out[_1] =
_17;
test.c:16:17: missed:  unsupported SLP instances
test.c:16:17: note:  re-trying with SLP disabled
test.c:16:17: note:  vectorization_factor = 4, niters = 8

I can't figure out why it can pass on LE, so I did a test on LE and found it
fails on LE too!?

[Bug target/115282] [15 regression] gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c fails after r15-812-gc71886f2ca2e46

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115282

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
           Priority|P3                          |P1
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
             Target|powerpc64-linux-gnu         |powerpc64*-linux-gnu
             Status|NEW                         |ASSIGNED

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ah, this is probably a case where we need to split because CSE causes us to
associate operations differently so SLP build for the whole thing fails.

The three-vector permute issue will go away when I manage to finish the load
part of the full SLP enablement.

It also fails on LE.  It's the

node 0x39913f0 (max_nunits=4, refcnt=2) vector(4) unsigned int
op template: _14 = in[_13];
    stmt 0 _14 = in[_13];
    load permutation { 6 }

note.  We split the 8-group into 6 and two times 1 element.  This needs
an intermediate (interleaving) permute and indeed the load part will fix it.

I suggest to leave this failing until then.  The loop is still vectorized
but using non-SLP full interleaving until then.

[Bug target/115282] [15 regression] gcc.dg/vect/costmodel/ppc/costmodel-slp-12.c fails after r15-812-gc71886f2ca2e46

[seurer at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115282

--- Comment #4 from seurer at gcc dot gnu.org ---
I originally saw this on a BE run but indeed it fails on LE too.