[Bug tree-optimization/109605] New: -fno-tree-vectorize does not disable vectorizer

[Bug tree-optimization/109605] New: -fno-tree-vectorize does not disable vectorizer

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109605

            Bug ID: 109605
           Summary: -fno-tree-vectorize does not disable vectorizer
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hubicka at gcc dot gnu.org
  Target Milestone: ---

-ftree-vectorize enables -ftree-slp-vectorize and -ftree-loop-vectorize however
-fno-tree-vectorize does not disable them.  This is quite counter-intuitive and
at least I got caught in this trap while doing some benchmarking.

[Bug driver/109605] -fno-tree-vectorize does not disable vectorizer

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109605

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |driver

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
You mean -ftree-slp-vectorize -fno-tree-vectorize doesn't disable SLP
vectorization?  I suspect this is since we use EnabledBy() which
doesn't seem to imply a DisabledBy() of the negative form(?).

[Bug driver/109605] -fno-tree-vectorize does not disable vectorizer

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109605

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-05-17
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

Take a simple LP64 testcase (just to make the aliasing happy):
```
int f1(long long *a, long *b, long *c)
{
        long a0, a1;
        a[0] = b[0] + c[0];
        a[1] = b[1] + c[1];
}
```
At `-O2`, SLP vectorizers it.
`-O2 -fno-tree-vectorize` disables the SLP vectorizer
But if you did:
`-O2 -ftree-slp-vectorize -fno-tree-vectorize` the SLP vectorizer is turned on
still. This is what is definitely counter-intuitive really.