[Bug target/119851] [12/13/14/15/16 regression] -O2 -Q --help=common suggests -ftree-vectorize is disabled by default (since r12-4240-g2b8453c401b699)

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119851

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2025-04-17
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The intent is to have =cheap the default with -O2 -ftree-vectorize:

  /* Use -fvect-cost-model=cheap instead of -fvect-cost-mode=very-cheap
     by default with explicit -ftree-{loop,slp}-vectorize.  */ 
  if (opts->x_optimize == 2
      && (opts_set->x_flag_tree_loop_vectorize
          || opts_set->x_flag_tree_vectorize)) 
    SET_OPTION_IF_UNSET (opts, opts_set, flag_vect_cost_model, 
                         VECT_COST_MODEL_CHEAP);

And there is -ftree-{loop,slp}-vectorize reported as enabled, correctly,
just not the combined -ftree-vectorize likely since we have

    { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_ftree_loop_vectorize, NULL, 1 },
    { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_ftree_slp_vectorize, NULL, 1 },

and that makes -ftree-vectorize not explicitly enabled.

> ./xgcc -B. t.c -O2 -S -Q --help=common | grep vect
  -Wvector-operation-performance        [disabled]
  -ftree-loop-vectorize                 [enabled]
  -ftree-slp-vectorize                  [enabled]
  -ftree-vect-loop-version              [ignored]
  -ftree-vectorize                      [disabled]
  -ftree-vectorizer-verbose=  
  -fvect-cost-model                     -fvect-cost-model=dynamic
  -fvect-cost-model=[unlimited|dynamic|cheap|very-cheap]        very-cheap