[Bug tree-optimization/122301] [16 Regression] ICE on dav1d-1.5.1: internal compiler error: in vect_analyze_slp_reduc_chain, at tree-vect-slp.cc:4215 since r16-4411-gb6e802fd55d37e

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122301

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixing the pattern updating of reduc_idx shows

t.c:6:21: note:   ==> examining statement: seg_id_21 = PHI <seg_id_14(10),
8(8)>
t.c:6:21: missed:   conversion in the reduction chain.
t.c:3:6: missed:   not vectorized: relevant stmt not supported: seg_id_21 = PHI
<seg_id_14(10), 8(8)>

so we then refuse to vectorize the MIN/MAX reduction that was narrowed from
int to char.  The pattern checks

  /* Punt for reductions where we don't handle the type conversions.  */
  if (STMT_VINFO_DEF_TYPE (last_stmt_info) == vect_reduction_def)
    return NULL;

but this isn't effective.

Testing a patch.