tree-optimization/97558 - avoid SLP analyzing irrelevant stmts

tree-optimization/97558 - avoid SLP analyzing irrelevant stmts

This avoids analyzing reductions that are not relevant (thus dead)
which eventually will lead into crashes because the participating
stmts meta is not analyzed.  For this to work the patch also
properly removes reduction groups that are not uniformly recognized
as patterns.

2020-11-02  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/97558
	* tree-vect-loop.c (vect_fixup_scalar_cycles_with_patterns):
	Check for any mismatch in pattern vs. non-pattern and dissolve
	the group if there is one.
	* tree-vect-slp.c (vect_analyze_slp_instance): Avoid
	analyzing not relevant reductions.
	(vect_analyze_slp): Avoid analyzing not relevant reduction
	groups.

	* gcc.dg/vect/pr97558.c: New testcase.