tree-optimization/91403 - avoid excessive code-generation

tree-optimization/91403 - avoid excessive code-generation

The vectorizer, for large permuted grouped loads, generates
inefficient intermediate code (cleaned up only later) that runs
into complexity issues in SCEV analysis and elsewhere.  For the
non-single-element interleaving case we already put a hard limit
in place, this applies the same limit to the missing case.

2021-01-11  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91403
	* tree-vect-data-refs.c (vect_analyze_group_access_1): Cap
	single-element interleaving group size at 4096 elements.

	* gcc.dg/vect/pr91403.c: New testcase.