tree-optimization/120808 - SLP patterns with FMA/FMS

tree-optimization/120808 - SLP patterns with FMA/FMS

The following amends the SLP addsub pattern to also match blends
of .FMA/.FMS and form .FMADDSUB even when -ffp-contract=off.

	PR tree-optimization/120808
	* tree-vect-slp-patterns.cc (vect_match_expression_p):
	Take a code_helper and also match calls.
	(addsub_pattern::recognize): Handle .FMA/.FMS pairs
	in addition to PLUS/MINUS.
	(addsub_pattern::build): Adjust.

	* gcc.dg/vect/bb-slp-pr120808.c: Now also expect FMADDSUB
	patterns to be matched.