Add vector_memory_operand and "Bm" constraint

SSE vector arithmetic and logic instructions only accept aligned memory
operand.  This patch adds vector_memory_operand and "Bm" constraint for
aligned SSE memory operand.  They are applied to SSE plusminus and
any_logic patterns.

gcc/

	PR target/68991
	* config/i386/constraints.md (Bm): New constraint.
	* config/i386/predicates.md (vector_memory_operand): New
	predicate.
	* config/i386/sse.md: Replace xm with xBm in plusminus and
	any_logic patterns.

gcc/testsuite/

	PR target/68991
	* g++.dg/pr68991-1.C: New test.
	* g++.dg/pr68991-2.C: Likewise.

From-SVN: r232087