[36/46] Add a pattern_stmt_p field to stmt_vec_info

[36/46] Add a pattern_stmt_p field to stmt_vec_info

This patch adds a pattern_stmt_p field to stmt_vec_info, so that it's
possible to tell whether the statement is a pattern statement without
referring to other statements.  The new field goes in what was
previously a hole in the structure, so the size is the same as before.

2018-07-31  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vectorizer.h (_stmt_vec_info::pattern_stmt_p): New field.
	(is_pattern_stmt_p): Use it.
	* tree-vect-patterns.c (vect_init_pattern_stmt): Set pattern_stmt_p
	on pattern statements.

From-SVN: r263151