[09/46] Add vec_info::lookup_single_use

This patch adds a helper function for seeing whether there is a single
user of an SSA name, and whether that user has a stmt_vec_info.

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

gcc/
	* tree-vectorizer.h (vec_info::lookup_single_use): Declare.
	* tree-vectorizer.c (vec_info::lookup_single_use): New function.
	* tree-vect-loop.c (vectorizable_reduction): Use it instead of
	a single_imm_use-based sequence.
	* tree-vect-stmts.c (supportable_widening_operation): Likewise.

From-SVN: r263124

1 files changed, 14 insertions, 0 deletions

diff --git a/gcc/tree-vectorizer.c b/gcc/tree-vectorizer.c
index 372cf69..2640aab 100644
--- a/gcc/tree-vectorizer.c
+++ b/gcc/tree-vectorizer.c
@@ -548,6 +548,20 @@ vec_info::lookup_def (tree name)
   return NULL;
 }
 
+/* See whether there is a single non-debug statement that uses LHS and
+   whether that statement has an associated stmt_vec_info.  Return the
+   stmt_vec_info if so, otherwise return null.  */
+
+stmt_vec_info
+vec_info::lookup_single_use (tree lhs)
+{
+  use_operand_p dummy;
+  gimple *use_stmt;
+  if (single_imm_use (lhs, &dummy, &use_stmt))
+    return lookup_stmt (use_stmt);
+  return NULL;
+}
+
 /* A helper function to free scev and LOOP niter information, as well as
    clear loop constraint LOOP_C_FINITE.  */