Fix nb_iterations calculation in tree-vect-loop-manip.c

We previously stored the number of loop iterations rather
than the number of latch iterations.

gcc/
2016-11-15  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* tree-vect-loop-manip.c (slpeel_make_loop_iterate_ntimes): Set
	nb_iterations to the number of latch iterations rather than the
	number of loop iterations.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r242493

gcc/ChangeLog

@@ -2,6 +2,14 @@
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 
+	* tree-vect-loop-manip.c (slpeel_make_loop_iterate_ntimes): Set
+	nb_iterations to the number of latch iterations rather than the
+	number of loop iterations.
+
+2016-11-16  Richard Sandiford  <richard.sandiford@arm.com>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
 	* combine.c (maybe_swap_commutative_operands): New function.
 	(combine_simplify_rtx): Use it.
 	(change_zero_ext): Likewise.

gcc/tree-vect-loop-manip.c

@@ -285,7 +285,10 @@ slpeel_make_loop_iterate_ntimes (struct loop *loop, tree niters)
 		     LOCATION_LINE (loop_loc));
       dump_gimple_stmt (MSG_NOTE, TDF_SLIM, cond_stmt, 0);
     }
-  loop->nb_iterations = niters;
+
+  /* Record the number of latch iterations.  */
+  loop->nb_iterations = fold_build2 (MINUS_EXPR, TREE_TYPE (niters), niters,
+				     build_int_cst (TREE_TYPE (niters), 1));
 }
 
 /* Helper routine of slpeel_tree_duplicate_loop_to_edge_cfg.