Fix vectorizable_live_operation handling of vector booleans

vectorizable_live_operation needs to use BIT_FIELD_REF to extract one
element of a vector.  For a packed vector boolean type, the number of
bits to extract should be taken from TYPE_PRECISION rather than TYPE_SIZE.

This is shown by existing tests once SVE is added.

2017-09-18  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* tree-vect-loop.c (vectorizable_live_operation): Fix element size
	calculation for vector booleans.

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

From-SVN: r252930

gcc/ChangeLog

@@ -2,6 +2,13 @@
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 
+	* tree-vect-loop.c (vectorizable_live_operation): Fix element size
+	calculation for vector booleans.
+
+2017-09-18  Richard Sandiford  <richard.sandiford@linaro.org>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
 	* tree-vect-stmts.c (can_vectorize_live_stmts): New function,
 	split out from...
 	(vect_transform_stmt): ...here.

gcc/tree-vect-loop.c

@@ -7066,7 +7066,9 @@ vectorizable_live_operation (gimple *stmt,
 	: gimple_get_lhs (stmt);
   lhs_type = TREE_TYPE (lhs);
 
-  bitsize = TYPE_SIZE (TREE_TYPE (vectype));
+  bitsize = (VECTOR_BOOLEAN_TYPE_P (vectype)
+	     ? bitsize_int (TYPE_PRECISION (TREE_TYPE (vectype)))
+	     : TYPE_SIZE (TREE_TYPE (vectype)));
   vec_bitsize = TYPE_SIZE (vectype);
 
   /* Get the vectorized lhs of STMT and the lane to use (counted in bits).  */