rtl.texi (Vector Operations): Clarify vec_select result mode.

2009-12-17  Sandra Loosemore  <sandra@codesourcery.com>

	gcc/
	* doc/rtl.texi (Vector Operations): Clarify vec_select result mode.

From-SVN: r155320

gcc/ChangeLog

+2009-12-17  Sandra Loosemore  <sandra@codesourcery.com>
+
+	* doc/rtl.texi (Vector Operations): Clarify vec_select result mode.
+
 2009-12-17  Julian Brown  <julian@codesourcery.com>
 
 	* config/arm/bpabi-v6m.S (test_div_by_zero): New macro.

gcc/doc/rtl.texi

@@ -2614,9 +2614,12 @@ a set bit indicates it is taken from @var{vec1}.
 @findex vec_select
 @item (vec_select:@var{m} @var{vec1} @var{selection})
 This describes an operation that selects parts of a vector.  @var{vec1} is
-the source vector, @var{selection} is a @code{parallel} that contains a
+the source vector, and @var{selection} is a @code{parallel} that contains a
 @code{const_int} for each of the subparts of the result vector, giving the
-number of the source subpart that should be stored into it.
+number of the source subpart that should be stored into it.  
+The result mode @var{m} is either the submode for a single element of
+@var{vec1} (if only one subpart is selected), or another vector mode 
+with that element submode (if multiple subparts are selected).
 
 @findex vec_concat
 @item (vec_concat:@var{m} @var{vec1} @var{vec2})