Missed opportunity to use [SU]ABD

This adds a recognition pattern for the non-widening
absolute difference (ABD).

gcc/ChangeLog:

	* doc/md.texi (sabd, uabd): Document them.
	* internal-fn.def (ABD): Use new optab.
	* optabs.def (sabd_optab, uabd_optab): New optabs,
	* tree-vect-patterns.cc (vect_recog_absolute_difference):
	Recognize the following idiom abs (a - b).
	(vect_recog_sad_pattern): Refactor to use
	vect_recog_absolute_difference.
	(vect_recog_abd_pattern): Use patterns found by
	vect_recog_absolute_difference to build a new ABD
	internal call.

1 files changed, 10 insertions, 0 deletions

diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 95f7fe1..4490507 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -5809,6 +5809,16 @@ Other shift and rotate instructions, analogous to the
 Vector shift and rotate instructions that take vectors as operand 2
 instead of a scalar type.
 
+@cindex @code{uabd@var{m}} instruction pattern
+@cindex @code{sabd@var{m}} instruction pattern
+@item @samp{uabd@var{m}}, @samp{sabd@var{m}}
+Signed and unsigned absolute difference instructions.  These
+instructions find the difference between operands 1 and 2
+then return the absolute value.  A C code equivalent would be:
+@smallexample
+op0 = op1 > op2 ? op1 - op2 : op2 - op1;
+@end smallexample
+
 @cindex @code{avg@var{m}3_floor} instruction pattern
 @cindex @code{uavg@var{m}3_floor} instruction pattern
 @item @samp{avg@var{m}3_floor}