simplify-rtx.c (simplify_const_unary_operation): Handle SS_ABS.

	* simplify-rtx.c (simplify_const_unary_operation): Handle
	SS_ABS.
	* doc/rtl.texi: Document ss_abs.

From-SVN: r153003

gcc/ChangeLog

+2009-10-20  Jie Zhang  <jie.zhang@analog.com>
+
+	* simplify-rtx.c (simplify_const_unary_operation): Handle
+	SS_ABS.
+	* doc/rtl.texi: Document ss_abs.
+
 2009-10-19  Jakub Jelinek  <jakub@redhat.com>
 
 	* c-common.c (c_parse_error): Handle CPP_UTF8STRING.

gcc/doc/rtl.texi

@@ -2364,9 +2364,14 @@ Similar but represent left and right rotate.  If @var{c} is a constant,
 use @code{rotate}.
 
 @findex abs
+@findex ss_abs
 @cindex absolute value
 @item (abs:@var{m} @var{x})
+@item (ss_abs:@var{m} @var{x})
 Represents the absolute value of @var{x}, computed in mode @var{m}.
+@code{ss_abs} ensures that an out-of-bounds result saturates to the
+maximum signed value.
+
 
 @findex sqrt
 @cindex square root

gcc/simplify-rtx.c

@@ -1245,6 +1245,7 @@ simplify_const_unary_operation (enum rtx_code code, enum machine_mode mode,
 	case US_TRUNCATE:
 	case SS_NEG:
 	case US_NEG:
+	case SS_ABS:
 	  return 0;
 
 	default: