re PR target/30315 (optimize unsigned-add overflow test on x86 to use cpu flags from addl)

	PR target/30315
	* config/i386/i386.h (CANONICALIZE_COMPARISON): Delete.
	* simplify-rtx.c (simplify_relational_operation_1): Add the
	canonicalization from i386.h.
	* doc/md.texi (Canonicalization of Instructions): Document it.

From-SVN: r128305

gcc/ChangeLog

+2007-09-09  Rask Ingemann Lambertsen  <rask@sygehus.dk>
+
+	PR target/30315
+	* config/i386/i386.h (CANONICALIZE_COMPARISON): Delete.
+	* simplify-rtx.c (simplify_relational_operation_1): Add the
+	canonicalization from i386.h.
+	* doc/md.texi (Canonicalization of Instructions): Document it.
+
 2007-09-09  Jan Hubicka  <jh@suse.cz>
             Dwarakanath Rajagopal <dwarak.rajagopal@amd.com>
 

gcc/config/i386/i386.h

@@ -2070,16 +2070,6 @@ do {							\
 
 #define SELECT_CC_MODE(OP, X, Y) ix86_cc_mode ((OP), (X), (Y))
 
-/* Canonicalize overflow checks to save on the insn patterns. We change
-   "a + b < b" into "a + b < a" and "a + b >= b" into "a + b >= a".  */
-#define CANONICALIZE_COMPARISON(code, op0, op1)	\
-{						\
-  if ((code == LTU || code == GEU)		\
-      && GET_CODE (op0) == PLUS			\
-      && rtx_equal_p (op1, XEXP (op0, 1)))	\
-    op1 = XEXP (op0, 0);			\
-}
-
 /* Return nonzero if MODE implies a floating point inequality can be
    reversed.  */
 

gcc/doc/md.texi

 @c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1996, 1998, 1999, 2000, 2001,
-@c 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+@c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
 @c This is part of the GCC manual.
 @c For copying conditions, see the file gcc.texi.
 
@@ -5514,6 +5514,11 @@ An operand of @code{neg}, @code{not}, @code{mult}, @code{plus}, or
 above.
 
 @item
+@code{(ltu (plus @var{a} @var{b}) @var{b})} is converted to
+@code{(ltu (plus @var{a} @var{b}) @var{a})}. Likewise with @code{geu} instead
+of @code{ltu}.
+
+@item
 @code{(minus @var{x} (const_int @var{n}))} is converted to
 @code{(plus @var{x} (const_int @var{-n}))}.
 

gcc/simplify-rtx.c

@@ -3813,6 +3813,12 @@ simplify_relational_operation_1 (enum rtx_code code, enum machine_mode mode,
 	}
     }
 
+  /* Canonicalize (LTU/GEU (PLUS a b) b) as (LTU/GEU (PLUS a b) a).  */
+  if ((code == LTU || code == GEU)
+      && GET_CODE (op0) == PLUS
+      && rtx_equal_p (op1, XEXP (op0, 1)))
+    return simplify_gen_relational (code, mode, cmp_mode, op0, XEXP (op0, 0));
+
   if (op1 == const0_rtx)
     {
       /* Canonicalize (GTU x 0) as (NE x 0).  */