From 5565e8744fd07733385f1925c8b949b6be5fa60a Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu@cs.umass.edu>
Date: Sun, 14 Sep 2003 18:31:13 +0000
Subject: [PATCH] combine.c (simplify_comparison): Convert (ne (and (lshiftrt
 (xor X CST) Y) 1) 0) into (eq (and (lshiftrt X Y) 1) 0).

	* combine.c (simplify_comparison): Convert
	(ne (and (lshiftrt (xor X CST) Y) 1) 0) into
	(eq (and (lshiftrt X Y) 1) 0).

From-SVN: r71385
---
 gcc/ChangeLog |  6 ++++++
 gcc/combine.c | 31 +++++++++++++++++++++----------
 2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 887e10dfef9..bf770b8c9d3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2003-09-14  Kazu Hirata  <kazu@cs.umass.edu>
+
+	* combine.c (simplify_comparison): Convert
+	(ne (and (lshiftrt (xor X CST) Y) 1) 0) into
+	(eq (and (lshiftrt X Y) 1) 0).
+
 2003-09-14  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* alias.c: Follow spelling conventions.
diff --git a/gcc/combine.c b/gcc/combine.c
index 2567ca9b2d7..c18c36e8091 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -10983,19 +10983,30 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
 	    }
 
 	  /* Convert (ne (and (lshiftrt (not X)) 1) 0) to
-	     (eq (and (lshiftrt X) 1) 0).  */
+	     (eq (and (lshiftrt X) 1) 0).
+	     Also handle the case where (not X) is expressed using xor.  */
 	  if (const_op == 0 && equality_comparison_p
 	      && XEXP (op0, 1) == const1_rtx
-	      && GET_CODE (XEXP (op0, 0)) == LSHIFTRT
-	      && GET_CODE (XEXP (XEXP (op0, 0), 0)) == NOT)
+	      && GET_CODE (XEXP (op0, 0)) == LSHIFTRT)
 	    {
-	      op0 = simplify_and_const_int
-		(op0, mode,
-		 gen_rtx_LSHIFTRT (mode, XEXP (XEXP (XEXP (op0, 0), 0), 0),
-				   XEXP (XEXP (op0, 0), 1)),
-		 (HOST_WIDE_INT) 1);
-	      code = (code == NE ? EQ : NE);
-	      continue;
+	      rtx shift_op = XEXP (XEXP (op0, 0), 0);
+	      rtx shift_count = XEXP (XEXP (op0, 0), 1);
+
+	      if (GET_CODE (shift_op) == NOT
+		  || (GET_CODE (shift_op) == XOR
+		      && GET_CODE (XEXP (shift_op, 1)) == CONST_INT
+		      && GET_CODE (shift_count) == CONST_INT
+		      && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
+		      && (INTVAL (XEXP (shift_op, 1))
+			  == (HOST_WIDE_INT) 1 << INTVAL (shift_count))))
+		{
+		  op0 = simplify_and_const_int
+		    (NULL_RTX, mode,
+		     gen_rtx_LSHIFTRT (mode, XEXP (shift_op, 0), shift_count),
+		     (HOST_WIDE_INT) 1);
+		  code = (code == NE ? EQ : NE);
+		  continue;
+		}
 	    }
 	  break;