Submitted By: Jim Gifford (patches at jg555 dot com)
Date: 2006-04-17
Initial Package Version: 4.1.0
Origin: Maintainers
Upstream Status: Fixed in SVN
Description: 
Fixes an optimization error that can result incorrectly code. See PR's below

Issues in CLFS book, this patch fixes the incorrect disk checksums in silo.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27176
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26763
 
diff -Naur gcc-4.1.0.orig/ChangeLog gcc-4.1.0/ChangeLog
--- gcc-4.1.0.orig/ChangeLog	2006-02-28 08:30:33.000000000 +0000
+++ gcc-4.1.0/ChangeLog	2006-04-17 19:32:36.000000000 +0000
@@ -1,3 +1,12 @@
+2006-04-05  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/26763
+	* fold-const.c (fold_binary): Fold PTR + CST CMP PTR + CST
+	only for EQ_EXPR and NE_EXPR.
+
+	* gcc.dg/torture/pr26763-1.c: New testcase.
+	* gcc.dg/torture/pr26763-2.c: Likewise.
+
 2006-02-28  Release Manager
 
 	* GCC 4.1.0 released.
diff -Naur gcc-4.1.0.orig/gcc/fold-const.c gcc-4.1.0/gcc/fold-const.c
--- gcc-4.1.0.orig/gcc/fold-const.c	2006-02-03 18:02:04.000000000 +0000
+++ gcc-4.1.0/gcc/fold-const.c	2006-04-17 19:33:55.000000000 +0000
@@ -8897,8 +8897,9 @@
 
       /* If this is a comparison of two exprs that look like an
 	 ARRAY_REF of the same object, then we can fold this to a
-	 comparison of the two offsets.  */
-      if (TREE_CODE_CLASS (code) == tcc_comparison)
+	 comparison of the two offsets.  This is only safe for
+	 EQ_EXPR and NE_EXPR because of overflow issues.  */
+      if (code == EQ_EXPR || code == NE_EXPR)
 	{
 	  tree base0, offset0, base1, offset1;
 
diff -Naur gcc-4.1.0.orig/gcc/testsuite/ChangeLog gcc-4.1.0/gcc/testsuite/ChangeLog
--- gcc-4.1.0.orig/gcc/testsuite/ChangeLog	2006-02-28 08:27:59.000000000 +0000
+++ gcc-4.1.0/gcc/testsuite/ChangeLog	2006-04-17 19:35:18.000000000 +0000
@@ -1,3 +1,12 @@
+2006-04-05  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/26763
+	* fold-const.c (fold_binary): Fold PTR + CST CMP PTR + CST
+	only for EQ_EXPR and NE_EXPR.
+
+	* gcc.dg/torture/pr26763-1.c: New testcase.
+	* gcc.dg/torture/pr26763-2.c: Likewise.
+
 2006-02-28  Release Manager
 
 	* GCC 4.1.0 released.
diff -Naur gcc-4.1.0.orig/gcc/testsuite/gcc.dg/pr26763-1.ch gcc-4.1.0/gcc/testsuite/gcc.dg/pr26763-1.ch
--- gcc-4.1.0.orig/gcc/testsuite/gcc.dg/pr26763-1.ch	1970-01-01 00:00:00.000000000 +0000
+++ gcc-4.1.0/gcc/testsuite/gcc.dg/pr26763-1.ch	2006-04-17 19:36:55.000000000 +0000
@@ -0,0 +1,18 @@
+/* { dg-do run } */
+
+extern void abort(void);
+
+int try (int *a)
+{
+  return a + -1 > a;
+}
+
+int main(void)
+{
+  int bla[100];
+
+  if (try (bla + 50))
+    abort ();
+
+  return 0;
+}
diff -Naur gcc-4.1.0.orig/gcc/testsuite/gcc.dg/pr26763-2.c gcc-4.1.0/gcc/testsuite/gcc.dg/pr26763-2.c
--- gcc-4.1.0.orig/gcc/testsuite/gcc.dg/pr26763-2.c	1970-01-01 00:00:00.000000000 +0000
+++ gcc-4.1.0/gcc/testsuite/gcc.dg/pr26763-2.c	2006-04-17 19:37:11.000000000 +0000
@@ -0,0 +1,18 @@
+/* { dg-do run } */
+
+extern void abort(void);
+
+int try (char *a, int d)
+{
+  return a + d > a;
+}
+
+int main(void)
+{
+  char bla[100];
+
+  if (try (bla + 50, -1))
+    abort ();
+
+  return 0;
+}