From: Richard Guenther <rguenther@suse.de>
Date: Wed, 16 Jan 2008 21:51:57 +0000 (+0000)
Subject: re PR middle-end/32628 (bogus integer overflow warning)
X-Git-Tag: releases/gcc-4.3.0~583
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bdb55eae5e08c10636c8882140b06eeee7921209;p=thirdparty%2Fgcc.git

re PR middle-end/32628 (bogus integer overflow warning)

2008-01-16  Richard Guenther  <rguenther@suse.de>

	PR middle-end/32628
	* fold-const.c (fold_convert_const_int_from_int): Do not
	set overflow if that occured only because of a sign extension
	change when converting from/to a sizetype with the same
	precision and signedness.

	* gcc.dg/overflow-warn-7.c: New testcase.

From-SVN: r131579
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9dc1e213afd7..0aa13b5c526f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2008-01-16  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/32628
+	* fold-const.c (fold_convert_const_int_from_int): Do not
+	set overflow if that occured only because of a sign extension
+	change when converting from/to a sizetype with the same
+	precision and signedness.
+
 2008-01-16  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR debug/34249
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 22350b98bf41..ea0b43e942d2 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -2122,8 +2122,22 @@ fold_convert_const_int_from_int (tree type, const_tree arg1)
   t = force_fit_type_double (type, TREE_INT_CST_LOW (arg1),
 			     TREE_INT_CST_HIGH (arg1),
 		             /* Don't set the overflow when
-		      		converting a pointer  */
-			     !POINTER_TYPE_P (TREE_TYPE (arg1)),
+		      		converting from a pointer,  */
+			     !POINTER_TYPE_P (TREE_TYPE (arg1))
+			     /* or to a sizetype with same signedness
+				and the precision is unchanged.
+				???  sizetype is always sign-extended,
+				but its signedness depends on the
+				frontend.  Thus we see spurious overflows
+				here if we do not check this.  */
+			     && !((TYPE_PRECISION (TREE_TYPE (arg1))
+				   == TYPE_PRECISION (type))
+				  && (TYPE_UNSIGNED (TREE_TYPE (arg1))
+				      == TYPE_UNSIGNED (type))
+				  && ((TREE_CODE (TREE_TYPE (arg1)) == INTEGER_TYPE
+				       && TYPE_IS_SIZETYPE (TREE_TYPE (arg1)))
+				      || (TREE_CODE (type) == INTEGER_TYPE
+					  && TYPE_IS_SIZETYPE (type)))),
 			     (TREE_INT_CST_HIGH (arg1) < 0
 		 	      && (TYPE_UNSIGNED (type)
 				  < TYPE_UNSIGNED (TREE_TYPE (arg1))))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 591ca646e928..155e98eb1c73 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2008-01-16  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/32628
+	* gcc.dg/overflow-warn-7.c: New testcase.
+
 2008-01-16  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* gcc.dg/tree-ssa/loop-19.c: Require nonpic.
diff --git a/gcc/testsuite/gcc.dg/overflow-warn-7.c b/gcc/testsuite/gcc.dg/overflow-warn-7.c
new file mode 100644
index 000000000000..7c0ce68df508
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/overflow-warn-7.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+int f(char *device)
+{
+  return device == ((char *)0 + ~0UL);  /* { dg-bogus "overflow" } */
+}
+