re PR middle-end/23518 (some gcc optimizations do not take overflow into account with -fwrapv)

gcc/
	PR tree-optimization/23518
	* fold-const.c (make_range): Don't move a constant to the
	other side of the comparison if the type is signed and -fwrapv
	is given.

gcc/testsuite/
	PR tree-optimization/23518
	* testsuite/gcc.dg/pr23518.c: New.

From-SVN: r108940

gcc/ChangeLog

 2005-12-22  Kazu Hirata  <kazu@codesourcery.com>
 
+	PR tree-optimization/23518
+	* fold-const.c (make_range): Don't move a constant to the
+	other side of the comparison if the type is signed and -fwrapv
+	is given.
+
+2005-12-22  Kazu Hirata  <kazu@codesourcery.com>
+
 	* tree-vrp.c (extract_range_from_binary_expr): Clean up uses
 	of vr0.type.
 

gcc/fold-const.c

@@ -3836,6 +3836,11 @@ make_range (tree exp, int *pin_p, tree *plow, tree *phigh)
 	  if (TREE_CODE (arg1) != INTEGER_CST)
 	    break;
 
+	  /* If flag_wrapv and ARG0_TYPE is signed, then we cannot
+	     move a constant to the other side.  */
+	  if (flag_wrapv && !TYPE_UNSIGNED (arg0_type))
+	    break;
+
 	  /* If EXP is signed, any overflow in the computation is undefined,
 	     so we don't worry about it so long as our computations on
 	     the bounds don't overflow.  For unsigned, overflow is defined

gcc/testsuite/ChangeLog

+2005-12-22  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/23518
+	* testsuite/gcc.dg/pr23518.c: New.
+
 2005-12-21  Mike Stump  <mrs@apple.com>
 
 	* gcc.dg/attr-weakref-1.c: Really skip on darwin.

gcc/testsuite/gcc.dg/pr23518.c

+/* PR tree-optimization/23518.
+   make_range used to transform a + 1 < 0 into a < -1 even when a is
+   signed and -fwrapv is given.  Make sure that no longer happens.  */
+
+/* { dg-do run } */
+/* { dg-options "-O2 -fwrapv" } */
+
+#include <limits.h>
+
+extern void abort (void);
+extern void exit (int);
+
+int
+main (void)
+{
+  int a = INT_MAX;
+  if ((a < 0) || (a + 1 < 0))
+    exit (0);
+
+  abort ();
+}