backport: re PR middle-end/30364 (Wrong variable ranges due to constant folding)

2007-03-05  Richard Guenther  <rguenther@suse.de>

	Backport from mainline:
	2007-02-28  Richard Guenther  <rguenther@suse.de>

	PR middle-end/30364
	* fold-const.c (fold_binary): Do not associate expressions
	with more than one variable for integer types that do not wrap.

	* gcc.dg/torture/pr30364-1.c: New testcase.
	* gcc.dg/torture/pr30364-2.c: Likewise.
	* gcc.dg/torture/pr30364-3.c: Likewise.

From-SVN: r122548

gcc/ChangeLog

@@ -1,3 +1,12 @@
+2007-03-05  Richard Guenther  <rguenther@suse.de>
+
+	Backport from mainline:
+	2007-02-28  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/30364
+	* fold-const.c (fold_binary): Do not associate expressions
+	with more than one variable for integer types that do not wrap.
+
 2007-03-04  Eric Botcazou  <ebotcazou@adacore.com>
 
 	PR ada/26797

gcc/fold-const.c

@@ -8635,6 +8635,7 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	{
 	  tree var0, con0, lit0, minus_lit0;
 	  tree var1, con1, lit1, minus_lit1;
+	  bool ok = true;
 
 	  /* Split both trees into variables, constants, and literals.  Then
 	     associate each group together, the constants with literals,
@@ -8645,12 +8646,33 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	  var1 = split_tree (arg1, code, &con1, &lit1, &minus_lit1,
 			     code == MINUS_EXPR);
 
+	  /* With undefined overflow we can only associate constants
+	     with one variable.  */
+	  if ((POINTER_TYPE_P (type)
+	       || (INTEGRAL_TYPE_P (type)
+		   && !(TYPE_UNSIGNED (type) || flag_wrapv)))
+	      && var0 && var1)
+	    {
+	      tree tmp0 = var0;
+	      tree tmp1 = var1;
+
+	      if (TREE_CODE (tmp0) == NEGATE_EXPR)
+	        tmp0 = TREE_OPERAND (tmp0, 0);
+	      if (TREE_CODE (tmp1) == NEGATE_EXPR)
+	        tmp1 = TREE_OPERAND (tmp1, 0);
+	      /* The only case we can still associate with two variables
+		 is if they are the same, modulo negation.  */
+	      if (!operand_equal_p (tmp0, tmp1, 0))
+	        ok = false;
+	    }
+
 	  /* Only do something if we found more than two objects.  Otherwise,
 	     nothing has changed and we risk infinite recursion.  */
-	  if (2 < ((var0 != 0) + (var1 != 0)
-		   + (con0 != 0) + (con1 != 0)
-		   + (lit0 != 0) + (lit1 != 0)
-		   + (minus_lit0 != 0) + (minus_lit1 != 0)))
+	  if (ok
+	      && (2 < ((var0 != 0) + (var1 != 0)
+		       + (con0 != 0) + (con1 != 0)
+		       + (lit0 != 0) + (lit1 != 0)
+		       + (minus_lit0 != 0) + (minus_lit1 != 0))))
 	    {
 	      /* Recombine MINUS_EXPR operands by using PLUS_EXPR.  */
 	      if (code == MINUS_EXPR)

gcc/testsuite/ChangeLog

@@ -1,3 +1,13 @@
+2007-03-05  Richard Guenther  <rguenther@suse.de>
+
+	Backport from mainline:
+	2007-02-28  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/30364
+	* gcc.dg/torture/pr30364-1.c: New testcase.
+	* gcc.dg/torture/pr30364-2.c: Likewise.
+	* gcc.dg/torture/pr30364-3.c: Likewise.
+
 2007-03-05  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/30968

gcc/testsuite/gcc.dg/torture/pr30364-1.c

@@ -0,0 +1,19 @@
+/* { dg-do run } */
+
+extern void abort (void);
+
+int f(int a, int b)
+{
+  if (a > 0x7FFFFFF0) return 0;
+  if (b > 0x7FFFFFF0) return 0;
+
+  int c = (a - 20) + (b - 20);
+  return c > 0x7FFFFFF0;
+}
+
+int main()
+{
+  if (f (0x7FFFFFF0, 41) != 1)
+    abort ();
+  return 0;
+}

gcc/testsuite/gcc.dg/torture/pr30364-2.c

@@ -0,0 +1,19 @@
+/* { dg-do run } */
+
+extern void abort (void);
+
+int f(unsigned int a, unsigned int b)
+{
+  if (a > 0x7FFFFFF0) return 0;
+  if (b > 0x7FFFFFF0) return 0;
+
+  int c = (a - 20) + (b - 20);
+  return c > 0x7FFFFFF0;
+}
+
+int main()
+{
+  if (f (0x7FFFFFF0, 41) != 1)
+    abort ();
+  return 0;
+}

gcc/testsuite/gcc.dg/torture/pr30364-3.c

@@ -0,0 +1,20 @@
+/* { dg-do run } */
+/* { dg-options "-fwrapv" } */
+
+extern void abort (void);
+
+int f(int a, int b)
+{
+  if (a > 0x7FFFFFF0) return 0;
+  if (b > 0x7FFFFFF0) return 0;
+
+  int c = (a - 20) + (b - 20);
+  return c > 0x7FFFFFF0;
+}
+
+int main()
+{
+  if (f (0x7FFFFFF0, 41) != 1)
+    abort ();
+  return 0;
+}