Fix PR 24141

[Diego Novillo <dnovillo at redhat dot com>]

We were forgetting to clear out the equivalence bitmap when creating an 
anti-range as a last resource in vrp_meet.  When vrp_meet cannot merge 
two ranges, it tries to see if it can at least create the anti-range 
~[0, 0] which is generally useful.  So, if the two ranges are non-zero,  
but have an empty intersection, it creates ~[0, 0].

But it was not clearing out the equivalence bitmap, causing an ICE later 
on.

Bootstrapped and tested x86, ia64, x86_64 (minus libjava) and ppc64.


	PR 24141
	* tree-vrp.c (vrp_meet): Clear VR0->EQUIV when building a
	non-null range as a last resort.

testsuite/

	* gcc.c-torture/execute/pr24141.c: New test.

Index: tree-vrp.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-vrp.c,v
retrieving revision 2.57
diff -d -u -p -r2.57 tree-vrp.c
--- tree-vrp.c	16 Sep 2005 07:54:03 -0000	2.57
+++ tree-vrp.c	1 Oct 2005 00:36:29 -0000
@@ -3424,7 +3459,14 @@ no_meet:
       && !range_includes_zero_p (vr0)
       && !symbolic_range_p (vr1)
       && !range_includes_zero_p (vr1))
-    set_value_range_to_nonnull (vr0, TREE_TYPE (vr0->min));
+    {
+      set_value_range_to_nonnull (vr0, TREE_TYPE (vr0->min));
+
+      /* Since this meet operation did not result from the meeting of
+	 two equivalent names, VR0 cannot have any equivalences.  */
+      if (vr0->equiv)
+	bitmap_clear (vr0->equiv);
+    }
   else
     set_value_range_to_varying (vr0);
 }
Index: testsuite/gcc.c-torture/execute/pr24141.c
===================================================================
RCS file: testsuite/gcc.c-torture/execute/pr24141.c
diff -N testsuite/gcc.c-torture/execute/pr24141.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gcc.c-torture/execute/pr24141.c	1 Oct 2005 00:36:30 -0000
@@ -0,0 +1,33 @@
+// reduced testcase, compile with -O2. Also, with --disable-checking
+// gcc produces wrong code.
+
+void abort (void);
+int i;
+
+void g (void)
+{
+  i = 1;
+}
+
+void f (int a, int b)
+{
+  int c = 0;
+  if (a == 0)
+    c = 1;
+  if (c)
+    return;
+  if (c == 1)
+    c = 0;
+  if (b == 0)
+    c = 1;
+  if (c)
+    g ();
+}
+
+int main (void)
+{
+  f (1, 0);
+  if (i != 1)
+    abort ();
+  return 0;
+}