tree-vrp.c (value_inside_range, [...]): Add FIXME note regarding quirky semantics.

	* tree-vrp.c (value_inside_range, range_includes_zero_p): Add
	FIXME note regarding quirky semantics.

From-SVN: r104860

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2971178cb4aa57c9ebaf18da9db27ae1feda1396..b644aaa85eff2c786bcaeaa683888ee74d811736 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2005-10-01  Diego Novillo  <dnovillo@redhat.com>
+
+       * tree-vrp.c (value_inside_range, range_includes_zero_p): Add
+       FIXME note regarding quirky semantics.
+
 2005-10-01  Diego Novillo  <dnovillo@redhat.com>
 
        PR 24141

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 0e5ea09b5d58034e9c1fb409ec0879a72edaebb2..de7a931cb1562b71372b3203e4fed6539a195998 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -564,7 +564,23 @@ compare_values (tree val1, tree val2)
 
 /* Return 1 if VAL is inside value range VR (VR->MIN <= VAL <= VR->MAX),
           0 if VAL is not inside VR,
-        -2 if we cannot tell either way.  */
+        -2 if we cannot tell either way.
+
+   FIXME, the current semantics of this functions are a bit quirky
+         when taken in the context of VRP.  In here we do not care
+         about VR's type.  If VR is the anti-range ~[3, 5] the call
+         value_inside_range (4, VR) will return 1.
+
+         This is counter-intuitive in a strict sense, but the callers
+         currently expect this.  They are calling the function
+         merely to determine whether VR->MIN <= VAL <= VR->MAX.  The
+         callers are applying the VR_RANGE/VR_ANTI_RANGE semantics
+         themselves.
+
+         This also applies to value_ranges_intersect_p and
+         range_includes_zero_p.  The semantics of VR_RANGE and
+         VR_ANTI_RANGE should be encoded here, but that also means
+         adapting the users of these functions to the new semantics.  */
 
 static inline int
 value_inside_range (tree val, value_range_t *vr)
@@ -596,7 +612,11 @@ value_ranges_intersect_p (value_range_t *vr0, value_range_t *vr1)
 }
 
 
-/* Return true if VR includes the value zero, false otherwise.  */
+/* Return true if VR includes the value zero, false otherwise.  FIXME,
+   currently this will return false for an anti-range like ~[-4, 3].
+   This will be wrong when the semantics of value_inside_range are
+   modified (currently the users of this function expect these
+   semantics).  */
 
 static inline bool
 range_includes_zero_p (value_range_t *vr)