https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84933
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Version|unknown |8.0.1
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
else if (is_min
/* As a special exception preserve non-null ranges. */
&& !(TYPE_UNSIGNED (TREE_TYPE (min))
&& integer_zerop (max)))
{
tree one = build_int_cst (TREE_TYPE (max), 1);
min = int_const_binop (PLUS_EXPR, max, one);
max = vrp_val_max (TREE_TYPE (max));
t = VR_RANGE;
}
the issue is we end up with ~[0, 2147483647] which we want to canonicalize
to [2147483647 + 1, type-max]. But with -fstrict-enums TYPE_MAX_VALUE
of the enumeral type is 1.
So we have out-of-bound ranges as input if we look at TYPE_MIN/MAX_VALUE
which leads to GIGO.
Not sure what to do here at this point. I was always uncomfortable with
using TYPE_MIN/MAX_VALUE and given we use wi::min/max_value in a lot of
places already we could do the same in vrp_val_min/max. Another fix
would be to prune those out-of-bound ranges in both
set_and_canonicalize_value_range and set_value_range. Or a more
localized fix in set_and_canonicalize_value_range instead of looking
for an exact match of vrp_val_is_min/max check <=/>= here and thus in
this case drop into
if (is_min && is_max)
{
/* We cannot deal with empty ranges, drop to varying.
??? This could be VR_UNDEFINED instead. */
set_value_range_to_varying (vr);
return;
}
we still have the issue of using TYPE_MIN/MAX_VALUE and allowing
out-of-bound ranges at the same time though.
vrp_val_is_min/max has the issue to only work reliably for integral
types as well. Auditing all users of vrp_val_[is_]{min,max} is
necessary here.
So the simplest fix I can think of is
Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c (revision 258641)
+++ gcc/tree-vrp.c (working copy)
@@ -386,8 +386,13 @@ set_and_canonicalize_value_range (value_
/* Anti-ranges that can be represented as ranges should be so. */
if (t == VR_ANTI_RANGE)
{
- bool is_min = vrp_val_is_min (min);
- bool is_max = vrp_val_is_max (max);
+ /* For -fstrict-enums we may receive out-of-range ranges so consider
+ values < -INF and values > INF as -INF/INF as well. */
+ tree type = TREE_TYPE (min);
+ bool is_min = (INTEGRAL_TYPE_P (type)
+ && tree_int_cst_compare (min, TYPE_MIN_VALUE (type)) <=
0);
+ bool is_max = (INTEGRAL_TYPE_P (type)
+ && tree_int_cst_compare (max, TYPE_MAX_VALUE (type)) >=
0);
if (is_min && is_max)
{
