Eric Botcazou wrote:
> This problem was already raised when Diego contributed the VRP pass and Diego
> ajusted it to cope with Ada. AFAIK Ada and VRP work fine on the 4.1 branch.
>
Which doesn't mean that Ada is DTRT. On the contrary, Ada ought to be
fixed. It's an ugly hack in extract_range_from_assert:
/* Special handling for integral types with super-types. Some FEs
construct integral types derived from other types and restrict
the range of values these new types may take.
It may happen that LIMIT is actually smaller than TYPE's minimum
value. For instance, the Ada FE is generating code like this
during bootstrap:
D.1480_32 = nam_30 - 300000361;
if (D.1480_32 <= 1) goto <L112>; else goto <L52>;
<L112>:;
D.1480_94 = ASSERT_EXPR <D.1480_32, D.1480_32 <= 1>;
All the names are of type types__name_id___XDLU_300000000__399999999
which has min == 300000000 and max == 399999999. This means that
the ASSERT_EXPR would try to create the range [3000000, 1] which
is invalid.
The fact that the type specifies MIN and MAX values does not
automatically mean that every variable of that type will always
be within that range, so the predicate may well be true at run
time. If we had symbolic -INF and +INF values, we could
represent this range, but we currently represent -INF and +INF
using the type's min and max values.
So, the only sensible thing we can do for now is set the
resulting range to VR_VARYING. TODO, would having symbolic -INF
and +INF values be worth the trouble? */
BTW, the answer to that 'TODO' question is 'no'. I briefly toyed with
that idea, but it is much more convenient to use TYPE_MAX_VALUE and
TYPE_MIN_VALUE. Otherwise, arithmetic on +INF and -INF becomes unpleasant.
