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Date: Fri, 05 Aug 2005 14:00:00 -0000
From: Diego Novillo <dnovillo@redhat.com>
To: Roger Sayle <roger@eyesopen.com>
Cc: gcc@gcc.gnu.org
Subject: PR 23046.  Folding predicates involving TYPE_MAX_VALUE/TYPE_MIN_VALUE
Message-ID: <20050805135953.GA23609@topo.toronto.redhat.com>
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In PR 23046 we ICE inside tree-vrp.c because fold() does not
realize that for

enum enumtype { ENUM1, ENUM2 } x;

the predicate 'if (x > 1)' is always false.  This causes VRP to
create the impossible range [2, 1] for that predicate.

While it would be trivial for VRP to paper over this problem, the
real fix should be in fold().  I looked at the logic that detects
these cases and it is fairly convoluted (fold-const.c:9174).

I'm wondering why doesn't fold() just use TYPE_MAX_VALUE/TYPE_MIN_VALUE
if they're available?


Thanks.