hash: use full width unsigned type for hash values.

Throughout the hashing framework, hashes are reduced into the
fixnum range, and returned as cnum.  This is not necessary;
only the hash-eql and hash-equal functions need to reduce
hashes to fixnums. Let's make it ucnum everywhere else, using
its full range (no reduction into the [0, NUM_MAX) range).

* hash.c (struct hash_ops): hash_fun function pointer returns
ucnum instead of cnum.
(hash_double): Return unreduced ucnum. Obsolete #ifdef-s
removed; the ucnum type gives us a pointer-wide unsigned
integer on all platforms.
(equal_hash, eql_hash): Return ucnum. Don't reduce values to
fixnum range. Some of the way we combine hashes from recursive
calls changes; we multiply by at most 2 not to lose too many
bits.
(eql_hash_op, cobj_eq_hash_op, hash_hash_op): Return ucnum.

* hash.h (equal_hash): Declaration updated.

* lib.c (cobj_handle_hash_op): Return value changes to ucnum.

* lib.h (struct cobj_ops): Hash function pointer's return
type changes.
(cobj_eq_hash_op, cobj_handle_hash_op): Declarations updated.

* struct.c (struct_inst_hash): Return value changes to ucnum.

1 files changed, 3 insertions, 2 deletions

diff --git a/struct.c b/struct.c
index d1887f19..5e8b1aef 100644
--- a/struct.c
+++ b/struct.c
@@ -1492,11 +1492,12 @@ static val struct_inst_equal(val left, val right)
   return t;
 }
 
-static cnum struct_inst_hash(val obj, int *count, ucnum seed)
+static ucnum struct_inst_hash(val obj, int *count, ucnum seed)
 {
   struct struct_inst *si = coerce(struct struct_inst *, obj->co.handle);
   struct struct_type *st = si->type;
-  cnum nslots = st->nslots, sl, out = equal_hash(st->self, count, seed);
+  cnum nslots = st->nslots, sl;
+  ucnum out = equal_hash(st->self, count, seed);
 
   check_init_lazy_struct(obj, si);