Fix double-rounding bug in ceiling etc.

This is doable now that we have bignums.
* src/floatfns.c (integer_value): Remove; no longer used.
(rescale_for_division): New function.
(rounding_driver): Use it to divide properly (by using bignums)
even when arguments are float, fixing a double-rounding FIXME.
* src/lisp.h (LOG2_FLT_RADIX): Move here ...
* src/timefns.c (frac_to_double): ... from here.
* test/src/floatfns-tests.el (big-round):
Add a test to catch the double-rounding bug.

1 files changed, 3 insertions, 1 deletions

diff --git a/test/src/floatfns-tests.el b/test/src/floatfns-tests.el
index 62201a877d0..7f1d4691bf0 100644
--- a/test/src/floatfns-tests.el
+++ b/test/src/floatfns-tests.el
@@ -122,6 +122,8 @@
 
 (ert-deftest big-round ()
   (should (= (floor 54043195528445955 3)
-             (floor 54043195528445955 3.0))))
+             (floor 54043195528445955 3.0)))
+  (should (= (floor 1.7976931348623157e+308 5e-324)
+             (ash (1- (ash 1 53)) 2045))))
 
 (provide 'floatfns-tests)