Commit 4e58e53c authored by Raymond Toy's avatar Raymond Toy
Browse files

Be more careful in computing the decode-float bounds 

If 0 is the lower bound then the smallest exponent is not for 0, but
for the least positive float because of denormals.

Also handle exclusive bounds.
parent 2292400e

src/compiler/float-tran.lisp

+23 −19
Original line number Diff line number Diff line
@@ -2031,29 +2031,33 @@ 
  (labels

      ((calc-exp (x)

	 (when x

	   (nth-value 1 (decode-float x))))

       (min-exp ()

	 ;; Use decode-float on the least positive float of the

	 ;; appropriate type to find the min exponent.  If we don't

	 ;; know the actual number format, use double, which has the

	 ;; widest range (including double-double-float).

	 (calc-exp (if (eq 'single-float (numeric-type-format arg))

	   (bound-func #'(lambda (arg)

			   (nth-value 1 (decode-float arg)))

		       x)))

       (min-exp (interval)

	 ;; (decode-float 0d0) returns an exponent of -1022.  But

	 ;; (decode-float least-positive-double-float returns -1073.

	 ;; Hence, if the low value is less than this, we need to

	 ;; return the exponent of the least positive number.

	 (let ((least (if (eq 'single-float (numeric-type-format arg))

			  least-positive-single-float

			  least-positive-double-float)))

       (max-exp ()

	   (if (or (interval-contains-p 0 interval)

		   (interval-contains-p least interval))

	     (calc-exp least)

	     (calc-exp (bound-value (interval-low interval))))))

       (max-exp (interval)

	 ;; Use decode-float on the most postive number of the

	 ;; appropriate type to find the max exponent.  If we don't

	 ;; know the actual number format, use double, which has the

	 ;; widest range (including double-double-float).

	 (or (calc-exp (bound-value (interval-high interval)))

	     (calc-exp (if (eq 'single-float (numeric-type-format arg))

			   most-positive-single-float

		       most-positive-double-float))))

    (let* ((interval (interval-func #'calc-exp

				    (interval-abs (numeric-type->interval arg))))

	   (lo (or (interval-low interval)

		   (min-exp)))

	   (hi (or (interval-high interval)

		   (max-exp))))

			   most-positive-double-float)))))

    (let* ((interval (interval-abs (numeric-type->interval arg)))

	   (lo (min-exp interval))

	   (hi (max-exp interval)))

      (specifier-type `(integer ,(or lo '*) ,(or hi '*))))))



(defun decode-float-sign-derive-type-aux (arg)