Assembly labels are generated like thisL .LDECIMAL_NUMBER
If instead of DECIMAL_NUMBER the hex version of the same number (or even better base 32 or base 64) the total assembly size would be reduced.

For combine.s the file size difference for using hex is %1.5 for -O2 -S (if I remember well)

Here's an emacs function that will estimate the size.  Evaluate the function, open the .s file and do M-x my-estimate, it will show the size savings estimate.

(defun my-estimate ()
  (interactive)
  (let ((crt-size (point-max)))
    (goto-char (point-min))
    (while (re-search-forward "\\([.]L[A-Z]*\\)\\([0-9]+\\)" nil t)
      (replace-match (format "%s%x" (match-string 1) (string-to-number (match-string 2))) nil nil))
    (message "Size %% change = %f" (/ (* 100.0 (- (point-max) crt-size)) (point-max)))))

This is a rather simple minded estimate, but it shouldn't bet too far.
Things like .LBB and .LBE need to be considered carefully.
This should help speed up the assembler a bit...