New size optimization

[Joern Rennecke <amylaar@cygnus.co.uk>]

Invariant code motion in general adds extra moves and register pressure.
AFAIK there are no common scenarios where it can be a precursor for
another optimization that leads to a code size saving.  Thus, I think it
should be turned off when optimizing for space.

I found this while trying to improve giv finding on the SH by correcting
RTX costs, and found that some other code increased significantly in size:
it went from 949 bytes to 997.
However, with the patch below, it went down to 893 bytes.

Mon Mar 30 23:43:58 1998  J"orn Rennecke <amylaar@cygnus.co.uk>

	* loop.c (scan_loop): Don't call move_moveables for optimize_size.

Index: loop.c
===================================================================
RCS file: /cvs/cvsfiles/devo/gcc/loop.c,v
retrieving revision 1.125
diff -p -r1.125 loop.c
*** loop.c	1998/03/25 18:34:32	1.125
--- loop.c	1998/03/30 22:44:19
*************** scan_loop (loop_start, end, nregs, unrol
*** 1052,1059 ****
    /* Now consider each movable insn to decide whether it is worth moving.
       Store 0 in n_times_set for each reg that is moved.  */
  
!   move_movables (movables, threshold,
! 		 insn_count, loop_start, end, nregs);
  
    /* Now candidates that still are negative are those not moved.
       Change n_times_set to indicate that those are not actually invariant.  */
--- 1052,1060 ----
    /* Now consider each movable insn to decide whether it is worth moving.
       Store 0 in n_times_set for each reg that is moved.  */
  
!   if (! optimize_size)
!     move_movables (movables, threshold,
! 		   insn_count, loop_start, end, nregs);
  
    /* Now candidates that still are negative are those not moved.
       Change n_times_set to indicate that those are not actually invariant.  */