more enable-checking patches

[Alasdair Baird <alasdair at wildcat dot demon dot co dot uk>]

These patches fix up a couple of uses of SET_DEST and SUBREG_REG where
the more appropriate thing to do, considering their arguments, is to
use XEXP.  This showed up trying to bootstrap using --enable-checking.

It also fixes up a usage comment in sched_analyze_1 which used to
indicate it only got passed SET and CLOBBER; looking at the code it
is apparent that it also gets passed PRE/POST_INC/DEC rtx too.


   Alasdair.


Sat Sep  4 11:52:34 BST 1999  Alasdair Baird  <alasdair@wildcat.demon.co.uk>
	 * flow.c (insn_dead_p): Use XEXP rather than SUBREG_REG.
	 * haifa-sched.c (sched_analyze_1): Use XEXP rather than SUBREG_REG
	 and SET_DEST. Update comment.


*** flow.c-orig	Sat Sep  4 01:37:42 1999
--- flow.c	Sat Sep  4 11:21:09 1999
*************** insn_dead_p (x, needed, call_ok, notes)
*** 2966,2972 ****
  
        while (GET_CODE (r) == SUBREG || GET_CODE (r) == STRICT_LOW_PART
  	     || GET_CODE (r) == ZERO_EXTRACT)
! 	r = SUBREG_REG (r);
  
        if (GET_CODE (r) == REG)
  	{
--- 2966,2972 ----
  
        while (GET_CODE (r) == SUBREG || GET_CODE (r) == STRICT_LOW_PART
  	     || GET_CODE (r) == ZERO_EXTRACT)
! 	r = XEXP (r, 0);
  
        if (GET_CODE (r) == REG)
  	{
*** haifa-sched.c-orig	Sat Sep  4 01:37:42 1999
--- haifa-sched.c	Sat Sep  4 11:19:26 1999
*************** flush_pending_lists (insn, only_write)
*** 3230,3237 ****
    last_pending_memory_flush = alloc_INSN_LIST (insn, NULL_RTX);
  }
  
! /* Analyze a single SET or CLOBBER rtx, X, creating all dependencies generated
!    by the write to the destination of X, and reads of everything mentioned.  */
  
  static void
  sched_analyze_1 (x, insn)
--- 3230,3238 ----
    last_pending_memory_flush = alloc_INSN_LIST (insn, NULL_RTX);
  }
  
! /* Analyze a single SET, CLOBBER, PRE_DEC, POST_DEC, PRE_INC or POST_INC
!    rtx, X, creating all dependencies generated by the write to the
!    destination of X, and reads of everything mentioned.  */
  
  static void
  sched_analyze_1 (x, insn)
*************** sched_analyze_1 (x, insn)
*** 3239,3245 ****
       rtx insn;
  {
    register int regno;
!   register rtx dest = SET_DEST (x);
    enum rtx_code code = GET_CODE (x);
  
    if (dest == 0)
--- 3240,3246 ----
       rtx insn;
  {
    register int regno;
!   register rtx dest = XEXP (x, 0);
    enum rtx_code code = GET_CODE (x);
  
    if (dest == 0)
*************** sched_analyze_1 (x, insn)
*** 3265,3271 ****
  	  sched_analyze_2 (XEXP (dest, 1), insn);
  	  sched_analyze_2 (XEXP (dest, 2), insn);
  	}
!       dest = SUBREG_REG (dest);
      }
  
    if (GET_CODE (dest) == REG)
--- 3266,3272 ----
  	  sched_analyze_2 (XEXP (dest, 1), insn);
  	  sched_analyze_2 (XEXP (dest, 2), insn);
  	}
!       dest = XEXP (dest, 0);
      }
  
    if (GET_CODE (dest) == REG)