biv elimination patch

[Joern Rennecke]

Currently, we inhibit biv elimination when a bivis used inside a libcall
for anything but directly setting a giv, even if the purpose of the entire
libcall is only to set a giv.
Here is a fix:

Mon Mar 29 19:02:12 1999  J"orn Rennecke <amylaar@cygnus.co.uk>

	* loop.c (maybe_eliminate_biv): For libcalls that set a giv, skip to
	end of libcall.

*** loop.c-1999032620	Fri Mar 26 20:09:56 1999
--- loop.c	Mon Mar 29 18:47:08 1999
*************** maybe_eliminate_biv (bl, loop_start, end
*** 8417,8422 ****
--- 8422,8447 ----
        enum rtx_code code = GET_CODE (p);
        rtx where = threshold >= insn_count ? loop_start : p;
  
+       /* If this is a libcall that sets a giv, skip ahead to its end.  */
+       if (GET_RTX_CLASS (code) == 'i')
+ 	{
+ 	  rtx note = find_reg_note (p, REG_LIBCALL, NULL_RTX);
+ 
+ 	  if (note)
+ 	    {
+ 	      rtx last = XEXP (note, 0);
+ 	      rtx set = single_set (last);
+ 
+ 	      if (set && GET_CODE (SET_DEST (set)) == REG)
+ 		{
+ 		  int regno = REGNO (SET_DEST (set));
+ 
+ 		  if (REG_IV_TYPE (regno) == GENERAL_INDUCT
+ 		      && REG_IV_INFO (regno)->src_reg == bl->biv->src_reg)
+ 		    p = last;
+ 		}
+ 	    }
+ 	}
        if ((code == INSN || code == JUMP_INSN || code == CALL_INSN)
  	  && reg_mentioned_p (reg, PATTERN (p))
  	  && ! maybe_eliminate_biv_1 (PATTERN (p), p, bl, eliminate_p, where))