Re: Update for cprop patch

[Jeffrey A Law <law at cygnus dot com>]

Opps.  Hit the send button rather than the "attach file button".  Here
the cprop improvement patch I installed for you

	* gcse.c (find_avail_set): Follow chains of register-register copies.
	Use oprs_not_set_p to guarantee that the returned value can be
	substituted.
	(cprop_insn): Don't verify the return value of find_avail_set with
	oprs_not_set_p.

Index: gcse.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/gcse.c,v
retrieving revision 1.43
diff -c -3 -p -r1.43 gcse.c
*** gcse.c	1999/08/25 03:30:45	1.43
--- gcse.c	1999/08/25 04:20:40
*************** find_avail_set (regno, insn)
*** 3656,3671 ****
       int regno;
       rtx insn;
  {
!   struct expr *set = lookup_set (regno, NULL_RTX);
  
!   while (set)
!     {
!       if (TEST_BIT (cprop_avin[BLOCK_NUM (insn)], set->bitmap_index))
  	break;
-       set = next_set (regno, set);
-     }
  
!   return set;
  }
  
  /* Subroutine of cprop_insn that tries to propagate constants into
--- 3656,3720 ----
       int regno;
       rtx insn;
  {
!   /* SET1 contains the last set found that can be returned to the caller for
!      use in a substitution.  */
!   struct expr *set1 = 0;
!  
!   /* Loops are not possible here.  To get a loop we would need two sets
!      available at the start of the block containing INSN.  ie we would
!      need two sets like this available at the start of the block:
! 
!        (set (reg X) (reg Y))
!        (set (reg Y) (reg X))
! 
!      This can not happen since the set of (reg Y) would have killed the
!      set of (reg X) making it unavailable at the start of this block.  */
!   while (1)
!      {
!       rtx src;
!       struct expr *set = lookup_set (regno, NULL_RTX);
! 
!       /* Find a set that is available at the start of the block
! 	 which contains INSN.  */
!       while (set)
! 	{
! 	  if (TEST_BIT (cprop_avin[BLOCK_NUM (insn)], set->bitmap_index))
! 	    break;
! 	  set = next_set (regno, set);
! 	}
  
!       /* If no available set was found we've reached the end of the
! 	 (possibly empty) copy chain.  */
!       if (set == 0)
!  	break;
! 
!       if (GET_CODE (set->expr) != SET)
! 	abort ();
! 
!       src = SET_SRC (set->expr);
! 
!       /* We know the set is available.
! 	 Now check that SRC is ANTLOC (i.e. none of the source operands
! 	 have changed since the start of the block).  
! 
!          If the source operand changed, we may still use it for the next
!          iteration of this loop, but we may not use it for substitutions.  */
!       if (CONSTANT_P (src) || oprs_not_set_p (src, insn))
! 	set1 = set;
! 
!       /* If the source of the set is anything except a register, then
! 	 we have reached the end of the copy chain.  */
!       if (GET_CODE (src) != REG)
  	break;
  
!       /* Follow the copy chain, ie start another iteration of the loop
! 	 and see if we have an available copy into SRC.  */
!       regno = REGNO (src);
!      }
! 
!   /* SET1 holds the last set that was available and anticipatable at
!      INSN.  */
!   return set1;
  }
  
  /* Subroutine of cprop_insn that tries to propagate constants into
*************** cprop_insn (insn, alter_jumps)
*** 3875,3901 ****
  	       && REGNO (src) >= FIRST_PSEUDO_REGISTER
  	       && REGNO (src) != regno)
  	{
! 	  /* We know the set is available.
! 	     Now check that SET_SRC is ANTLOC (i.e. none of the source operands
! 	     have changed since the start of the block).  */
! 	  if (oprs_not_set_p (src, insn))
  	    {
! 	      if (try_replace_reg (reg_used->reg_rtx, src, insn))
  		{
! 		  changed = 1;
! 		  copy_prop_count++;
! 		  if (gcse_file != NULL)
! 		    {
! 		      fprintf (gcse_file, "COPY-PROP: Replacing reg %d in insn %d with reg %d\n",
! 			       regno, INSN_UID (insn), REGNO (src));
! 		    }
! 
! 		  /* The original insn setting reg_used may or may not now be
! 		     deletable.  We leave the deletion to flow.  */
! 		  /* FIXME: If it turns out that the insn isn't deletable,
! 		     then we may have unnecessarily extended register lifetimes
! 		     and made things worse.  */
  		}
  	    }
  	}
      }
--- 3924,3944 ----
  	       && REGNO (src) >= FIRST_PSEUDO_REGISTER
  	       && REGNO (src) != regno)
  	{
! 	  if (try_replace_reg (reg_used->reg_rtx, src, insn))
  	    {
! 	      changed = 1;
! 	      copy_prop_count++;
! 	      if (gcse_file != NULL)
  		{
! 		  fprintf (gcse_file, "COPY-PROP: Replacing reg %d in insn %d with reg %d\n",
! 			   regno, INSN_UID (insn), REGNO (src));
  		}
+ 
+ 	      /* The original insn setting reg_used may or may not now be
+ 		 deletable.  We leave the deletion to flow.  */
+ 	      /* FIXME: If it turns out that the insn isn't deletable,
+ 		 then we may have unnecessarily extended register lifetimes
+ 		 and made things worse.  */
  	    }
  	}
      }