RFA: patch cheking dangerous insns in sched-ebb.c

[Richard Henderson]

On Sat, Feb 22, 2003 at 11:00:29AM -0500, Vladimir N. Makarov wrote:
> The function may add at most one dependency for insn to a jump (because the
> nested loop contains break when the dependency has been found).  The loop is
> really not necessary for all insn except PFREE_CANDIDATE.

I see.

> Meanwhile, I improved the code (made loop explicitly only for
> PFREE_CANDIDATEs) and attached it.

That is clearer, thanks.

> It can be improved more by creating and
> modifying an additional structure (containing all preceding blocks and
> adding a loop through the blocks in block_has_similiar_load.  The algorithm
> will be still potentially n**2 but faster).

This seems easy enough to accomplish.  Untested, but...

> + static void
> + add_deps_for_risky_insns (head, tail)
> +      rtx head, tail;
> + {
> +   rtx insn, prev;
> +   int class;
> +   rtx last_jump = NULL_RTX;
> +   rtx prev_head = PREV_INSN (head);
> +   rtx next_tail = NEXT_INSN (tail);
      basic_block last_block = NULL, bb;
> +   
> +   for (insn = head; insn != next_tail; insn = NEXT_INSN (insn))
> +     if (GET_CODE (insn) == JUMP_INSN)
	  {
	    bb = BLOCK_FOR_INSN (insn);
	    bb->aux = last_block;
	    last_block = bb;
> +       last_jump = insn;
	  }
> +     else if (INSN_P (insn) && last_jump != NULL_RTX)
> +       {
> + 	class = haifa_classify_insn (insn);
	switch (class)
	  {
	  case PFREE_CANDIDATE:
	    if (flag_schedule_speculative_load)
	      {
		for (bb = last_block; bb ; bb = bb->aux)
		  if (!block_has_similiar_load (bb, insn))
		    break;
		if (!bb)
		  break;
		prev = bb->end;
	      }
	    /* FALLTHRU */
	  case TRAP_RISKY:
	  case IRISKY:
	  case PRISKY_CANDIDATE:
> + 	    /* ??? We could implement better checking PRISKY_CANDIATEs
> + 	       analogous to sched-rgn.c.  */
> + 	    /* We can not change the mode of the backward
> + 	       dependency because REG_DEP_ANTI has the lowest
> + 	       rank.  */
> + 	    if (add_dependence (insn, last_jump, REG_DEP_ANTI))
> + 	      add_forward_dependence (last_jump, insn, REG_DEP_ANTI);
	    break;

	  default:
	    break;
> + 	  }
> +       }

	/* Maintain the invariant that bb->aux is clear after use.  */
	while (last_block)
	  {
	    bb = last_block->aux;
	    last_block->aux = NULL;
	    last_block = bb;
	  }
> + }
> + 


Seem good?


r~