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Re: RFA: RTL typesafety improvements for ira.c

On Wed, 2014-10-01 at 16:34 -0600, Jeff Law wrote:
> This was inspired by a discussion with Felix who was making changes in 
> this area.
> Basically this promotes the "init_insns" field within struct equivalence 
> from an rtx to an rtx_insn_list.
> The only thing that's really interesting here is the old code exploits 
> the fact that we could put any RTX in the list by shoving const0_rtx 
> into the init_insns list as a marker to indicate we've already 
> determined the relevant pseudo must not have an equivalence.
> Thus we could have the following objects in the init_insns field:
> const0_rtx
> This patch uses INSN_LIST (NULL_RTX, NULL) as the special marker.  Thus 
> the only two things that would exist in the init_insns field would be 
> NULL or an INSN_LIST.  Goodness.
> Rather than stash away the special marker INSN_LIST into a global 
> variable or something similar, we instead to do a two step check for the 
> marker.  First verify that the insn_list field is non-NULL, then look at 
> the first insn in the list and see if that is NULL.
> Bootstrapped and regression tested on i686-unknown-linux-gnu and 
> x86_64-unknown-linux-gnu.
> Ok for the trunk?


> 	* ira.c (struct equivalence): Promote INIT_INSNs field to
> 	an rtx_insn_list.  Add comments.
> 	(no_equiv): Promote LIST to an rtx_insn_list.  Update
> 	testing for and creating the special marker.  Use methods
> 	to extract the insn and next pointers.
> 	(update_equiv_regs): Update test for special marker in the
> 	INIT_INSNs list.
> diff --git a/gcc/ira.c b/gcc/ira.c

> @@ -3258,9 +3266,9 @@ no_equiv (rtx reg, const_rtx store ATTRIBUTE_UNUSED,
>      return;
>    ira_reg_equiv[regno].defined_p = false;
>    ira_reg_equiv[regno].init_insns = NULL;
> -  for (; list; list =  XEXP (list, 1))
> +  for (; list; list = list->next ())
>      {
> -      rtx insn = XEXP (list, 0);
> +      rtx insn = list->insn ();
>        remove_note (insn, find_reg_note (insn, REG_EQUIV, NULL_RTX));

FWIW, presumably "insn" here also can now be an rtx_insn *?

(I'd like to eventually strengthen the params to the note-handling
functions, so fixing this up now would help with that).

>      }


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