RTL frontend input format again (was Re: [PATCH 15/16] RTL frontend (rtl1), on top of dump reader)

David Malcolm dmalcolm@redhat.com
Wed Oct 19 17:54:00 GMT 2016


On Wed, 2016-10-19 at 19:22 +0200, Bernd Schmidt wrote:
> On 10/19/2016 07:19 PM, David Malcolm wrote:
> > I already dropped LABEL_NUSES in compact mode in r241120; I think
> > it's
> > possible to regenerate that information.
> > 
> > But how would we go about recreating the JUMP_LABEL data?  As far
> > as I
> > can tell, it can be set up by reorg.c:make_return_insns
> > via comparison against function_return_label and
> > function_simple_return_label, which are set up by find_end_label;
> > the
> > functions in question are non-trivial, and can lead to extra insns
> > being emitted.  Also, in shrink-wrap.c:handle_simple_exit, which
> > has
> > similar state considerations.
> 
> I'd expect every return/simple_return insn to contain the
> corresponding 
> rtx code. mark_jump_label_1 has this, which supports the theory:
> 
>      case RETURN:
>      case SIMPLE_RETURN:
>        if (is_target)
>          {
>            gcc_assert (JUMP_LABEL (insn) == NULL || JUMP_LABEL (insn)
> == x);
>            JUMP_LABEL (insn) = x;
>          }
>        return;
> 
> This is called via mark_all_labels from rebuild_jump_labels_1, so it 
> should Just Work - in theory.
> 
> > It seems simpler to serialize this information.
> 
> Simpler, probably, but it would be nice to omit it if it really is 
> redundant.

Thanks, that gave me the pointer I needed.  I think it is indeed
redundant and I'll work on regenerating it in class function_reader.



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