Re: [PATCH 007/236] New function: for_each_rtx_in_insn

[Richard Sandiford <rdsandiford at googlemail dot com>]

David Malcolm <dmalcolm@redhat.com> writes:
> On Tue, 2014-08-12 at 15:08 -0600, Jeff Law wrote:
>> On 08/06/14 11:19, David Malcolm wrote:
>> > gcc/
>> > 	* rtl.h (for_each_rtx_in_insn): New function.
>> > 	* rtlanal.c (for_each_rtx_in_insn): Likewise.
>> OK.  Note that we're moving away from for_each_rtx...   I haven't 
>> looked, but there's a reasonable chance we may not need it after Richard 
>> S.'s work is committed.  Something to watch.
>
> CCing Richard S, as a "heads up".
>
> Richard, for context, the patch in this thread is this one:
> https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00494.html
>
> which adds a "for_each_rtx_in_insn" function, to work on a top-level
> insn node, as part of a big cleanup I'm working on that distinguishes
> between insn nodes vs arbitrary rtx nodes:
> https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00498.html
>
> I believe that your rtl-iter reworking:
>  https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00133.html
> hasn't landed in trunk yet (I don't see an rtl-iter.h there yet).

Right.  I think they're held up on patch 40 (ironically the one that
conflicts with yours).

> More detailed notes follow:
>
> My reading of Richard's patch series is that it optimizes many specific
> for_each_rtx implementations, but keeps the existing generic one around.

Yes, but that's only temporary.  The eventual aim is to get rid of
for_each_rtx altogether.  The series I posted dealt with all calls
in gcc/ itself and the next series will get rid of all other calls
(in config/).

> Some notes on all of the places in which I've made use of the new
> "for_each_rtx_in_insn" in my patchkit:
>
> cfgcleanup.c:1728:		  for_each_rtx_in_insn (&BB_END (bb1), replace_label, &rr);
> cfgcleanup.c:1742:		  for_each_rtx_in_insn (&BB_END (bb1), replace_label, &rr);
>   (both in outgoing_edges_match; I don't think Richard's patchkit
> touches this one).
>
>
> cfgcleanup.c:2002:		for_each_rtx_in_insn (&insn, replace_label, &rr);
>   (in try_crossjump_to_edge; likewise, I don't think Richard's kit
> touches this)

These are patch 38: https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00175.html

> rtlanal.c:3103:  return for_each_rtx_in_insn (insn, for_each_inc_dec_find_mem, &data);
>   ...in for_each_inc_dec, the use added in my:
> "[PATCH 176/236] cselib and incdec":
> https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00711.html
>
> Looks like Richard's
> "[PATCH 40/50] rtlanal.c:for_each_inc_dec":
> https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00177.html
> optimizes this.
>
> Merging these looks more involved: in my patch series I establish that
> the first param to for_each_inc_dec is an rtx_insn **, which may cause
> type issues in Richard's new code as is - but perhaps may allow some
> simplification?  Given that the loc passed in is an insn, am I right in
> thinking we're only interested in MEM within the PATTERN of insn, right?
> Also, am I right in thinking that that particular callback can't modify
> the ptr that's passed in (I don't see writes back to *r)?  If so, that
> suggests that we can lose an indirection from the first param, and
> simply work on PATTERN (insn).

Yeah, that's true, we could lose the indirection.  I'll fix up patch 40
accordingly.

Thanks,
Richard