[RFC 0/6] Flags outputs for asms

[Richard Henderson]

On 05/08/2015 02:14 PM, Segher Boessenkool wrote:
> "Cleaner"?  In this code?  Heh.

Heh.

> use_crosses_set_p often estimates pessimistically.  Is that what is
> happening here?  Using real dataflow in combine would fix that (and many
> other problems).  Not that that helps you right now ;-)

Yes, I think so.  Proper data flow would fix this.  But...

My thought is that the use_crosses_set_p could grow another parameter,
ignore_luid, so that if it matches DF_INSN_LUID (rsp->last_set) we don't fail
the test.

Then can_combine_p has to adjust its use like so:

  use_crosses_set_p (src, DF_INSN_LUID (insn),
		     succ ? DF_INSN_LUID (succ) : -1)

which at least handles the 3-insn combine case, if not the 4-insn combine case.

I'll try out both this and Law's set_noop_p suggestion soon.



r~