Re: PATCH: [5 Regression] r219037 caused FAIL: gcc.dg/pr44194-1.c

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Jan 05, 2015 at 10:23:57PM +0100, Jakub Jelinek wrote:
> On Mon, Jan 05, 2015 at 03:16:46PM -0500, John David Anglin wrote:
> > I think there may be one situation after reload that's not handled
> > by the above.  frame_read is only used for const calls.  What about
> > the situation where we have a non const sibcall and the frame pointer
> > isn't eliminated?
> 
> After reload DSE is run after threading prologues/epilogues, end
> the prologue/epilogue sequences usually contain wild reads, e.g.
> (mem:BLK (scratch)) in some insn etc.
> Do you have some particular testcase in mind?
> 
> That said, DSE after reload is much more limited than the DSE before reload,
> so is less important, so perhaps even
>   if ((HARD_FRAME_POINTER_IS_ARG_POINTER || reload_completed)
>       && SIBLING_CALL_P (insn))
>     {
>       add_wild_read (bb_info);                                                                                                                 
>       return;                                                                                                                                  
>     }
> might be good enough.

Or you could e.g. do the
  if (HARD_FRAME_POINTER_IS_ARG_POINTER
      && !reload_completed
      && SIBLING_CALL_P (insn))
    { add_wild_read (bb_info); return; }
case first, then compute const_call and memset_call,
  if (const_call || memset_call)
    { current_big_block }
  else if (reload_completed && SIBLING_CALL_P (insn))
    add_wild_read (bb_info);
  else
    add_non_frame_wild_read (bb_info);

That way, you would not punish const/memset calls unnecessarily after reload
when they are sibling calls.

	Jakub