Fix Eh delivery in partitioned functions

[Richard Biener]

On Wed, 19 Jul 2017, Jan Hubicka wrote:

> > Did you see the inline comments?
> 
> I missed them, sorry :)
> This is updated patch I am testing.

Ok with adding

+  maybe_add_nop_after_section_switch ();

in pass_convert_to_eh_region_ranges::execute instead.

Richard.

> Index: except.c
> ===================================================================
> --- except.c	(revision 250312)
> +++ except.c	(working copy)
> @@ -2444,6 +2444,61 @@ emit_note_eh_region_end (rtx_insn *insn)
>    return emit_note_after (NOTE_INSN_EH_REGION_END, insn);
>  }
>  
> +/* Add NOP after NOTE_INSN_SWITCH_TEXT_SECTIONS when the cold section starts
> +   with landing pad.
> +   With landing pad being at offset 0 from the start label of the section
> +   we would miss EH delivery because 0 is special and means no landing pad.  */
> +
> +bool
> +maybe_add_nop_after_section_switch (void)
> +{
> +  if (!crtl->uses_eh_lsda
> +      || !crtl->eh.call_site_record_v[1])
> +    return false;
> +  int n = vec_safe_length (crtl->eh.call_site_record_v[1]);
> +  hash_set<rtx_insn *> visited;
> +
> +  for (int i = 0; i < n; ++i)
> +    {
> +      struct call_site_record_d *cs
> +	 = (*crtl->eh.call_site_record_v[1])[i];
> +      if (cs->landing_pad)
> +	{
> +	  rtx_insn *insn = as_a <rtx_insn *> (cs->landing_pad);
> +	  while (true)
> +	    {
> +	      /* Landing pads have LABEL_PRESERVE_P flag set.  This check make
> +		 sure that we do not walk past landing pad visited earlier
> +		 which would result in possible quadratic behaviour.  */
> +	      if (LABEL_P (insn) && LABEL_PRESERVE_P (insn)
> +		  && visited.add (insn))
> +		break;
> +
> +	      /* Conservatively assume that ASM insn may be empty.  We have
> +		 now way to tell what they contain.  */
> +	      if (active_insn_p (insn)
> +		  && GET_CODE (PATTERN (insn)) != ASM_INPUT
> +		  && GET_CODE (PATTERN (insn)) != ASM_OPERANDS)
> +		break;
> +
> +	      /* If we reached the start of hot section, then NOP will be
> +		 needed.  */
> +	      if (GET_CODE (insn) == NOTE
> +		  && NOTE_KIND (insn) == NOTE_INSN_SWITCH_TEXT_SECTIONS)
> +		{
> +		  emit_insn_after (gen_nop (), insn);
> +		  break;
> +		}
> +
> +	      /* We visit only labels from cold section.  We should never hit
> +		 begining of the insn stream here.  */
> +	      insn = PREV_INSN (insn);
> +	    }
> +	}
> +    }
> +  return false;
> +}
> +
>  /* Turn REG_EH_REGION notes back into NOTE_INSN_EH_REGION notes.
>     The new note numbers will not refer to region numbers, but
>     instead to call site entries.  */
> @@ -2466,6 +2521,8 @@ convert_to_eh_region_ranges (void)
>    rtx_insn *last_no_action_insn_before_switch = NULL;
>    int saved_call_site_base = call_site_base;
>  
> +  maybe_add_nop_after_section_switch ();
> +
>    vec_alloc (crtl->eh.action_record_data, 64);
>  
>    for (iter = get_insns (); iter ; iter = NEXT_INSN (iter))
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)