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Date: Thu, 14 Jul 2011 13:09:00 -0000
From: Bernd Schmidt <bernds@codesourcery.com>
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To: Eric Botcazou <ebotcazou@adacore.com>
CC: GCC Patches <gcc-patches@gcc.gnu.org>, Steve Ellcey <sje@cup.hp.com>,  "Vladimir N. Makarov" <vmakarov@redhat.com>
Subject: Re: Correct fix for scheduler bug PR11320
References: <4E1EBEFE.3080002@codesourcery.com> <201107141357.15147.ebotcazou@adacore.com> <4E1EDDB1.2060008@codesourcery.com> <201107141418.34087.ebotcazou@adacore.com>
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On 07/14/11 14:18, Eric Botcazou wrote:
>> Any particular bits you still see that don't get reverted with this patch?
> 
> The ebb_compute_jump_reg_dependencies changes.  The original patch has:
> 
> 	* sched-ebb.c (compute_jump_reg_dependencies): New prototype.
> 	Mark registers live on entry of the fallthrough block and conditionally
> 	set as set by the jump. Mark registers live on entry of non-fallthrough
> 	blocks as used by the jump.
> 
> but you're reverting only:
> 
> 	* sched-ebb.c (compute_jump_reg_dependencies): New prototype.
> 	Mark registers live on entry of the fallthrough block and conditionally
> 	set as set by the jump.
> 

??? Original code:

   basic_block b = BLOCK_FOR_INSN (insn);
    edge e;
    for (e = b->succ; e; e = e->succ_next)
!     if ((e->flags & EDGE_FALLTHRU) == 0)
!       {
! 	bitmap_operation (set, set, e->dest->global_live_at_start,
! 			  BITMAP_IOR);
!       }
  }

Code after the revert:

   FOR_EACH_EDGE (e, ei, b->succs)
+    if ((e->flags & EDGE_FALLTHRU) == 0)
       bitmap_ior_into (used, df_get_live_in (e->dest));

As far as I can tell these are identical, modulo the change in variable
name ("set" -> "used" which seems like a better name).


Bernd