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Re: fwprop: fix REG_DEAD notes rendered incorrect

From: Alexandre Oliva <aoliva at redhat dot com>
To: Eric Botcazou <ebotcazou at adacore dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Thu, 27 Oct 2011 14:06:35 -0200
Subject: Re: fwprop: fix REG_DEAD notes rendered incorrect
References: <orr51y3744.fsf@livre.localdomain> <201110271532.17592.ebotcazou@adacore.com>

On Oct 27, 2011, Eric Botcazou <ebotcazou@adacore.com> wrote:

>> fwprop may propagate a SET_SRC that contains the last use of a REG to a
>> later point, but it will leave the REG_DEAD note in place, even though
>> it is no longer correct.  I noticed this while investigating PR50826:
>> the initialization of the internal_arg_pointer has a REG_DEAD note for
>> %r29, but even after it is fwpropped, the note remains there.  This
>> patch fixes this bug.

> This isn't necessarily a bug, i.e. passes aren't required to maintain
> REG_DEAD and REG_UNUSED notes up-to-date (another example is PR
> rtl-opt/48773).  Instead passes consuming these notes have to invoke
> df_note_add_problem on entry.

It looked confusing, and it wasn't hard to fix, but, ok, patch
withdrawn.

-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer

References:
- fwprop: fix REG_DEAD notes rendered incorrect
  - From: Alexandre Oliva
- Re: fwprop: fix REG_DEAD notes rendered incorrect
  - From: Eric Botcazou

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