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Re: update address taken: don't drop clobbers

From: Jeff Law <law at redhat dot com>
To: Marc Glisse <marc dot glisse at inria dot fr>
Cc: Richard Biener <richard dot guenther at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
Date: Fri, 24 Oct 2014 14:21:59 -0600
Subject: Re: update address taken: don't drop clobbers
Authentication-results: sourceware.org; auth=none
References: <alpine dot DEB dot 2 dot 02 dot 1406282350110 dot 31815 at stedding dot saclay dot inria dot fr> <CAFiYyc0fRhV09A3C2WT8yQ1ndp9dcyWntCVSPHzhwHb3tgNZLg at mail dot gmail dot com> <alpine dot DEB dot 2 dot 11 dot 1407271853200 dot 22972 at stedding dot saclay dot inria dot fr> <alpine dot DEB dot 2 dot 11 dot 1409071654310 dot 5483 at laptop-mg dot saclay dot inria dot fr> <alpine dot DEB dot 2 dot 11 dot 1410151621380 dot 8286 at stedding dot saclay dot inria dot fr> <543E9BED dot 4070905 at redhat dot com> <CAFiYyc27PjA1A_DZnfWGzU2y10Lp3rEoZs1m7hknq1eJDOqK_Q at mail dot gmail dot com> <alpine dot DEB dot 2 dot 11 dot 1410161321450 dot 27920 at stedding dot saclay dot inria dot fr> <543FFFD8 dot 4090406 at redhat dot com> <6255313F-DDD4-4DA6-B07E-832B251E167F at gmail dot com> <54400741 dot 9010203 at redhat dot com> <alpine dot DEB dot 2 dot 11 dot 1410171212370 dot 2952 at stedding dot saclay dot inria dot fr>

On 10/17/14 14:41, Marc Glisse wrote:

On Thu, 16 Oct 2014, Jeff Law wrote:

BTW, I dislike having multiple DCE implementations...

Similarly.  The proposal above was just to determine if we should
schedule DCE or not.


Thinking about it some more, I don't think we should need any kind of
DCE here. The rewriting in update_ssa already does a form of forward
propagation that avoids generating dead assignments, the problem only
occurs if we explicitly introduce this new assignment. So I believe we
should go back to an earlier version, like the attached, which is less
work for the compiler.

And now I can go re-read the old discussion (apparently I should avoid
gsi_replace, and there may be other ways to handle the coalescing).

I'm starting to agree -- a later message indicated you wanted to dropthe unlink_stmt_vdef call and you wanted to avoid gsi_replace, thatseems fine. I'll approve once those things are taken care of.


jeff

Follow-Ups:
- Re: update address taken: don't drop clobbers
  - From: Marc Glisse
- Re: update address taken: don't drop clobbers
  - From: Marc Glisse

References:
- Re: update address taken: don't drop clobbers
  - From: Marc Glisse
- Re: update address taken: don't drop clobbers
  - From: Jeff Law
- Re: update address taken: don't drop clobbers
  - From: Richard Biener
- Re: update address taken: don't drop clobbers
  - From: Marc Glisse
- Re: update address taken: don't drop clobbers
  - From: Jeff Law
- Re: update address taken: don't drop clobbers
  - From: Richard Biener
- Re: update address taken: don't drop clobbers
  - From: Jeff Law
- Re: update address taken: don't drop clobbers
  - From: Marc Glisse

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