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    <div class="moz-cite-prefix">Same here.  Committed under an off by
      default flag is far preferred over "apply this patch".<br>
      <br>
      Also, once it's in tree, it's much easier for multiple people to
      work on it at once.  Beyond all the algorithmic stuff, there's all
      the standard code cleanup and refactoring changes going on in
      tree.  Keeping an out of tree patch up to date w.r.t. API changes
      can be a real pain.<br>
      <br>
      Philip<br>
      <br>
      On 11/25/2016 03:11 PM, Greg Bedwell via llvm-dev wrote:<br>
    </div>
    <blockquote
cite="mid:CANWqj-vtquWi-=ZDS3u97vNnHAuQgstVBwXNhKyqn=CncQo0mA@mail.gmail.com"
      type="cite">
      <div style="white-space:pre-wrap">Right. On trunk I can have it run through swathes of internal test code with a new flag in a matter of mouse clicks through our CI.  Having to apply a patch manually is a more involved affair with a lot more manual steps. That's not to say it can't be done, but it's something I'd rather avoid where a far easier solution exists. At that point it becomes a piece of work that I have to schedule and prioritise vs my other responsibilities (and therefore might get done much later or not at all). If it's just kicking off an automated test run and reporting any bugs that turn up it's probably something I can just squeeze in straight away without any real planning.

-Greg</div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr">On Fri, 25 Nov 2016 at 18:46, Michael Spencer via
          llvm-dev <<a moz-do-not-send="true"
            href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>>
          wrote:<br>
        </div>
        <blockquote class="gmail_quote" style="margin:0 0 0
          .8ex;border-left:1px #ccc solid;padding-left:1ex">
          <div dir="ltr" class="gmail_msg">
            <div class="gmail_extra gmail_msg">
              <div class="gmail_msg">
                <div class="m_-7529597248691630291gmail_signature
                  gmail_msg">On Tue, Nov 22, 2016 at 10:27 AM, Jack
                  Howarth via llvm-dev <span dir="ltr"
                    class="gmail_msg"><<a moz-do-not-send="true"
                      href="mailto:llvm-dev@lists.llvm.org"
                      class="gmail_msg" target="_blank">llvm-dev@lists.llvm.org</a>></span>
                  wrote:<br class="gmail_msg">
                </div>
              </div>
            </div>
          </div>
          <div dir="ltr" class="gmail_msg">
            <div class="gmail_extra gmail_msg">
              <div class="gmail_quote gmail_msg">
                <blockquote class="gmail_quote gmail_msg"
                  style="margin:0px 0px 0px 0.8ex;border-left:1px solid
                  rgb(204,204,204);padding-left:1ex">>>On Fri, Nov
                  18, 2016 at 8:43 AM, Philip Reames via llvm-dev<br
                    class="gmail_msg">
                  ><llvm-dev at <a moz-do-not-send="true"
                    href="http://lists.llvm.org" rel="noreferrer"
                    class="gmail_msg" target="_blank">lists.llvm.org</a>>
                  wrote:<br class="gmail_msg">
                  >> Glad to see this landing!  It's been a long
                  time coming.<br class="gmail_msg">
                  >><br class="gmail_msg">
                  >> Once this is in, please do not turn it on by
                  default immediately.  Let's<br class="gmail_msg">
                  >> call for volunteers to find some of the most
                  egregious miscompiles, fix<br class="gmail_msg">
                  >> them, and then turn this on by default.<br
                    class="gmail_msg">
                  >><br class="gmail_msg">
                  >There are no immediate plans to enable NewGVN by
                  default (at least,<br class="gmail_msg">
                  >not in the near future). In fact, the mail that I
                  originally wrote<br class="gmail_msg">
                  >doesn't at all mention the switch, neither any
                  follow-ups from me or<br class="gmail_msg">
                  >Daniel, so, I'm not entirely sure where you got
                  that idea from. If you<br class="gmail_msg">
                  >take a look more closely (at the mail, or a the
                  patch), you'll realize<br class="gmail_msg">
                  >that "key" pieces that are in old GVN are still
                  missing. The most<br class="gmail_msg">
                  >noticeable are PRE and load coercion. In other
                  words, the patch<br class="gmail_msg">
                  >proposed is not (yet) on par with what the current
                  GVN does (although<br class="gmail_msg">
                  >all the missing pieces are already implemented
                  out-of-tree).<br class="gmail_msg">
                  >Also, let me try to clarify one point. This is
                  already a call for<br class="gmail_msg">
                  >volunteers. If you feel adventurous, you can
                  download the<br class="gmail_msg">
                  >patch/apply/test/report issues. I can and I will
                  spend time<br class="gmail_msg">
                  i>ntegrating the rest of the work and fix all the
                  reported<br class="gmail_msg">
                  >bugs/miscompiles. If there's something that can we
                  do in a cleaner<br class="gmail_msg">
                  >way, a discussion will happen on the mailing
                  list/on the review thread<br class="gmail_msg">
                  >and everybody will have a chance to comment, as
                  it's happening for the<br class="gmail_msg">
                  >initial patch (and as I always try to do).<br
                    class="gmail_msg">
                  >Once the first patch lands, I'll commit a
                  temporary cl::opt to enable<br class="gmail_msg">
                  >NewGVN for those interested in testing and send
                  another CFT e-mail.<br class="gmail_msg">
                  >FWIW, The patch had already a round of light
                  testing internally. Of<br class="gmail_msg">
                  >course, this is not enough or indicative of its
                  maturity/robustness. I<br class="gmail_msg">
                  >plan to have it tested more carefully inside my
                  organization in<br class="gmail_msg">
                  >parallel.<br class="gmail_msg">
                  >That said, thanks for you input.<br
                    class="gmail_msg">
                  <br class="gmail_msg">
                  Why even commit the patch to enable the pass into
                  trunk. Just leave it<br class="gmail_msg">
                  up on Phabricator for testers to apply locally to
                  their tree?<br class="gmail_msg">
                               Jack<br class="gmail_msg">
                  <br class="gmail_msg">
                </blockquote>
                <div class="gmail_msg"><br class="gmail_msg">
                </div>
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            </div>
          </div>
          <div dir="ltr" class="gmail_msg">
            <div class="gmail_extra gmail_msg">
              <div class="gmail_quote gmail_msg">
                <div class="gmail_msg">Because that increase friction to
                  testing it. Asking people to pass -mllvm -newgvn will
                  end up with a lot more testing than "please apply this
                  patch and recompile everything".</div>
              </div>
            </div>
          </div>
          <div dir="ltr" class="gmail_msg">
            <div class="gmail_extra gmail_msg">
              <div class="gmail_quote gmail_msg">
                <div class="gmail_msg"><br class="gmail_msg">
                </div>
                <div class="gmail_msg">- Michael Spencer<br
                    class="gmail_msg">
                </div>
              </div>
            </div>
          </div>
          <div dir="ltr" class="gmail_msg">
            <div class="gmail_extra gmail_msg">
              <div class="gmail_quote gmail_msg">
                <div class="gmail_msg"> </div>
                <blockquote class="gmail_quote gmail_msg"
                  style="margin:0px 0px 0px 0.8ex;border-left:1px solid
                  rgb(204,204,204);padding-left:1ex">
                  <br class="gmail_msg">
                  >--<br class="gmail_msg">
                  >Davide<br class="gmail_msg">
                  _______________________________________________<br
                    class="gmail_msg">
                  LLVM Developers mailing list<br class="gmail_msg">
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                    class="gmail_msg">
                </blockquote>
              </div>
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          </div>
          _______________________________________________<br
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      <pre wrap="">_______________________________________________
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