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<p>The general assumption is that you use RS4GC to lower the
abstract machine model.</p>
<p>I think there's IRBuilder support. If not, patches welcome!<br>
</p>
<p>Philip<br>
</p>
<div class="moz-cite-prefix">On 10/21/19 12:06 AM, Yafei Liu wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAMUQRevKS9Dt5a0nUtr3Dgy9H63fr_50xXAhESRwM1N+hNZkmw@mail.gmail.com">
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<div dir="ltr">Hi Philip, are there any C++ APIs to generate the
llvm statepoint instructions? I didn't found APIs similar to how
to generate gcroot instructions.</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, Oct 21, 2019 at 2:03
PM Yafei Liu <<a href="mailto:yfliu@mobvoi.com"
moz-do-not-send="true">yfliu@mobvoi.com</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Thanks Philip, I'll keep investigating.</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, Oct 21, 2019 at
9:52 AM Philip Reames <<a
href="mailto:listmail@philipreames.com" target="_blank"
moz-do-not-send="true">listmail@philipreames.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<p>Correct, with a couple of nit picks.</p>
<p>Relocation isn't an optimization the collector
performs. It's a key primitive the collector is built
upon. Being unable to relocate is not an allowed
state. (i.e. pinning can't be required by the
compiler)</p>
<p>When you talk about variables, that's true for the
*source* language and for the *abstract* machine
before lowering. After lowering from the abstract
machine, relocations are represented in the IR
explicitly as an entirely new set of defs.</p>
<p>Philip<br>
</p>
<div>On 10/20/19 6:40 PM, Yafei Liu wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Correct me if I'm wrong:
<div>Relocation in this conversation "relocation"
means GC trying to move objects in the heap for
optimization (make the data more impact for bigger
room for example), this move is invisible to a
programmer, and if a compiler support to
" relocate objects directly reachable from running
code", a variable (Foo foo) may points to a
different address after a GC happens, while a
programmer could still use the name foo in the
code as if nothing happened.</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Oct 20,
2019 at 4:35 AM Philip Reames via llvm-dev <<a
href="mailto:llvm-dev@lists.llvm.org"
target="_blank" moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px
0px 0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<p>Exactly this. (As the person who wrote the
line in question.) <br>
</p>
<div>On 10/18/19 8:50 AM, Hiroshi Yamauchi via
llvm-dev wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">I
think it's referring to a "moving" garbage
collector (as opposed to a "non-moving"
garbage collector that never
moves/relocates objects.) The difference
is that for a moving one, all pointers
need to be tracked and potentially
updated, whereas for a non-moving one,
it's sufficient that at least one pointer
to a live object is seen (when there may
be other pointers to the same object
elsewhere) for correctness.</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri,
Oct 18, 2019 at 2:12 AM Yafei Liu via
llvm-dev <<a
href="mailto:llvm-dev@lists.llvm.org"
target="_blank" moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<p>Hi all,</p>
<p>I'm investigating on integrating a gc
to my llvm project, and when I read <a
href="http://llvm.org/docs/Statepoints.html" rel="nofollow noreferrer"
style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;color:rgb(0,89,153)"
target="_blank"
moz-do-not-send="true">this document</a>,
one sentence confused me:</p>
<blockquote>
<p
style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both">However,
for a collector which wishes to
relocate objects directly reachable
from running code, a higher standard
is required.</p>
</blockquote>
<p>I don't understand what the move
"relocate objects directly reachable
from running code" trying to do.</p>
<p>For my information, the concept
"relocate" means the gc pointer
refereed to a new location of an
object, for example:</p>
<p>in Java:</p>
<pre style="margin-top:0px;margin-bottom:1em;padding:12px 8px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas,Menlo,Monaco,"Lucida Console","Liberation Mono","DejaVu Sans Mono","Bitstream Vera Sans Mono","Courier New",monospace,sans-serif;font-size:13px;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto;background-color:rgb(239,240,241);border-radius:3px;color:rgb(36,39,41)"><code style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:Consolas,Menlo,Monaco,"Lucida Console","Liberation Mono","DejaVu Sans Mono","Bitstream Vera Sans Mono","Courier New",monospace,sans-serif;vertical-align:baseline;box-sizing:inherit;white-space:inherit">Foo foo = new Foo();
foo = new Foo(); // ---> a relocation happens
</code></pre>
<p>So can anyone explain what the
"relocate objects directly reachable
from running code" trying to do?</p>
</div>
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