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<div class="moz-cite-prefix">On 01/02/2018 02:11 PM, Daniel Neilson
via llvm-dev wrote:<br>
</div>
<blockquote cite="mid:B976E989-E455-4275-A483-24BF811487A4@azul.com"
type="cite">
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<div class="">Good day all,</div>
<div class=""> I’ve spent a few days resurrecting the circa-2015
work on removing the explicit alignment argument (4th arg) from
the @llvm.memcpy/memmove/memset intrinsics in favour of using
the alignment attribute on the pointer args of calls to the
intrinsic. This work was first proposed back in August 2015 by
Lang Hames:</div>
<div class=""><a moz-do-not-send="true"
href="http://lists.llvm.org/pipermail/llvm-dev/2015-August/089384.html"
class="">http://lists.llvm.org/pipermail/llvm-dev/2015-August/089384.html</a>
(item 2)</div>
<div class=""> and an attempt at landing the work was made by Pete
Cooper in November 2015, but then backed out due to unspecified
bot failures:</div>
<div class=""><a moz-do-not-send="true"
href="http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html"
class="">http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html</a></div>
<div class=""><br class="">
</div>
<div class=""> I’ve prepared changes for LLVM, Clang, and Polly
that are now up for review:</div>
<div class="">* <a moz-do-not-send="true"
href="https://reviews.llvm.org/D41675" class="">https://reviews.llvm.org/D41675</a>
(LLVM part)</div>
<div class="">* <a moz-do-not-send="true"
href="https://reviews.llvm.org/D41676" class="">https://reviews.llvm.org/D41676</a>
(polly part)</div>
<div class="">* <a moz-do-not-send="true"
href="https://reviews.llvm.org/D41677" class="">https://reviews.llvm.org/D41677</a>
(Clang part)</div>
<div class=""><br class="">
</div>
<div class=""> Importantly for those maintaining downstream users
of the LLVM API, this changes the prototypes for the
@llvm.memcpy/memmove/memset intrinsics and changes the IRBuilder
API for creating memcpy and memmove calls.</div>
<div class=""><br class="">
</div>
<div class="">For example, IR which used to read:<br class="">
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src,
i32 100, i32 4, i1 false)<br class="">
will now read<br class="">
call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 %dest, i8*
align 4 %src, i32 100, i1 false)</div>
<div class=""><br class="">
</div>
The LLVM change includes auto upgrade of the old IR. However,
match expressions in IR tests and calls to IRBuilder’s
CreateMemCpy & CreateMemMove will need to be updated.
<div class=""><br class="">
</div>
<div class=""> My plan is to post another note to the list when
the change is landed, and stable.</div>
<div class=""><br class="">
</div>
<div class=""> Comments? Concerns?</div>
</blockquote>
<br>
Thanks for working on this. This still seems like the right thing to
do (and will let us represent separate source and destination
alignments).<br>
<br>
-Hal<br>
<br>
<blockquote cite="mid:B976E989-E455-4275-A483-24BF811487A4@azul.com"
type="cite">
<div class=""><br class="">
</div>
<div class="">-Daniel<br class="">
<div class=""><br class="">
<div class="">
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---</div>
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Daniel Neilson, Ph.D.</div>
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Azul Systems</div>
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<br>
<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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