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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 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 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>
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<div class=""> I’ve prepared changes for LLVM, Clang, and Polly that are now up for review:</div>
<div class="">* <a href="https://reviews.llvm.org/D41675" class="">https://reviews.llvm.org/D41675</a> (LLVM part)</div>
<div class="">* <a href="https://reviews.llvm.org/D41676" class="">https://reviews.llvm.org/D41676</a> (polly part)</div>
<div class="">* <a href="https://reviews.llvm.org/D41677" class="">https://reviews.llvm.org/D41677</a> (Clang part)</div>
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<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>
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<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>
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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.
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<div class=""> My plan is to post another note to the list when the change is landed, and stable.</div>
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<div class=""> Comments? Concerns?</div>
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<div class="">-Daniel<br class="">
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Daniel Neilson, Ph.D.</div>
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Azul Systems</div>
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