<div dir="ltr">Furthermore .. in the articles you reference, the -DCLS=$(getconf LEVEL1_DCACHE_LINESIZE) is passed when compiling the user's program -- one doing extensive blocked matrix operations -- and not when building the *compiler*.<div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 19, 2018 at 12:12 PM, U.Mutlu via llvm-dev <span dir="ltr"><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">Tim Northover wrote on 06/19/2018 08:54 PM:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Why are you passing that argument in the first place? The compiler<br>
completely ignores it.<br>
</blockquote>
<br>
CLS stands for cacheline size. It is an important parameter<br>
for optimization of the generated code, at least with gcc/g++.<br>
-DCLS=n should have the same importance like for example -DNDEBUG.<br>
</blockquote>
<br>
The GCC source doesn't appear to mention it, and neither does any<br>
documentation I can find. NDEBUG on the other hand is in both the C<br>
and C++ standards.<br>
<br>
I still think there's some weird library out there that interprets it<br>
the way you're suggesting, and Clang is not that weird library.<br>
</blockquote>
<br></span>
This is from a famous article series titled "What every programmer should know about memory":<br>
  gcc -DCLS=$(getconf LEVEL1_DCACHE_LINESIZE) ...<br>
<br>
<a href="https://lwn.net/Articles/255364/" rel="noreferrer" target="_blank">https://lwn.net/Articles/25536<wbr>4/</a><br>
<a href="http://mosermichael.github.io/cstuff/all/blog/2015/12/11/wepskn.html" rel="noreferrer" target="_blank">http://mosermichael.github.io/<wbr>cstuff/all/blog/2015/12/11/wep<wbr>skn.html</a><br>
<a href="https://www.dcl.hpi.uni-potsdam.de/teaching/numasem/slides/NUMASem_Matrix_multiplication.pdf" rel="noreferrer" target="_blank">https://www.dcl.hpi.uni-potsda<wbr>m.de/teaching/numasem/slides/<wbr>NUMASem_Matrix_multiplication.<wbr>pdf</a><br>
<br>
You can find more examples by searching for "DCLS getconf LEVEL1_DCACHE_LINESIZE".<div class="HOEnZb"><div class="h5"><br>
<br>
<br>
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