<div dir="ltr">Dear John,<div>I intend to implement the improvements on DSA.</div><div>After running DSA on SPEC, I found DSA gives low precision for mcf and bzip2.</div><div>I have checked the most imprecise c files in mcf an found that the code seems to be a mixture of "PHI" and "GEP" instructions.</div><div><br></div><div>Could you please give me some hints about what the big picture of the improvement should be and how to start?</div><div><br></div><div>Thank you!</div><div><br></div><div>Regards,</div><div>Zhiyuan</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Apr 6, 2015 at 5:22 PM, John Criswell <span dir="ltr"><<a href="mailto:jtcriswel@gmail.com" target="_blank">jtcriswel@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Dear Zhiyuan,<br>
<br>
In order to reproduce the results from the paper, you'll need to
replicate a system from that era. You'll need to use the same
version of LLVM and DSA that the paper used. I think that was
LLVM 1.9 (the release_19 branch of LLVM and poolalloc), but I'm
not sure. You should check to see if the paper specifies the
version.<br>
<br>
As you'll be using a very old version of LLVM, it may be worth
setting up a VM with a corresponding old version of Linux. I
suspect newer compilers will not compile a version of LLVM that is
that old, so using an old version of Linux with an old version of
GCC may be needed. I think Fedora Core 2 is the OS we were using
at the time.<br>
<br>
To answer the question of why you can't use a modern version of
LLVM and poolalloc, it's because LLVM has changed significantly.
DSA relies upon the type annotations provided in the LLVM IR to
"bootstrap" its type inference (bootstrap is not quite the right
word, but it's the closest one of which I could think). As LLVM
matured, transformations would ditch the type information (e.g.,
transforming typed GEPs into untyped GEPs into a byte array),
making DSA's ability to do type-inference (and thereby improving
field sensitivity) more difficult. Throw into the mix the fact
that DSA is maintained by an academic research group, and the
result is that modern DSA doesn't have the accuracy that the
original DSA did.<br>
<br>
The good news is that I think DSA can be fixed by making its
type-inferencing code smarter. The bad news is that it'd be a
fair amount of work to do. So far, no one has had sufficient
desire/motivation to design and implement the improvements.<br>
<br>
Regards,<br>
<br>
John Criswell<div><div class="h5"><br>
<br>
<br>
On 4/6/15 4:56 PM, Wan Zhiyuan wrote:<br>
</div></div></div>
<blockquote type="cite"><div><div class="h5">
<div dir="ltr">Dear all,
<div>
<div>I am trying to reproduce the "Percent May Alias" result
described in PLDI 07's paper "Making Context-Sensitive
Points-to Analysis with Heap Cloning Practical For The Real
World" (<a href="http://llvm.org/pubs/2007-06-10-PLDI-DSA.html" target="_blank">http://llvm.org/pubs/2007-06-10-PLDI-DSA.html</a>).</div>
</div>
<div><br>
</div>
<div>However, my "Percent May Alias" for all the benchmarks is
much greater, especially "bzip2".</div>
<div><br>
</div>
<div>The DSA code I use is from "<a href="https://github.com/smackers/smack" target="_blank">https://github.com/smackers/smack</a>".
I have diff the code between smack and poolalloc_32. They are
almost the same except the "#include" statements.</div>
<div><br>
</div>
<div>I was wondering whether I need to do some configuration to
make DSA work properly.</div>
<div><br>
</div>
<div>Thank you!</div>
<div><br>
</div>
<div>Zhiyuan</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<fieldset></fieldset>
<br>
</div></div><pre>_______________________________________________
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<pre cols="72">--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
<a href="http://www.cs.rochester.edu/u/criswell" target="_blank">http://www.cs.rochester.edu/u/criswell</a></pre>
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