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<div class="moz-cite-prefix">Dear Xiaohui,<br>
<br>
I'm not very familiar with the Clang AST, but I suspect the answer
is no: you probably can't generate LLVM IR for just an arbitrary
subset of the Clang AST.<br>
<br>
That said, if you have the LLVM IR, you can use existing analysis
passes to loops, control-dependences, and that sort of thing.
However, if you want to find a CFG for a subset of a Clang AST,
then I do not know if there is existing code to do that.<br>
<br>
Regards,<br>
<br>
John Criswell<br>
<br>
On 2/17/16 5:02 PM, xiaohui chen wrote:<br>
</div>
<blockquote
cite="mid:CALpPt0-nEx=2_C3+0f3zDE+EfaAe9VLjZDjFo94SnJSTLh6c0A@mail.gmail.com"
type="cite">
<meta http-equiv="Context-Type" content="text/html; charset=UTF-8">
<div dir="ltr">Dear John,
<div><br>
</div>
<div>Thanks for your reply! I understand. </div>
<div><br>
</div>
<div>My question is more subtle. Could I obtain the LLVM IR for
a specific stmt ?</div>
<div><br>
</div>
<div>For example, </div>
<div><br>
</div>
<div>void foo()</div>
<div>{</div>
<div> ... // some stmts</div>
<div><br>
</div>
<div> for(...) {</div>
<div> ...</div>
<div> }</div>
<div><br>
</div>
<div> ... // some stmts</div>
<div>} </div>
<div><br>
</div>
<div>Once I built the Clang AST, there is a node to represent
that for-loop, say nodeFor. </div>
<div><br>
</div>
<div>Then I could take nodeFor as parameter to call buildCFG()
to generate the source code level CFG of that for-loop.</div>
<div><br>
</div>
<div>Could I use a similar method to get the LLVM IR for that
for-loop? Again I do not want to generate LLVM IR for other
stmts other than that for-loop.</div>
<div>Hope my question is clear.</div>
<div><br>
</div>
<div>Sincerely</div>
<div>xiaohui </div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, Feb 17, 2016 at 12:27 PM, John
Criswell <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:jtcriswel@gmail.com" target="_blank">jtcriswel@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote">
<div><span class="">
<div>On 2/15/16 8:57 PM, xiaohui chen via cfe-dev wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Dear All:
<div><br>
</div>
<div><span>I am working on Clang/LLVM and interested
to know if there is a programmatic way to
extract the CFG of a specific</span></div>
<div><span>node in AST like a for loop? </span></div>
<div><span><br>
</span></div>
<div><span> I am aware of </span><code>-emit-llvm</code><span>option,
but it will apply on the whole TU.</span><span><br>
</span></div>
<div><span><br>
</span></div>
<div><span>For example,</span></div>
<div><span>we could use </span><span>CFG</span><span>::</span><span>buildCFG
to extract the source level CFG of a specific
node.</span></div>
<div><span>Is there a counterpart API to extract the
LLVM IR level CFG of a specific node?</span></div>
</div>
</blockquote>
<br>
</span> The LLVM IR expresses each function as a set of
basic blocks with an explicit CFG. In other words, the
LLVM IR encodes the CFG of each function explicitly. If
you have the LLVM IR of a function, you already have the
CFG.<br>
<br>
Regards,<br>
<br>
John Criswell<br>
<br>
<blockquote type="cite">
<div dir="ltr">
<div><span><br>
</span></div>
<div><span>Sincerely</span></div>
<div><span>xiaohui</span></div>
</div>
<br>
<fieldset></fieldset>
<br>
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<span class="HOEnZb"> </span></blockquote>
<span class="HOEnZb"> <br>
<br>
<pre cols="72">--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
<a moz-do-not-send="true" href="http://www.cs.rochester.edu/u/criswell" target="_blank">http://www.cs.rochester.edu/u/criswell</a></pre>
</span></div>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
<a class="moz-txt-link-freetext" href="http://www.cs.rochester.edu/u/criswell">http://www.cs.rochester.edu/u/criswell</a></pre>
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