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Dear Tarun,<br>
<br>
It just occurred to me that this may or may not be what you are
asking about. This only finds basic blocks along the def-use chain
of an instruction; it does not find all basic blocks along all paths
between two instructions. I don't know of an algorithm off-hand for
the latter, but if you understand how to iterate over def-use chains
and the control-flow graph, then writing up an algorithm for the
latter should be pretty easy.<br>
<br>
-- John T.<br>
<br>
<br>
On 5/3/11 8:24 PM, John Criswell wrote:
<blockquote cite="mid:4DC0AACA.9040007@illinois.edu" type="cite">
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On 5/3/11 4:08 PM, tarun agrawal wrote:
<blockquote
cite="mid:BANLkTikdgWRykEQEEk6QDHChbzRNdu8D1A@mail.gmail.com"
type="cite"> HI <br>
<br>
I know it is a very simple question not worth asking here but I
am really struggling pls help me out..<br>
</blockquote>
<br>
This is a question worth asking; it's just that not everyone can
answer all the time.<br>
:)<br>
<br>
If all you want to do is to follow the SSA def-use chain within a
single function, then this is very easy. All you have to do is
use the use_iterator of the Instruction object to iterate through
its def-use chain. For all uses that are instructions, use the
getParent() method to find the basic block containing the
instruction. That's it.<br>
<br>
This approach won't work in two cases:<br>
<br>
1) If you want to trace def/use through memory. Memory is not in
SSA form, and so you have to use extra analysis to track from
which store the result of a load originates.<br>
<br>
2) If you want to track def/use inter-procedurally through
function arguments and return values. If you don't care about
tracking through memory, this is a fairly easy inter-procedural
analysis to do, and we have some code internally at University of
Illinois that does it. If you need it, I can talk to Vikram and
see if we can give you a copy.<br>
<br>
For more information on how to iterate through def-use chains, see
the LLVM Programmer's Manual:<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://llvm.org/docs/ProgrammersManual.html#iterate_chains">http://llvm.org/docs/ProgrammersManual.html#iterate_chains</a><br>
<br>
-- John T.<br>
<br>
<blockquote
cite="mid:BANLkTikdgWRykEQEEk6QDHChbzRNdu8D1A@mail.gmail.com"
type="cite"><br>
<div class="gmail_quote">On Tue, May 3, 2011 at 10:10 PM, tarun
agrawal <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:tarun@cse.iitb.ac.in">tarun@cse.iitb.ac.in</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">Hi,<br>
<br>
I need to get all the basic blocks that are there, in the
path from definition of an instruction to use of that
instruction.<br>
<br>
<br>
Regards <br>
<font color="#888888">Tarun<br>
</font></blockquote>
</div>
<br>
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