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Document LoopPass. 

llvm-svn: 35191
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Devang Patel 2007-03-19 22:21:25 +00:00
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llvm/docs/WritingAnLLVMPass.html
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@ -43,6 +43,14 @@
<li><a href="#doFinalization_mod">The <tt>doFinalization(Module
&amp;)</tt> method</a></li>
</ul></li>
<li><a href="#LoopPass">The <tt>LoopPass</tt> class</a>
<ul>
<li><a href="#doInitialization_loop">The <tt>doInitialization(Loop *,
LPPassManager &amp;)</tt> method</a></li>
<li><a href="#runOnLoop">The <tt>runOnLoop</tt> method</a></li>
<li><a href="#doFinalization_loop">The <tt>doFinalization()
</tt> method</a></li>
</ul></li>
<li><a href="#BasicBlockPass">The <tt>BasicBlockPass</tt> class</a>
<ul>
<li><a href="#doInitialization_fn">The <tt>doInitialization(Function
@ -126,6 +134,7 @@ from <tt>Pass</tt>. Depending on how your pass works, you should inherit from
the <tt><a href="#ModulePass">ModulePass</a></tt>, <tt><a
href="#CallGraphSCCPass">CallGraphSCCPass</a></tt>, <tt><a
href="#FunctionPass">FunctionPass</a></tt>, or <tt><a
href="#LoopPass">LoopPass</a></tt>, or <tt><a
href="#BasicBlockPass">BasicBlockPass</a></tt> classes, which gives the system
more information about what your pass does, and how it can be combined with
other passes. One of the main features of the LLVM Pass Framework is that it
@ -687,6 +696,85 @@ program being compiled.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="LoopPass">The <tt>LoopPass</tt> class </a>
</div>
<div class="doc_text">
<p> All <tt>LoopPass</tt> execute on each loop in the function independent of
all of the other loops in the function. <tt>LoopPass</tt> processes loops in
loop nest order such that outer most loop is processed last. </p>
<p> <tt>LoopPass</tt> subclasses are allowed to update loop nest using
<tt>LPPassManager</tt> interface. Implementing a loop pass is usually
straightforward. <tt>Looppass</tt>'s may overload three virtual methods to
do their work. All these methods should return true if they modified the
program, or false if they didn't. </p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="doInitialization_loop">The <tt>doInitialization(Loop *,
LPPassManager &amp;)</tt>
method</a>
</div>
<div class="doc_text">
<div class="doc_code"><pre>
<b>virtual bool</b> doInitialization(Loop *, LPPassManager &amp;LPM);
</pre></div>
The <tt>doInitialization</tt> method is designed to do simple initialization
type of stuff that does not depend on the functions being processed. The
<tt>doInitialization</tt> method call is not scheduled to overlap with any
other pass executions (thus it should be very fast). LPPassManager
interface should be used to access Function or Module level analysis
information.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="runOnLoop">The <tt>runOnLoop</tt> method</a>
</div>
<div class="doc_text">
<div class="doc_code"><pre>
<b>virtual bool</b> runOnLoop(Loop *, LPPassManager &amp;LPM) = 0;
</pre></div><p>
<p>The <tt>runOnLoop</tt> method must be implemented by your subclass to do
the transformation or analysis work of your pass. As usual, a true value should
be returned if the function is modified. <tt>LPPassManager</tt> interface
should be used to update loop nest.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="doFinalization_loop">The <tt>doFinalization()</tt> method</a>
</div>
<div class="doc_text">
<div class="doc_code"><pre>
<b>virtual bool</b> doFinalization();
</pre></div>
<p>The <tt>doFinalization</tt> method is an infrequently used method that is
called when the pass framework has finished calling <a
href="#runOnLoop"><tt>runOnLoop</tt></a> for every loop in the
program being compiled. </p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="BasicBlockPass">The <tt>BasicBlockPass</tt> class</a>