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Document how, module pass can require function pass. 

llvm-svn: 36171
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Devang Patel 2007-04-16 21:28:14 +00:00
parent e0a060043b
commit 9b5e8e5c32
1 changed files with 18 additions and 2 deletions
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20
llvm/docs/WritingAnLLVMPass.html
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@ -466,7 +466,9 @@ class is the most general of all superclasses that you can use. Deriving from
<tt>ModulePass</tt> indicates that your pass uses the entire program as a unit,
refering to function bodies in no predictable order, or adding and removing
functions. Because nothing is known about the behavior of <tt>ModulePass</tt>
subclasses, no optimization can be done for their execution.</p>
subclasses, no optimization can be done for their execution. A module pass
can use function level passes (e.g. dominators) using getAnalysis interface
<tt> getAnalysis<DominatorTree>(Function)</tt>. </p>
<p>To write a correct <tt>ModulePass</tt> subclass, derive from
<tt>ModulePass</tt> and overload the <tt>runOnModule</tt> method with the
@ -1127,7 +1129,21 @@ runtime assertion failure if you attempt to get an analysis that you did not
declare as required in your <a
href="#getAnalysisUsage"><tt>getAnalysisUsage</tt></a> implementation. This
method can be called by your <tt>run*</tt> method implementation, or by any
other local method invoked by your <tt>run*</tt> method.</p>
other local method invoked by your <tt>run*</tt> method.
A module level pass can use function level analysis info using this interface.
For example:</p>
<div class="doc_code"><pre>
bool ModuleLevelPass::runOnModule(Module &amp;M) {
...
DominatorTree &amp;DT = getAnalysis&lt;DominatorTree&gt;(Function &amp;F);
...
}
</pre></div>
In above example, runOnFunction for DominatorTree is called by pass manager
before returning a reference to the desired pass.</p>
<p>
If your pass is capable of updating analyses if they exist (e.g.,