<div class="doc_code"><pre>
# Makefile for hello pass
-# Path to top level of LLVM heirarchy
+# Path to top level of LLVM hierarchy
LEVEL = ../../..
# Name of the library to build
<div class="doc_code"><pre>
<b>#include</b> "<a href="http://llvm.org/doxygen/Pass_8h-source.html">llvm/Pass.h</a>"
<b>#include</b> "<a href="http://llvm.org/doxygen/Function_8h-source.html">llvm/Function.h</a>"
+<b>#include</b> "<a href="http://llvm.org/doxygen/raw__ostream_8h.html">llvm/Support/raw_ostream.h</a>"
</pre></div>
<p>Which are needed because we are writing a <tt><a
-href="http://llvm.org/doxygen/classllvm_1_1Pass.html">Pass</a></tt>, and
+href="http://llvm.org/doxygen/classllvm_1_1Pass.html">Pass</a></tt>,
we are operating on <tt><a
-href="http://llvm.org/doxygen/classllvm_1_1Function.html">Function</a></tt>'s.</p>
+href="http://llvm.org/doxygen/classllvm_1_1Function.html">Function</a></tt>'s,
+and we will be doing some printing.</p>
<p>Next we have:</p>
<div class="doc_code"><pre>
<div class="doc_code"><pre>
<b>virtual bool</b> <a href="#runOnFunction">runOnFunction</a>(Function &F) {
- llvm::cerr << "<i>Hello: </i>" << F.getName() << "\n";
+ errs() << "<i>Hello: </i>" << F.getName() << "\n";
<b>return false</b>;
}
}; <i>// end of struct Hello</i>
<div class="doc_code"><pre>
<b>#include</b> "<a href="http://llvm.org/doxygen/Pass_8h-source.html">llvm/Pass.h</a>"
<b>#include</b> "<a href="http://llvm.org/doxygen/Function_8h-source.html">llvm/Function.h</a>"
+<b>#include</b> "<a href="http://llvm.org/doxygen/raw__ostream_8h.html">llvm/Support/raw_ostream.h</a>"
<b>using namespace llvm;</b>
Hello() : FunctionPass(&ID) {}
<b>virtual bool</b> <a href="#runOnFunction">runOnFunction</a>(Function &F) {
- llvm::cerr << "<i>Hello: </i>" << F.getName() << "\n";
+ errs() << "<i>Hello: </i>" << F.getName() << "\n";
<b>return false</b>;
}
};
<tt>/dev/null</tt>).</p>
<p>To see what happened to the other string you registered, try running
-<tt>opt</tt> with the <tt>--help</tt> option:</p>
+<tt>opt</tt> with the <tt>-help</tt> option:</p>
<div class="doc_code"><pre>
-$ opt -load ../../../Debug/lib/Hello.so --help
+$ opt -load ../../../Debug/lib/Hello.so -help
OVERVIEW: llvm .bc -> .bc modular optimizer
USAGE: opt [options] <input bitcode>
<p>When choosing a superclass for your Pass, you should choose the <b>most
specific</b> class possible, while still being able to meet the requirements
listed. This gives the LLVM Pass Infrastructure information necessary to
-optimize how passes are run, so that the resultant compiler isn't unneccesarily
+optimize how passes are run, so that the resultant compiler isn't unnecessarily
slow.</p>
</div>
href="http://llvm.org/doxygen/classllvm_1_1ModulePass.html">ModulePass</a></tt>"
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
+referring 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. A module pass
-can use function level passes (e.g. dominators) using getAnalysis interface
-<tt> getAnalysis<DominatorTree>(Function)</tt>, if the function pass
-does not require any module passes. </p>
+subclasses, no optimization can be done for their execution.</p>
+
+<p>A module pass can use function level passes (e.g. dominators) using
+the getAnalysis interface
+<tt>getAnalysis<DominatorTree>(llvm::Function *)</tt> to provide the
+function to retrieve analysis result for, if the function pass does not require
+any module or immutable passes. Note that this can only be done for functions for which the
+analysis ran, e.g. in the case of dominators you should only ask for the
+DominatorTree for function definitions, not declarations.</p>
<p>To write a correct <tt>ModulePass</tt> subclass, derive from
<tt>ModulePass</tt> and overload the <tt>runOnModule</tt> method with the
parameters. The first parameter is the name of the pass that is to be used on
the command line to specify that the pass should be added to a program (for
example, with <tt>opt</tt> or <tt>bugpoint</tt>). The second argument is the
-name of the pass, which is to be used for the <tt>--help</tt> output of
+name of the pass, which is to be used for the <tt>-help</tt> output of
programs, as
well as for debug output generated by the <tt>--debug-pass</tt> option.</p>
options that is useful for debugging pass execution, seeing how things work, and
diagnosing when you should be preserving more analyses than you currently are
(To get information about all of the variants of the <tt>--debug-pass</tt>
-option, just type '<tt>opt --help-hidden</tt>').</p>
+option, just type '<tt>opt -help-hidden</tt>').</p>
<p>By using the <tt>--debug-pass=Structure</tt> option, for example, we can see
how our <a href="#basiccode">Hello World</a> pass interacts with other passes.
</pre></div>
<p>Note the two spaces prior to the help string produces a tidy result on the
---help query.</p>
+-help query.</p>
<div class="doc_code"><pre>
-$ llc --help
+$ llc -help
...
- -regalloc - Register allocator to use: (default = linearscan)
+ -regalloc - Register allocator to use (default=linearscan)
=linearscan - linear scan register allocator
=local - local register allocator
=simple - simple register allocator
projects / oota-llvm.git / blobdiff