above all, a structuring technique for compiler code.</p>
<p>All LLVM passes are subclasses of the <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Pass.html">Pass</a></tt>
+href="http://llvm.org/doxygen/classllvm_1_1Pass.html">Pass</a></tt>
class, which implement functionality by overriding virtual methods inherited
from <tt>Pass</tt>. Depending on how your pass works, you should inherit from
the <tt><a href="#ModulePass">ModulePass</a></tt>, <tt><a
# Make the shared library become a loadable module so the tools can
# dlopen/dlsym on the resulting library.
-LOADABLE_MODULE
+LOADABLE_MODULE = 1
# Include the makefile implementation stuff
include $(LEVEL)/Makefile.common
Start out with:</p>
<pre>
-<b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Pass_8h-source.html">llvm/Pass.h</a>"
-<b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Function_8h-source.html">llvm/Function.h</a>"
+<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>"
</pre>
<p>Which are needed because we are writing a <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Pass.html">Pass</a></tt>, and
+href="http://llvm.org/doxygen/classllvm_1_1Pass.html">Pass</a></tt>, and
we are operating on <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Function.html">Function</a></tt>'s.</p>
+href="http://llvm.org/doxygen/classllvm_1_1Function.html">Function</a></tt>'s.</p>
<p>Next we have:</p>
<pre>
</pre><p>
<p>This declares a "<tt>Hello</tt>" class that is a subclass of <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1FunctionPass.html">FunctionPass</a></tt>.
+href="http://llvm.org/doxygen/classllvm_1_1FunctionPass.html">FunctionPass</a></tt>.
The different builtin pass subclasses are described in detail <a
href="#passtype">later</a>, but for now, know that <a
href="#FunctionPass"><tt>FunctionPass</tt></a>'s operate a function at a
<p>As a whole, the <tt>.cpp</tt> file looks like:</p>
<pre>
-<b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Pass_8h-source.html">llvm/Pass.h</a>"
-<b>#include</b> "<a href="http://llvm.cs.uiuc.edu/doxygen/Function_8h-source.html">llvm/Function.h</a>"
+<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>using namespace llvm;</b>
<div class="doc_text">
<p>The most plain and boring type of pass is the "<tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1ImmutablePass.html">ImmutablePass</a></tt>"
+href="http://llvm.org/doxygen/classllvm_1_1ImmutablePass.html">ImmutablePass</a></tt>"
class. This pass type is used for passes that do not have to be run, do not
change state, and never need to be updated. This is not a normal type of
transformation or analysis, but can provide information about the current
<div class="doc_text">
<p>The "<tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1ModulePass.html">ModulePass</a></tt>"
+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
<b>virtual bool</b> runOnModule(Module &M) = 0;
</pre>
-<p>The <tt>runOnModule</tt> method performs the interesting work of the pass,
-and should return true if the module was modified by the transformation, false
-otherwise.</p>
+<p>The <tt>runOnModule</tt> method performs the interesting work of the pass.
+It should return true if the module was modified by the transformation and
+false otherwise.</p>
</div>
<div class="doc_text">
<p>The "<tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1CallGraphSCCPass.html">CallGraphSCCPass</a></tt>"
+href="http://llvm.org/doxygen/classllvm_1_1CallGraphSCCPass.html">CallGraphSCCPass</a></tt>"
is used by passes that need to traverse the program bottom-up on the call graph
(callees before callers). Deriving from CallGraphSCCPass provides some
mechanics for building and traversing the CallGraph, but also allows the system
<div class="doc_text">
<p>In contrast to <tt>ModulePass</tt> subclasses, <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1Pass.html">FunctionPass</a></tt>
+href="http://llvm.org/doxygen/classllvm_1_1Pass.html">FunctionPass</a></tt>
subclasses do have a predictable, local behavior that can be expected by the
system. All <tt>FunctionPass</tt> execute on each function in the program
independent of all of the other functions in the program.
fast).</p>
<p>A good example of how this method should be used is the <a
-href="http://llvm.cs.uiuc.edu/doxygen/LowerAllocations_8cpp-source.html">LowerAllocations</a>
+href="http://llvm.org/doxygen/LowerAllocations_8cpp-source.html">LowerAllocations</a>
pass. This pass converts <tt>malloc</tt> and <tt>free</tt> instructions into
platform dependent <tt>malloc()</tt> and <tt>free()</tt> function calls. It
uses the <tt>doInitialization</tt> method to get a reference to the malloc and
<tt>Register*</tt> templates that should be used if you want your pass listed by
multiple or no utilities. This template takes an extra third argument that
specifies which tools it should be listed in. See the <a
-href="http://llvm.cs.uiuc.edu/doxygen/PassSupport_8h-source.html">PassSupport.h</a>
+href="http://llvm.org/doxygen/PassSupport_8h-source.html">PassSupport.h</a>
file for more information.</li>
</ul>
<p>By implementing the <tt>getAnalysisUsage</tt> method, the required and
invalidated sets may be specified for your transformation. The implementation
should fill in the <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AnalysisUsage.html">AnalysisUsage</a></tt>
+href="http://llvm.org/doxygen/classllvm_1_1AnalysisUsage.html">AnalysisUsage</a></tt>
object with information about which passes are required and not invalidated. To
do this, a pass may call any of the following methods on the AnalysisUsage
object:</p>
<pre>
<i>// This is an example implementation from an analysis, which does not modify
// the program at all, yet has a prerequisite.</i>
- <b>void</b> <a href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1PostDominanceFrontier.html">PostDominanceFrontier</a>::getAnalysisUsage(AnalysisUsage &AU) <b>const</b> {
+ <b>void</b> <a href="http://llvm.org/doxygen/classllvm_1_1PostDominanceFrontier.html">PostDominanceFrontier</a>::getAnalysisUsage(AnalysisUsage &AU) <b>const</b> {
AU.setPreservesAll();
- AU.addRequired<<a href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1PostDominatorTree.html">PostDominatorTree</a>>();
+ AU.addRequired<<a href="http://llvm.org/doxygen/classllvm_1_1PostDominatorTree.html">PostDominatorTree</a>>();
}
</pre>
<pre>
<i>// This example modifies the program, but does not modify the CFG</i>
- <b>void</b> <a href="http://llvm.cs.uiuc.edu/doxygen/structLICM.html">LICM</a>::getAnalysisUsage(AnalysisUsage &AU) <b>const</b> {
+ <b>void</b> <a href="http://llvm.org/doxygen/structLICM.html">LICM</a>::getAnalysisUsage(AnalysisUsage &AU) <b>const</b> {
AU.setPreservesCFG();
- AU.addRequired<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1LoopInfo.html">LoopInfo</a>>();
+ AU.addRequired<<a href="http://llvm.org/doxygen/classllvm_1_1LoopInfo.html">LoopInfo</a>>();
}
</pre>
href="#registerag"><tt>RegisterAnalysisGroup</tt></a>.</p>
<p>As a concrete example of an Analysis Group in action, consider the <a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>
+href="http://llvm.org/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>
analysis group. The default implementation of the alias analysis interface (the
<tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">basicaa</a></tt>
+href="http://llvm.org/doxygen/structBasicAliasAnalysis.html">basicaa</a></tt>
pass) just does a few simple checks that don't require significant analysis to
compute (such as: two different globals can never alias each other, etc).
Passes that use the <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a></tt>
+href="http://llvm.org/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a></tt>
interface (for example the <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/structGCSE.html">gcse</a></tt> pass), do
+href="http://llvm.org/doxygen/structGCSE.html">gcse</a></tt> pass), do
not care which implementation of alias analysis is actually provided, they just
use the designated interface.</p>
for the Analysis Group Interface itself, because it is "abstract":</p>
<pre>
- <b>static</b> RegisterAnalysisGroup<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>> A("<i>Alias Analysis</i>");
+ <b>static</b> RegisterAnalysisGroup<<a href="http://llvm.org/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>> A("<i>Alias Analysis</i>");
</pre>
<p>Once the analysis is registered, passes can declare that they are valid
B("<i>somefancyaa</i>", "<i>A more complex alias analysis implementation</i>");
//<i> Declare that we implement the AliasAnalysis interface</i>
- RegisterAnalysisGroup<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>, FancyAA> C;
+ RegisterAnalysisGroup<<a href="http://llvm.org/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>, FancyAA> C;
}
</pre>
<p>This just shows a class <tt>FancyAA</tt> that is registered normally, then
uses the <tt>RegisterAnalysisGroup</tt> template to "join" the <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a></tt>
+href="http://llvm.org/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a></tt>
analysis group. Every implementation of an analysis group should join using
this template. A single pass may join multiple different analysis groups with
no problem.</p>
<pre>
<b>namespace</b> {
//<i> Analysis Group implementations <b>must</b> be registered normally...</i>
- RegisterOpt<<a href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a>>
+ RegisterOpt<<a href="http://llvm.org/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a>>
D("<i>basicaa</i>", "<i>Basic Alias Analysis (default AA impl)</i>");
//<i> Declare that we implement the AliasAnalysis interface</i>
- RegisterAnalysisGroup<<a href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>, <a href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a>, <b>true</b>> E;
+ RegisterAnalysisGroup<<a href="http://llvm.org/doxygen/classllvm_1_1AliasAnalysis.html">AliasAnalysis</a>, <a href="http://llvm.org/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a>, <b>true</b>> E;
}
</pre>
argument to the <tt>RegisterAnalysisGroup</tt> template). There must be exactly
one default implementation available at all times for an Analysis Group to be
used. Here we declare that the <tt><a
-href="http://llvm.cs.uiuc.edu/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a></tt>
+href="http://llvm.org/doxygen/structBasicAliasAnalysis.html">BasicAliasAnalysis</a></tt>
pass is the default implementation for the interface.</p>
</div>
<div class="doc_text">
<p>The <a
-href="http://llvm.cs.uiuc.edu/doxygen/Statistic_8h-source.html"><tt>Statistic</tt></a>
-class, is designed to be an easy way to expose various success
+href="http://llvm.org/doxygen/Statistic_8h-source.html"><tt>Statistic</tt></a>
+class is designed to be an easy way to expose various success
metrics from passes. These statistics are printed at the end of a
run, when the -stats command line option is enabled on the command
line. See the <a href="http://llvm.org/docs/ProgrammersManual.html#Statistic">Statistics section</a> in the Programmer's Manual for details.
<div class="doc_text">
<p>The <a
-href="http://llvm.cs.uiuc.edu/doxygen/PassManager_8h-source.html"><tt>PassManager</tt></a>
+href="http://llvm.org/doxygen/PassManager_8h-source.html"><tt>PassManager</tt></a>
<a
-href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1PassManager.html">class</a>
+href="http://llvm.org/doxygen/classllvm_1_1PassManager.html">class</a>
takes a list of passes, ensures their <a href="#interaction">prerequisites</a>
are set up correctly, and then schedules passes to run efficiently. All of the
LLVM tools that run passes use the <tt>PassManager</tt> for execution of these
the LLVM program representation for a single function at a time, instead of
traversing the entire program. It reduces the memory consumption of compiler,
because, for example, only one <a
-href="http://llvm.cs.uiuc.edu/doxygen/structllvm_1_1DominatorSet.html"><tt>DominatorSet</tt></a>
+href="http://llvm.org/doxygen/classllvm_1_1DominatorSet.html"><tt>DominatorSet</tt></a>
needs to be calculated at a time. This also makes it possible some <a
href="#SMP">interesting enhancements</a> in the future.</p></li>
src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
- <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
</address>
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