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10 <div class="doc_title">
11 LLVM Programmer's Manual
15 <li><a href="#introduction">Introduction</a></li>
16 <li><a href="#general">General Information</a>
18 <li><a href="#stl">The C++ Standard Template Library</a></li>
20 <li>The <tt>-time-passes</tt> option</li>
21 <li>How to use the LLVM Makefile system</li>
22 <li>How to write a regression test</li>
27 <li><a href="#apis">Important and useful LLVM APIs</a>
29 <li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
30 and <tt>dyn_cast<></tt> templates</a> </li>
31 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt>
34 <li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
35 and the <tt>-debug-only</tt> option</a> </li>
38 <li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
41 <li>The <tt>InstVisitor</tt> template
42 <li>The general graph API
44 <li><a href="#ViewGraph">Viewing graphs while debugging code</a></li>
47 <li><a href="#common">Helpful Hints for Common Operations</a>
49 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
51 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
52 in a <tt>Function</tt></a> </li>
53 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
54 in a <tt>BasicBlock</tt></a> </li>
55 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
56 in a <tt>Function</tt></a> </li>
57 <li><a href="#iterate_convert">Turning an iterator into a
58 class pointer</a> </li>
59 <li><a href="#iterate_complex">Finding call sites: a more
60 complex example</a> </li>
61 <li><a href="#calls_and_invokes">Treating calls and invokes
62 the same way</a> </li>
63 <li><a href="#iterate_chains">Iterating over def-use &
64 use-def chains</a> </li>
67 <li><a href="#simplechanges">Making simple changes</a>
69 <li><a href="#schanges_creating">Creating and inserting new
70 <tt>Instruction</tt>s</a> </li>
71 <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
72 <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
73 with another <tt>Value</tt></a> </li>
77 <li>Working with the Control Flow Graph
79 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
87 <li><a href="#advanced">Advanced Topics</a>
89 <li><a href="#TypeResolve">LLVM Type Resolution</a>
91 <li><a href="#BuildRecType">Basic Recursive Type Construction</a></li>
92 <li><a href="#refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a></li>
93 <li><a href="#PATypeHolder">The PATypeHolder Class</a></li>
94 <li><a href="#AbstractTypeUser">The AbstractTypeUser Class</a></li>
97 <li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
100 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
102 <li><a href="#Value">The <tt>Value</tt> class</a>
104 <li><a href="#User">The <tt>User</tt> class</a>
106 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
108 <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
111 <li><a href="#Module">The <tt>Module</tt> class</a></li>
112 <li><a href="#Constant">The <tt>Constant</tt> class</a>
114 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
116 <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
117 <li><a href="#Function">The <tt>Function</tt> class</a></li>
118 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
125 <li><a href="#Type">The <tt>Type</tt> class</a> </li>
126 <li><a href="#Argument">The <tt>Argument</tt> class</a></li>
133 <div class="doc_author">
134 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
135 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
136 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
137 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
140 <!-- *********************************************************************** -->
141 <div class="doc_section">
142 <a name="introduction">Introduction </a>
144 <!-- *********************************************************************** -->
146 <div class="doc_text">
148 <p>This document is meant to highlight some of the important classes and
149 interfaces available in the LLVM source-base. This manual is not
150 intended to explain what LLVM is, how it works, and what LLVM code looks
151 like. It assumes that you know the basics of LLVM and are interested
152 in writing transformations or otherwise analyzing or manipulating the
155 <p>This document should get you oriented so that you can find your
156 way in the continuously growing source code that makes up the LLVM
157 infrastructure. Note that this manual is not intended to serve as a
158 replacement for reading the source code, so if you think there should be
159 a method in one of these classes to do something, but it's not listed,
160 check the source. Links to the <a href="/doxygen/">doxygen</a> sources
161 are provided to make this as easy as possible.</p>
163 <p>The first section of this document describes general information that is
164 useful to know when working in the LLVM infrastructure, and the second describes
165 the Core LLVM classes. In the future this manual will be extended with
166 information describing how to use extension libraries, such as dominator
167 information, CFG traversal routines, and useful utilities like the <tt><a
168 href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
172 <!-- *********************************************************************** -->
173 <div class="doc_section">
174 <a name="general">General Information</a>
176 <!-- *********************************************************************** -->
178 <div class="doc_text">
180 <p>This section contains general information that is useful if you are working
181 in the LLVM source-base, but that isn't specific to any particular API.</p>
185 <!-- ======================================================================= -->
186 <div class="doc_subsection">
187 <a name="stl">The C++ Standard Template Library</a>
190 <div class="doc_text">
192 <p>LLVM makes heavy use of the C++ Standard Template Library (STL),
193 perhaps much more than you are used to, or have seen before. Because of
194 this, you might want to do a little background reading in the
195 techniques used and capabilities of the library. There are many good
196 pages that discuss the STL, and several books on the subject that you
197 can get, so it will not be discussed in this document.</p>
199 <p>Here are some useful links:</p>
203 <li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
204 reference</a> - an excellent reference for the STL and other parts of the
205 standard C++ library.</li>
207 <li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
208 O'Reilly book in the making. It has a decent
210 Reference that rivals Dinkumware's, and is unfortunately no longer free since the book has been
213 <li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
216 <li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
218 href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
221 <li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
224 <li><a href="http://64.78.49.204/">
225 Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
230 <p>You are also encouraged to take a look at the <a
231 href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
232 to write maintainable code more than where to put your curly braces.</p>
236 <!-- ======================================================================= -->
237 <div class="doc_subsection">
238 <a name="stl">Other useful references</a>
241 <div class="doc_text">
244 <li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
245 Branch and Tag Primer</a></li>
246 <li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
247 static and shared libraries across platforms</a></li>
252 <!-- *********************************************************************** -->
253 <div class="doc_section">
254 <a name="apis">Important and useful LLVM APIs</a>
256 <!-- *********************************************************************** -->
258 <div class="doc_text">
260 <p>Here we highlight some LLVM APIs that are generally useful and good to
261 know about when writing transformations.</p>
265 <!-- ======================================================================= -->
266 <div class="doc_subsection">
267 <a name="isa">The <tt>isa<></tt>, <tt>cast<></tt> and
268 <tt>dyn_cast<></tt> templates</a>
271 <div class="doc_text">
273 <p>The LLVM source-base makes extensive use of a custom form of RTTI.
274 These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
275 operator, but they don't have some drawbacks (primarily stemming from
276 the fact that <tt>dynamic_cast<></tt> only works on classes that
277 have a v-table). Because they are used so often, you must know what they
278 do and how they work. All of these templates are defined in the <a
279 href="/doxygen/Casting_8h-source.html"><tt>llvm/Support/Casting.h</tt></a>
280 file (note that you very rarely have to include this file directly).</p>
283 <dt><tt>isa<></tt>: </dt>
285 <dd>The <tt>isa<></tt> operator works exactly like the Java
286 "<tt>instanceof</tt>" operator. It returns true or false depending on whether
287 a reference or pointer points to an instance of the specified class. This can
288 be very useful for constraint checking of various sorts (example below).</dd>
290 <dt><tt>cast<></tt>: </dt>
292 <dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
293 converts a pointer or reference from a base class to a derived cast, causing
294 an assertion failure if it is not really an instance of the right type. This
295 should be used in cases where you have some information that makes you believe
296 that something is of the right type. An example of the <tt>isa<></tt>
297 and <tt>cast<></tt> template is:
300 static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
301 if (isa<<a href="#Constant">Constant</a>>(V) || isa<<a href="#Argument">Argument</a>>(V) || isa<<a href="#GlobalValue">GlobalValue</a>>(V))
304 <i>// Otherwise, it must be an instruction...</i>
305 return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
309 <p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
310 by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
315 <dt><tt>dyn_cast<></tt>:</dt>
317 <dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
318 checks to see if the operand is of the specified type, and if so, returns a
319 pointer to it (this operator does not work with references). If the operand is
320 not of the correct type, a null pointer is returned. Thus, this works very
321 much like the <tt>dynamic_cast<></tt> operator in C++, and should be
322 used in the same circumstances. Typically, the <tt>dyn_cast<></tt>
323 operator is used in an <tt>if</tt> statement or some other flow control
327 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
332 <p>This form of the <tt>if</tt> statement effectively combines together a call
333 to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
334 statement, which is very convenient.</p>
336 <p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
337 <tt>dynamic_cast<></tt> or Java's <tt>instanceof</tt> operator, can be
338 abused. In particular, you should not use big chained <tt>if/then/else</tt>
339 blocks to check for lots of different variants of classes. If you find
340 yourself wanting to do this, it is much cleaner and more efficient to use the
341 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
345 <dt><tt>cast_or_null<></tt>: </dt>
347 <dd>The <tt>cast_or_null<></tt> operator works just like the
348 <tt>cast<></tt> operator, except that it allows for a null pointer as an
349 argument (which it then propagates). This can sometimes be useful, allowing
350 you to combine several null checks into one.</dd>
352 <dt><tt>dyn_cast_or_null<></tt>: </dt>
354 <dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
355 <tt>dyn_cast<></tt> operator, except that it allows for a null pointer
356 as an argument (which it then propagates). This can sometimes be useful,
357 allowing you to combine several null checks into one.</dd>
361 <p>These five templates can be used with any classes, whether they have a
362 v-table or not. To add support for these templates, you simply need to add
363 <tt>classof</tt> static methods to the class you are interested casting
364 to. Describing this is currently outside the scope of this document, but there
365 are lots of examples in the LLVM source base.</p>
369 <!-- ======================================================================= -->
370 <div class="doc_subsection">
371 <a name="DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt> option</a>
374 <div class="doc_text">
376 <p>Often when working on your pass you will put a bunch of debugging printouts
377 and other code into your pass. After you get it working, you want to remove
378 it... but you may need it again in the future (to work out new bugs that you run
381 <p> Naturally, because of this, you don't want to delete the debug printouts,
382 but you don't want them to always be noisy. A standard compromise is to comment
383 them out, allowing you to enable them if you need them in the future.</p>
385 <p>The "<tt><a href="/doxygen/Debug_8h-source.html">llvm/Support/Debug.h</a></tt>"
386 file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
387 this problem. Basically, you can put arbitrary code into the argument of the
388 <tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
389 tool) is run with the '<tt>-debug</tt>' command line argument:</p>
391 <pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
393 <p>Then you can run your pass like this:</p>
395 <pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> I am here!<br> $<br></pre>
397 <p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
398 to not have to create "yet another" command line option for the debug output for
399 your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
400 so they do not cause a performance impact at all (for the same reason, they
401 should also not contain side-effects!).</p>
403 <p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
404 enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
405 "<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
406 program hasn't been started yet, you can always just run it with
411 <!-- _______________________________________________________________________ -->
412 <div class="doc_subsubsection">
413 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt> and
414 the <tt>-debug-only</tt> option</a>
417 <div class="doc_text">
419 <p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
420 just turns on <b>too much</b> information (such as when working on the code
421 generator). If you want to enable debug information with more fine-grained
422 control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
423 option as follows:</p>
425 <pre> ...<br> DEBUG(std::cerr << "No debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "foo"<br> DEBUG(std::cerr << "'foo' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "bar"<br> DEBUG(std::cerr << "'bar' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE ""<br> DEBUG(std::cerr << "No debug type (2)\n");<br> ...<br></pre>
427 <p>Then you can run your pass like this:</p>
429 <pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> No debug type<br> 'foo' debug type<br> 'bar' debug type<br> No debug type (2)<br> $ opt < a.bc > /dev/null -mypass -debug-only=foo<br> 'foo' debug type<br> $ opt < a.bc > /dev/null -mypass -debug-only=bar<br> 'bar' debug type<br> $<br></pre>
431 <p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
432 a file, to specify the debug type for the entire module (if you do this before
433 you <tt>#include "llvm/Support/Debug.h"</tt>, you don't have to insert the ugly
434 <tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
435 "bar", because there is no system in place to ensure that names do not
436 conflict. If two different modules use the same string, they will all be turned
437 on when the name is specified. This allows, for example, all debug information
438 for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
439 even if the source lives in multiple files.</p>
443 <!-- ======================================================================= -->
444 <div class="doc_subsection">
445 <a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
449 <div class="doc_text">
452 href="/doxygen/Statistic_8h-source.html">llvm/ADT/Statistic.h</a></tt>" file
453 provides a template named <tt>Statistic</tt> that is used as a unified way to
454 keep track of what the LLVM compiler is doing and how effective various
455 optimizations are. It is useful to see what optimizations are contributing to
456 making a particular program run faster.</p>
458 <p>Often you may run your pass on some big program, and you're interested to see
459 how many times it makes a certain transformation. Although you can do this with
460 hand inspection, or some ad-hoc method, this is a real pain and not very useful
461 for big programs. Using the <tt>Statistic</tt> template makes it very easy to
462 keep track of this information, and the calculated information is presented in a
463 uniform manner with the rest of the passes being executed.</p>
465 <p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
466 it are as follows:</p>
469 <li>Define your statistic like this:
470 <pre>static Statistic<> NumXForms("mypassname", "The # of times I did stuff");<br></pre>
472 <p>The <tt>Statistic</tt> template can emulate just about any data-type,
473 but if you do not specify a template argument, it defaults to acting like
474 an unsigned int counter (this is usually what you want).</p></li>
476 <li>Whenever you make a transformation, bump the counter:
477 <pre> ++NumXForms; // I did stuff<br></pre>
481 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
482 statistics gathered, use the '<tt>-stats</tt>' option:</p>
484 <pre> $ opt -stats -mypassname < program.bc > /dev/null<br> ... statistic output ...<br></pre>
486 <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
487 suite, it gives a report that looks like this:</p>
489 <pre> 7646 bytecodewriter - Number of normal instructions<br> 725 bytecodewriter - Number of oversized instructions<br> 129996 bytecodewriter - Number of bytecode bytes written<br> 2817 raise - Number of insts DCEd or constprop'd<br> 3213 raise - Number of cast-of-self removed<br> 5046 raise - Number of expression trees converted<br> 75 raise - Number of other getelementptr's formed<br> 138 raise - Number of load/store peepholes<br> 42 deadtypeelim - Number of unused typenames removed from symtab<br> 392 funcresolve - Number of varargs functions resolved<br> 27 globaldce - Number of global variables removed<br> 2 adce - Number of basic blocks removed<br> 134 cee - Number of branches revectored<br> 49 cee - Number of setcc instruction eliminated<br> 532 gcse - Number of loads removed<br> 2919 gcse - Number of instructions removed<br> 86 indvars - Number of canonical indvars added<br> 87 indvars - Number of aux indvars removed<br> 25 instcombine - Number of dead inst eliminate<br> 434 instcombine - Number of insts combined<br> 248 licm - Number of load insts hoisted<br> 1298 licm - Number of insts hoisted to a loop pre-header<br> 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)<br> 75 mem2reg - Number of alloca's promoted<br> 1444 cfgsimplify - Number of blocks simplified<br></pre>
491 <p>Obviously, with so many optimizations, having a unified framework for this
492 stuff is very nice. Making your pass fit well into the framework makes it more
493 maintainable and useful.</p>
497 <!-- ======================================================================= -->
498 <div class="doc_subsection">
499 <a name="ViewGraph">Viewing graphs while debugging code</a>
502 <div class="doc_text">
504 <p>Several of the important data structures in LLVM are graphs: for example
505 CFGs made out of LLVM <a href="#BasicBlock">BasicBlock</a>s, CFGs made out of
506 LLVM <a href="CodeGenerator.html#machinebasicblock">MachineBasicBlock</a>s, and
507 <a href="CodeGenerator.html#selectiondag_intro">Instruction Selection
508 DAGs</a>. In many cases, while debugging various parts of the compiler, it is
509 nice to instantly visualize these graphs.</p>
511 <p>LLVM provides several callbacks that are available in a debug build to do
512 exactly that. If you call the <tt>Function::viewCFG()</tt> method, for example,
513 the current LLVM tool will pop up a window containing the CFG for the function
514 where each basic block is a node in the graph, and each node contains the
515 instructions in the block. Similarly, there also exists
516 <tt>Function::viewCFGOnly()</tt> (does not include the instructions), the
517 <tt>MachineFunction::viewCFG()</tt> and <tt>MachineFunction::viewCFGOnly()</tt>,
518 and the <tt>SelectionDAG::viewGraph()</tt> methods. Within GDB, for example,
519 you can usually use something like <tt>call DAG.viewGraph()</tt> to pop
520 up a window. Alternatively, you can sprinkle calls to these functions in your
521 code in places you want to debug.</p>
523 <p>Getting this to work requires a small amount of configuration. On Unix
524 systems with X11, install the <a href="http://www.graphviz.org">graphviz</a>
525 toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
526 Mac OS/X, download and install the Mac OS/X <a
527 href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
528 <tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or whereever you install
529 it) to your path. Once in your system and path are set up, rerun the LLVM
530 configure script and rebuild LLVM to enable this functionality.</p>
532 <p><tt>SelectionDAG</tt> has been extended to make it easier to locate
533 <i>interesting</i> nodes in large complex graphs. From gdb, if you
534 <tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
535 next <tt>call DAG.viewGraph()</tt> would hilight the node in the
536 specified color (choices of colors can be found at <a
537 href="http://www.graphviz.org/doc/info/colors.html">Colors<a>.) More
538 complex node attributes can be provided with <tt>call
539 DAG.setGraphAttrs(<i>node</i>, "<i>attributes</i>")</tt> (choices can be
540 found at <a href="http://www.graphviz.org/doc/info/attrs.html">Graph
541 Attributes</a>.) If you want to restart and clear all the current graph
542 attributes, then you can <tt>call DAG.clearGraphAttrs()</tt>. </p>
547 <!-- *********************************************************************** -->
548 <div class="doc_section">
549 <a name="common">Helpful Hints for Common Operations</a>
551 <!-- *********************************************************************** -->
553 <div class="doc_text">
555 <p>This section describes how to perform some very simple transformations of
556 LLVM code. This is meant to give examples of common idioms used, showing the
557 practical side of LLVM transformations. <p> Because this is a "how-to" section,
558 you should also read about the main classes that you will be working with. The
559 <a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
560 and descriptions of the main classes that you should know about.</p>
564 <!-- NOTE: this section should be heavy on example code -->
565 <!-- ======================================================================= -->
566 <div class="doc_subsection">
567 <a name="inspection">Basic Inspection and Traversal Routines</a>
570 <div class="doc_text">
572 <p>The LLVM compiler infrastructure have many different data structures that may
573 be traversed. Following the example of the C++ standard template library, the
574 techniques used to traverse these various data structures are all basically the
575 same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
576 method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
577 function returns an iterator pointing to one past the last valid element of the
578 sequence, and there is some <tt>XXXiterator</tt> data type that is common
579 between the two operations.</p>
581 <p>Because the pattern for iteration is common across many different aspects of
582 the program representation, the standard template library algorithms may be used
583 on them, and it is easier to remember how to iterate. First we show a few common
584 examples of the data structures that need to be traversed. Other data
585 structures are traversed in very similar ways.</p>
589 <!-- _______________________________________________________________________ -->
590 <div class="doc_subsubsection">
591 <a name="iterate_function">Iterating over the </a><a
592 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
593 href="#Function"><tt>Function</tt></a>
596 <div class="doc_text">
598 <p>It's quite common to have a <tt>Function</tt> instance that you'd like to
599 transform in some way; in particular, you'd like to manipulate its
600 <tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
601 the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
602 an example that prints the name of a <tt>BasicBlock</tt> and the number of
603 <tt>Instruction</tt>s it contains:</p>
605 <pre> // func is a pointer to a Function instance<br> for (Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {<br><br> // print out the name of the basic block if it has one, and then the<br> // number of instructions that it contains<br><br> std::cerr << "Basic block (name=" << i->getName() << ") has " <br> << i->size() << " instructions.\n";<br> }<br></pre>
607 <p>Note that i can be used as if it were a pointer for the purposes of
608 invoking member functions of the <tt>Instruction</tt> class. This is
609 because the indirection operator is overloaded for the iterator
610 classes. In the above code, the expression <tt>i->size()</tt> is
611 exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
615 <!-- _______________________________________________________________________ -->
616 <div class="doc_subsubsection">
617 <a name="iterate_basicblock">Iterating over the </a><a
618 href="#Instruction"><tt>Instruction</tt></a>s in a <a
619 href="#BasicBlock"><tt>BasicBlock</tt></a>
622 <div class="doc_text">
624 <p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
625 easy to iterate over the individual instructions that make up
626 <tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
627 a <tt>BasicBlock</tt>:</p>
630 // blk is a pointer to a BasicBlock instance
631 for (BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)
632 // the next statement works since operator<<(ostream&,...)
633 // is overloaded for Instruction&
634 std::cerr << *i << "\n";
637 <p>However, this isn't really the best way to print out the contents of a
638 <tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
639 anything you'll care about, you could have just invoked the print routine on the
640 basic block itself: <tt>std::cerr << *blk << "\n";</tt>.</p>
644 <!-- _______________________________________________________________________ -->
645 <div class="doc_subsubsection">
646 <a name="iterate_institer">Iterating over the </a><a
647 href="#Instruction"><tt>Instruction</tt></a>s in a <a
648 href="#Function"><tt>Function</tt></a>
651 <div class="doc_text">
653 <p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
654 <tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
655 <tt>InstIterator</tt> should be used instead. You'll need to include <a
656 href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
657 and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
658 small example that shows how to dump all instructions in a function to the standard error stream:<p>
660 <pre>#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"<br>...<br>// Suppose F is a ptr to a function<br>for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)<br> std::cerr << *i << "\n";<br></pre>
661 Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
662 worklist with its initial contents. For example, if you wanted to
663 initialize a worklist to contain all instructions in a <tt>Function</tt>
664 F, all you would need to do is something like:
665 <pre>std::set<Instruction*> worklist;<br>worklist.insert(inst_begin(F), inst_end(F));<br></pre>
667 <p>The STL set <tt>worklist</tt> would now contain all instructions in the
668 <tt>Function</tt> pointed to by F.</p>
672 <!-- _______________________________________________________________________ -->
673 <div class="doc_subsubsection">
674 <a name="iterate_convert">Turning an iterator into a class pointer (and
678 <div class="doc_text">
680 <p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
681 instance when all you've got at hand is an iterator. Well, extracting
682 a reference or a pointer from an iterator is very straight-forward.
683 Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
684 is a <tt>BasicBlock::const_iterator</tt>:</p>
686 <pre> Instruction& inst = *i; // grab reference to instruction reference<br> Instruction* pinst = &*i; // grab pointer to instruction reference<br> const Instruction& inst = *j;<br></pre>
688 <p>However, the iterators you'll be working with in the LLVM framework are
689 special: they will automatically convert to a ptr-to-instance type whenever they
690 need to. Instead of dereferencing the iterator and then taking the address of
691 the result, you can simply assign the iterator to the proper pointer type and
692 you get the dereference and address-of operation as a result of the assignment
693 (behind the scenes, this is a result of overloading casting mechanisms). Thus
694 the last line of the last example,</p>
696 <pre>Instruction* pinst = &*i;</pre>
698 <p>is semantically equivalent to</p>
700 <pre>Instruction* pinst = i;</pre>
702 <p>It's also possible to turn a class pointer into the corresponding iterator,
703 and this is a constant time operation (very efficient). The following code
704 snippet illustrates use of the conversion constructors provided by LLVM
705 iterators. By using these, you can explicitly grab the iterator of something
706 without actually obtaining it via iteration over some structure:</p>
708 <pre>void printNextInstruction(Instruction* inst) {<br> BasicBlock::iterator it(inst);<br> ++it; // after this line, it refers to the instruction after *inst.<br> if (it != inst->getParent()->end()) std::cerr << *it << "\n";<br>}<br></pre>
712 <!--_______________________________________________________________________-->
713 <div class="doc_subsubsection">
714 <a name="iterate_complex">Finding call sites: a slightly more complex
718 <div class="doc_text">
720 <p>Say that you're writing a FunctionPass and would like to count all the
721 locations in the entire module (that is, across every <tt>Function</tt>) where a
722 certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
723 learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
724 much more straight-forward manner, but this example will allow us to explore how
725 you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
726 is what we want to do:</p>
728 <pre>initialize callCounter to zero<br>for each Function f in the Module<br> for each BasicBlock b in f<br> for each Instruction i in b<br> if (i is a CallInst and calls the given function)<br> increment callCounter<br></pre>
730 <p>And the actual code is (remember, since we're writing a
731 <tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
732 override the <tt>runOnFunction</tt> method...):</p>
734 <pre>Function* targetFunc = ...;<br><br>class OurFunctionPass : public FunctionPass {<br> public:<br> OurFunctionPass(): callCounter(0) { }<br><br> virtual runOnFunction(Function& F) {<br> for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {<br> for (BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {<br> if (<a
735 href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
736 href="#CallInst">CallInst</a>>(&*i)) {<br> // we know we've encountered a call instruction, so we<br> // need to determine if it's a call to the<br> // function pointed to by m_func or not.<br> <br> if (callInst->getCalledFunction() == targetFunc)<br> ++callCounter;<br> }<br> }<br> }<br> <br> private:<br> unsigned callCounter;<br>};<br></pre>
740 <!--_______________________________________________________________________-->
741 <div class="doc_subsubsection">
742 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
745 <div class="doc_text">
747 <p>You may have noticed that the previous example was a bit oversimplified in
748 that it did not deal with call sites generated by 'invoke' instructions. In
749 this, and in other situations, you may find that you want to treat
750 <tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
751 most-specific common base class is <tt>Instruction</tt>, which includes lots of
752 less closely-related things. For these cases, LLVM provides a handy wrapper
754 href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
755 It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
756 methods that provide functionality common to <tt>CallInst</tt>s and
757 <tt>InvokeInst</tt>s.</p>
759 <p>This class has "value semantics": it should be passed by value, not by
760 reference and it should not be dynamically allocated or deallocated using
761 <tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
762 assignable and constructable, with costs equivalents to that of a bare pointer.
763 If you look at its definition, it has only a single pointer member.</p>
767 <!--_______________________________________________________________________-->
768 <div class="doc_subsubsection">
769 <a name="iterate_chains">Iterating over def-use & use-def chains</a>
772 <div class="doc_text">
774 <p>Frequently, we might have an instance of the <a
775 href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
776 determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
777 <tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
778 For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
779 particular function <tt>foo</tt>. Finding all of the instructions that
780 <i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
783 <pre>Function* F = ...;<br><br>for (Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {<br> if (Instruction *Inst = dyn_cast<Instruction>(*i)) {<br> std::cerr << "F is used in instruction:\n";<br> std::cerr << *Inst << "\n";<br> }<br>}<br></pre>
785 <p>Alternately, it's common to have an instance of the <a
786 href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
787 <tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
788 <tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
789 <tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
790 all of the values that a particular instruction uses (that is, the operands of
791 the particular <tt>Instruction</tt>):</p>
793 <pre>Instruction* pi = ...;<br><br>for (User::op_iterator i = pi->op_begin(), e = pi->op_end(); i != e; ++i) {<br> Value* v = *i;<br> ...<br>}<br></pre>
796 def-use chains ("finding all users of"): Value::use_begin/use_end
797 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
802 <!-- ======================================================================= -->
803 <div class="doc_subsection">
804 <a name="simplechanges">Making simple changes</a>
807 <div class="doc_text">
809 <p>There are some primitive transformation operations present in the LLVM
810 infrastructure that are worth knowing about. When performing
811 transformations, it's fairly common to manipulate the contents of basic
812 blocks. This section describes some of the common methods for doing so
813 and gives example code.</p>
817 <!--_______________________________________________________________________-->
818 <div class="doc_subsubsection">
819 <a name="schanges_creating">Creating and inserting new
820 <tt>Instruction</tt>s</a>
823 <div class="doc_text">
825 <p><i>Instantiating Instructions</i></p>
827 <p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
828 constructor for the kind of instruction to instantiate and provide the necessary
829 parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
830 (const-ptr-to) <tt>Type</tt>. Thus:</p>
832 <pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
834 <p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
835 one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
836 subclass is likely to have varying default parameters which change the semantics
837 of the instruction, so refer to the <a
838 href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
839 Instruction</a> that you're interested in instantiating.</p>
841 <p><i>Naming values</i></p>
843 <p>It is very useful to name the values of instructions when you're able to, as
844 this facilitates the debugging of your transformations. If you end up looking
845 at generated LLVM machine code, you definitely want to have logical names
846 associated with the results of instructions! By supplying a value for the
847 <tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
848 associate a logical name with the result of the instruction's execution at
849 runtime. For example, say that I'm writing a transformation that dynamically
850 allocates space for an integer on the stack, and that integer is going to be
851 used as some kind of index by some other code. To accomplish this, I place an
852 <tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
853 <tt>Function</tt>, and I'm intending to use it within the same
854 <tt>Function</tt>. I might do:</p>
856 <pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
858 <p>where <tt>indexLoc</tt> is now the logical name of the instruction's
859 execution value, which is a pointer to an integer on the runtime stack.</p>
861 <p><i>Inserting instructions</i></p>
863 <p>There are essentially two ways to insert an <tt>Instruction</tt>
864 into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
867 <li>Insertion into an explicit instruction list
869 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
870 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
871 before <tt>*pi</tt>, we do the following: </p>
873 <pre> BasicBlock *pb = ...;<br> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb<br></pre>
875 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
876 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
877 classes provide constructors which take a pointer to a
878 <tt>BasicBlock</tt> to be appended to. For example code that
881 <pre> BasicBlock *pb = ...;<br> Instruction *newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
885 <pre> BasicBlock *pb = ...;<br> Instruction *newInst = new Instruction(..., pb);<br></pre>
887 <p>which is much cleaner, especially if you are creating
888 long instruction streams.</p></li>
890 <li>Insertion into an implicit instruction list
892 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
893 are implicitly associated with an existing instruction list: the instruction
894 list of the enclosing basic block. Thus, we could have accomplished the same
895 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
898 <pre> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
900 <p>In fact, this sequence of steps occurs so frequently that the
901 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
902 constructors which take (as a default parameter) a pointer to an
903 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
904 precede. That is, <tt>Instruction</tt> constructors are capable of
905 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
906 provided instruction, immediately before that instruction. Using an
907 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
908 parameter, the above code becomes:</p>
910 <pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
912 <p>which is much cleaner, especially if you're creating a lot of
913 instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
918 <!--_______________________________________________________________________-->
919 <div class="doc_subsubsection">
920 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
923 <div class="doc_text">
925 <p>Deleting an instruction from an existing sequence of instructions that form a
926 <a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
927 you must have a pointer to the instruction that you wish to delete. Second, you
928 need to obtain the pointer to that instruction's basic block. You use the
929 pointer to the basic block to get its list of instructions and then use the
930 erase function to remove your instruction. For example:</p>
932 <pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
933 href="#BasicBlock">BasicBlock</a> *BB = I->getParent();<br> BB->getInstList().erase(I);<br></pre>
937 <!--_______________________________________________________________________-->
938 <div class="doc_subsubsection">
939 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
943 <div class="doc_text">
945 <p><i>Replacing individual instructions</i></p>
947 <p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
948 permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
949 and <tt>ReplaceInstWithInst</tt>.</p>
951 <h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
954 <li><tt>ReplaceInstWithValue</tt>
956 <p>This function replaces all uses (within a basic block) of a given
957 instruction with a value, and then removes the original instruction. The
958 following example illustrates the replacement of the result of a particular
959 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
960 pointer to an integer.</p>
962 <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
964 <li><tt>ReplaceInstWithInst</tt>
966 <p>This function replaces a particular instruction with another
967 instruction. The following example illustrates the replacement of one
968 <tt>AllocaInst</tt> with another.</p>
970 <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithInst(instToReplace->getParent()->getInstList(), ii,<br> new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));<br></pre></li>
973 <p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
975 <p>You can use <tt>Value::replaceAllUsesWith</tt> and
976 <tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
977 doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
978 and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
981 <!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
982 include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
983 ReplaceInstWithValue, ReplaceInstWithInst -->
987 <!-- *********************************************************************** -->
988 <div class="doc_section">
989 <a name="advanced">Advanced Topics</a>
991 <!-- *********************************************************************** -->
993 <div class="doc_text">
995 This section describes some of the advanced or obscure API's that most clients
996 do not need to be aware of. These API's tend manage the inner workings of the
997 LLVM system, and only need to be accessed in unusual circumstances.
1001 <!-- ======================================================================= -->
1002 <div class="doc_subsection">
1003 <a name="TypeResolve">LLVM Type Resolution</a>
1006 <div class="doc_text">
1009 The LLVM type system has a very simple goal: allow clients to compare types for
1010 structural equality with a simple pointer comparison (aka a shallow compare).
1011 This goal makes clients much simpler and faster, and is used throughout the LLVM
1016 Unfortunately achieving this goal is not a simple matter. In particular,
1017 recursive types and late resolution of opaque types makes the situation very
1018 difficult to handle. Fortunately, for the most part, our implementation makes
1019 most clients able to be completely unaware of the nasty internal details. The
1020 primary case where clients are exposed to the inner workings of it are when
1021 building a recursive type. In addition to this case, the LLVM bytecode reader,
1022 assembly parser, and linker also have to be aware of the inner workings of this
1027 For our purposes below, we need three concepts. First, an "Opaque Type" is
1028 exactly as defined in the <a href="LangRef.html#t_opaque">language
1029 reference</a>. Second an "Abstract Type" is any type which includes an
1030 opaque type as part of its type graph (for example "<tt>{ opaque, int }</tt>").
1031 Third, a concrete type is a type that is not an abstract type (e.g. "<tt>[ int,
1037 <!-- ______________________________________________________________________ -->
1038 <div class="doc_subsubsection">
1039 <a name="BuildRecType">Basic Recursive Type Construction</a>
1042 <div class="doc_text">
1045 Because the most common question is "how do I build a recursive type with LLVM",
1046 we answer it now and explain it as we go. Here we include enough to cause this
1047 to be emitted to an output .ll file:
1051 %mylist = type { %mylist*, int }
1055 To build this, use the following LLVM APIs:
1059 //<i> Create the initial outer struct.</i>
1060 <a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
1061 std::vector<const Type*> Elts;
1062 Elts.push_back(PointerType::get(StructTy));
1063 Elts.push_back(Type::IntTy);
1064 StructType *NewSTy = StructType::get(Elts);
1066 //<i> At this point, NewSTy = "{ opaque*, int }". Tell VMCore that</i>
1067 //<i> the struct and the opaque type are actually the same.</i>
1068 cast<OpaqueType>(StructTy.get())-><a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
1070 // <i>NewSTy is potentially invalidated, but StructTy (a <a href="#PATypeHolder">PATypeHolder</a>) is</i>
1071 // <i>kept up-to-date.</i>
1072 NewSTy = cast<StructType>(StructTy.get());
1074 // <i>Add a name for the type to the module symbol table (optional).</i>
1075 MyModule->addTypeName("mylist", NewSTy);
1079 This code shows the basic approach used to build recursive types: build a
1080 non-recursive type using 'opaque', then use type unification to close the cycle.
1081 The type unification step is performed by the <tt><a
1082 ref="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
1083 described next. After that, we describe the <a
1084 href="#PATypeHolder">PATypeHolder class</a>.
1089 <!-- ______________________________________________________________________ -->
1090 <div class="doc_subsubsection">
1091 <a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
1094 <div class="doc_text">
1096 The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
1097 While this method is actually a member of the DerivedType class, it is most
1098 often used on OpaqueType instances. Type unification is actually a recursive
1099 process. After unification, types can become structurally isomorphic to
1100 existing types, and all duplicates are deleted (to preserve pointer equality).
1104 In the example above, the OpaqueType object is definitely deleted.
1105 Additionally, if there is an "{ \2*, int}" type already created in the system,
1106 the pointer and struct type created are <b>also</b> deleted. Obviously whenever
1107 a type is deleted, any "Type*" pointers in the program are invalidated. As
1108 such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
1109 live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
1110 types can never move or be deleted). To deal with this, the <a
1111 href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
1112 reference to a possibly refined type, and the <a
1113 href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
1114 complex datastructures.
1119 <!-- ______________________________________________________________________ -->
1120 <div class="doc_subsubsection">
1121 <a name="PATypeHolder">The PATypeHolder Class</a>
1124 <div class="doc_text">
1126 PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
1127 happily goes about nuking types that become isomorphic to existing types, it
1128 automatically updates all PATypeHolder objects to point to the new type. In the
1129 example above, this allows the code to maintain a pointer to the resultant
1130 resolved recursive type, even though the Type*'s are potentially invalidated.
1134 PATypeHolder is an extremely light-weight object that uses a lazy union-find
1135 implementation to update pointers. For example the pointer from a Value to its
1136 Type is maintained by PATypeHolder objects.
1141 <!-- ______________________________________________________________________ -->
1142 <div class="doc_subsubsection">
1143 <a name="AbstractTypeUser">The AbstractTypeUser Class</a>
1146 <div class="doc_text">
1149 Some data structures need more to perform more complex updates when types get
1150 resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
1151 move and potentially merge type planes in its representation when a pointer
1155 To support this, a class can derive from the AbstractTypeUser class. This class
1156 allows it to get callbacks when certain types are resolved. To register to get
1157 callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
1158 methods can be called on a type. Note that these methods only work for <i>
1159 abstract</i> types. Concrete types (those that do not include an opaque objects
1160 somewhere) can never be refined.
1165 <!-- ======================================================================= -->
1166 <div class="doc_subsection">
1167 <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
1170 <div class="doc_text">
1171 <p>This class provides a symbol table that the <a
1172 href="#Function"><tt>Function</tt></a> and <a href="#Module">
1173 <tt>Module</tt></a> classes use for naming definitions. The symbol table can
1174 provide a name for any <a href="#Value"><tt>Value</tt></a> or <a
1175 href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
1176 type. It hides the data it contains and provides access to it through a
1177 controlled interface.</p>
1179 <p>Note that the symbol table class is should not be directly accessed by most
1180 clients. It should only be used when iteration over the symbol table names
1181 themselves are required, which is very special purpose. Note that not all LLVM
1182 <a href="#Value">Value</a>s have names, and those without names (i.e. they have
1183 an empty name) do not exist in the symbol table.
1186 <p>To use the <tt>SymbolTable</tt> well, you need to understand the
1187 structure of the information it holds. The class contains two
1188 <tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
1189 <tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
1190 The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
1191 are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
1192 however, are stored in a single dimension and accessed only by name.</p>
1194 <p>The interface of this class provides three basic types of operations:
1196 <li><em>Accessors</em>. Accessors provide read-only access to information
1197 such as finding a value for a name with the
1198 <a href="#SymbolTable_lookup">lookup</a> method.</li>
1199 <li><em>Mutators</em>. Mutators allow the user to add information to the
1200 <tt>SymbolTable</tt> with methods like
1201 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
1202 <li><em>Iterators</em>. Iterators allow the user to traverse the content
1203 of the symbol table in well defined ways, such as the method
1204 <a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
1209 <dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
1211 <dd>The <tt>lookup</tt> method searches the type plane given by the
1212 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
1213 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
1215 <dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
1216 <dd>The <tt>lookupType</tt> method searches through the types for a
1217 <tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
1218 is not found, null is returned.</dd>
1220 <dt><tt>bool hasTypes() const</tt>:</dt>
1221 <dd>This function returns true if an entry has been made into the type
1224 <dt><tt>bool isEmpty() const</tt>:</dt>
1225 <dd>This function returns true if both the value and types maps are
1231 <dt><tt>void insert(Value *Val)</tt>:</dt>
1232 <dd>This method adds the provided value to the symbol table. The Value must
1233 have both a name and a type which are extracted and used to place the value
1234 in the correct type plane under the value's name.</dd>
1236 <dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
1237 <dd> Inserts a constant or type into the symbol table with the specified
1238 name. There can be a many to one mapping between names and constants
1241 <dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
1242 <dd> Inserts a type into the symbol table with the specified name. There
1243 can be a many-to-one mapping between names and types. This method
1244 allows a type with an existing entry in the symbol table to get
1247 <dt><tt>void remove(Value* Val)</tt>:</dt>
1248 <dd> This method removes a named value from the symbol table. The
1249 type and name of the Value are extracted from \p N and used to
1250 lookup the Value in the correct type plane. If the Value is
1251 not in the symbol table, this method silently ignores the
1254 <dt><tt>void remove(Type* Typ)</tt>:</dt>
1255 <dd> This method removes a named type from the symbol table. The
1256 name of the type is extracted from \P T and used to look up
1257 the Type in the type map. If the Type is not in the symbol
1258 table, this method silently ignores the request.</dd>
1260 <dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
1261 <dd> Remove a constant or type with the specified name from the
1264 <dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
1265 <dd> Remove a type with the specified name from the symbol table.
1266 Returns the removed Type.</dd>
1268 <dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
1269 <dd> Removes a specific value from the symbol table.
1270 Returns the removed value.</dd>
1272 <dt><tt>bool strip()</tt>:</dt>
1273 <dd> This method will strip the symbol table of its names leaving
1274 the type and values. </dd>
1276 <dt><tt>void clear()</tt>:</dt>
1277 <dd>Empty the symbol table completely.</dd>
1281 <p>The following functions describe three types of iterators you can obtain
1282 the beginning or end of the sequence for both const and non-const. It is
1283 important to keep track of the different kinds of iterators. There are
1284 three idioms worth pointing out:</p>
1286 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1288 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1289 <td align="left"><pre><tt>
1290 for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1291 PE = ST.plane_end(); PI != PE; ++PI ) {
1292 PI->first // This is the Type* of the plane
1293 PI->second // This is the SymbolTable::ValueMap of name/Value pairs
1297 <td align="left">All name/Type Pairs</td><td>TI</td>
1298 <td align="left"><pre><tt>
1299 for (SymbolTable::type_const_iterator TI = ST.type_begin(),
1300 TE = ST.type_end(); TI != TE; ++TI )
1301 TI->first // This is the name of the type
1302 TI->second // This is the Type* value associated with the name
1306 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1307 <td align="left"><pre><tt>
1308 for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
1309 VE = ST.value_end(SomeType); VI != VE; ++VI )
1310 VI->first // This is the name of the Value
1311 VI->second // This is the Value* value associated with the name
1316 <p>Using the recommended iterator names and idioms will help you avoid
1317 making mistakes. Of particular note, make sure that whenever you use
1318 value_begin(SomeType) that you always compare the resulting iterator
1319 with value_end(SomeType) not value_end(SomeOtherType) or else you
1320 will loop infinitely.</p>
1324 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1325 <dd>Get an iterator that starts at the beginning of the type planes.
1326 The iterator will iterate over the Type/ValueMap pairs in the
1329 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1330 <dd>Get a const_iterator that starts at the beginning of the type
1331 planes. The iterator will iterate over the Type/ValueMap pairs
1332 in the type planes. </dd>
1334 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1335 <dd>Get an iterator at the end of the type planes. This serves as
1336 the marker for end of iteration over the type planes.</dd>
1338 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
1339 <dd>Get a const_iterator at the end of the type planes. This serves as
1340 the marker for end of iteration over the type planes.</dd>
1342 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
1343 <dd>Get an iterator that starts at the beginning of a type plane.
1344 The iterator will iterate over the name/value pairs in the type plane.
1345 Note: The type plane must already exist before using this.</dd>
1347 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
1348 <dd>Get a const_iterator that starts at the beginning of a type plane.
1349 The iterator will iterate over the name/value pairs in the type plane.
1350 Note: The type plane must already exist before using this.</dd>
1352 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
1353 <dd>Get an iterator to the end of a type plane. This serves as the marker
1354 for end of iteration of the type plane.
1355 Note: The type plane must already exist before using this.</dd>
1357 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
1358 <dd>Get a const_iterator to the end of a type plane. This serves as the
1359 marker for end of iteration of the type plane.
1360 Note: the type plane must already exist before using this.</dd>
1362 <dt><tt>type_iterator type_begin()</tt>:</dt>
1363 <dd>Get an iterator to the start of the name/Type map.</dd>
1365 <dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
1366 <dd> Get a const_iterator to the start of the name/Type map.</dd>
1368 <dt><tt>type_iterator type_end()</tt>:</dt>
1369 <dd>Get an iterator to the end of the name/Type map. This serves as the
1370 marker for end of iteration of the types.</dd>
1372 <dt><tt>type_const_iterator type_end() const</tt>:</dt>
1373 <dd>Get a const-iterator to the end of the name/Type map. This serves
1374 as the marker for end of iteration of the types.</dd>
1376 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
1377 <dd>This method returns a plane_const_iterator for iteration over
1378 the type planes starting at a specific plane, given by \p Ty.</dd>
1380 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
1381 <dd>This method returns a plane_iterator for iteration over the
1382 type planes starting at a specific plane, given by \p Ty.</dd>
1389 <!-- *********************************************************************** -->
1390 <div class="doc_section">
1391 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
1393 <!-- *********************************************************************** -->
1395 <div class="doc_text">
1397 <p>The Core LLVM classes are the primary means of representing the program
1398 being inspected or transformed. The core LLVM classes are defined in
1399 header files in the <tt>include/llvm/</tt> directory, and implemented in
1400 the <tt>lib/VMCore</tt> directory.</p>
1404 <!-- ======================================================================= -->
1405 <div class="doc_subsection">
1406 <a name="Value">The <tt>Value</tt> class</a>
1411 <p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
1413 doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
1415 <p>The <tt>Value</tt> class is the most important class in the LLVM Source
1416 base. It represents a typed value that may be used (among other things) as an
1417 operand to an instruction. There are many different types of <tt>Value</tt>s,
1418 such as <a href="#Constant"><tt>Constant</tt></a>s,<a
1419 href="#Argument"><tt>Argument</tt></a>s. Even <a
1420 href="#Instruction"><tt>Instruction</tt></a>s and <a
1421 href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
1423 <p>A particular <tt>Value</tt> may be used many times in the LLVM representation
1424 for a program. For example, an incoming argument to a function (represented
1425 with an instance of the <a href="#Argument">Argument</a> class) is "used" by
1426 every instruction in the function that references the argument. To keep track
1427 of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
1428 href="#User"><tt>User</tt></a>s that is using it (the <a
1429 href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
1430 graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
1431 def-use information in the program, and is accessible through the <tt>use_</tt>*
1432 methods, shown below.</p>
1434 <p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
1435 and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
1436 method. In addition, all LLVM values can be named. The "name" of the
1437 <tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
1439 <pre> %<b>foo</b> = add int 1, 2<br></pre>
1441 <p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
1442 that the name of any value may be missing (an empty string), so names should
1443 <b>ONLY</b> be used for debugging (making the source code easier to read,
1444 debugging printouts), they should not be used to keep track of values or map
1445 between them. For this purpose, use a <tt>std::map</tt> of pointers to the
1446 <tt>Value</tt> itself instead.</p>
1448 <p>One important aspect of LLVM is that there is no distinction between an SSA
1449 variable and the operation that produces it. Because of this, any reference to
1450 the value produced by an instruction (or the value available as an incoming
1451 argument, for example) is represented as a direct pointer to the instance of
1453 represents this value. Although this may take some getting used to, it
1454 simplifies the representation and makes it easier to manipulate.</p>
1458 <!-- _______________________________________________________________________ -->
1459 <div class="doc_subsubsection">
1460 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
1463 <div class="doc_text">
1466 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
1468 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
1470 <tt>unsigned use_size()</tt> - Returns the number of users of the
1472 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
1473 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
1475 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
1477 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
1478 element in the list.
1479 <p> These methods are the interface to access the def-use
1480 information in LLVM. As with all other iterators in LLVM, the naming
1481 conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
1483 <li><tt><a href="#Type">Type</a> *getType() const</tt>
1484 <p>This method returns the Type of the Value.</p>
1486 <li><tt>bool hasName() const</tt><br>
1487 <tt>std::string getName() const</tt><br>
1488 <tt>void setName(const std::string &Name)</tt>
1489 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
1490 be aware of the <a href="#nameWarning">precaution above</a>.</p>
1492 <li><tt>void replaceAllUsesWith(Value *V)</tt>
1494 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
1495 href="#User"><tt>User</tt>s</a> of the current value to refer to
1496 "<tt>V</tt>" instead. For example, if you detect that an instruction always
1497 produces a constant value (for example through constant folding), you can
1498 replace all uses of the instruction with the constant like this:</p>
1500 <pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
1505 <!-- ======================================================================= -->
1506 <div class="doc_subsection">
1507 <a name="User">The <tt>User</tt> class</a>
1510 <div class="doc_text">
1513 <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
1514 doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
1515 Superclass: <a href="#Value"><tt>Value</tt></a></p>
1517 <p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
1518 refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1519 that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1520 referring to. The <tt>User</tt> class itself is a subclass of
1523 <p>The operands of a <tt>User</tt> point directly to the LLVM <a
1524 href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1525 Single Assignment (SSA) form, there can only be one definition referred to,
1526 allowing this direct connection. This connection provides the use-def
1527 information in LLVM.</p>
1531 <!-- _______________________________________________________________________ -->
1532 <div class="doc_subsubsection">
1533 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
1536 <div class="doc_text">
1538 <p>The <tt>User</tt> class exposes the operand list in two ways: through
1539 an index access interface and through an iterator based interface.</p>
1542 <li><tt>Value *getOperand(unsigned i)</tt><br>
1543 <tt>unsigned getNumOperands()</tt>
1544 <p> These two methods expose the operands of the <tt>User</tt> in a
1545 convenient form for direct access.</p></li>
1547 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
1549 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
1550 the operand list.<br>
1551 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
1553 <p> Together, these methods make up the iterator based interface to
1554 the operands of a <tt>User</tt>.</p></li>
1559 <!-- ======================================================================= -->
1560 <div class="doc_subsection">
1561 <a name="Instruction">The <tt>Instruction</tt> class</a>
1564 <div class="doc_text">
1566 <p><tt>#include "</tt><tt><a
1567 href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
1568 doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
1569 Superclasses: <a href="#User"><tt>User</tt></a>, <a
1570 href="#Value"><tt>Value</tt></a></p>
1572 <p>The <tt>Instruction</tt> class is the common base class for all LLVM
1573 instructions. It provides only a few methods, but is a very commonly used
1574 class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1575 opcode (instruction type) and the parent <a
1576 href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1577 into. To represent a specific type of instruction, one of many subclasses of
1578 <tt>Instruction</tt> are used.</p>
1580 <p> Because the <tt>Instruction</tt> class subclasses the <a
1581 href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1582 way as for other <a href="#User"><tt>User</tt></a>s (with the
1583 <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1584 <tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
1585 the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
1586 file contains some meta-data about the various different types of instructions
1587 in LLVM. It describes the enum values that are used as opcodes (for example
1588 <tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
1589 concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
1590 example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1591 href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1592 this file confuses doxygen, so these enum values don't show up correctly in the
1593 <a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
1597 <!-- _______________________________________________________________________ -->
1598 <div class="doc_subsubsection">
1599 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
1603 <div class="doc_text">
1606 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
1607 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
1608 this <tt>Instruction</tt> is embedded into.</p></li>
1609 <li><tt>bool mayWriteToMemory()</tt>
1610 <p>Returns true if the instruction writes to memory, i.e. it is a
1611 <tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
1612 <li><tt>unsigned getOpcode()</tt>
1613 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
1614 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
1615 <p>Returns another instance of the specified instruction, identical
1616 in all ways to the original except that the instruction has no parent
1617 (ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
1618 and it has no name</p></li>
1623 <!-- ======================================================================= -->
1624 <div class="doc_subsection">
1625 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1628 <div class="doc_text">
1631 href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
1632 doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
1634 Superclass: <a href="#Value"><tt>Value</tt></a></p>
1636 <p>This class represents a single entry multiple exit section of the code,
1637 commonly known as a basic block by the compiler community. The
1638 <tt>BasicBlock</tt> class maintains a list of <a
1639 href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
1640 Matching the language definition, the last element of this list of instructions
1641 is always a terminator instruction (a subclass of the <a
1642 href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
1644 <p>In addition to tracking the list of instructions that make up the block, the
1645 <tt>BasicBlock</tt> class also keeps track of the <a
1646 href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
1648 <p>Note that <tt>BasicBlock</tt>s themselves are <a
1649 href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1650 like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1655 <!-- _______________________________________________________________________ -->
1656 <div class="doc_subsubsection">
1657 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
1661 <div class="doc_text">
1665 <li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
1666 href="#Function">Function</a> *Parent = 0)</tt>
1668 <p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1669 insertion into a function. The constructor optionally takes a name for the new
1670 block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
1671 the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
1672 automatically inserted at the end of the specified <a
1673 href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1674 manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
1676 <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1677 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1678 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1679 <tt>size()</tt>, <tt>empty()</tt>
1680 STL-style functions for accessing the instruction list.
1682 <p>These methods and typedefs are forwarding functions that have the same
1683 semantics as the standard library methods of the same names. These methods
1684 expose the underlying instruction list of a basic block in a way that is easy to
1685 manipulate. To get the full complement of container operations (including
1686 operations to update the list), you must use the <tt>getInstList()</tt>
1689 <li><tt>BasicBlock::InstListType &getInstList()</tt>
1691 <p>This method is used to get access to the underlying container that actually
1692 holds the Instructions. This method must be used when there isn't a forwarding
1693 function in the <tt>BasicBlock</tt> class for the operation that you would like
1694 to perform. Because there are no forwarding functions for "updating"
1695 operations, you need to use this if you want to update the contents of a
1696 <tt>BasicBlock</tt>.</p></li>
1698 <li><tt><a href="#Function">Function</a> *getParent()</tt>
1700 <p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1701 embedded into, or a null pointer if it is homeless.</p></li>
1703 <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
1705 <p> Returns a pointer to the terminator instruction that appears at the end of
1706 the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1707 instruction in the block is not a terminator, then a null pointer is
1714 <!-- ======================================================================= -->
1715 <div class="doc_subsection">
1716 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1719 <div class="doc_text">
1722 href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
1723 doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
1725 Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
1726 <a href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
1728 <p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1729 href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1730 visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1731 Because they are visible at global scope, they are also subject to linking with
1732 other globals defined in different translation units. To control the linking
1733 process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
1734 <tt>GlobalValue</tt>s know whether they have internal or external linkage, as
1735 defined by the <tt>LinkageTypes</tt> enumeration.</p>
1737 <p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
1738 <tt>static</tt> in C), it is not visible to code outside the current translation
1739 unit, and does not participate in linking. If it has external linkage, it is
1740 visible to external code, and does participate in linking. In addition to
1741 linkage information, <tt>GlobalValue</tt>s keep track of which <a
1742 href="#Module"><tt>Module</tt></a> they are currently part of.</p>
1744 <p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
1745 by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
1746 global is always a pointer to its contents. It is important to remember this
1747 when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
1748 be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
1749 subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
1750 int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
1751 the address of the first element of this array and the value of the
1752 <tt>GlobalVariable</tt> are the same, they have different types. The
1753 <tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
1754 is <tt>int.</tt> Because of this, accessing a global value requires you to
1755 dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
1756 can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
1757 Language Reference Manual</a>.</p>
1761 <!-- _______________________________________________________________________ -->
1762 <div class="doc_subsubsection">
1763 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
1767 <div class="doc_text">
1770 <li><tt>bool hasInternalLinkage() const</tt><br>
1771 <tt>bool hasExternalLinkage() const</tt><br>
1772 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
1773 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
1776 <li><tt><a href="#Module">Module</a> *getParent()</tt>
1777 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
1778 GlobalValue is currently embedded into.</p></li>
1783 <!-- ======================================================================= -->
1784 <div class="doc_subsection">
1785 <a name="Function">The <tt>Function</tt> class</a>
1788 <div class="doc_text">
1791 href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
1792 info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
1793 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
1794 <a href="#Constant"><tt>Constant</tt></a>,
1795 <a href="#User"><tt>User</tt></a>,
1796 <a href="#Value"><tt>Value</tt></a></p>
1798 <p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
1799 actually one of the more complex classes in the LLVM heirarchy because it must
1800 keep track of a large amount of data. The <tt>Function</tt> class keeps track
1801 of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
1802 <a href="#Argument"><tt>Argument</tt></a>s, and a
1803 <a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
1805 <p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
1806 commonly used part of <tt>Function</tt> objects. The list imposes an implicit
1807 ordering of the blocks in the function, which indicate how the code will be
1808 layed out by the backend. Additionally, the first <a
1809 href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
1810 <tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
1811 block. There are no implicit exit nodes, and in fact there may be multiple exit
1812 nodes from a single <tt>Function</tt>. If the <a
1813 href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
1814 the <tt>Function</tt> is actually a function declaration: the actual body of the
1815 function hasn't been linked in yet.</p>
1817 <p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
1818 <tt>Function</tt> class also keeps track of the list of formal <a
1819 href="#Argument"><tt>Argument</tt></a>s that the function receives. This
1820 container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
1821 nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
1822 the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
1824 <p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
1825 LLVM feature that is only used when you have to look up a value by name. Aside
1826 from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
1827 internally to make sure that there are not conflicts between the names of <a
1828 href="#Instruction"><tt>Instruction</tt></a>s, <a
1829 href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
1830 href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
1832 <p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
1833 and therefore also a <a href="#Constant">Constant</a>. The value of the function
1834 is its address (after linking) which is guaranteed to be constant.</p>
1837 <!-- _______________________________________________________________________ -->
1838 <div class="doc_subsubsection">
1839 <a name="m_Function">Important Public Members of the <tt>Function</tt>
1843 <div class="doc_text">
1846 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
1847 *Ty, LinkageTypes Linkage, const std::string &N = "", Module* Parent = 0)</tt>
1849 <p>Constructor used when you need to create new <tt>Function</tt>s to add
1850 the the program. The constructor must specify the type of the function to
1851 create and what type of linkage the function should have. The <a
1852 href="#FunctionType"><tt>FunctionType</tt></a> argument
1853 specifies the formal arguments and return value for the function. The same
1854 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
1855 create multiple functions. The <tt>Parent</tt> argument specifies the Module
1856 in which the function is defined. If this argument is provided, the function
1857 will automatically be inserted into that module's list of
1860 <li><tt>bool isExternal()</tt>
1862 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
1863 function is "external", it does not have a body, and thus must be resolved
1864 by linking with a function defined in a different translation unit.</p></li>
1866 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
1867 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
1869 <tt>begin()</tt>, <tt>end()</tt>
1870 <tt>size()</tt>, <tt>empty()</tt>
1872 <p>These are forwarding methods that make it easy to access the contents of
1873 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1876 <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
1878 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
1879 is necessary to use when you need to update the list or perform a complex
1880 action that doesn't have a forwarding method.</p></li>
1882 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
1884 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
1886 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
1887 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
1889 <p>These are forwarding methods that make it easy to access the contents of
1890 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
1893 <li><tt>Function::ArgumentListType &getArgumentList()</tt>
1895 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
1896 necessary to use when you need to update the list or perform a complex
1897 action that doesn't have a forwarding method.</p></li>
1899 <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
1901 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1902 function. Because the entry block for the function is always the first
1903 block, this returns the first block of the <tt>Function</tt>.</p></li>
1905 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1906 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
1908 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
1909 <tt>Function</tt> and returns the return type of the function, or the <a
1910 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
1913 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
1915 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
1916 for this <tt>Function</tt>.</p></li>
1921 <!-- ======================================================================= -->
1922 <div class="doc_subsection">
1923 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1926 <div class="doc_text">
1929 href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
1931 doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
1933 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
1934 <a href="#Constant"><tt>Constant</tt></a>,
1935 <a href="#User"><tt>User</tt></a>,
1936 <a href="#Value"><tt>Value</tt></a></p>
1938 <p>Global variables are represented with the (suprise suprise)
1939 <tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
1940 subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
1941 always referenced by their address (global values must live in memory, so their
1942 "name" refers to their constant address). See
1943 <a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
1944 variables may have an initial value (which must be a
1945 <a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
1946 they may be marked as "constant" themselves (indicating that their contents
1947 never change at runtime).</p>
1950 <!-- _______________________________________________________________________ -->
1951 <div class="doc_subsubsection">
1952 <a name="m_GlobalVariable">Important Public Members of the
1953 <tt>GlobalVariable</tt> class</a>
1956 <div class="doc_text">
1959 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
1960 isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
1961 *Initializer = 0, const std::string &Name = "", Module* Parent = 0)</tt>
1963 <p>Create a new global variable of the specified type. If
1964 <tt>isConstant</tt> is true then the global variable will be marked as
1965 unchanging for the program. The Linkage parameter specifies the type of
1966 linkage (internal, external, weak, linkonce, appending) for the variable. If
1967 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage, then
1968 the resultant global variable will have internal linkage. AppendingLinkage
1969 concatenates together all instances (in different translation units) of the
1970 variable into a single variable but is only applicable to arrays. See
1971 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
1972 further details on linkage types. Optionally an initializer, a name, and the
1973 module to put the variable into may be specified for the global variable as
1976 <li><tt>bool isConstant() const</tt>
1978 <p>Returns true if this is a global variable that is known not to
1979 be modified at runtime.</p></li>
1981 <li><tt>bool hasInitializer()</tt>
1983 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
1985 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
1987 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
1988 to call this method if there is no initializer.</p></li>
1993 <!-- ======================================================================= -->
1994 <div class="doc_subsection">
1995 <a name="Module">The <tt>Module</tt> class</a>
1998 <div class="doc_text">
2001 href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
2002 <a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
2004 <p>The <tt>Module</tt> class represents the top level structure present in LLVM
2005 programs. An LLVM module is effectively either a translation unit of the
2006 original program or a combination of several translation units merged by the
2007 linker. The <tt>Module</tt> class keeps track of a list of <a
2008 href="#Function"><tt>Function</tt></a>s, a list of <a
2009 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
2010 href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
2011 helpful member functions that try to make common operations easy.</p>
2015 <!-- _______________________________________________________________________ -->
2016 <div class="doc_subsubsection">
2017 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
2020 <div class="doc_text">
2023 <li><tt>Module::Module(std::string name = "")</tt></li>
2026 <p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
2027 provide a name for it (probably based on the name of the translation unit).</p>
2030 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
2031 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
2033 <tt>begin()</tt>, <tt>end()</tt>
2034 <tt>size()</tt>, <tt>empty()</tt>
2036 <p>These are forwarding methods that make it easy to access the contents of
2037 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
2040 <li><tt>Module::FunctionListType &getFunctionList()</tt>
2042 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
2043 necessary to use when you need to update the list or perform a complex
2044 action that doesn't have a forwarding method.</p>
2046 <p><!-- Global Variable --></p></li>
2052 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
2054 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
2056 <tt>global_begin()</tt>, <tt>global_end()</tt>
2057 <tt>global_size()</tt>, <tt>global_empty()</tt>
2059 <p> These are forwarding methods that make it easy to access the contents of
2060 a <tt>Module</tt> object's <a
2061 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
2063 <li><tt>Module::GlobalListType &getGlobalList()</tt>
2065 <p>Returns the list of <a
2066 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
2067 use when you need to update the list or perform a complex action that
2068 doesn't have a forwarding method.</p>
2070 <p><!-- Symbol table stuff --> </p></li>
2076 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
2078 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2079 for this <tt>Module</tt>.</p>
2081 <p><!-- Convenience methods --></p></li>
2087 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
2088 &Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
2090 <p>Look up the specified function in the <tt>Module</tt> <a
2091 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
2092 <tt>null</tt>.</p></li>
2094 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
2095 std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
2097 <p>Look up the specified function in the <tt>Module</tt> <a
2098 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
2099 external declaration for the function and return it.</p></li>
2101 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
2103 <p>If there is at least one entry in the <a
2104 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
2105 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
2108 <li><tt>bool addTypeName(const std::string &Name, const <a
2109 href="#Type">Type</a> *Ty)</tt>
2111 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2112 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
2113 name, true is returned and the <a
2114 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
2119 <!-- ======================================================================= -->
2120 <div class="doc_subsection">
2121 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
2124 <div class="doc_text">
2126 <p>Constant represents a base class for different types of constants. It
2127 is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
2128 ConstantArray etc for representing the various types of Constants.</p>
2132 <!-- _______________________________________________________________________ -->
2133 <div class="doc_subsubsection">
2134 <a name="m_Constant">Important Public Methods</a>
2136 <div class="doc_text">
2139 <!-- _______________________________________________________________________ -->
2140 <div class="doc_subsubsection">Important Subclasses of Constant </div>
2141 <div class="doc_text">
2143 <li>ConstantSInt : This subclass of Constant represents a signed integer
2146 <li><tt>int64_t getValue() const</tt>: Returns the underlying value of
2147 this constant. </li>
2150 <li>ConstantUInt : This class represents an unsigned integer.
2152 <li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
2153 this constant. </li>
2156 <li>ConstantFP : This class represents a floating point constant.
2158 <li><tt>double getValue() const</tt>: Returns the underlying value of
2159 this constant. </li>
2162 <li>ConstantBool : This represents a boolean constant.
2164 <li><tt>bool getValue() const</tt>: Returns the underlying value of this
2168 <li>ConstantArray : This represents a constant array.
2170 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns
2171 a vector of component constants that makeup this array. </li>
2174 <li>ConstantStruct : This represents a constant struct.
2176 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns
2177 a vector of component constants that makeup this array. </li>
2180 <li>GlobalValue : This represents either a global variable or a function. In
2181 either case, the value is a constant fixed address (after linking).
2186 <!-- ======================================================================= -->
2187 <div class="doc_subsection">
2188 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
2191 <div class="doc_text">
2193 <p>Type as noted earlier is also a subclass of a Value class. Any primitive
2194 type (like int, short etc) in LLVM is an instance of Type Class. All other
2195 types are instances of subclasses of type like FunctionType, ArrayType
2196 etc. DerivedType is the interface for all such dervied types including
2197 FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
2198 be recursive (StructType). There exists exactly one instance of any type
2199 structure at a time. This allows using pointer equality of Type *s for comparing
2204 <!-- _______________________________________________________________________ -->
2205 <div class="doc_subsubsection">
2206 <a name="m_Value">Important Public Methods</a>
2209 <div class="doc_text">
2213 <li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
2214 is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
2215 not true for Float and Double. </li>
2217 <li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
2218 unsigned. This is not quite the complement of isSigned... nonnumeric types
2219 return false as they do with isSigned. This returns true for UByteTy,
2220 UShortTy, UIntTy, and ULongTy. </li>
2222 <li><tt>bool isInteger() const</tt>: Equivalent to isSigned() || isUnsigned().</li>
2224 <li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
2225 type, which is either Bool type or one of the Integer types.</li>
2227 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
2228 floating point types.</li>
2230 <li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
2231 this type can be converted to 'Ty' without any reinterpretation of bits. For
2232 example, uint to int or one pointer type to another.</li>
2236 <!-- _______________________________________________________________________ -->
2237 <div class="doc_subsubsection">
2238 <a name="m_Value">Important Derived Types</a>
2240 <div class="doc_text">
2242 <li>SequentialType : This is subclassed by ArrayType and PointerType
2244 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
2245 of the elements in the sequential type. </li>
2248 <li>ArrayType : This is a subclass of SequentialType and defines interface for
2251 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
2252 elements in the array. </li>
2255 <li>PointerType : Subclass of SequentialType for pointer types. </li>
2256 <li>StructType : subclass of DerivedTypes for struct types </li>
2257 <li>FunctionType : subclass of DerivedTypes for function types.
2259 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
2261 <li><tt> const Type * getReturnType() const</tt>: Returns the
2262 return type of the function.</li>
2263 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
2264 the type of the ith parameter.</li>
2265 <li><tt> const unsigned getNumParams() const</tt>: Returns the
2266 number of formal parameters.</li>
2272 <!-- ======================================================================= -->
2273 <div class="doc_subsection">
2274 <a name="Argument">The <tt>Argument</tt> class</a>
2277 <div class="doc_text">
2279 <p>This subclass of Value defines the interface for incoming formal
2280 arguments to a function. A Function maintains a list of its formal
2281 arguments. An argument has a pointer to the parent Function.</p>
2285 <!-- *********************************************************************** -->
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2293 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
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2295 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
2296 Last modified: $Date$