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6 <title>Kaleidoscope: Adding JIT and Optimizer Support</title>
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8 <meta name="author" content="Chris Lattner">
9 <link rel="stylesheet" href="../llvm.css" type="text/css">
10</head>
11
12<body>
13
14<div class="doc_title">Kaleidoscope: Adding JIT and Optimizer Support</div>
15
Chris Lattner128eb862007-11-05 19:06:59 +0000[diff] [blame]16<ul>
Chris Lattner0e555b12007-11-05 20:04:56 +0000[diff] [blame]17<li><a href="index.html">Up to Tutorial Index</a></li>
Chris Lattner128eb862007-11-05 19:06:59 +0000[diff] [blame]18<li>Chapter 4
19 <ol>
20 <li><a href="#intro">Chapter 4 Introduction</a></li>
21 <li><a href="#trivialconstfold">Trivial Constant Folding</a></li>
22 <li><a href="#optimizerpasses">LLVM Optimization Passes</a></li>
23 <li><a href="#jit">Adding a JIT Compiler</a></li>
24 <li><a href="#code">Full Code Listing</a></li>
25 </ol>
26</li>
Chris Lattner0e555b12007-11-05 20:04:56 +0000[diff] [blame]27<li><a href="LangImpl5.html">Chapter 5</a>: Extending the Language: Control
28Flow</li>
Chris Lattner128eb862007-11-05 19:06:59 +0000[diff] [blame]29</ul>
30
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]31<div class="doc_author">
32 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
33</div>
34
35<!-- *********************************************************************** -->
Chris Lattner128eb862007-11-05 19:06:59 +0000[diff] [blame]36<div class="doc_section"><a name="intro">Chapter 4 Introduction</a></div>
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]37<!-- *********************************************************************** -->
38
39<div class="doc_text">
40
Chris Lattner128eb862007-11-05 19:06:59 +0000[diff] [blame]41<p>Welcome to Chapter 4 of the "<a href="index.html">Implementing a language
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]42with LLVM</a>" tutorial. Chapters 1-3 described the implementation of a simple
43language and added support for generating LLVM IR. This chapter describes
Chris Lattner128eb862007-11-05 19:06:59 +0000[diff] [blame]44two new techniques: adding optimizer support to your language, and adding JIT
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]45compiler support. These additions will demonstrate how to get nice, efficient code
46for the Kaleidoscope language.</p>
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]47
48</div>
49
50<!-- *********************************************************************** -->
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]51<div class="doc_section"><a name="trivialconstfold">Trivial Constant
52Folding</a></div>
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]53<!-- *********************************************************************** -->
54
55<div class="doc_text">
56
57<p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]58Our demonstration for Chapter 3 is elegant and easy to extend. Unfortunately,
Duncan Sands89f6d882008-04-13 06:22:09 +0000[diff] [blame]59it does not produce wonderful code. The IRBuilder, however, does give us
60obvious optimizations when compiling simple code:</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]61
62<div class="doc_code">
63<pre>
64ready&gt; <b>def test(x) 1+2+x;</b>
65Read function definition:
66define double @test(double %x) {
67entry:
68 %addtmp = add double 3.000000e+00, %x
69 ret double %addtmp
70}
71</pre>
72</div>
73
Duncan Sands89f6d882008-04-13 06:22:09 +0000[diff] [blame]74<p>This code is not a literal transcription of the AST built by parsing the
75input. That would be:
76
77<div class="doc_code">
78<pre>
79ready&gt; <b>def test(x) 1+2+x;</b>
80Read function definition:
81define double @test(double %x) {
82entry:
83 %addtmp = add double 2.000000e+00, 1.000000e+00
84 %addtmp1 = add double %addtmp, %x
85 ret double %addtmp1
86}
87</pre>
88</div>
89
Gabor Greif94244f32009-03-11 20:04:08 +0000[diff] [blame]90<p>Constant folding, as seen above, in particular, is a very common and very
Duncan Sands89f6d882008-04-13 06:22:09 +0000[diff] [blame]91important optimization: so much so that many language implementors implement
92constant folding support in their AST representation.</p>
93
94<p>With LLVM, you don't need this support in the AST. Since all calls to build
95LLVM IR go through the LLVM IR builder, the builder itself checked to see if
96there was a constant folding opportunity when you call it. If so, it just does
97the constant fold and return the constant instead of creating an instruction.
98
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]99<p>Well, that was easy :). In practice, we recommend always using
Duncan Sands89f6d882008-04-13 06:22:09 +0000[diff] [blame]100<tt>IRBuilder</tt> when generating code like this. It has no
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]101"syntactic overhead" for its use (you don't have to uglify your compiler with
102constant checks everywhere) and it can dramatically reduce the amount of
103LLVM IR that is generated in some cases (particular for languages with a macro
104preprocessor or that use a lot of constants).</p>
105
Duncan Sands89f6d882008-04-13 06:22:09 +0000[diff] [blame]106<p>On the other hand, the <tt>IRBuilder</tt> is limited by the fact
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]107that it does all of its analysis inline with the code as it is built. If you
108take a slightly more complex example:</p>
109
110<div class="doc_code">
111<pre>
112ready&gt; <b>def test(x) (1+2+x)*(x+(1+2));</b>
113ready> Read function definition:
114define double @test(double %x) {
115entry:
116 %addtmp = add double 3.000000e+00, %x
117 %addtmp1 = add double %x, 3.000000e+00
118 %multmp = mul double %addtmp, %addtmp1
119 ret double %multmp
120}
121</pre>
122</div>
123
124<p>In this case, the LHS and RHS of the multiplication are the same value. We'd
125really like to see this generate "<tt>tmp = x+3; result = tmp*tmp;</tt>" instead
Chris Lattner1ace67c2008-04-15 16:59:22 +0000[diff] [blame]126of computing "<tt>x+3</tt>" twice.</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]127
128<p>Unfortunately, no amount of local analysis will be able to detect and correct
129this. This requires two transformations: reassociation of expressions (to
130make the add's lexically identical) and Common Subexpression Elimination (CSE)
131to delete the redundant add instruction. Fortunately, LLVM provides a broad
132range of optimizations that you can use, in the form of "passes".</p>
133
134</div>
135
136<!-- *********************************************************************** -->
137<div class="doc_section"><a name="optimizerpasses">LLVM Optimization
138 Passes</a></div>
139<!-- *********************************************************************** -->
140
141<div class="doc_text">
142
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]143<p>LLVM provides many optimization passes, which do many different sorts of
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]144things and have different tradeoffs. Unlike other systems, LLVM doesn't hold
145to the mistaken notion that one set of optimizations is right for all languages
146and for all situations. LLVM allows a compiler implementor to make complete
147decisions about what optimizations to use, in which order, and in what
148situation.</p>
149
150<p>As a concrete example, LLVM supports both "whole module" passes, which look
151across as large of body of code as they can (often a whole file, but if run
152at link time, this can be a substantial portion of the whole program). It also
153supports and includes "per-function" passes which just operate on a single
154function at a time, without looking at other functions. For more information
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]155on passes and how they are run, see the <a href="../WritingAnLLVMPass.html">How
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]156to Write a Pass</a> document and the <a href="../Passes.html">List of LLVM
157Passes</a>.</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]158
159<p>For Kaleidoscope, we are currently generating functions on the fly, one at
160a time, as the user types them in. We aren't shooting for the ultimate
161optimization experience in this setting, but we also want to catch the easy and
162quick stuff where possible. As such, we will choose to run a few per-function
163optimizations as the user types the function in. If we wanted to make a "static
164Kaleidoscope compiler", we would use exactly the code we have now, except that
165we would defer running the optimizer until the entire file has been parsed.</p>
166
167<p>In order to get per-function optimizations going, we need to set up a
168<a href="../WritingAnLLVMPass.html#passmanager">FunctionPassManager</a> to hold and
169organize the LLVM optimizations that we want to run. Once we have that, we can
170add a set of optimizations to run. The code looks like this:</p>
171
172<div class="doc_code">
173<pre>
Jeffrey Yasskinf0356fe2010-01-27 20:34:15 +0000[diff] [blame]174 FunctionPassManager OurFPM(TheModule);
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]175
Reid Kleckner60130f02009-08-26 20:58:25 +0000[diff] [blame]176 // Set up the optimizer pipeline. Start with registering info about how the
177 // target lays out data structures.
178 OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData()));
179 // Do simple "peephole" optimizations and bit-twiddling optzns.
180 OurFPM.add(createInstructionCombiningPass());
181 // Reassociate expressions.
182 OurFPM.add(createReassociatePass());
183 // Eliminate Common SubExpressions.
184 OurFPM.add(createGVNPass());
185 // Simplify the control flow graph (deleting unreachable blocks, etc).
186 OurFPM.add(createCFGSimplificationPass());
187
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]188 OurFPM.doInitialization();
189
Reid Kleckner60130f02009-08-26 20:58:25 +0000[diff] [blame]190 // Set the global so the code gen can use this.
191 TheFPM = &amp;OurFPM;
192
193 // Run the main "interpreter loop" now.
194 MainLoop();
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]195</pre>
196</div>
197
Jeffrey Yasskinf0356fe2010-01-27 20:34:15 +0000[diff] [blame]198<p>This code defines a <tt>FunctionPassManager</tt>, "<tt>OurFPM</tt>". It
199requires a pointer to the <tt>Module</tt> to construct itself. Once it is set
200up, we use a series of "add" calls to add a bunch of LLVM passes. The first
201pass is basically boilerplate, it adds a pass so that later optimizations know
202how the data structures in the program are laid out. The
203"<tt>TheExecutionEngine</tt>" variable is related to the JIT, which we will get
204to in the next section.</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]205
206<p>In this case, we choose to add 4 optimization passes. The passes we chose
207here are a pretty standard set of "cleanup" optimizations that are useful for
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]208a wide variety of code. I won't delve into what they do but, believe me,
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]209they are a good starting place :).</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]210
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]211<p>Once the PassManager is set up, we need to make use of it. We do this by
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]212running it after our newly created function is constructed (in
213<tt>FunctionAST::Codegen</tt>), but before it is returned to the client:</p>
214
215<div class="doc_code">
216<pre>
217 if (Value *RetVal = Body->Codegen()) {
218 // Finish off the function.
219 Builder.CreateRet(RetVal);
220
221 // Validate the generated code, checking for consistency.
222 verifyFunction(*TheFunction);
223
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]224 <b>// Optimize the function.
225 TheFPM-&gt;run(*TheFunction);</b>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]226
227 return TheFunction;
228 }
229</pre>
230</div>
231
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]232<p>As you can see, this is pretty straightforward. The
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]233<tt>FunctionPassManager</tt> optimizes and updates the LLVM Function* in place,
234improving (hopefully) its body. With this in place, we can try our test above
235again:</p>
236
237<div class="doc_code">
238<pre>
239ready&gt; <b>def test(x) (1+2+x)*(x+(1+2));</b>
240ready> Read function definition:
241define double @test(double %x) {
242entry:
243 %addtmp = add double %x, 3.000000e+00
244 %multmp = mul double %addtmp, %addtmp
245 ret double %multmp
246}
247</pre>
248</div>
249
250<p>As expected, we now get our nicely optimized code, saving a floating point
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]251add instruction from every execution of this function.</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]252
253<p>LLVM provides a wide variety of optimizations that can be used in certain
Chris Lattner72714232007-10-25 17:52:39 +0000[diff] [blame]254circumstances. Some <a href="../Passes.html">documentation about the various
255passes</a> is available, but it isn't very complete. Another good source of
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]256ideas can come from looking at the passes that <tt>llvm-gcc</tt> or
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]257<tt>llvm-ld</tt> run to get started. The "<tt>opt</tt>" tool allows you to
258experiment with passes from the command line, so you can see if they do
259anything.</p>
260
261<p>Now that we have reasonable code coming out of our front-end, lets talk about
262executing it!</p>
263
264</div>
265
266<!-- *********************************************************************** -->
267<div class="doc_section"><a name="jit">Adding a JIT Compiler</a></div>
268<!-- *********************************************************************** -->
269
270<div class="doc_text">
271
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]272<p>Code that is available in LLVM IR can have a wide variety of tools
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]273applied to it. For example, you can run optimizations on it (as we did above),
274you can dump it out in textual or binary forms, you can compile the code to an
275assembly file (.s) for some target, or you can JIT compile it. The nice thing
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]276about the LLVM IR representation is that it is the "common currency" between
277many different parts of the compiler.
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]278</p>
279
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]280<p>In this section, we'll add JIT compiler support to our interpreter. The
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]281basic idea that we want for Kaleidoscope is to have the user enter function
282bodies as they do now, but immediately evaluate the top-level expressions they
283type in. For example, if they type in "1 + 2;", we should evaluate and print
284out 3. If they define a function, they should be able to call it from the
285command line.</p>
286
287<p>In order to do this, we first declare and initialize the JIT. This is done
288by adding a global variable and a call in <tt>main</tt>:</p>
289
290<div class="doc_code">
291<pre>
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]292<b>static ExecutionEngine *TheExecutionEngine;</b>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]293...
294int main() {
295 ..
Jeffrey Yasskinf0356fe2010-01-27 20:34:15 +0000[diff] [blame]296 <b>// Create the JIT. This takes ownership of the module.
297 TheExecutionEngine = EngineBuilder(TheModule).create();</b>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]298 ..
299}
300</pre>
301</div>
302
303<p>This creates an abstract "Execution Engine" which can be either a JIT
304compiler or the LLVM interpreter. LLVM will automatically pick a JIT compiler
305for you if one is available for your platform, otherwise it will fall back to
306the interpreter.</p>
307
308<p>Once the <tt>ExecutionEngine</tt> is created, the JIT is ready to be used.
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]309There are a variety of APIs that are useful, but the simplest one is the
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]310"<tt>getPointerToFunction(F)</tt>" method. This method JIT compiles the
311specified LLVM Function and returns a function pointer to the generated machine
312code. In our case, this means that we can change the code that parses a
313top-level expression to look like this:</p>
314
315<div class="doc_code">
316<pre>
317static void HandleTopLevelExpression() {
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]318 // Evaluate a top-level expression into an anonymous function.
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]319 if (FunctionAST *F = ParseTopLevelExpr()) {
320 if (Function *LF = F-&gt;Codegen()) {
321 LF->dump(); // Dump the function for exposition purposes.
322
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]323 <b>// JIT the function, returning a function pointer.
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]324 void *FPtr = TheExecutionEngine-&gt;getPointerToFunction(LF);
325
326 // Cast it to the right type (takes no arguments, returns a double) so we
327 // can call it as a native function.
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]328 double (*FP)() = (double (*)())(intptr_t)FPtr;
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]329 fprintf(stderr, "Evaluated to %f\n", FP());</b>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]330 }
331</pre>
332</div>
333
334<p>Recall that we compile top-level expressions into a self-contained LLVM
335function that takes no arguments and returns the computed double. Because the
336LLVM JIT compiler matches the native platform ABI, this means that you can just
337cast the result pointer to a function pointer of that type and call it directly.
Chris Lattner41fcea32007-11-13 07:06:30 +0000[diff] [blame]338This means, there is no difference between JIT compiled code and native machine
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]339code that is statically linked into your application.</p>
340
341<p>With just these two changes, lets see how Kaleidoscope works now!</p>
342
343<div class="doc_code">
344<pre>
345ready&gt; <b>4+5;</b>
346define double @""() {
347entry:
348 ret double 9.000000e+00
349}
350
351<em>Evaluated to 9.000000</em>
352</pre>
353</div>
354
355<p>Well this looks like it is basically working. The dump of the function
356shows the "no argument function that always returns double" that we synthesize
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]357for each top-level expression that is typed in. This demonstrates very basic
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]358functionality, but can we do more?</p>
359
360<div class="doc_code">
361<pre>
Chris Lattner2e89f3a2007-10-31 07:30:39 +0000[diff] [blame]362ready&gt; <b>def testfunc(x y) x + y*2; </b>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]363Read function definition:
364define double @testfunc(double %x, double %y) {
365entry:
366 %multmp = mul double %y, 2.000000e+00
367 %addtmp = add double %multmp, %x
368 ret double %addtmp
369}
370
371ready&gt; <b>testfunc(4, 10);</b>
372define double @""() {
373entry:
374 %calltmp = call double @testfunc( double 4.000000e+00, double 1.000000e+01 )
375 ret double %calltmp
376}
377
378<em>Evaluated to 24.000000</em>
379</pre>
380</div>
381
Jeffrey Yasskindc857242009-10-27 20:30:28 +0000[diff] [blame]382<p>This illustrates that we can now call user code, but there is something a bit
383subtle going on here. Note that we only invoke the JIT on the anonymous
384functions that <em>call testfunc</em>, but we never invoked it
385on <em>testfunc</em> itself. What actually happened here is that the JIT
386scanned for all non-JIT'd functions transitively called from the anonymous
387function and compiled all of them before returning
388from <tt>getPointerToFunction()</tt>.</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]389
Jeffrey Yasskindc857242009-10-27 20:30:28 +0000[diff] [blame]390<p>The JIT provides a number of other more advanced interfaces for things like
391freeing allocated machine code, rejit'ing functions to update them, etc.
392However, even with this simple code, we get some surprisingly powerful
393capabilities - check this out (I removed the dump of the anonymous functions,
394you should get the idea by now :) :</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]395
396<div class="doc_code">
397<pre>
398ready&gt; <b>extern sin(x);</b>
399Read extern:
400declare double @sin(double)
401
402ready&gt; <b>extern cos(x);</b>
403Read extern:
404declare double @cos(double)
405
406ready&gt; <b>sin(1.0);</b>
407<em>Evaluated to 0.841471</em>
Chris Lattner72714232007-10-25 17:52:39 +0000[diff] [blame]408
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]409ready&gt; <b>def foo(x) sin(x)*sin(x) + cos(x)*cos(x);</b>
410Read function definition:
411define double @foo(double %x) {
412entry:
413 %calltmp = call double @sin( double %x )
414 %multmp = mul double %calltmp, %calltmp
415 %calltmp2 = call double @cos( double %x )
416 %multmp4 = mul double %calltmp2, %calltmp2
417 %addtmp = add double %multmp, %multmp4
418 ret double %addtmp
419}
420
421ready&gt; <b>foo(4.0);</b>
422<em>Evaluated to 1.000000</em>
423</pre>
424</div>
425
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]426<p>Whoa, how does the JIT know about sin and cos? The answer is surprisingly
427simple: in this
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]428example, the JIT started execution of a function and got to a function call. It
429realized that the function was not yet JIT compiled and invoked the standard set
430of routines to resolve the function. In this case, there is no body defined
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]431for the function, so the JIT ended up calling "<tt>dlsym("sin")</tt>" on the
432Kaleidoscope process itself.
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]433Since "<tt>sin</tt>" is defined within the JIT's address space, it simply
434patches up calls in the module to call the libm version of <tt>sin</tt>
435directly.</p>
436
437<p>The LLVM JIT provides a number of interfaces (look in the
438<tt>ExecutionEngine.h</tt> file) for controlling how unknown functions get
439resolved. It allows you to establish explicit mappings between IR objects and
440addresses (useful for LLVM global variables that you want to map to static
441tables, for example), allows you to dynamically decide on the fly based on the
Jeffrey Yasskindc857242009-10-27 20:30:28 +0000[diff] [blame]442function name, and even allows you to have the JIT compile functions lazily the
443first time they're called.</p>
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]444
Chris Lattner72714232007-10-25 17:52:39 +0000[diff] [blame]445<p>One interesting application of this is that we can now extend the language
446by writing arbitrary C++ code to implement operations. For example, if we add:
447</p>
448
449<div class="doc_code">
450<pre>
451/// putchard - putchar that takes a double and returns 0.
452extern "C"
453double putchard(double X) {
454 putchar((char)X);
455 return 0;
456}
457</pre>
458</div>
459
460<p>Now we can produce simple output to the console by using things like:
461"<tt>extern putchard(x); putchard(120);</tt>", which prints a lowercase 'x' on
Chris Lattnera54c2012007-11-07 05:28:43 +0000[diff] [blame]462the console (120 is the ASCII code for 'x'). Similar code could be used to
Chris Lattner72714232007-10-25 17:52:39 +0000[diff] [blame]463implement file I/O, console input, and many other capabilities in
464Kaleidoscope.</p>
465
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]466<p>This completes the JIT and optimizer chapter of the Kaleidoscope tutorial. At
467this point, we can compile a non-Turing-complete programming language, optimize
468and JIT compile it in a user-driven way. Next up we'll look into <a
469href="LangImpl5.html">extending the language with control flow constructs</a>,
470tackling some interesting LLVM IR issues along the way.</p>
471
472</div>
473
474<!-- *********************************************************************** -->
475<div class="doc_section"><a name="code">Full Code Listing</a></div>
476<!-- *********************************************************************** -->
477
478<div class="doc_text">
479
480<p>
481Here is the complete code listing for our running example, enhanced with the
482LLVM JIT and optimizer. To build this example, use:
483</p>
484
485<div class="doc_code">
486<pre>
487 # Compile
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]488 g++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit interpreter native` -O3 -o toy
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]489 # Run
490 ./toy
491</pre>
492</div>
493
Chris Lattner7c770892009-02-09 00:04:40 +0000[diff] [blame]494<p>
495If you are compiling this on Linux, make sure to add the "-rdynamic" option
496as well. This makes sure that the external functions are resolved properly
497at runtime.</p>
498
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]499<p>Here is the code:</p>
500
501<div class="doc_code">
502<pre>
503#include "llvm/DerivedTypes.h"
504#include "llvm/ExecutionEngine/ExecutionEngine.h"
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]505#include "llvm/ExecutionEngine/Interpreter.h"
506#include "llvm/ExecutionEngine/JIT.h"
Owen Andersond1fbd142009-07-08 20:50:47 +0000[diff] [blame]507#include "llvm/LLVMContext.h"
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]508#include "llvm/Module.h"
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]509#include "llvm/PassManager.h"
510#include "llvm/Analysis/Verifier.h"
511#include "llvm/Target/TargetData.h"
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]512#include "llvm/Target/TargetSelect.h"
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]513#include "llvm/Transforms/Scalar.h"
Duncan Sands89f6d882008-04-13 06:22:09 +0000[diff] [blame]514#include "llvm/Support/IRBuilder.h"
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]515#include &lt;cstdio&gt;
516#include &lt;string&gt;
517#include &lt;map&gt;
518#include &lt;vector&gt;
519using namespace llvm;
520
521//===----------------------------------------------------------------------===//
522// Lexer
523//===----------------------------------------------------------------------===//
524
525// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
526// of these for known things.
527enum Token {
528 tok_eof = -1,
529
530 // commands
531 tok_def = -2, tok_extern = -3,
532
533 // primary
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]534 tok_identifier = -4, tok_number = -5
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]535};
536
537static std::string IdentifierStr; // Filled in if tok_identifier
538static double NumVal; // Filled in if tok_number
539
540/// gettok - Return the next token from standard input.
541static int gettok() {
542 static int LastChar = ' ';
543
544 // Skip any whitespace.
545 while (isspace(LastChar))
546 LastChar = getchar();
547
548 if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
549 IdentifierStr = LastChar;
550 while (isalnum((LastChar = getchar())))
551 IdentifierStr += LastChar;
552
553 if (IdentifierStr == "def") return tok_def;
554 if (IdentifierStr == "extern") return tok_extern;
555 return tok_identifier;
556 }
557
558 if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
559 std::string NumStr;
560 do {
561 NumStr += LastChar;
562 LastChar = getchar();
563 } while (isdigit(LastChar) || LastChar == '.');
564
565 NumVal = strtod(NumStr.c_str(), 0);
566 return tok_number;
567 }
568
569 if (LastChar == '#') {
570 // Comment until end of line.
571 do LastChar = getchar();
Chris Lattnerc80c23f2007-12-02 22:46:01 +0000[diff] [blame]572 while (LastChar != EOF &amp;&amp; LastChar != '\n' &amp;&amp; LastChar != '\r');
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]573
574 if (LastChar != EOF)
575 return gettok();
576 }
577
578 // Check for end of file. Don't eat the EOF.
579 if (LastChar == EOF)
580 return tok_eof;
581
582 // Otherwise, just return the character as its ascii value.
583 int ThisChar = LastChar;
584 LastChar = getchar();
585 return ThisChar;
586}
587
588//===----------------------------------------------------------------------===//
589// Abstract Syntax Tree (aka Parse Tree)
590//===----------------------------------------------------------------------===//
591
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]592/// ExprAST - Base class for all expression nodes.
593class ExprAST {
594public:
595 virtual ~ExprAST() {}
596 virtual Value *Codegen() = 0;
597};
598
599/// NumberExprAST - Expression class for numeric literals like "1.0".
600class NumberExprAST : public ExprAST {
601 double Val;
602public:
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]603 NumberExprAST(double val) : Val(val) {}
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]604 virtual Value *Codegen();
605};
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]606
607/// VariableExprAST - Expression class for referencing a variable, like "a".
608class VariableExprAST : public ExprAST {
609 std::string Name;
610public:
611 VariableExprAST(const std::string &amp;name) : Name(name) {}
612 virtual Value *Codegen();
613};
614
615/// BinaryExprAST - Expression class for a binary operator.
616class BinaryExprAST : public ExprAST {
617 char Op;
618 ExprAST *LHS, *RHS;
619public:
620 BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
621 : Op(op), LHS(lhs), RHS(rhs) {}
622 virtual Value *Codegen();
623};
624
625/// CallExprAST - Expression class for function calls.
626class CallExprAST : public ExprAST {
627 std::string Callee;
628 std::vector&lt;ExprAST*&gt; Args;
629public:
630 CallExprAST(const std::string &amp;callee, std::vector&lt;ExprAST*&gt; &amp;args)
631 : Callee(callee), Args(args) {}
632 virtual Value *Codegen();
633};
634
635/// PrototypeAST - This class represents the "prototype" for a function,
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]636/// which captures its name, and its argument names (thus implicitly the number
637/// of arguments the function takes).
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]638class PrototypeAST {
639 std::string Name;
640 std::vector&lt;std::string&gt; Args;
641public:
642 PrototypeAST(const std::string &amp;name, const std::vector&lt;std::string&gt; &amp;args)
643 : Name(name), Args(args) {}
644
645 Function *Codegen();
646};
647
648/// FunctionAST - This class represents a function definition itself.
649class FunctionAST {
650 PrototypeAST *Proto;
651 ExprAST *Body;
652public:
653 FunctionAST(PrototypeAST *proto, ExprAST *body)
654 : Proto(proto), Body(body) {}
655
656 Function *Codegen();
657};
658
659//===----------------------------------------------------------------------===//
660// Parser
661//===----------------------------------------------------------------------===//
662
663/// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]664/// token the parser is looking at. getNextToken reads another token from the
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]665/// lexer and updates CurTok with its results.
666static int CurTok;
667static int getNextToken() {
668 return CurTok = gettok();
669}
670
671/// BinopPrecedence - This holds the precedence for each binary operator that is
672/// defined.
673static std::map&lt;char, int&gt; BinopPrecedence;
674
675/// GetTokPrecedence - Get the precedence of the pending binary operator token.
676static int GetTokPrecedence() {
677 if (!isascii(CurTok))
678 return -1;
679
680 // Make sure it's a declared binop.
681 int TokPrec = BinopPrecedence[CurTok];
682 if (TokPrec &lt;= 0) return -1;
683 return TokPrec;
684}
685
686/// Error* - These are little helper functions for error handling.
687ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
688PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
689FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
690
691static ExprAST *ParseExpression();
692
693/// identifierexpr
Chris Lattner20a0c802007-11-05 17:54:34 +0000[diff] [blame]694/// ::= identifier
695/// ::= identifier '(' expression* ')'
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]696static ExprAST *ParseIdentifierExpr() {
697 std::string IdName = IdentifierStr;
698
Chris Lattner20a0c802007-11-05 17:54:34 +0000[diff] [blame]699 getNextToken(); // eat identifier.
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]700
701 if (CurTok != '(') // Simple variable ref.
702 return new VariableExprAST(IdName);
703
704 // Call.
705 getNextToken(); // eat (
706 std::vector&lt;ExprAST*&gt; Args;
Chris Lattner71155212007-11-06 01:39:12 +0000[diff] [blame]707 if (CurTok != ')') {
708 while (1) {
709 ExprAST *Arg = ParseExpression();
710 if (!Arg) return 0;
711 Args.push_back(Arg);
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]712
Chris Lattner71155212007-11-06 01:39:12 +0000[diff] [blame]713 if (CurTok == ')') break;
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]714
Chris Lattner71155212007-11-06 01:39:12 +0000[diff] [blame]715 if (CurTok != ',')
Chris Lattner6c4be9c2008-04-14 16:44:41 +0000[diff] [blame]716 return Error("Expected ')' or ',' in argument list");
Chris Lattner71155212007-11-06 01:39:12 +0000[diff] [blame]717 getNextToken();
718 }
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]719 }
720
721 // Eat the ')'.
722 getNextToken();
723
724 return new CallExprAST(IdName, Args);
725}
726
727/// numberexpr ::= number
728static ExprAST *ParseNumberExpr() {
729 ExprAST *Result = new NumberExprAST(NumVal);
730 getNextToken(); // consume the number
731 return Result;
732}
733
734/// parenexpr ::= '(' expression ')'
735static ExprAST *ParseParenExpr() {
736 getNextToken(); // eat (.
737 ExprAST *V = ParseExpression();
738 if (!V) return 0;
739
740 if (CurTok != ')')
741 return Error("expected ')'");
742 getNextToken(); // eat ).
743 return V;
744}
745
746/// primary
747/// ::= identifierexpr
748/// ::= numberexpr
749/// ::= parenexpr
750static ExprAST *ParsePrimary() {
751 switch (CurTok) {
752 default: return Error("unknown token when expecting an expression");
753 case tok_identifier: return ParseIdentifierExpr();
754 case tok_number: return ParseNumberExpr();
755 case '(': return ParseParenExpr();
756 }
757}
758
759/// binoprhs
760/// ::= ('+' primary)*
761static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
762 // If this is a binop, find its precedence.
763 while (1) {
764 int TokPrec = GetTokPrecedence();
765
766 // If this is a binop that binds at least as tightly as the current binop,
767 // consume it, otherwise we are done.
768 if (TokPrec &lt; ExprPrec)
769 return LHS;
770
771 // Okay, we know this is a binop.
772 int BinOp = CurTok;
773 getNextToken(); // eat binop
774
775 // Parse the primary expression after the binary operator.
776 ExprAST *RHS = ParsePrimary();
777 if (!RHS) return 0;
778
779 // If BinOp binds less tightly with RHS than the operator after RHS, let
780 // the pending operator take RHS as its LHS.
781 int NextPrec = GetTokPrecedence();
782 if (TokPrec &lt; NextPrec) {
783 RHS = ParseBinOpRHS(TokPrec+1, RHS);
784 if (RHS == 0) return 0;
785 }
786
787 // Merge LHS/RHS.
788 LHS = new BinaryExprAST(BinOp, LHS, RHS);
789 }
790}
791
792/// expression
793/// ::= primary binoprhs
794///
795static ExprAST *ParseExpression() {
796 ExprAST *LHS = ParsePrimary();
797 if (!LHS) return 0;
798
799 return ParseBinOpRHS(0, LHS);
800}
801
802/// prototype
803/// ::= id '(' id* ')'
804static PrototypeAST *ParsePrototype() {
805 if (CurTok != tok_identifier)
806 return ErrorP("Expected function name in prototype");
807
808 std::string FnName = IdentifierStr;
809 getNextToken();
810
811 if (CurTok != '(')
812 return ErrorP("Expected '(' in prototype");
813
814 std::vector&lt;std::string&gt; ArgNames;
815 while (getNextToken() == tok_identifier)
816 ArgNames.push_back(IdentifierStr);
817 if (CurTok != ')')
818 return ErrorP("Expected ')' in prototype");
819
820 // success.
821 getNextToken(); // eat ')'.
822
823 return new PrototypeAST(FnName, ArgNames);
824}
825
826/// definition ::= 'def' prototype expression
827static FunctionAST *ParseDefinition() {
828 getNextToken(); // eat def.
829 PrototypeAST *Proto = ParsePrototype();
830 if (Proto == 0) return 0;
831
832 if (ExprAST *E = ParseExpression())
833 return new FunctionAST(Proto, E);
834 return 0;
835}
836
837/// toplevelexpr ::= expression
838static FunctionAST *ParseTopLevelExpr() {
839 if (ExprAST *E = ParseExpression()) {
840 // Make an anonymous proto.
841 PrototypeAST *Proto = new PrototypeAST("", std::vector&lt;std::string&gt;());
842 return new FunctionAST(Proto, E);
843 }
844 return 0;
845}
846
847/// external ::= 'extern' prototype
848static PrototypeAST *ParseExtern() {
849 getNextToken(); // eat extern.
850 return ParsePrototype();
851}
852
853//===----------------------------------------------------------------------===//
854// Code Generation
855//===----------------------------------------------------------------------===//
856
857static Module *TheModule;
Owen Andersond1fbd142009-07-08 20:50:47 +0000[diff] [blame]858static IRBuilder&lt;&gt; Builder(getGlobalContext());
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]859static std::map&lt;std::string, Value*&gt; NamedValues;
860static FunctionPassManager *TheFPM;
861
862Value *ErrorV(const char *Str) { Error(Str); return 0; }
863
864Value *NumberExprAST::Codegen() {
Owen Anderson6f83c9c2009-07-27 20:59:43 +0000[diff] [blame]865 return ConstantFP::get(getGlobalContext(), APFloat(Val));
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]866}
867
868Value *VariableExprAST::Codegen() {
869 // Look this variable up in the function.
870 Value *V = NamedValues[Name];
871 return V ? V : ErrorV("Unknown variable name");
872}
873
874Value *BinaryExprAST::Codegen() {
875 Value *L = LHS-&gt;Codegen();
876 Value *R = RHS-&gt;Codegen();
877 if (L == 0 || R == 0) return 0;
878
879 switch (Op) {
880 case '+': return Builder.CreateAdd(L, R, "addtmp");
881 case '-': return Builder.CreateSub(L, R, "subtmp");
882 case '*': return Builder.CreateMul(L, R, "multmp");
883 case '&lt;':
Chris Lattner71155212007-11-06 01:39:12 +0000[diff] [blame]884 L = Builder.CreateFCmpULT(L, R, "cmptmp");
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]885 // Convert bool 0/1 to double 0.0 or 1.0
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]886 return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
887 "booltmp");
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]888 default: return ErrorV("invalid binary operator");
889 }
890}
891
892Value *CallExprAST::Codegen() {
893 // Look up the name in the global module table.
894 Function *CalleeF = TheModule-&gt;getFunction(Callee);
895 if (CalleeF == 0)
896 return ErrorV("Unknown function referenced");
897
898 // If argument mismatch error.
899 if (CalleeF-&gt;arg_size() != Args.size())
900 return ErrorV("Incorrect # arguments passed");
901
902 std::vector&lt;Value*&gt; ArgsV;
903 for (unsigned i = 0, e = Args.size(); i != e; ++i) {
904 ArgsV.push_back(Args[i]-&gt;Codegen());
905 if (ArgsV.back() == 0) return 0;
906 }
907
908 return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
909}
910
911Function *PrototypeAST::Codegen() {
912 // Make the function type: double(double,double) etc.
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]913 std::vector&lt;const Type*&gt; Doubles(Args.size(),
914 Type::getDoubleTy(getGlobalContext()));
915 FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
916 Doubles, false);
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]917
Gabor Greifdf7d2b42008-04-19 22:25:09 +0000[diff] [blame]918 Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]919
920 // If F conflicted, there was already something named 'Name'. If it has a
921 // body, don't allow redefinition or reextern.
922 if (F-&gt;getName() != Name) {
923 // Delete the one we just made and get the existing one.
924 F-&gt;eraseFromParent();
925 F = TheModule-&gt;getFunction(Name);
926
927 // If F already has a body, reject this.
928 if (!F-&gt;empty()) {
929 ErrorF("redefinition of function");
930 return 0;
931 }
932
933 // If F took a different number of args, reject.
934 if (F-&gt;arg_size() != Args.size()) {
935 ErrorF("redefinition of function with different # args");
936 return 0;
937 }
938 }
939
940 // Set names for all arguments.
941 unsigned Idx = 0;
942 for (Function::arg_iterator AI = F-&gt;arg_begin(); Idx != Args.size();
943 ++AI, ++Idx) {
944 AI-&gt;setName(Args[Idx]);
945
946 // Add arguments to variable symbol table.
947 NamedValues[Args[Idx]] = AI;
948 }
949
950 return F;
951}
952
953Function *FunctionAST::Codegen() {
954 NamedValues.clear();
955
956 Function *TheFunction = Proto-&gt;Codegen();
957 if (TheFunction == 0)
958 return 0;
959
960 // Create a new basic block to start insertion into.
Owen Anderson1d0be152009-08-13 21:58:54 +0000[diff] [blame]961 BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]962 Builder.SetInsertPoint(BB);
963
964 if (Value *RetVal = Body-&gt;Codegen()) {
965 // Finish off the function.
966 Builder.CreateRet(RetVal);
967
968 // Validate the generated code, checking for consistency.
969 verifyFunction(*TheFunction);
970
971 // Optimize the function.
972 TheFPM-&gt;run(*TheFunction);
973
974 return TheFunction;
975 }
976
977 // Error reading body, remove function.
978 TheFunction-&gt;eraseFromParent();
979 return 0;
980}
981
982//===----------------------------------------------------------------------===//
983// Top-Level parsing and JIT Driver
984//===----------------------------------------------------------------------===//
985
986static ExecutionEngine *TheExecutionEngine;
987
988static void HandleDefinition() {
989 if (FunctionAST *F = ParseDefinition()) {
990 if (Function *LF = F-&gt;Codegen()) {
991 fprintf(stderr, "Read function definition:");
992 LF-&gt;dump();
993 }
994 } else {
995 // Skip token for error recovery.
996 getNextToken();
997 }
998}
999
1000static void HandleExtern() {
1001 if (PrototypeAST *P = ParseExtern()) {
1002 if (Function *F = P-&gt;Codegen()) {
1003 fprintf(stderr, "Read extern: ");
1004 F-&gt;dump();
1005 }
1006 } else {
1007 // Skip token for error recovery.
1008 getNextToken();
1009 }
1010}
1011
1012static void HandleTopLevelExpression() {
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]1013 // Evaluate a top-level expression into an anonymous function.
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1014 if (FunctionAST *F = ParseTopLevelExpr()) {
1015 if (Function *LF = F-&gt;Codegen()) {
1016 // JIT the function, returning a function pointer.
1017 void *FPtr = TheExecutionEngine-&gt;getPointerToFunction(LF);
1018
1019 // Cast it to the right type (takes no arguments, returns a double) so we
1020 // can call it as a native function.
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]1021 double (*FP)() = (double (*)())(intptr_t)FPtr;
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1022 fprintf(stderr, "Evaluated to %f\n", FP());
1023 }
1024 } else {
1025 // Skip token for error recovery.
1026 getNextToken();
1027 }
1028}
1029
1030/// top ::= definition | external | expression | ';'
1031static void MainLoop() {
1032 while (1) {
1033 fprintf(stderr, "ready&gt; ");
1034 switch (CurTok) {
1035 case tok_eof: return;
Erick Tryzelaarfd1ec5e2009-09-22 21:14:49 +0000[diff] [blame]1036 case ';': getNextToken(); break; // ignore top-level semicolons.
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1037 case tok_def: HandleDefinition(); break;
1038 case tok_extern: HandleExtern(); break;
1039 default: HandleTopLevelExpression(); break;
1040 }
1041 }
1042}
1043
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1044//===----------------------------------------------------------------------===//
1045// "Library" functions that can be "extern'd" from user code.
1046//===----------------------------------------------------------------------===//
1047
1048/// putchard - putchar that takes a double and returns 0.
1049extern "C"
1050double putchard(double X) {
1051 putchar((char)X);
1052 return 0;
1053}
1054
1055//===----------------------------------------------------------------------===//
1056// Main driver code.
1057//===----------------------------------------------------------------------===//
1058
1059int main() {
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]1060 InitializeNativeTarget();
1061 LLVMContext &amp;Context = getGlobalContext();
1062
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1063 // Install standard binary operators.
1064 // 1 is lowest precedence.
1065 BinopPrecedence['&lt;'] = 10;
1066 BinopPrecedence['+'] = 20;
1067 BinopPrecedence['-'] = 20;
1068 BinopPrecedence['*'] = 40; // highest.
1069
1070 // Prime the first token.
1071 fprintf(stderr, "ready&gt; ");
1072 getNextToken();
1073
1074 // Make the module, which holds all the code.
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]1075 TheModule = new Module("my cool jit", Context);
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1076
Jeffrey Yasskinf0356fe2010-01-27 20:34:15 +0000[diff] [blame]1077 // Create the JIT. This takes ownership of the module.
1078 TheExecutionEngine = EngineBuilder(TheModule).create();
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1079
Jeffrey Yasskinf0356fe2010-01-27 20:34:15 +0000[diff] [blame]1080 FunctionPassManager OurFPM(TheModule);
Reid Kleckner60130f02009-08-26 20:58:25 +0000[diff] [blame]1081
1082 // Set up the optimizer pipeline. Start with registering info about how the
1083 // target lays out data structures.
1084 OurFPM.add(new TargetData(*TheExecutionEngine-&gt;getTargetData()));
1085 // Do simple "peephole" optimizations and bit-twiddling optzns.
1086 OurFPM.add(createInstructionCombiningPass());
1087 // Reassociate expressions.
1088 OurFPM.add(createReassociatePass());
1089 // Eliminate Common SubExpressions.
1090 OurFPM.add(createGVNPass());
1091 // Simplify the control flow graph (deleting unreachable blocks, etc).
1092 OurFPM.add(createCFGSimplificationPass());
1093
Nick Lewycky422094c2009-09-13 21:38:54 +0000[diff] [blame]1094 OurFPM.doInitialization();
1095
Reid Kleckner60130f02009-08-26 20:58:25 +0000[diff] [blame]1096 // Set the global so the code gen can use this.
1097 TheFPM = &amp;OurFPM;
1098
1099 // Run the main "interpreter loop" now.
1100 MainLoop();
1101
1102 TheFPM = 0;
1103
1104 // Print out all of the generated code.
1105 TheModule-&gt;dump();
1106
Chris Lattner118749e2007-10-25 06:23:36 +0000[diff] [blame]1107 return 0;
1108}
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]1109</pre>
1110</div>
1111
Chris Lattner729eb142008-02-10 19:11:04 +0000[diff] [blame]1112<a href="LangImpl5.html">Next: Extending the language: control flow</a>
Chris Lattnerc0b42e92007-10-23 06:27:55 +0000[diff] [blame]1113</div>
1114
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