Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" |
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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 Lattner | 128eb86 | 2007-11-05 19:06:59 +0000 | [diff] [blame] | 16 | <ul> |
Chris Lattner | 0e555b1 | 2007-11-05 20:04:56 +0000 | [diff] [blame] | 17 | <li><a href="index.html">Up to Tutorial Index</a></li> |
Chris Lattner | 128eb86 | 2007-11-05 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 Lattner | 0e555b1 | 2007-11-05 20:04:56 +0000 | [diff] [blame] | 27 | <li><a href="LangImpl5.html">Chapter 5</a>: Extending the Language: Control |
| 28 | Flow</li> |
Chris Lattner | 128eb86 | 2007-11-05 19:06:59 +0000 | [diff] [blame] | 29 | </ul> |
| 30 | |
Chris Lattner | c0b42e9 | 2007-10-23 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 Lattner | 128eb86 | 2007-11-05 19:06:59 +0000 | [diff] [blame] | 36 | <div class="doc_section"><a name="intro">Chapter 4 Introduction</a></div> |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 37 | <!-- *********************************************************************** --> |
| 38 | |
| 39 | <div class="doc_text"> |
| 40 | |
Chris Lattner | 128eb86 | 2007-11-05 19:06:59 +0000 | [diff] [blame] | 41 | <p>Welcome to Chapter 4 of the "<a href="index.html">Implementing a language |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 42 | with LLVM</a>" tutorial. Chapters 1-3 described the implementation of a simple |
| 43 | language and added support for generating LLVM IR. This chapter describes |
Chris Lattner | 128eb86 | 2007-11-05 19:06:59 +0000 | [diff] [blame] | 44 | two new techniques: adding optimizer support to your language, and adding JIT |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 45 | compiler support. These additions will demonstrate how to get nice, efficient code |
| 46 | for the Kaleidoscope language.</p> |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 47 | |
| 48 | </div> |
| 49 | |
| 50 | <!-- *********************************************************************** --> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 51 | <div class="doc_section"><a name="trivialconstfold">Trivial Constant |
| 52 | Folding</a></div> |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 53 | <!-- *********************************************************************** --> |
| 54 | |
| 55 | <div class="doc_text"> |
| 56 | |
| 57 | <p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 58 | Our demonstration for Chapter 3 is elegant and easy to extend. Unfortunately, |
| 59 | it does not produce wonderful code. For example, when compiling simple code, |
| 60 | we don't get obvious optimizations:</p> |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 61 | |
| 62 | <div class="doc_code"> |
| 63 | <pre> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 64 | ready> <b>def test(x) 1+2+x;</b> |
| 65 | Read function definition: |
| 66 | define double @test(double %x) { |
| 67 | entry: |
| 68 | %addtmp = add double 1.000000e+00, 2.000000e+00 |
| 69 | %addtmp1 = add double %addtmp, %x |
| 70 | ret double %addtmp1 |
| 71 | } |
| 72 | </pre> |
| 73 | </div> |
| 74 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 75 | <p>This code is a very, very literal transcription of the AST built by parsing |
| 76 | the input. As such, this transcription lacks optimizations like constant folding (we'd like to get "<tt>add x, 3.0</tt>" in the example above) as well as other more important |
| 77 | optimizations. Constant folding, in particular, is a very common and very |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 78 | important optimization: so much so that many language implementors implement |
| 79 | constant folding support in their AST representation.</p> |
| 80 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 81 | <p>With LLVM, you don't need this support in the AST. Since all calls to build LLVM IR go through |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 82 | the LLVM builder, it would be nice if the builder itself checked to see if there |
| 83 | was a constant folding opportunity when you call it. If so, it could just do |
| 84 | the constant fold and return the constant instead of creating an instruction. |
| 85 | This is exactly what the <tt>LLVMFoldingBuilder</tt> class does. Lets make one |
| 86 | change: |
| 87 | |
| 88 | <div class="doc_code"> |
| 89 | <pre> |
| 90 | static LLVMFoldingBuilder Builder; |
| 91 | </pre> |
| 92 | </div> |
| 93 | |
| 94 | <p>All we did was switch from <tt>LLVMBuilder</tt> to |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 95 | <tt>LLVMFoldingBuilder</tt>. Though we change no other code, we now have all of our |
| 96 | instructions implicitly constant folded without us having to do anything |
| 97 | about it. For example, the input above now compiles to:</p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 98 | |
| 99 | <div class="doc_code"> |
| 100 | <pre> |
| 101 | ready> <b>def test(x) 1+2+x;</b> |
| 102 | Read function definition: |
| 103 | define double @test(double %x) { |
| 104 | entry: |
| 105 | %addtmp = add double 3.000000e+00, %x |
| 106 | ret double %addtmp |
| 107 | } |
| 108 | </pre> |
| 109 | </div> |
| 110 | |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 111 | <p>Well, that was easy :). In practice, we recommend always using |
Owen Anderson | 6867aec | 2007-10-25 06:50:30 +0000 | [diff] [blame] | 112 | <tt>LLVMFoldingBuilder</tt> when generating code like this. It has no |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 113 | "syntactic overhead" for its use (you don't have to uglify your compiler with |
| 114 | constant checks everywhere) and it can dramatically reduce the amount of |
| 115 | LLVM IR that is generated in some cases (particular for languages with a macro |
| 116 | preprocessor or that use a lot of constants).</p> |
| 117 | |
| 118 | <p>On the other hand, the <tt>LLVMFoldingBuilder</tt> is limited by the fact |
| 119 | that it does all of its analysis inline with the code as it is built. If you |
| 120 | take a slightly more complex example:</p> |
| 121 | |
| 122 | <div class="doc_code"> |
| 123 | <pre> |
| 124 | ready> <b>def test(x) (1+2+x)*(x+(1+2));</b> |
| 125 | ready> Read function definition: |
| 126 | define double @test(double %x) { |
| 127 | entry: |
| 128 | %addtmp = add double 3.000000e+00, %x |
| 129 | %addtmp1 = add double %x, 3.000000e+00 |
| 130 | %multmp = mul double %addtmp, %addtmp1 |
| 131 | ret double %multmp |
| 132 | } |
| 133 | </pre> |
| 134 | </div> |
| 135 | |
| 136 | <p>In this case, the LHS and RHS of the multiplication are the same value. We'd |
| 137 | really like to see this generate "<tt>tmp = x+3; result = tmp*tmp;</tt>" instead |
| 138 | of computing "<tt>x*3</tt>" twice.</p> |
| 139 | |
| 140 | <p>Unfortunately, no amount of local analysis will be able to detect and correct |
| 141 | this. This requires two transformations: reassociation of expressions (to |
| 142 | make the add's lexically identical) and Common Subexpression Elimination (CSE) |
| 143 | to delete the redundant add instruction. Fortunately, LLVM provides a broad |
| 144 | range of optimizations that you can use, in the form of "passes".</p> |
| 145 | |
| 146 | </div> |
| 147 | |
| 148 | <!-- *********************************************************************** --> |
| 149 | <div class="doc_section"><a name="optimizerpasses">LLVM Optimization |
| 150 | Passes</a></div> |
| 151 | <!-- *********************************************************************** --> |
| 152 | |
| 153 | <div class="doc_text"> |
| 154 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 155 | <p>LLVM provides many optimization passes, which do many different sorts of |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 156 | things and have different tradeoffs. Unlike other systems, LLVM doesn't hold |
| 157 | to the mistaken notion that one set of optimizations is right for all languages |
| 158 | and for all situations. LLVM allows a compiler implementor to make complete |
| 159 | decisions about what optimizations to use, in which order, and in what |
| 160 | situation.</p> |
| 161 | |
| 162 | <p>As a concrete example, LLVM supports both "whole module" passes, which look |
| 163 | across as large of body of code as they can (often a whole file, but if run |
| 164 | at link time, this can be a substantial portion of the whole program). It also |
| 165 | supports and includes "per-function" passes which just operate on a single |
| 166 | function at a time, without looking at other functions. For more information |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 167 | on passes and how they are run, see the <a href="../WritingAnLLVMPass.html">How |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 168 | to Write a Pass</a> document and the <a href="../Passes.html">List of LLVM |
| 169 | Passes</a>.</p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 170 | |
| 171 | <p>For Kaleidoscope, we are currently generating functions on the fly, one at |
| 172 | a time, as the user types them in. We aren't shooting for the ultimate |
| 173 | optimization experience in this setting, but we also want to catch the easy and |
| 174 | quick stuff where possible. As such, we will choose to run a few per-function |
| 175 | optimizations as the user types the function in. If we wanted to make a "static |
| 176 | Kaleidoscope compiler", we would use exactly the code we have now, except that |
| 177 | we would defer running the optimizer until the entire file has been parsed.</p> |
| 178 | |
| 179 | <p>In order to get per-function optimizations going, we need to set up a |
| 180 | <a href="../WritingAnLLVMPass.html#passmanager">FunctionPassManager</a> to hold and |
| 181 | organize the LLVM optimizations that we want to run. Once we have that, we can |
| 182 | add a set of optimizations to run. The code looks like this:</p> |
| 183 | |
| 184 | <div class="doc_code"> |
| 185 | <pre> |
| 186 | ExistingModuleProvider OurModuleProvider(TheModule); |
| 187 | FunctionPassManager OurFPM(&OurModuleProvider); |
| 188 | |
| 189 | // Set up the optimizer pipeline. Start with registering info about how the |
| 190 | // target lays out data structures. |
| 191 | OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData())); |
| 192 | // Do simple "peephole" optimizations and bit-twiddling optzns. |
| 193 | OurFPM.add(createInstructionCombiningPass()); |
| 194 | // Reassociate expressions. |
| 195 | OurFPM.add(createReassociatePass()); |
| 196 | // Eliminate Common SubExpressions. |
| 197 | OurFPM.add(createGVNPass()); |
| 198 | // Simplify the control flow graph (deleting unreachable blocks, etc). |
| 199 | OurFPM.add(createCFGSimplificationPass()); |
| 200 | |
| 201 | // Set the global so the code gen can use this. |
| 202 | TheFPM = &OurFPM; |
| 203 | |
| 204 | // Run the main "interpreter loop" now. |
| 205 | MainLoop(); |
| 206 | </pre> |
| 207 | </div> |
| 208 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 209 | <p>This code defines two objects, an <tt>ExistingModuleProvider</tt> and a |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 210 | <tt>FunctionPassManager</tt>. The former is basically a wrapper around our |
| 211 | <tt>Module</tt> that the PassManager requires. It provides certain flexibility |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 212 | that we're not going to take advantage of here, so I won't dive into any details |
| 213 | about it.</p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 214 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 215 | <p>The meat of the matter here, is the definition of "<tt>OurFPM</tt>". It |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 216 | requires a pointer to the <tt>Module</tt> (through the <tt>ModuleProvider</tt>) |
| 217 | to construct itself. Once it is set up, we use a series of "add" calls to add |
| 218 | a bunch of LLVM passes. The first pass is basically boilerplate, it adds a pass |
| 219 | so that later optimizations know how the data structures in the program are |
| 220 | layed out. The "<tt>TheExecutionEngine</tt>" variable is related to the JIT, |
| 221 | which we will get to in the next section.</p> |
| 222 | |
| 223 | <p>In this case, we choose to add 4 optimization passes. The passes we chose |
| 224 | here are a pretty standard set of "cleanup" optimizations that are useful for |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 225 | a wide variety of code. I won't delve into what they do but, believe me, |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 226 | they are a good starting place :).</p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 227 | |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 228 | <p>Once the PassManager is set up, we need to make use of it. We do this by |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 229 | running it after our newly created function is constructed (in |
| 230 | <tt>FunctionAST::Codegen</tt>), but before it is returned to the client:</p> |
| 231 | |
| 232 | <div class="doc_code"> |
| 233 | <pre> |
| 234 | if (Value *RetVal = Body->Codegen()) { |
| 235 | // Finish off the function. |
| 236 | Builder.CreateRet(RetVal); |
| 237 | |
| 238 | // Validate the generated code, checking for consistency. |
| 239 | verifyFunction(*TheFunction); |
| 240 | |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 241 | <b>// Optimize the function. |
| 242 | TheFPM->run(*TheFunction);</b> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 243 | |
| 244 | return TheFunction; |
| 245 | } |
| 246 | </pre> |
| 247 | </div> |
| 248 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 249 | <p>As you can see, this is pretty straightforward. The |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 250 | <tt>FunctionPassManager</tt> optimizes and updates the LLVM Function* in place, |
| 251 | improving (hopefully) its body. With this in place, we can try our test above |
| 252 | again:</p> |
| 253 | |
| 254 | <div class="doc_code"> |
| 255 | <pre> |
| 256 | ready> <b>def test(x) (1+2+x)*(x+(1+2));</b> |
| 257 | ready> Read function definition: |
| 258 | define double @test(double %x) { |
| 259 | entry: |
| 260 | %addtmp = add double %x, 3.000000e+00 |
| 261 | %multmp = mul double %addtmp, %addtmp |
| 262 | ret double %multmp |
| 263 | } |
| 264 | </pre> |
| 265 | </div> |
| 266 | |
| 267 | <p>As expected, we now get our nicely optimized code, saving a floating point |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 268 | add instruction from every execution of this function.</p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 269 | |
| 270 | <p>LLVM provides a wide variety of optimizations that can be used in certain |
Chris Lattner | 7271423 | 2007-10-25 17:52:39 +0000 | [diff] [blame] | 271 | circumstances. Some <a href="../Passes.html">documentation about the various |
| 272 | passes</a> is available, but it isn't very complete. Another good source of |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 273 | ideas can come from looking at the passes that <tt>llvm-gcc</tt> or |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 274 | <tt>llvm-ld</tt> run to get started. The "<tt>opt</tt>" tool allows you to |
| 275 | experiment with passes from the command line, so you can see if they do |
| 276 | anything.</p> |
| 277 | |
| 278 | <p>Now that we have reasonable code coming out of our front-end, lets talk about |
| 279 | executing it!</p> |
| 280 | |
| 281 | </div> |
| 282 | |
| 283 | <!-- *********************************************************************** --> |
| 284 | <div class="doc_section"><a name="jit">Adding a JIT Compiler</a></div> |
| 285 | <!-- *********************************************************************** --> |
| 286 | |
| 287 | <div class="doc_text"> |
| 288 | |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 289 | <p>Code that is available in LLVM IR can have a wide variety of tools |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 290 | applied to it. For example, you can run optimizations on it (as we did above), |
| 291 | you can dump it out in textual or binary forms, you can compile the code to an |
| 292 | assembly file (.s) for some target, or you can JIT compile it. The nice thing |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 293 | about the LLVM IR representation is that it is the "common currency" between |
| 294 | many different parts of the compiler. |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 295 | </p> |
| 296 | |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 297 | <p>In this section, we'll add JIT compiler support to our interpreter. The |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 298 | basic idea that we want for Kaleidoscope is to have the user enter function |
| 299 | bodies as they do now, but immediately evaluate the top-level expressions they |
| 300 | type in. For example, if they type in "1 + 2;", we should evaluate and print |
| 301 | out 3. If they define a function, they should be able to call it from the |
| 302 | command line.</p> |
| 303 | |
| 304 | <p>In order to do this, we first declare and initialize the JIT. This is done |
| 305 | by adding a global variable and a call in <tt>main</tt>:</p> |
| 306 | |
| 307 | <div class="doc_code"> |
| 308 | <pre> |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 309 | <b>static ExecutionEngine *TheExecutionEngine;</b> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 310 | ... |
| 311 | int main() { |
| 312 | .. |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 313 | <b>// Create the JIT. |
| 314 | TheExecutionEngine = ExecutionEngine::create(TheModule);</b> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 315 | .. |
| 316 | } |
| 317 | </pre> |
| 318 | </div> |
| 319 | |
| 320 | <p>This creates an abstract "Execution Engine" which can be either a JIT |
| 321 | compiler or the LLVM interpreter. LLVM will automatically pick a JIT compiler |
| 322 | for you if one is available for your platform, otherwise it will fall back to |
| 323 | the interpreter.</p> |
| 324 | |
| 325 | <p>Once the <tt>ExecutionEngine</tt> is created, the JIT is ready to be used. |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 326 | There are a variety of APIs that are useful, but the simplest one is the |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 327 | "<tt>getPointerToFunction(F)</tt>" method. This method JIT compiles the |
| 328 | specified LLVM Function and returns a function pointer to the generated machine |
| 329 | code. In our case, this means that we can change the code that parses a |
| 330 | top-level expression to look like this:</p> |
| 331 | |
| 332 | <div class="doc_code"> |
| 333 | <pre> |
| 334 | static void HandleTopLevelExpression() { |
| 335 | // Evaluate a top level expression into an anonymous function. |
| 336 | if (FunctionAST *F = ParseTopLevelExpr()) { |
| 337 | if (Function *LF = F->Codegen()) { |
| 338 | LF->dump(); // Dump the function for exposition purposes. |
| 339 | |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 340 | <b>// JIT the function, returning a function pointer. |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 341 | void *FPtr = TheExecutionEngine->getPointerToFunction(LF); |
| 342 | |
| 343 | // Cast it to the right type (takes no arguments, returns a double) so we |
| 344 | // can call it as a native function. |
| 345 | double (*FP)() = (double (*)())FPtr; |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 346 | fprintf(stderr, "Evaluated to %f\n", FP());</b> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 347 | } |
| 348 | </pre> |
| 349 | </div> |
| 350 | |
| 351 | <p>Recall that we compile top-level expressions into a self-contained LLVM |
| 352 | function that takes no arguments and returns the computed double. Because the |
| 353 | LLVM JIT compiler matches the native platform ABI, this means that you can just |
| 354 | cast the result pointer to a function pointer of that type and call it directly. |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 355 | This means, there is no difference between JIT compiled code and native machine |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 356 | code that is statically linked into your application.</p> |
| 357 | |
| 358 | <p>With just these two changes, lets see how Kaleidoscope works now!</p> |
| 359 | |
| 360 | <div class="doc_code"> |
| 361 | <pre> |
| 362 | ready> <b>4+5;</b> |
| 363 | define double @""() { |
| 364 | entry: |
| 365 | ret double 9.000000e+00 |
| 366 | } |
| 367 | |
| 368 | <em>Evaluated to 9.000000</em> |
| 369 | </pre> |
| 370 | </div> |
| 371 | |
| 372 | <p>Well this looks like it is basically working. The dump of the function |
| 373 | shows the "no argument function that always returns double" that we synthesize |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 374 | for each top level expression that is typed in. This demonstrates very basic |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 375 | functionality, but can we do more?</p> |
| 376 | |
| 377 | <div class="doc_code"> |
| 378 | <pre> |
Chris Lattner | 2e89f3a | 2007-10-31 07:30:39 +0000 | [diff] [blame] | 379 | ready> <b>def testfunc(x y) x + y*2; </b> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 380 | Read function definition: |
| 381 | define double @testfunc(double %x, double %y) { |
| 382 | entry: |
| 383 | %multmp = mul double %y, 2.000000e+00 |
| 384 | %addtmp = add double %multmp, %x |
| 385 | ret double %addtmp |
| 386 | } |
| 387 | |
| 388 | ready> <b>testfunc(4, 10);</b> |
| 389 | define double @""() { |
| 390 | entry: |
| 391 | %calltmp = call double @testfunc( double 4.000000e+00, double 1.000000e+01 ) |
| 392 | ret double %calltmp |
| 393 | } |
| 394 | |
| 395 | <em>Evaluated to 24.000000</em> |
| 396 | </pre> |
| 397 | </div> |
| 398 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 399 | <p>This illustrates that we can now call user code, but there is something a bit subtle |
| 400 | going on here. Note that we only invoke the JIT on the anonymous functions |
| 401 | that <em>call testfunc</em>, but we never invoked it on <em>testfunc |
| 402 | </em>itself.</p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 403 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 404 | <p>What actually happened here is that the anonymous function was |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 405 | JIT'd when requested. When the Kaleidoscope app calls through the function |
| 406 | pointer that is returned, the anonymous function starts executing. It ends up |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 407 | making the call to the "testfunc" function, and ends up in a stub that invokes |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 408 | the JIT, lazily, on testfunc. Once the JIT finishes lazily compiling testfunc, |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 409 | it returns and the code re-executes the call.</p> |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 410 | |
Chris Lattner | 41fcea3 | 2007-11-13 07:06:30 +0000 | [diff] [blame] | 411 | <p>In summary, the JIT will lazily JIT code, on the fly, as it is needed. The |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 412 | JIT provides a number of other more advanced interfaces for things like freeing |
| 413 | allocated machine code, rejit'ing functions to update them, etc. However, even |
| 414 | with this simple code, we get some surprisingly powerful capabilities - check |
| 415 | this out (I removed the dump of the anonymous functions, you should get the idea |
| 416 | by now :) :</p> |
| 417 | |
| 418 | <div class="doc_code"> |
| 419 | <pre> |
| 420 | ready> <b>extern sin(x);</b> |
| 421 | Read extern: |
| 422 | declare double @sin(double) |
| 423 | |
| 424 | ready> <b>extern cos(x);</b> |
| 425 | Read extern: |
| 426 | declare double @cos(double) |
| 427 | |
| 428 | ready> <b>sin(1.0);</b> |
| 429 | <em>Evaluated to 0.841471</em> |
Chris Lattner | 7271423 | 2007-10-25 17:52:39 +0000 | [diff] [blame] | 430 | |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 431 | ready> <b>def foo(x) sin(x)*sin(x) + cos(x)*cos(x);</b> |
| 432 | Read function definition: |
| 433 | define double @foo(double %x) { |
| 434 | entry: |
| 435 | %calltmp = call double @sin( double %x ) |
| 436 | %multmp = mul double %calltmp, %calltmp |
| 437 | %calltmp2 = call double @cos( double %x ) |
| 438 | %multmp4 = mul double %calltmp2, %calltmp2 |
| 439 | %addtmp = add double %multmp, %multmp4 |
| 440 | ret double %addtmp |
| 441 | } |
| 442 | |
| 443 | ready> <b>foo(4.0);</b> |
| 444 | <em>Evaluated to 1.000000</em> |
| 445 | </pre> |
| 446 | </div> |
| 447 | |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 448 | <p>Whoa, how does the JIT know about sin and cos? The answer is surprisingly |
| 449 | simple: in this |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 450 | example, the JIT started execution of a function and got to a function call. It |
| 451 | realized that the function was not yet JIT compiled and invoked the standard set |
| 452 | of routines to resolve the function. In this case, there is no body defined |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 453 | for the function, so the JIT ended up calling "<tt>dlsym("sin")</tt>" on the |
| 454 | Kaleidoscope process itself. |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 455 | Since "<tt>sin</tt>" is defined within the JIT's address space, it simply |
| 456 | patches up calls in the module to call the libm version of <tt>sin</tt> |
| 457 | directly.</p> |
| 458 | |
| 459 | <p>The LLVM JIT provides a number of interfaces (look in the |
| 460 | <tt>ExecutionEngine.h</tt> file) for controlling how unknown functions get |
| 461 | resolved. It allows you to establish explicit mappings between IR objects and |
| 462 | addresses (useful for LLVM global variables that you want to map to static |
| 463 | tables, for example), allows you to dynamically decide on the fly based on the |
| 464 | function name, and even allows you to have the JIT abort itself if any lazy |
| 465 | compilation is attempted.</p> |
| 466 | |
Chris Lattner | 7271423 | 2007-10-25 17:52:39 +0000 | [diff] [blame] | 467 | <p>One interesting application of this is that we can now extend the language |
| 468 | by writing arbitrary C++ code to implement operations. For example, if we add: |
| 469 | </p> |
| 470 | |
| 471 | <div class="doc_code"> |
| 472 | <pre> |
| 473 | /// putchard - putchar that takes a double and returns 0. |
| 474 | extern "C" |
| 475 | double putchard(double X) { |
| 476 | putchar((char)X); |
| 477 | return 0; |
| 478 | } |
| 479 | </pre> |
| 480 | </div> |
| 481 | |
| 482 | <p>Now we can produce simple output to the console by using things like: |
| 483 | "<tt>extern putchard(x); putchard(120);</tt>", which prints a lowercase 'x' on |
Chris Lattner | a54c201 | 2007-11-07 05:28:43 +0000 | [diff] [blame] | 484 | the console (120 is the ASCII code for 'x'). Similar code could be used to |
Chris Lattner | 7271423 | 2007-10-25 17:52:39 +0000 | [diff] [blame] | 485 | implement file I/O, console input, and many other capabilities in |
| 486 | Kaleidoscope.</p> |
| 487 | |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 488 | <p>This completes the JIT and optimizer chapter of the Kaleidoscope tutorial. At |
| 489 | this point, we can compile a non-Turing-complete programming language, optimize |
| 490 | and JIT compile it in a user-driven way. Next up we'll look into <a |
| 491 | href="LangImpl5.html">extending the language with control flow constructs</a>, |
| 492 | tackling some interesting LLVM IR issues along the way.</p> |
| 493 | |
| 494 | </div> |
| 495 | |
| 496 | <!-- *********************************************************************** --> |
| 497 | <div class="doc_section"><a name="code">Full Code Listing</a></div> |
| 498 | <!-- *********************************************************************** --> |
| 499 | |
| 500 | <div class="doc_text"> |
| 501 | |
| 502 | <p> |
| 503 | Here is the complete code listing for our running example, enhanced with the |
| 504 | LLVM JIT and optimizer. To build this example, use: |
| 505 | </p> |
| 506 | |
| 507 | <div class="doc_code"> |
| 508 | <pre> |
| 509 | # Compile |
| 510 | g++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy |
| 511 | # Run |
| 512 | ./toy |
| 513 | </pre> |
| 514 | </div> |
| 515 | |
| 516 | <p>Here is the code:</p> |
| 517 | |
| 518 | <div class="doc_code"> |
| 519 | <pre> |
| 520 | #include "llvm/DerivedTypes.h" |
| 521 | #include "llvm/ExecutionEngine/ExecutionEngine.h" |
| 522 | #include "llvm/Module.h" |
| 523 | #include "llvm/ModuleProvider.h" |
| 524 | #include "llvm/PassManager.h" |
| 525 | #include "llvm/Analysis/Verifier.h" |
| 526 | #include "llvm/Target/TargetData.h" |
| 527 | #include "llvm/Transforms/Scalar.h" |
| 528 | #include "llvm/Support/LLVMBuilder.h" |
| 529 | #include <cstdio> |
| 530 | #include <string> |
| 531 | #include <map> |
| 532 | #include <vector> |
| 533 | using namespace llvm; |
| 534 | |
| 535 | //===----------------------------------------------------------------------===// |
| 536 | // Lexer |
| 537 | //===----------------------------------------------------------------------===// |
| 538 | |
| 539 | // The lexer returns tokens [0-255] if it is an unknown character, otherwise one |
| 540 | // of these for known things. |
| 541 | enum Token { |
| 542 | tok_eof = -1, |
| 543 | |
| 544 | // commands |
| 545 | tok_def = -2, tok_extern = -3, |
| 546 | |
| 547 | // primary |
| 548 | tok_identifier = -4, tok_number = -5, |
| 549 | }; |
| 550 | |
| 551 | static std::string IdentifierStr; // Filled in if tok_identifier |
| 552 | static double NumVal; // Filled in if tok_number |
| 553 | |
| 554 | /// gettok - Return the next token from standard input. |
| 555 | static int gettok() { |
| 556 | static int LastChar = ' '; |
| 557 | |
| 558 | // Skip any whitespace. |
| 559 | while (isspace(LastChar)) |
| 560 | LastChar = getchar(); |
| 561 | |
| 562 | if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]* |
| 563 | IdentifierStr = LastChar; |
| 564 | while (isalnum((LastChar = getchar()))) |
| 565 | IdentifierStr += LastChar; |
| 566 | |
| 567 | if (IdentifierStr == "def") return tok_def; |
| 568 | if (IdentifierStr == "extern") return tok_extern; |
| 569 | return tok_identifier; |
| 570 | } |
| 571 | |
| 572 | if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+ |
| 573 | std::string NumStr; |
| 574 | do { |
| 575 | NumStr += LastChar; |
| 576 | LastChar = getchar(); |
| 577 | } while (isdigit(LastChar) || LastChar == '.'); |
| 578 | |
| 579 | NumVal = strtod(NumStr.c_str(), 0); |
| 580 | return tok_number; |
| 581 | } |
| 582 | |
| 583 | if (LastChar == '#') { |
| 584 | // Comment until end of line. |
| 585 | do LastChar = getchar(); |
Chris Lattner | c80c23f | 2007-12-02 22:46:01 +0000 | [diff] [blame] | 586 | while (LastChar != EOF && LastChar != '\n' && LastChar != '\r'); |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 587 | |
| 588 | if (LastChar != EOF) |
| 589 | return gettok(); |
| 590 | } |
| 591 | |
| 592 | // Check for end of file. Don't eat the EOF. |
| 593 | if (LastChar == EOF) |
| 594 | return tok_eof; |
| 595 | |
| 596 | // Otherwise, just return the character as its ascii value. |
| 597 | int ThisChar = LastChar; |
| 598 | LastChar = getchar(); |
| 599 | return ThisChar; |
| 600 | } |
| 601 | |
| 602 | //===----------------------------------------------------------------------===// |
| 603 | // Abstract Syntax Tree (aka Parse Tree) |
| 604 | //===----------------------------------------------------------------------===// |
| 605 | |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 606 | /// ExprAST - Base class for all expression nodes. |
| 607 | class ExprAST { |
| 608 | public: |
| 609 | virtual ~ExprAST() {} |
| 610 | virtual Value *Codegen() = 0; |
| 611 | }; |
| 612 | |
| 613 | /// NumberExprAST - Expression class for numeric literals like "1.0". |
| 614 | class NumberExprAST : public ExprAST { |
| 615 | double Val; |
| 616 | public: |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 617 | NumberExprAST(double val) : Val(val) {} |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 618 | virtual Value *Codegen(); |
| 619 | }; |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 620 | |
| 621 | /// VariableExprAST - Expression class for referencing a variable, like "a". |
| 622 | class VariableExprAST : public ExprAST { |
| 623 | std::string Name; |
| 624 | public: |
| 625 | VariableExprAST(const std::string &name) : Name(name) {} |
| 626 | virtual Value *Codegen(); |
| 627 | }; |
| 628 | |
| 629 | /// BinaryExprAST - Expression class for a binary operator. |
| 630 | class BinaryExprAST : public ExprAST { |
| 631 | char Op; |
| 632 | ExprAST *LHS, *RHS; |
| 633 | public: |
| 634 | BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) |
| 635 | : Op(op), LHS(lhs), RHS(rhs) {} |
| 636 | virtual Value *Codegen(); |
| 637 | }; |
| 638 | |
| 639 | /// CallExprAST - Expression class for function calls. |
| 640 | class CallExprAST : public ExprAST { |
| 641 | std::string Callee; |
| 642 | std::vector<ExprAST*> Args; |
| 643 | public: |
| 644 | CallExprAST(const std::string &callee, std::vector<ExprAST*> &args) |
| 645 | : Callee(callee), Args(args) {} |
| 646 | virtual Value *Codegen(); |
| 647 | }; |
| 648 | |
| 649 | /// PrototypeAST - This class represents the "prototype" for a function, |
| 650 | /// which captures its argument names as well as if it is an operator. |
| 651 | class PrototypeAST { |
| 652 | std::string Name; |
| 653 | std::vector<std::string> Args; |
| 654 | public: |
| 655 | PrototypeAST(const std::string &name, const std::vector<std::string> &args) |
| 656 | : Name(name), Args(args) {} |
| 657 | |
| 658 | Function *Codegen(); |
| 659 | }; |
| 660 | |
| 661 | /// FunctionAST - This class represents a function definition itself. |
| 662 | class FunctionAST { |
| 663 | PrototypeAST *Proto; |
| 664 | ExprAST *Body; |
| 665 | public: |
| 666 | FunctionAST(PrototypeAST *proto, ExprAST *body) |
| 667 | : Proto(proto), Body(body) {} |
| 668 | |
| 669 | Function *Codegen(); |
| 670 | }; |
| 671 | |
| 672 | //===----------------------------------------------------------------------===// |
| 673 | // Parser |
| 674 | //===----------------------------------------------------------------------===// |
| 675 | |
| 676 | /// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current |
| 677 | /// token the parser it looking at. getNextToken reads another token from the |
| 678 | /// lexer and updates CurTok with its results. |
| 679 | static int CurTok; |
| 680 | static int getNextToken() { |
| 681 | return CurTok = gettok(); |
| 682 | } |
| 683 | |
| 684 | /// BinopPrecedence - This holds the precedence for each binary operator that is |
| 685 | /// defined. |
| 686 | static std::map<char, int> BinopPrecedence; |
| 687 | |
| 688 | /// GetTokPrecedence - Get the precedence of the pending binary operator token. |
| 689 | static int GetTokPrecedence() { |
| 690 | if (!isascii(CurTok)) |
| 691 | return -1; |
| 692 | |
| 693 | // Make sure it's a declared binop. |
| 694 | int TokPrec = BinopPrecedence[CurTok]; |
| 695 | if (TokPrec <= 0) return -1; |
| 696 | return TokPrec; |
| 697 | } |
| 698 | |
| 699 | /// Error* - These are little helper functions for error handling. |
| 700 | ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;} |
| 701 | PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; } |
| 702 | FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; } |
| 703 | |
| 704 | static ExprAST *ParseExpression(); |
| 705 | |
| 706 | /// identifierexpr |
Chris Lattner | 20a0c80 | 2007-11-05 17:54:34 +0000 | [diff] [blame] | 707 | /// ::= identifier |
| 708 | /// ::= identifier '(' expression* ')' |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 709 | static ExprAST *ParseIdentifierExpr() { |
| 710 | std::string IdName = IdentifierStr; |
| 711 | |
Chris Lattner | 20a0c80 | 2007-11-05 17:54:34 +0000 | [diff] [blame] | 712 | getNextToken(); // eat identifier. |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 713 | |
| 714 | if (CurTok != '(') // Simple variable ref. |
| 715 | return new VariableExprAST(IdName); |
| 716 | |
| 717 | // Call. |
| 718 | getNextToken(); // eat ( |
| 719 | std::vector<ExprAST*> Args; |
Chris Lattner | 7115521 | 2007-11-06 01:39:12 +0000 | [diff] [blame] | 720 | if (CurTok != ')') { |
| 721 | while (1) { |
| 722 | ExprAST *Arg = ParseExpression(); |
| 723 | if (!Arg) return 0; |
| 724 | Args.push_back(Arg); |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 725 | |
Chris Lattner | 7115521 | 2007-11-06 01:39:12 +0000 | [diff] [blame] | 726 | if (CurTok == ')') break; |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 727 | |
Chris Lattner | 7115521 | 2007-11-06 01:39:12 +0000 | [diff] [blame] | 728 | if (CurTok != ',') |
| 729 | return Error("Expected ')'"); |
| 730 | getNextToken(); |
| 731 | } |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 732 | } |
| 733 | |
| 734 | // Eat the ')'. |
| 735 | getNextToken(); |
| 736 | |
| 737 | return new CallExprAST(IdName, Args); |
| 738 | } |
| 739 | |
| 740 | /// numberexpr ::= number |
| 741 | static ExprAST *ParseNumberExpr() { |
| 742 | ExprAST *Result = new NumberExprAST(NumVal); |
| 743 | getNextToken(); // consume the number |
| 744 | return Result; |
| 745 | } |
| 746 | |
| 747 | /// parenexpr ::= '(' expression ')' |
| 748 | static ExprAST *ParseParenExpr() { |
| 749 | getNextToken(); // eat (. |
| 750 | ExprAST *V = ParseExpression(); |
| 751 | if (!V) return 0; |
| 752 | |
| 753 | if (CurTok != ')') |
| 754 | return Error("expected ')'"); |
| 755 | getNextToken(); // eat ). |
| 756 | return V; |
| 757 | } |
| 758 | |
| 759 | /// primary |
| 760 | /// ::= identifierexpr |
| 761 | /// ::= numberexpr |
| 762 | /// ::= parenexpr |
| 763 | static ExprAST *ParsePrimary() { |
| 764 | switch (CurTok) { |
| 765 | default: return Error("unknown token when expecting an expression"); |
| 766 | case tok_identifier: return ParseIdentifierExpr(); |
| 767 | case tok_number: return ParseNumberExpr(); |
| 768 | case '(': return ParseParenExpr(); |
| 769 | } |
| 770 | } |
| 771 | |
| 772 | /// binoprhs |
| 773 | /// ::= ('+' primary)* |
| 774 | static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) { |
| 775 | // If this is a binop, find its precedence. |
| 776 | while (1) { |
| 777 | int TokPrec = GetTokPrecedence(); |
| 778 | |
| 779 | // If this is a binop that binds at least as tightly as the current binop, |
| 780 | // consume it, otherwise we are done. |
| 781 | if (TokPrec < ExprPrec) |
| 782 | return LHS; |
| 783 | |
| 784 | // Okay, we know this is a binop. |
| 785 | int BinOp = CurTok; |
| 786 | getNextToken(); // eat binop |
| 787 | |
| 788 | // Parse the primary expression after the binary operator. |
| 789 | ExprAST *RHS = ParsePrimary(); |
| 790 | if (!RHS) return 0; |
| 791 | |
| 792 | // If BinOp binds less tightly with RHS than the operator after RHS, let |
| 793 | // the pending operator take RHS as its LHS. |
| 794 | int NextPrec = GetTokPrecedence(); |
| 795 | if (TokPrec < NextPrec) { |
| 796 | RHS = ParseBinOpRHS(TokPrec+1, RHS); |
| 797 | if (RHS == 0) return 0; |
| 798 | } |
| 799 | |
| 800 | // Merge LHS/RHS. |
| 801 | LHS = new BinaryExprAST(BinOp, LHS, RHS); |
| 802 | } |
| 803 | } |
| 804 | |
| 805 | /// expression |
| 806 | /// ::= primary binoprhs |
| 807 | /// |
| 808 | static ExprAST *ParseExpression() { |
| 809 | ExprAST *LHS = ParsePrimary(); |
| 810 | if (!LHS) return 0; |
| 811 | |
| 812 | return ParseBinOpRHS(0, LHS); |
| 813 | } |
| 814 | |
| 815 | /// prototype |
| 816 | /// ::= id '(' id* ')' |
| 817 | static PrototypeAST *ParsePrototype() { |
| 818 | if (CurTok != tok_identifier) |
| 819 | return ErrorP("Expected function name in prototype"); |
| 820 | |
| 821 | std::string FnName = IdentifierStr; |
| 822 | getNextToken(); |
| 823 | |
| 824 | if (CurTok != '(') |
| 825 | return ErrorP("Expected '(' in prototype"); |
| 826 | |
| 827 | std::vector<std::string> ArgNames; |
| 828 | while (getNextToken() == tok_identifier) |
| 829 | ArgNames.push_back(IdentifierStr); |
| 830 | if (CurTok != ')') |
| 831 | return ErrorP("Expected ')' in prototype"); |
| 832 | |
| 833 | // success. |
| 834 | getNextToken(); // eat ')'. |
| 835 | |
| 836 | return new PrototypeAST(FnName, ArgNames); |
| 837 | } |
| 838 | |
| 839 | /// definition ::= 'def' prototype expression |
| 840 | static FunctionAST *ParseDefinition() { |
| 841 | getNextToken(); // eat def. |
| 842 | PrototypeAST *Proto = ParsePrototype(); |
| 843 | if (Proto == 0) return 0; |
| 844 | |
| 845 | if (ExprAST *E = ParseExpression()) |
| 846 | return new FunctionAST(Proto, E); |
| 847 | return 0; |
| 848 | } |
| 849 | |
| 850 | /// toplevelexpr ::= expression |
| 851 | static FunctionAST *ParseTopLevelExpr() { |
| 852 | if (ExprAST *E = ParseExpression()) { |
| 853 | // Make an anonymous proto. |
| 854 | PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>()); |
| 855 | return new FunctionAST(Proto, E); |
| 856 | } |
| 857 | return 0; |
| 858 | } |
| 859 | |
| 860 | /// external ::= 'extern' prototype |
| 861 | static PrototypeAST *ParseExtern() { |
| 862 | getNextToken(); // eat extern. |
| 863 | return ParsePrototype(); |
| 864 | } |
| 865 | |
| 866 | //===----------------------------------------------------------------------===// |
| 867 | // Code Generation |
| 868 | //===----------------------------------------------------------------------===// |
| 869 | |
| 870 | static Module *TheModule; |
| 871 | static LLVMFoldingBuilder Builder; |
| 872 | static std::map<std::string, Value*> NamedValues; |
| 873 | static FunctionPassManager *TheFPM; |
| 874 | |
| 875 | Value *ErrorV(const char *Str) { Error(Str); return 0; } |
| 876 | |
| 877 | Value *NumberExprAST::Codegen() { |
| 878 | return ConstantFP::get(Type::DoubleTy, APFloat(Val)); |
| 879 | } |
| 880 | |
| 881 | Value *VariableExprAST::Codegen() { |
| 882 | // Look this variable up in the function. |
| 883 | Value *V = NamedValues[Name]; |
| 884 | return V ? V : ErrorV("Unknown variable name"); |
| 885 | } |
| 886 | |
| 887 | Value *BinaryExprAST::Codegen() { |
| 888 | Value *L = LHS->Codegen(); |
| 889 | Value *R = RHS->Codegen(); |
| 890 | if (L == 0 || R == 0) return 0; |
| 891 | |
| 892 | switch (Op) { |
| 893 | case '+': return Builder.CreateAdd(L, R, "addtmp"); |
| 894 | case '-': return Builder.CreateSub(L, R, "subtmp"); |
| 895 | case '*': return Builder.CreateMul(L, R, "multmp"); |
| 896 | case '<': |
Chris Lattner | 7115521 | 2007-11-06 01:39:12 +0000 | [diff] [blame] | 897 | L = Builder.CreateFCmpULT(L, R, "cmptmp"); |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 898 | // Convert bool 0/1 to double 0.0 or 1.0 |
| 899 | return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp"); |
| 900 | default: return ErrorV("invalid binary operator"); |
| 901 | } |
| 902 | } |
| 903 | |
| 904 | Value *CallExprAST::Codegen() { |
| 905 | // Look up the name in the global module table. |
| 906 | Function *CalleeF = TheModule->getFunction(Callee); |
| 907 | if (CalleeF == 0) |
| 908 | return ErrorV("Unknown function referenced"); |
| 909 | |
| 910 | // If argument mismatch error. |
| 911 | if (CalleeF->arg_size() != Args.size()) |
| 912 | return ErrorV("Incorrect # arguments passed"); |
| 913 | |
| 914 | std::vector<Value*> ArgsV; |
| 915 | for (unsigned i = 0, e = Args.size(); i != e; ++i) { |
| 916 | ArgsV.push_back(Args[i]->Codegen()); |
| 917 | if (ArgsV.back() == 0) return 0; |
| 918 | } |
| 919 | |
| 920 | return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp"); |
| 921 | } |
| 922 | |
| 923 | Function *PrototypeAST::Codegen() { |
| 924 | // Make the function type: double(double,double) etc. |
| 925 | std::vector<const Type*> Doubles(Args.size(), Type::DoubleTy); |
| 926 | FunctionType *FT = FunctionType::get(Type::DoubleTy, Doubles, false); |
| 927 | |
| 928 | Function *F = new Function(FT, Function::ExternalLinkage, Name, TheModule); |
| 929 | |
| 930 | // If F conflicted, there was already something named 'Name'. If it has a |
| 931 | // body, don't allow redefinition or reextern. |
| 932 | if (F->getName() != Name) { |
| 933 | // Delete the one we just made and get the existing one. |
| 934 | F->eraseFromParent(); |
| 935 | F = TheModule->getFunction(Name); |
| 936 | |
| 937 | // If F already has a body, reject this. |
| 938 | if (!F->empty()) { |
| 939 | ErrorF("redefinition of function"); |
| 940 | return 0; |
| 941 | } |
| 942 | |
| 943 | // If F took a different number of args, reject. |
| 944 | if (F->arg_size() != Args.size()) { |
| 945 | ErrorF("redefinition of function with different # args"); |
| 946 | return 0; |
| 947 | } |
| 948 | } |
| 949 | |
| 950 | // Set names for all arguments. |
| 951 | unsigned Idx = 0; |
| 952 | for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size(); |
| 953 | ++AI, ++Idx) { |
| 954 | AI->setName(Args[Idx]); |
| 955 | |
| 956 | // Add arguments to variable symbol table. |
| 957 | NamedValues[Args[Idx]] = AI; |
| 958 | } |
| 959 | |
| 960 | return F; |
| 961 | } |
| 962 | |
| 963 | Function *FunctionAST::Codegen() { |
| 964 | NamedValues.clear(); |
| 965 | |
| 966 | Function *TheFunction = Proto->Codegen(); |
| 967 | if (TheFunction == 0) |
| 968 | return 0; |
| 969 | |
| 970 | // Create a new basic block to start insertion into. |
| 971 | BasicBlock *BB = new BasicBlock("entry", TheFunction); |
| 972 | Builder.SetInsertPoint(BB); |
| 973 | |
| 974 | if (Value *RetVal = Body->Codegen()) { |
| 975 | // Finish off the function. |
| 976 | Builder.CreateRet(RetVal); |
| 977 | |
| 978 | // Validate the generated code, checking for consistency. |
| 979 | verifyFunction(*TheFunction); |
| 980 | |
| 981 | // Optimize the function. |
| 982 | TheFPM->run(*TheFunction); |
| 983 | |
| 984 | return TheFunction; |
| 985 | } |
| 986 | |
| 987 | // Error reading body, remove function. |
| 988 | TheFunction->eraseFromParent(); |
| 989 | return 0; |
| 990 | } |
| 991 | |
| 992 | //===----------------------------------------------------------------------===// |
| 993 | // Top-Level parsing and JIT Driver |
| 994 | //===----------------------------------------------------------------------===// |
| 995 | |
| 996 | static ExecutionEngine *TheExecutionEngine; |
| 997 | |
| 998 | static void HandleDefinition() { |
| 999 | if (FunctionAST *F = ParseDefinition()) { |
| 1000 | if (Function *LF = F->Codegen()) { |
| 1001 | fprintf(stderr, "Read function definition:"); |
| 1002 | LF->dump(); |
| 1003 | } |
| 1004 | } else { |
| 1005 | // Skip token for error recovery. |
| 1006 | getNextToken(); |
| 1007 | } |
| 1008 | } |
| 1009 | |
| 1010 | static void HandleExtern() { |
| 1011 | if (PrototypeAST *P = ParseExtern()) { |
| 1012 | if (Function *F = P->Codegen()) { |
| 1013 | fprintf(stderr, "Read extern: "); |
| 1014 | F->dump(); |
| 1015 | } |
| 1016 | } else { |
| 1017 | // Skip token for error recovery. |
| 1018 | getNextToken(); |
| 1019 | } |
| 1020 | } |
| 1021 | |
| 1022 | static void HandleTopLevelExpression() { |
| 1023 | // Evaluate a top level expression into an anonymous function. |
| 1024 | if (FunctionAST *F = ParseTopLevelExpr()) { |
| 1025 | if (Function *LF = F->Codegen()) { |
| 1026 | // JIT the function, returning a function pointer. |
| 1027 | void *FPtr = TheExecutionEngine->getPointerToFunction(LF); |
| 1028 | |
| 1029 | // Cast it to the right type (takes no arguments, returns a double) so we |
| 1030 | // can call it as a native function. |
| 1031 | double (*FP)() = (double (*)())FPtr; |
| 1032 | fprintf(stderr, "Evaluated to %f\n", FP()); |
| 1033 | } |
| 1034 | } else { |
| 1035 | // Skip token for error recovery. |
| 1036 | getNextToken(); |
| 1037 | } |
| 1038 | } |
| 1039 | |
| 1040 | /// top ::= definition | external | expression | ';' |
| 1041 | static void MainLoop() { |
| 1042 | while (1) { |
| 1043 | fprintf(stderr, "ready> "); |
| 1044 | switch (CurTok) { |
| 1045 | case tok_eof: return; |
| 1046 | case ';': getNextToken(); break; // ignore top level semicolons. |
| 1047 | case tok_def: HandleDefinition(); break; |
| 1048 | case tok_extern: HandleExtern(); break; |
| 1049 | default: HandleTopLevelExpression(); break; |
| 1050 | } |
| 1051 | } |
| 1052 | } |
| 1053 | |
| 1054 | |
| 1055 | |
| 1056 | //===----------------------------------------------------------------------===// |
| 1057 | // "Library" functions that can be "extern'd" from user code. |
| 1058 | //===----------------------------------------------------------------------===// |
| 1059 | |
| 1060 | /// putchard - putchar that takes a double and returns 0. |
| 1061 | extern "C" |
| 1062 | double putchard(double X) { |
| 1063 | putchar((char)X); |
| 1064 | return 0; |
| 1065 | } |
| 1066 | |
| 1067 | //===----------------------------------------------------------------------===// |
| 1068 | // Main driver code. |
| 1069 | //===----------------------------------------------------------------------===// |
| 1070 | |
| 1071 | int main() { |
| 1072 | // Install standard binary operators. |
| 1073 | // 1 is lowest precedence. |
| 1074 | BinopPrecedence['<'] = 10; |
| 1075 | BinopPrecedence['+'] = 20; |
| 1076 | BinopPrecedence['-'] = 20; |
| 1077 | BinopPrecedence['*'] = 40; // highest. |
| 1078 | |
| 1079 | // Prime the first token. |
| 1080 | fprintf(stderr, "ready> "); |
| 1081 | getNextToken(); |
| 1082 | |
| 1083 | // Make the module, which holds all the code. |
| 1084 | TheModule = new Module("my cool jit"); |
| 1085 | |
| 1086 | // Create the JIT. |
| 1087 | TheExecutionEngine = ExecutionEngine::create(TheModule); |
| 1088 | |
| 1089 | { |
| 1090 | ExistingModuleProvider OurModuleProvider(TheModule); |
| 1091 | FunctionPassManager OurFPM(&OurModuleProvider); |
| 1092 | |
| 1093 | // Set up the optimizer pipeline. Start with registering info about how the |
| 1094 | // target lays out data structures. |
| 1095 | OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData())); |
| 1096 | // Do simple "peephole" optimizations and bit-twiddling optzns. |
| 1097 | OurFPM.add(createInstructionCombiningPass()); |
| 1098 | // Reassociate expressions. |
| 1099 | OurFPM.add(createReassociatePass()); |
| 1100 | // Eliminate Common SubExpressions. |
| 1101 | OurFPM.add(createGVNPass()); |
| 1102 | // Simplify the control flow graph (deleting unreachable blocks, etc). |
| 1103 | OurFPM.add(createCFGSimplificationPass()); |
| 1104 | |
| 1105 | // Set the global so the code gen can use this. |
| 1106 | TheFPM = &OurFPM; |
| 1107 | |
| 1108 | // Run the main "interpreter loop" now. |
| 1109 | MainLoop(); |
| 1110 | |
| 1111 | TheFPM = 0; |
Chris Lattner | 515686b | 2008-02-05 06:18:42 +0000 | [diff] [blame] | 1112 | |
| 1113 | // Print out all of the generated code. |
| 1114 | TheModule->dump(); |
| 1115 | } // Free module provider (and thus the module) and pass manager. |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 1116 | |
Chris Lattner | 118749e | 2007-10-25 06:23:36 +0000 | [diff] [blame] | 1117 | return 0; |
| 1118 | } |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 1119 | </pre> |
| 1120 | </div> |
| 1121 | |
Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 1122 | </div> |
| 1123 | |
| 1124 | <!-- *********************************************************************** --> |
| 1125 | <hr> |
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Chris Lattner | c0b42e9 | 2007-10-23 06:27:55 +0000 | [diff] [blame] | 1131 | |
| 1132 | <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> |
| 1133 | <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br> |
| 1134 | Last modified: $Date: 2007-10-17 11:05:13 -0700 (Wed, 17 Oct 2007) $ |
| 1135 | </address> |
| 1136 | </body> |
| 1137 | </html> |