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Diffstat (limited to 'docs/tutorial/LangImpl5.html')
| -rw-r--r-- | docs/tutorial/LangImpl5.html | 91 |
1 files changed, 41 insertions, 50 deletions
diff --git a/docs/tutorial/LangImpl5.html b/docs/tutorial/LangImpl5.html index d2c3bd0..4fc23a1 100644 --- a/docs/tutorial/LangImpl5.html +++ b/docs/tutorial/LangImpl5.html @@ -11,7 +11,7 @@ <body> -<div class="doc_title">Kaleidoscope: Extending the Language: Control Flow</div> +<h1>Kaleidoscope: Extending the Language: Control Flow</h1> <ul> <li><a href="index.html">Up to Tutorial Index</a></li> @@ -48,10 +48,10 @@ User-defined Operators</li> </div> <!-- *********************************************************************** --> -<div class="doc_section"><a name="intro">Chapter 5 Introduction</a></div> +<h2><a name="intro">Chapter 5 Introduction</a></h2> <!-- *********************************************************************** --> -<div class="doc_text"> +<div> <p>Welcome to Chapter 5 of the "<a href="index.html">Implementing a language with LLVM</a>" tutorial. Parts 1-4 described the implementation of the simple @@ -65,14 +65,14 @@ have an if/then/else expression plus a simple 'for' loop.</p> </div> <!-- *********************************************************************** --> -<div class="doc_section"><a name="ifthen">If/Then/Else</a></div> +<h2><a name="ifthen">If/Then/Else</a></h2> <!-- *********************************************************************** --> -<div class="doc_text"> +<div> <p> Extending Kaleidoscope to support if/then/else is quite straightforward. It -basically requires adding lexer support for this "new" concept to the lexer, +basically requires adding support for this "new" concept to the lexer, parser, AST, and LLVM code emitter. This example is nice, because it shows how easy it is to "grow" a language over time, incrementally extending it as new ideas are discovered.</p> @@ -108,15 +108,12 @@ Since Kaleidoscope allows side-effects, this behavior is important to nail down. <p>Now that we know what we "want", lets break this down into its constituent pieces.</p> -</div> - <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="iflexer">Lexer Extensions for -If/Then/Else</a></div> +<h4><a name="iflexer">Lexer Extensions for If/Then/Else</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>The lexer extensions are straightforward. First we add new enum values for the relevant tokens:</p> @@ -146,11 +143,10 @@ stuff:</p> </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="ifast">AST Extensions for - If/Then/Else</a></div> +<h4><a name="ifast">AST Extensions for If/Then/Else</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>To represent the new expression we add a new AST node for it:</p> @@ -172,11 +168,10 @@ public: </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="ifparser">Parser Extensions for -If/Then/Else</a></div> +<h4><a name="ifparser">Parser Extensions for If/Then/Else</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>Now that we have the relevant tokens coming from the lexer and we have the AST node to build, our parsing logic is relatively straightforward. First we @@ -231,10 +226,10 @@ static ExprAST *ParsePrimary() { </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="ifir">LLVM IR for If/Then/Else</a></div> +<h4><a name="ifir">LLVM IR for If/Then/Else</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>Now that we have it parsing and building the AST, the final piece is adding LLVM code generation support. This is the most interesting part of the @@ -347,11 +342,10 @@ directly.</p> </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="ifcodegen">Code Generation for -If/Then/Else</a></div> +<h4><a name="ifcodegen">Code Generation for If/Then/Else</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>In order to generate code for this, we implement the <tt>Codegen</tt> method for <tt>IfExprAST</tt>:</p> @@ -472,7 +466,7 @@ are emitted, we can finish up with the merge code:</p> // Emit merge block. TheFunction->getBasicBlockList().push_back(MergeBB); Builder.SetInsertPoint(MergeBB); - PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), + PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2, "iftmp"); PN->addIncoming(ThenV, ThenBB); @@ -500,11 +494,13 @@ another useful expression that is familiar from non-functional languages...</p> </div> +</div> + <!-- *********************************************************************** --> -<div class="doc_section"><a name="for">'for' Loop Expression</a></div> +<h2><a name="for">'for' Loop Expression</a></h2> <!-- *********************************************************************** --> -<div class="doc_text"> +<div> <p>Now that we know how to add basic control flow constructs to the language, we have the tools to add more powerful things. Lets add something more @@ -533,14 +529,11 @@ variables, it will get more useful.</p> <p>As before, lets talk about the changes that we need to Kaleidoscope to support this.</p> -</div> - <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="forlexer">Lexer Extensions for -the 'for' Loop</a></div> +<h4><a name="forlexer">Lexer Extensions for the 'for' Loop</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>The lexer extensions are the same sort of thing as for if/then/else:</p> @@ -566,11 +559,10 @@ the 'for' Loop</a></div> </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="forast">AST Extensions for -the 'for' Loop</a></div> +<h4><a name="forast">AST Extensions for the 'for' Loop</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>The AST node is just as simple. It basically boils down to capturing the variable name and the constituent expressions in the node.</p> @@ -593,11 +585,10 @@ public: </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="forparser">Parser Extensions for -the 'for' Loop</a></div> +<h4><a name="forparser">Parser Extensions for the 'for' Loop</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>The parser code is also fairly standard. The only interesting thing here is handling of the optional step value. The parser code handles it by checking to @@ -653,11 +644,10 @@ static ExprAST *ParseForExpr() { </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="forir">LLVM IR for -the 'for' Loop</a></div> +<h4><a name="forir">LLVM IR for the 'for' Loop</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>Now we get to the good part: the LLVM IR we want to generate for this thing. With the simple example above, we get this LLVM IR (note that this dump is @@ -699,11 +689,10 @@ expressions, and some basic blocks. Lets see how this fits together.</p> </div> <!-- ======================================================================= --> -<div class="doc_subsubsection"><a name="forcodegen">Code Generation for -the 'for' Loop</a></div> +<h4><a name="forcodegen">Code Generation for the 'for' Loop</a></h4> <!-- ======================================================================= --> -<div class="doc_text"> +<div> <p>The first part of Codegen is very simple: we just output the start expression for the loop value:</p> @@ -746,7 +735,7 @@ create an unconditional branch for the fall-through between the two blocks.</p> Builder.SetInsertPoint(LoopBB); // Start the PHI node with an entry for Start. - PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), VarName.c_str()); + PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2, VarName.c_str()); Variable->addIncoming(StartVal, PreheaderBB); </pre> </div> @@ -876,11 +865,13 @@ language.</p> </div> +</div> + <!-- *********************************************************************** --> -<div class="doc_section"><a name="code">Full Code Listing</a></div> +<h2><a name="code">Full Code Listing</a></h2> <!-- *********************************************************************** --> -<div class="doc_text"> +<div> <p> Here is the complete code listing for our running example, enhanced with the @@ -1452,7 +1443,7 @@ Value *IfExprAST::Codegen() { // Emit merge block. TheFunction->getBasicBlockList().push_back(MergeBB); Builder.SetInsertPoint(MergeBB); - PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), + PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2, "iftmp"); PN->addIncoming(ThenV, ThenBB); @@ -1494,7 +1485,7 @@ Value *ForExprAST::Codegen() { Builder.SetInsertPoint(LoopBB); // Start the PHI node with an entry for Start. - PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), VarName.c_str()); + PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2, VarName.c_str()); Variable->addIncoming(StartVal, PreheaderBB); // Within the loop, the variable is defined equal to the PHI node. If it @@ -1721,7 +1712,7 @@ int main() { // Create the JIT. This takes ownership of the module. std::string ErrStr; - TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create(); + TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create(); if (!TheExecutionEngine) { fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str()); exit(1); @@ -1773,8 +1764,8 @@ int main() { src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a> <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> - <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br> - Last modified: $Date: 2010-11-16 18:28:22 +0100 (Tue, 16 Nov 2010) $ + <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br> + Last modified: $Date: 2011-04-23 02:30:22 +0200 (Sat, 23 Apr 2011) $ </address> </body> </html> |
