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start of chapter 3
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docs/tutorial/LangImpl3.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>Kaleidoscope: Implementing code generation to LLVM IR</title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="author" content="Chris Lattner">
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<link rel="stylesheet" href="../llvm.css" type="text/css">
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</head>
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<body>
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<div class="doc_title">Kaleidoscope: Code generation to LLVM IR</div>
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<div class="doc_author">
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<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="intro">Part 3 Introduction</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>Welcome to part 3 of the "<a href="index.html">Implementing a language with
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LLVM</a>" tutorial. This chapter shows you how to transform the <a
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href="LangImpl2.html">Abstract Syntax Tree built in Chapter 2</a> into LLVM IR.
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This will teach you a little bit about how LLVM does things, as well as
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demonstrate how easy it is to use. It's much more work to build a lexer and
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parser than it is to generate LLVM IR code.
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</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="basics">Code Generation setup</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>
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In order to generate LLVM IR, we want some simple setup to get started. First,
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we define virtual codegen methods in each AST class:</p>
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<div class="doc_code">
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<pre>
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/// ExprAST - Base class for all expression nodes.
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class ExprAST {
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public:
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virtual ~ExprAST() {}
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virtual Value *Codegen() = 0;
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};
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/// NumberExprAST - Expression class for numeric literals like "1.0".
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class NumberExprAST : public ExprAST {
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double Val;
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public:
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NumberExprAST(double val) : Val(val) {}
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virtual Value *Codegen();
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};
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...
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</pre>
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</div>
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<p>"Value" is the class used to represent a "register" in LLVM. The Codegen()
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method says to emit IR for that AST node and all things it depends on. The
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second thing we want is an "Error" method like we used for parser, which will
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be used to report errors found during code generation (for example, use of an
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undeclared parameter):</p>
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<div class="doc_code">
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<pre>
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Value *ErrorV(const char *Str) { Error(Str); return 0; }
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static Module *TheModule;
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static LLVMBuilder Builder;
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static std::map<std::string, Value*> NamedValues;
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</pre>
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</div>
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<p>The static variables will be used during code generation. <tt>TheModule</tt>
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is the LLVM construct that contains all of the functions and global variables in
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a chunk of code. In many ways, it is the top-level structure that the LLVM IR
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uses to contain code.</p>
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<p>The <tt>Builder</tt> object is a helper object that makes it easy to generate
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LLVM instructions. The <tt>Builder</tt> keeps track of the current place to
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insert instructions and has methods to create new instructions.</p>
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<p>The <tt>NamedValues</tt> map keeps track of which values are defined in the
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current scope and what their LLVM representation is. In this form of
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Kaleidoscope, the only things that can be referenced are function parameters.
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As such, function parameters will be in this map when generating code for their
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function body.</p>
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<p>
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With these basics in place, we can start talking about how to generate code for
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each expression. Note that this assumes that the <tt>Builder</tt> has been set
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up to generate code <em>into</em> something. For now, we'll assume that this
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has already been done, and we'll just use it to emit code.
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</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="exprs">Expression Code Generation</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>Generating LLVM code for expression nodes is very straight-forward: less
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than 45 lines of commented code for all four of our expression nodes. First,
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we'll do numeric literals:</p>
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<div class="doc_code">
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<pre>
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Value *NumberExprAST::Codegen() {
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return ConstantFP::get(Type::DoubleTy, APFloat(Val));
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}
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</pre>
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</div>
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<p>In the LLVM IR, numeric constants are represented with the ConstantFP class,
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which holds the numeric value in an APFloat internally (APFloat has the
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capability of holding floating point constants of arbitrary precision). This
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code basically just creates and returns a ConstantFP. Note that in the LLVM IR
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that constants are all uniqued together and shared. For this reason, the API
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uses "the foo::get(...)" idiom instead of a "create" method or "new foo".</p>
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<div class="doc_code">
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<pre>
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Value *VariableExprAST::Codegen() {
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// Look this variable up in the function.
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Value *V = NamedValues[Name];
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return V ? V : ErrorV("Unknown variable name");
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}
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</pre>
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</div>
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<p>References to variables is also quite simple here. In our system, we assume
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that the variable has already been emited somewhere and its value is available.
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In practice, the only values in the NamedValues map will be arguments. This
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code simply checks to see that the specified name is in the map (if not, an
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unknown variable is being referenced) and returns the value for it.</p>
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<div class="doc_code">
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<pre>
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Value *BinaryExprAST::Codegen() {
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Value *L = LHS->Codegen();
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Value *R = RHS->Codegen();
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if (L == 0 || R == 0) return 0;
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switch (Op) {
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case '+': return Builder.CreateAdd(L, R, "addtmp");
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case '-': return Builder.CreateSub(L, R, "subtmp");
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case '*': return Builder.CreateMul(L, R, "multmp");
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case '<':
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L = Builder.CreateFCmpULT(L, R, "multmp");
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// Convert bool 0/1 to double 0.0 or 1.0
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return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp");
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default: return ErrorV("invalid binary operator");
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}
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}
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</pre>
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</div>
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<div class="doc_code">
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<pre>
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Value *CallExprAST::Codegen() {
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// Look up the name in the global module table.
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Function *CalleeF = TheModule->getFunction(Callee);
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if (CalleeF == 0)
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return ErrorV("Unknown function referenced");
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// If argument mismatch error.
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if (CalleeF->arg_size() != Args.size())
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return ErrorV("Incorrect # arguments passed");
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std::vector<Value*> ArgsV;
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for (unsigned i = 0, e = Args.size(); i != e; ++i) {
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ArgsV.push_back(Args[i]->Codegen());
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if (ArgsV.back() == 0) return 0;
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}
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return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
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}
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</pre>
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</div>
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<h1> more todo</h1>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="code">Conclusions and the Full Code</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<div class="doc_code">
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<pre>
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// To build this:
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// g++ -g toy.cpp `llvm-config --cppflags` `llvm-config --ldflags` \
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// `llvm-config --libs core` -I ~/llvm/include/
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// ./a.out
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// See example below.
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#include "llvm/DerivedTypes.h"
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#include "llvm/Module.h"
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#include "llvm/Support/LLVMBuilder.h"
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#include <cstdio>
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#include <string>
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#include <map>
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#include <vector>
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// Lexer
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//===----------------------------------------------------------------------===//
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// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
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// of these for known things.
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enum Token {
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tok_eof = -1,
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// commands
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tok_def = -2, tok_extern = -3,
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// primary
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tok_identifier = -4, tok_number = -5,
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};
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static std::string IdentifierStr; // Filled in if tok_identifier
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static double NumVal; // Filled in if tok_number
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/// gettok - Return the next token from standard input.
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static int gettok() {
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static int LastChar = ' ';
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|
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// Skip any whitespace.
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while (isspace(LastChar))
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LastChar = getchar();
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if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
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IdentifierStr = LastChar;
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while (isalnum((LastChar = getchar())))
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IdentifierStr += LastChar;
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if (IdentifierStr == "def") return tok_def;
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if (IdentifierStr == "extern") return tok_extern;
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return tok_identifier;
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||||
}
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||||
|
||||
if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
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||||
std::string NumStr;
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||||
do {
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NumStr += LastChar;
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||||
LastChar = getchar();
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||||
} while (isdigit(LastChar) || LastChar == '.');
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||||
|
||||
NumVal = strtod(NumStr.c_str(), 0);
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return tok_number;
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}
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||||
|
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if (LastChar == '#') {
|
||||
// Comment until end of line.
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do LastChar = getchar();
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while (LastChar != EOF && LastChar != '\n' & LastChar != '\r');
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||||
|
||||
if (LastChar != EOF)
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||||
return gettok();
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||||
}
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||||
|
||||
// Check for end of file. Don't eat the EOF.
|
||||
if (LastChar == EOF)
|
||||
return tok_eof;
|
||||
|
||||
// Otherwise, just return the character as its ascii value.
|
||||
int ThisChar = LastChar;
|
||||
LastChar = getchar();
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return ThisChar;
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||||
}
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||||
|
||||
//===----------------------------------------------------------------------===//
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||||
// Abstract Syntax Tree (aka Parse Tree)
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
/// ExprAST - Base class for all expression nodes.
|
||||
class ExprAST {
|
||||
public:
|
||||
virtual ~ExprAST() {}
|
||||
virtual Value *Codegen() = 0;
|
||||
};
|
||||
|
||||
/// NumberExprAST - Expression class for numeric literals like "1.0".
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||||
class NumberExprAST : public ExprAST {
|
||||
double Val;
|
||||
public:
|
||||
NumberExprAST(double val) : Val(val) {}
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||||
virtual Value *Codegen();
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||||
};
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||||
|
||||
/// VariableExprAST - Expression class for referencing a variable, like "a".
|
||||
class VariableExprAST : public ExprAST {
|
||||
std::string Name;
|
||||
public:
|
||||
VariableExprAST(const std::string &name) : Name(name) {}
|
||||
virtual Value *Codegen();
|
||||
};
|
||||
|
||||
/// BinaryExprAST - Expression class for a binary operator.
|
||||
class BinaryExprAST : public ExprAST {
|
||||
char Op;
|
||||
ExprAST *LHS, *RHS;
|
||||
public:
|
||||
BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
|
||||
: Op(op), LHS(lhs), RHS(rhs) {}
|
||||
virtual Value *Codegen();
|
||||
};
|
||||
|
||||
/// CallExprAST - Expression class for function calls.
|
||||
class CallExprAST : public ExprAST {
|
||||
std::string Callee;
|
||||
std::vector<ExprAST*> Args;
|
||||
public:
|
||||
CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
|
||||
: Callee(callee), Args(args) {}
|
||||
virtual Value *Codegen();
|
||||
};
|
||||
|
||||
/// PrototypeAST - This class represents the "prototype" for a function,
|
||||
/// which captures its argument names as well as if it is an operator.
|
||||
class PrototypeAST {
|
||||
std::string Name;
|
||||
std::vector<std::string> Args;
|
||||
public:
|
||||
PrototypeAST(const std::string &name, const std::vector<std::string> &args)
|
||||
: Name(name), Args(args) {}
|
||||
|
||||
Function *Codegen();
|
||||
};
|
||||
|
||||
/// FunctionAST - This class represents a function definition itself.
|
||||
class FunctionAST {
|
||||
PrototypeAST *Proto;
|
||||
ExprAST *Body;
|
||||
public:
|
||||
FunctionAST(PrototypeAST *proto, ExprAST *body)
|
||||
: Proto(proto), Body(body) {}
|
||||
|
||||
Function *Codegen();
|
||||
};
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// Parser
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
/// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
|
||||
/// token the parser it looking at. getNextToken reads another token from the
|
||||
/// lexer and updates CurTok with its results.
|
||||
static int CurTok;
|
||||
static int getNextToken() {
|
||||
return CurTok = gettok();
|
||||
}
|
||||
|
||||
/// BinopPrecedence - This holds the precedence for each binary operator that is
|
||||
/// defined.
|
||||
static std::map<char, int> BinopPrecedence;
|
||||
|
||||
/// GetTokPrecedence - Get the precedence of the pending binary operator token.
|
||||
static int GetTokPrecedence() {
|
||||
if (!isascii(CurTok))
|
||||
return -1;
|
||||
|
||||
// Make sure it's a declared binop.
|
||||
int TokPrec = BinopPrecedence[CurTok];
|
||||
if (TokPrec <= 0) return -1;
|
||||
return TokPrec;
|
||||
}
|
||||
|
||||
/// Error* - These are little helper functions for error handling.
|
||||
ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
|
||||
PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
|
||||
FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
|
||||
|
||||
static ExprAST *ParseExpression();
|
||||
|
||||
/// identifierexpr
|
||||
/// ::= identifer
|
||||
/// ::= identifer '(' expression* ')'
|
||||
static ExprAST *ParseIdentifierExpr() {
|
||||
std::string IdName = IdentifierStr;
|
||||
|
||||
getNextToken(); // eat identifer.
|
||||
|
||||
if (CurTok != '(') // Simple variable ref.
|
||||
return new VariableExprAST(IdName);
|
||||
|
||||
// Call.
|
||||
getNextToken(); // eat (
|
||||
std::vector<ExprAST*> Args;
|
||||
while (1) {
|
||||
ExprAST *Arg = ParseExpression();
|
||||
if (!Arg) return 0;
|
||||
Args.push_back(Arg);
|
||||
|
||||
if (CurTok == ')') break;
|
||||
|
||||
if (CurTok != ',')
|
||||
return Error("Expected ')'");
|
||||
getNextToken();
|
||||
}
|
||||
|
||||
// Eat the ')'.
|
||||
getNextToken();
|
||||
|
||||
return new CallExprAST(IdName, Args);
|
||||
}
|
||||
|
||||
/// numberexpr ::= number
|
||||
static ExprAST *ParseNumberExpr() {
|
||||
ExprAST *Result = new NumberExprAST(NumVal);
|
||||
getNextToken(); // consume the number
|
||||
return Result;
|
||||
}
|
||||
|
||||
/// parenexpr ::= '(' expression ')'
|
||||
static ExprAST *ParseParenExpr() {
|
||||
getNextToken(); // eat (.
|
||||
ExprAST *V = ParseExpression();
|
||||
if (!V) return 0;
|
||||
|
||||
if (CurTok != ')')
|
||||
return Error("expected ')'");
|
||||
getNextToken(); // eat ).
|
||||
return V;
|
||||
}
|
||||
|
||||
/// primary
|
||||
/// ::= identifierexpr
|
||||
/// ::= numberexpr
|
||||
/// ::= parenexpr
|
||||
static ExprAST *ParsePrimary() {
|
||||
switch (CurTok) {
|
||||
default: return Error("unknown token when expecting an expression");
|
||||
case tok_identifier: return ParseIdentifierExpr();
|
||||
case tok_number: return ParseNumberExpr();
|
||||
case '(': return ParseParenExpr();
|
||||
}
|
||||
}
|
||||
|
||||
/// binoprhs
|
||||
/// ::= ('+' primary)*
|
||||
static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
|
||||
// If this is a binop, find its precedence.
|
||||
while (1) {
|
||||
int TokPrec = GetTokPrecedence();
|
||||
|
||||
// If this is a binop that binds at least as tightly as the current binop,
|
||||
// consume it, otherwise we are done.
|
||||
if (TokPrec < ExprPrec)
|
||||
return LHS;
|
||||
|
||||
// Okay, we know this is a binop.
|
||||
int BinOp = CurTok;
|
||||
getNextToken(); // eat binop
|
||||
|
||||
// Parse the primary expression after the binary operator.
|
||||
ExprAST *RHS = ParsePrimary();
|
||||
if (!RHS) return 0;
|
||||
|
||||
// If BinOp binds less tightly with RHS than the operator after RHS, let
|
||||
// the pending operator take RHS as its LHS.
|
||||
int NextPrec = GetTokPrecedence();
|
||||
if (TokPrec < NextPrec) {
|
||||
RHS = ParseBinOpRHS(TokPrec+1, RHS);
|
||||
if (RHS == 0) return 0;
|
||||
}
|
||||
|
||||
// Merge LHS/RHS.
|
||||
LHS = new BinaryExprAST(BinOp, LHS, RHS);
|
||||
}
|
||||
}
|
||||
|
||||
/// expression
|
||||
/// ::= primary binoprhs
|
||||
///
|
||||
static ExprAST *ParseExpression() {
|
||||
ExprAST *LHS = ParsePrimary();
|
||||
if (!LHS) return 0;
|
||||
|
||||
return ParseBinOpRHS(0, LHS);
|
||||
}
|
||||
|
||||
/// prototype
|
||||
/// ::= id '(' id* ')'
|
||||
static PrototypeAST *ParsePrototype() {
|
||||
if (CurTok != tok_identifier)
|
||||
return ErrorP("Expected function name in prototype");
|
||||
|
||||
std::string FnName = IdentifierStr;
|
||||
getNextToken();
|
||||
|
||||
if (CurTok != '(')
|
||||
return ErrorP("Expected '(' in prototype");
|
||||
|
||||
std::vector<std::string> ArgNames;
|
||||
while (getNextToken() == tok_identifier)
|
||||
ArgNames.push_back(IdentifierStr);
|
||||
if (CurTok != ')')
|
||||
return ErrorP("Expected ')' in prototype");
|
||||
|
||||
// success.
|
||||
getNextToken(); // eat ')'.
|
||||
|
||||
return new PrototypeAST(FnName, ArgNames);
|
||||
}
|
||||
|
||||
/// definition ::= 'def' prototype expression
|
||||
static FunctionAST *ParseDefinition() {
|
||||
getNextToken(); // eat def.
|
||||
PrototypeAST *Proto = ParsePrototype();
|
||||
if (Proto == 0) return 0;
|
||||
|
||||
if (ExprAST *E = ParseExpression())
|
||||
return new FunctionAST(Proto, E);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/// toplevelexpr ::= expression
|
||||
static FunctionAST *ParseTopLevelExpr() {
|
||||
if (ExprAST *E = ParseExpression()) {
|
||||
// Make an anonymous proto.
|
||||
PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
|
||||
return new FunctionAST(Proto, E);
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
/// external ::= 'extern' prototype
|
||||
static PrototypeAST *ParseExtern() {
|
||||
getNextToken(); // eat extern.
|
||||
return ParsePrototype();
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// Code Generation
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
static Module *TheModule;
|
||||
static LLVMBuilder Builder;
|
||||
static std::map<std::string, Value*> NamedValues;
|
||||
|
||||
Value *ErrorV(const char *Str) { Error(Str); return 0; }
|
||||
|
||||
Value *NumberExprAST::Codegen() {
|
||||
return ConstantFP::get(Type::DoubleTy, APFloat(Val));
|
||||
}
|
||||
|
||||
Value *VariableExprAST::Codegen() {
|
||||
// Look this variable up in the function.
|
||||
Value *V = NamedValues[Name];
|
||||
return V ? V : ErrorV("Unknown variable name");
|
||||
}
|
||||
|
||||
Value *BinaryExprAST::Codegen() {
|
||||
Value *L = LHS->Codegen();
|
||||
Value *R = RHS->Codegen();
|
||||
if (L == 0 || R == 0) return 0;
|
||||
|
||||
switch (Op) {
|
||||
case '+': return Builder.CreateAdd(L, R, "addtmp");
|
||||
case '-': return Builder.CreateSub(L, R, "subtmp");
|
||||
case '*': return Builder.CreateMul(L, R, "multmp");
|
||||
case '<':
|
||||
L = Builder.CreateFCmpULT(L, R, "multmp");
|
||||
// Convert bool 0/1 to double 0.0 or 1.0
|
||||
return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp");
|
||||
default: return ErrorV("invalid binary operator");
|
||||
}
|
||||
}
|
||||
|
||||
Value *CallExprAST::Codegen() {
|
||||
// Look up the name in the global module table.
|
||||
Function *CalleeF = TheModule->getFunction(Callee);
|
||||
if (CalleeF == 0)
|
||||
return ErrorV("Unknown function referenced");
|
||||
|
||||
// If argument mismatch error.
|
||||
if (CalleeF->arg_size() != Args.size())
|
||||
return ErrorV("Incorrect # arguments passed");
|
||||
|
||||
std::vector<Value*> ArgsV;
|
||||
for (unsigned i = 0, e = Args.size(); i != e; ++i) {
|
||||
ArgsV.push_back(Args[i]->Codegen());
|
||||
if (ArgsV.back() == 0) return 0;
|
||||
}
|
||||
|
||||
return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
|
||||
}
|
||||
|
||||
Function *PrototypeAST::Codegen() {
|
||||
// Make the function type: double(double,double) etc.
|
||||
FunctionType *FT =
|
||||
FunctionType::get(Type::DoubleTy, std::vector<const Type*>(Args.size(),
|
||||
Type::DoubleTy),
|
||||
false);
|
||||
|
||||
Function *F = new Function(FT, Function::ExternalLinkage, Name, TheModule);
|
||||
|
||||
// If F conflicted, there was already something named 'Name'. If it has a
|
||||
// body, don't allow redefinition or reextern.
|
||||
if (F->getName() != Name) {
|
||||
// Delete the one we just made and get the existing one.
|
||||
F->eraseFromParent();
|
||||
F = TheModule->getFunction(Name);
|
||||
|
||||
// If F already has a body, reject this.
|
||||
if (!F->empty()) {
|
||||
ErrorF("redefinition of function");
|
||||
return 0;
|
||||
}
|
||||
|
||||
// If F took a different number of args, reject.
|
||||
if (F->arg_size() != Args.size()) {
|
||||
ErrorF("redefinition of function with different # args");
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
|
||||
// Set names for all arguments.
|
||||
unsigned Idx = 0;
|
||||
for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
|
||||
++AI, ++Idx) {
|
||||
AI->setName(Args[Idx]);
|
||||
|
||||
// Add arguments to variable symbol table.
|
||||
NamedValues[Args[Idx]] = AI;
|
||||
}
|
||||
|
||||
return F;
|
||||
}
|
||||
|
||||
Function *FunctionAST::Codegen() {
|
||||
NamedValues.clear();
|
||||
|
||||
Function *TheFunction = Proto->Codegen();
|
||||
if (TheFunction == 0)
|
||||
return 0;
|
||||
|
||||
// Create a new basic block to start insertion into.
|
||||
Builder.SetInsertPoint(new BasicBlock("entry", TheFunction));
|
||||
|
||||
if (Value *RetVal = Body->Codegen()) {
|
||||
// Finish off the function.
|
||||
Builder.CreateRet(RetVal);
|
||||
return TheFunction;
|
||||
}
|
||||
|
||||
// Error reading body, remove function.
|
||||
TheFunction->eraseFromParent();
|
||||
return 0;
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// Top-Level parsing and JIT Driver
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
static void HandleDefinition() {
|
||||
if (FunctionAST *F = ParseDefinition()) {
|
||||
if (Function *LF = F->Codegen()) {
|
||||
fprintf(stderr, "Read function definition:");
|
||||
LF->dump();
|
||||
}
|
||||
} else {
|
||||
// Skip token for error recovery.
|
||||
getNextToken();
|
||||
}
|
||||
}
|
||||
|
||||
static void HandleExtern() {
|
||||
if (PrototypeAST *P = ParseExtern()) {
|
||||
if (Function *F = P->Codegen()) {
|
||||
fprintf(stderr, "Read extern: ");
|
||||
F->dump();
|
||||
}
|
||||
} else {
|
||||
// Skip token for error recovery.
|
||||
getNextToken();
|
||||
}
|
||||
}
|
||||
|
||||
static void HandleTopLevelExpression() {
|
||||
// Evaluate a top level expression into an anonymous function.
|
||||
if (FunctionAST *F = ParseTopLevelExpr()) {
|
||||
if (Function *LF = F->Codegen()) {
|
||||
fprintf(stderr, "Read top-level expression:");
|
||||
LF->dump();
|
||||
}
|
||||
} else {
|
||||
// Skip token for error recovery.
|
||||
getNextToken();
|
||||
}
|
||||
}
|
||||
|
||||
/// top ::= definition | external | expression | ';'
|
||||
static void MainLoop() {
|
||||
while (1) {
|
||||
fprintf(stderr, "ready> ");
|
||||
switch (CurTok) {
|
||||
case tok_eof: return;
|
||||
case ';': getNextToken(); break; // ignore top level semicolons.
|
||||
case tok_def: HandleDefinition(); break;
|
||||
case tok_extern: HandleExtern(); break;
|
||||
default: HandleTopLevelExpression(); break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// "Library" functions that can be "extern'd" from user code.
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
/// putchard - putchar that takes a double and returns 0.
|
||||
extern "C"
|
||||
double putchard(double X) {
|
||||
putchar((char)X);
|
||||
return 0;
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// Main driver code.
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
int main() {
|
||||
TheModule = new Module("my cool jit");
|
||||
|
||||
// Install standard binary operators.
|
||||
// 1 is lowest precedence.
|
||||
BinopPrecedence['<'] = 10;
|
||||
BinopPrecedence['+'] = 20;
|
||||
BinopPrecedence['-'] = 20;
|
||||
BinopPrecedence['*'] = 40; // highest.
|
||||
|
||||
// Prime the first token.
|
||||
fprintf(stderr, "ready> ");
|
||||
getNextToken();
|
||||
|
||||
MainLoop();
|
||||
TheModule->dump();
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Examples:
|
||||
|
||||
def fib(x)
|
||||
if (x < 3) then
|
||||
1
|
||||
else
|
||||
fib(x-1)+fib(x-2);
|
||||
|
||||
fib(10);
|
||||
|
||||
*/
|
||||
</pre>
|
||||
</div>
|
||||
</div>
|
||||
|
||||
<!-- *********************************************************************** -->
|
||||
<hr>
|
||||
<address>
|
||||
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
|
||||
src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
|
||||
<a href="http://validator.w3.org/check/referer"><img
|
||||
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: 2007-10-17 11:05:13 -0700 (Wed, 17 Oct 2007) $
|
||||
</address>
|
||||
</body>
|
||||
</html>
|
||||
@ -29,7 +29,7 @@
|
||||
<ol>
|
||||
<li><a href="LangImpl1.html">The basic language, with its lexer</a></li>
|
||||
<li><a href="LangImpl2.html">Implementing a Parser and AST</a></li>
|
||||
<li>Implementing code generation to LLVM IR</li>
|
||||
<li><a href="LangImpl3.html">Implementing code generation to LLVM IR</a></li>
|
||||
<li>Adding JIT codegen support</li>
|
||||
<li>Extending the language: if/then/else</li>
|
||||
<li>Extending the language: operator overloading</li>
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user