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849 lines
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849 lines
26 KiB
HTML
<!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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explicit 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>The Codegen() method says to emit IR for that AST node and all things it
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depends on, and they all return an LLVM Value object.
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"Value" is the class used to represent a "<a
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href="http://en.wikipedia.org/wiki/Static_single_assignment_form">Static Single
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Assignment (SSA)</a> register" or "SSA value" in LLVM. The most distinct aspect
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of SSA values is that their value is computed as the related instruction
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executes, and it does not get a new value until (and if) the instruction
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re-executes. In order words, there is no way to "change" an SSA value. For
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more information, please read up on <a
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href="http://en.wikipedia.org/wiki/Static_single_assignment_form">Static Single
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Assignment</a> - the concepts are really quite natural once you grok them.</p>
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<p>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
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<tt>ConstantFP</tt> class, which holds the numeric value in an <tt>APFloat</tt>
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internally (<tt>APFloat</tt> has the capability of holding floating point
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constants of <em>A</em>rbitrary <em>P</em>recision). This code basically just
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creates and returns a <tt>ConstantFP</tt>. 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 "new foo(..)" or "foo::create(..).</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 the simple version
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of Kaleidoscope, we assume that the variable has already been emited somewhere
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and its value is available. In practice, the only values that can be in the
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<tt>NamedValues</tt> map are function 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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<p>Binary operators start to get more interesting. The basic idea here is that
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we recursively emit code for the left-hand side of the expression, then the
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right-hand side, then we compute the result of the binary expression. In this
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code, we do a simple switch on the opcode to create the right LLVM instruction.
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</p>
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<p>In this example, the LLVM builder class is starting to show its value.
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Because it knows where to insert the newly created instruction, you just have to
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specificy what instruction to create (e.g. with <tt>CreateAdd</tt>), which
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operands to use (<tt>L</tt> and <tt>R</tt> here) and optionally provide a name
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for the generated instruction. One nice thing about LLVM is that the name is
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just a hint: if there are multiple additions in a single function, the first
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will be named "addtmp" and the second will be "autorenamed" by adding a suffix,
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giving it a name like "addtmp42". Local value names for instructions are purely
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optional, but it makes it much easier to read the IR dumps.</p>
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<p><a href="../LangRef.html#instref">LLVM instructions</a> are constrained to
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have very strict type properties: for example, the Left and Right operators of
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an <a href="../LangRef.html#i_add">add instruction</a> have to have the same
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type, and that the result of the add matches the operands. Because all values
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in Kaleidoscope are doubles, this makes for very simple code for add, sub and
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mul.</p>
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<p>On the other hand, LLVM specifies that the <a
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href="../LangRef.html#i_fcmp">fcmp instruction</a> always returns an 'i1' value
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(a one bit integer). However, Kaleidoscope wants the value to be a 0.0 or 1.0
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value. In order to get these semantics, we combine the fcmp instruction with
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a <a href="../LangRef.html#i_uitofp">uitofp instruction</a>. This instruction
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converts its input integer into a floating point value by treating the input
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as an unsigned value. In contrast, if we used the <a
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href="../LangRef.html#i_sitofp">sitofp instruction</a>, the Kaleidoscope '<'
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operator would return 0.0 and -1.0, depending on the input value.</p>
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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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<p>Code generation for function calls is quite straight-forward with LLVM. The
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code above first looks the name of the function up in the LLVM Module's symbol
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table. Recall that the LLVM Module is the container that holds all of the
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functions we are JIT'ing. By giving each function the same name as what the
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user specifies, we can use the LLVM symbol table to resolve function names for
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us.</p>
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<p>Once we have the function to call, we recursively codegen each argument that
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is to be passed in, and create an LLVM <a href="../LangRef.html#i_call">call
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instruction</a>. Note that LLVM uses the native C calling conventions by
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default, allowing these calls to call into standard library functions like
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"sin" and "cos" with no additional effort.</p>
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<p>This wraps up our handling of the four basic expressions that we have so far
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in Kaleidoscope. Feel free to go in and add some more. For example, by
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browsing the <a href="../LangRef.html">LLVM language reference</a> you'll find
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several other interesting instructions that are really easy to plug into our
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basic framework.</p>
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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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// 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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if (LastChar == '#') {
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// 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.
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if (LastChar == EOF)
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return tok_eof;
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// Otherwise, just return the character as its ascii value.
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int ThisChar = LastChar;
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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)
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//===----------------------------------------------------------------------===//
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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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explicit 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".
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class VariableExprAST : public ExprAST {
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std::string Name;
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public:
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explicit VariableExprAST(const std::string &name) : Name(name) {}
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virtual Value *Codegen();
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};
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/// BinaryExprAST - Expression class for a binary operator.
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class BinaryExprAST : public ExprAST {
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char Op;
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ExprAST *LHS, *RHS;
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public:
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BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
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: Op(op), LHS(lhs), RHS(rhs) {}
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virtual Value *Codegen();
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};
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/// CallExprAST - Expression class for function calls.
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class CallExprAST : public ExprAST {
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std::string Callee;
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std::vector<ExprAST*> Args;
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public:
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CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
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: Callee(callee), Args(args) {}
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virtual Value *Codegen();
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};
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/// PrototypeAST - This class represents the "prototype" for a function,
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/// which captures its argument names as well as if it is an operator.
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class PrototypeAST {
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std::string Name;
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std::vector<std::string> Args;
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public:
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PrototypeAST(const std::string &name, const std::vector<std::string> &args)
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: Name(name), Args(args) {}
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Function *Codegen();
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};
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/// FunctionAST - This class represents a function definition itself.
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class FunctionAST {
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PrototypeAST *Proto;
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ExprAST *Body;
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public:
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FunctionAST(PrototypeAST *proto, ExprAST *body)
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: Proto(proto), Body(body) {}
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Function *Codegen();
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};
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//===----------------------------------------------------------------------===//
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// Parser
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//===----------------------------------------------------------------------===//
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/// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
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/// token the parser it looking at. getNextToken reads another token from the
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/// lexer and updates CurTok with its results.
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static int CurTok;
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static int getNextToken() {
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return CurTok = gettok();
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}
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/// BinopPrecedence - This holds the precedence for each binary operator that is
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/// defined.
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static std::map<char, int> BinopPrecedence;
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/// GetTokPrecedence - Get the precedence of the pending binary operator token.
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static int GetTokPrecedence() {
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if (!isascii(CurTok))
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return -1;
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// Make sure it's a declared binop.
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int TokPrec = BinopPrecedence[CurTok];
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if (TokPrec <= 0) return -1;
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return TokPrec;
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}
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/// Error* - These are little helper functions for error handling.
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ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
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PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
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FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
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static ExprAST *ParseExpression();
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/// identifierexpr
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/// ::= identifer
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/// ::= identifer '(' expression* ')'
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static ExprAST *ParseIdentifierExpr() {
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std::string IdName = IdentifierStr;
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getNextToken(); // eat identifer.
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if (CurTok != '(') // Simple variable ref.
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return new VariableExprAST(IdName);
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// Call.
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getNextToken(); // eat (
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std::vector<ExprAST*> Args;
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while (1) {
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ExprAST *Arg = ParseExpression();
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if (!Arg) return 0;
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Args.push_back(Arg);
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if (CurTok == ')') break;
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if (CurTok != ',')
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return Error("Expected ')'");
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getNextToken();
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}
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// Eat the ')'.
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getNextToken();
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return new CallExprAST(IdName, Args);
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}
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/// numberexpr ::= number
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static ExprAST *ParseNumberExpr() {
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ExprAST *Result = new NumberExprAST(NumVal);
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getNextToken(); // consume the number
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return Result;
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}
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/// parenexpr ::= '(' expression ')'
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static ExprAST *ParseParenExpr() {
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getNextToken(); // eat (.
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ExprAST *V = ParseExpression();
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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>
|