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@indutny indutny/jit.js
Last active Dec 27, 2015

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var jit = require('jit.js'),
esprima = require('esprima'),
assert = require('assert');
var ast = esprima.parse(process.argv[2]);
// Compile
var fn = jit.compile(function() {
// This will generate default entry boilerplate
this.Proc(functon() {
visit.call(this, ast);
// The result should be in 'rax' at this point
// This will generate default exit boilerplate
this.Return();
});
});
// Execute
console.log(fn());
function visit(ast) {
if (ast.type === 'Program')
visitProgram.call(this, ast);
else if (ast.type === 'Literal')
visitLiteral.call(this, ast);
else if (ast.type === 'UnaryExpression')
visitUnary.call(this, ast);
else if (ast.type === 'BinaryExpression')
visitBinary.call(this, ast);
else
throw new Error('Unknown ast node: ' + ast.type);
}
function visitProgram(ast) {
assert.equal(ast.body.length, 1, 'Only one statement programs are supported');
assert.equal(ast.body[0].type, 'ExpressionStatement');
visit.call(this, ast.body[0].expression);
}
function visitLiteral(ast) {
assert.equal(typeof ast.value, 'number');
assert.equal(ast.value | 0, ast.value, 'Only integer numbers are supported');
this.mov('rax', ast.value);
}
function visitBinary(ast) {
// Preserve 'rbx' after leaving the AST node
this.push('rbx');
// Visit right side of expresion
visit.call(this, ast.right);
// Move it to 'rbx'
this.mov('rbx', 'rax');
// Visit left side of expression (the result is in 'rax')
visit.call(this, ast.left);
//
// So, to conclude, we've left side in 'rax' and right in 'rbx'
//
// Execute binary operation
if (ast.operator === '+') {
this.add('rax', 'rbx');
} else if (ast.operator === '-') {
this.sub('rax', 'rbx');
} else if (ast.operator === '*') {
// Signed multiplication
// rax = rax * rbx
this.imul('rbx');
} else if (ast.operator === '/') {
// Preserve 'rdx'
this.push('rdx');
// idiv is diving rdx:rax by rbx, therefore we need to clear rdx
// before running it
this.xor('rdx', 'rdx');
// Signed division, rax = rax / rbx
this.idiv('rbx');
// Restore 'rdx'
this.pop('rdx');
} else if (ast.operator === '%') {
// Preserve 'rdx'
this.push('rdx');
// Prepare to execute idiv
this.xor('rdx', 'rdx');
this.idiv('rbx');
// imul puts remainedr in 'rdx'
this.mov('rax', 'rdx');
// Restore 'rdx'
this.pop('rdx');
} else {
throw new Error('Unsupported binary operator: ' + ast.operator);
}
// Restore 'rbx'
this.pop('rbx');
// The result is in 'rax'
}
function visitUnary(ast) {
// Visit argument and put result into 'rax'
visit.call(this, ast.argument);
if (ast.operator === '-') {
// Negate argument
this.neg('rax');
} else {
throw new Error('Unsupported unary operator: ' + ast.operator);
}
}
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