Practical JavaScript Compiler

Todo

Language Features

• Lists
  • Runtime
  • Normal implementation
  • Thinking of making it a C type array with only one type of element
• Error productions:
  • Declaration statments without a semicolon
  • Empty statements
• Register Allocation:
  • Remove redundancy as both caller and callee are flushing registers.
  • Make use of dirty bit
  • Update flushtemporary and flsuh registers to make used of function name and dirty bit
  • Use nextReg heuristic
• Arguments of functions
  • Make use of the number of parameters
  • Replace with arguments array
  • At function call time, we know the number of parameters passed

Optimizations

• Code Motion
• Common Sub expression removal

Issues

Language Specification

Unique Stuff

• Breaks and continues don't signal errors, but they are silently removed
• The idea of callbacks:
  • Callbacks are the pascal equivalent of procedures.
  • They don't return values and hence cannot be used in expressions.
  • Callbacks can be passed to functions.
  • Callbacks can be returned from functions.
• Typing
  • Strongly typed.
  • Parameters are not type checked.
• Functions
  • Not hoisted, you have to define them before using them.
  • No closures
  • The number of parameters is not checked
  • Type Hinting: The types of function parameters needs to be hinted
• Strings defined using double quotes are constants
• Blocks must have curly braces
• Scoping
  • Lexical Scoping
  • Function is the fundamental unit of scope

Features not implemented

• Data types:
  • Only one number type: Integers
  • Objects
  • No NaN, INFINITY and NULL
• Language Constructs
  • Ternary Operator
  • with
  • do while
  • switch case
  • RegEx
  • try, catch, finally and throw
  • for
  • SIAF
• OOP features of ES5.1
  • new
  • this
  • instanceof
  • delete
• Bitwise Operations and operators

    - & | ^ ~ >> << >>>
    - &= |= ^= >>= <<= >>>=

• Unused keywords
  • class
  • const
  • extends
  • field
  • final
  • import
  • package
  • private
  • protected
  • public
  • super
• Library routines are not implemented.
  • OOP features are not implemented because it is a library feature.
• Type coercion
  • '+' does not change type to string
  • '!' does not change type to string, it can be only used on boolean operators
  • expression are not automatically converted to boolean in case of logical expressions

Warts of the language

• eval
• Semicolon insertion
• comma at the end of arrays and objects
• '==' and '===' mean the same thing, strict checking
• '!=' and '!==' mean the same thing, strict checking
• '++' and '--' are not supported

Meetings

First Meeting

• All lists are of a fixed size.
• No need of an input, a main will do the initializations
• anonymous function can be handled by giving out unique names
• new can be handled using sbreak.
• eval is left for the end: Done using the runtime
• Handling exceptions using a runtime object.
• overloading is left for the end:
• The concept of an event loop as in Node?
• A runtime library for lists, hasmaps and inheritance.

Technical Specifications

• Version : EC5.1
• Target : SPIM
• Lexer Generator : PLY
• Parser Generator : PLY
• Implementation : Python

Dependencies

• Python 2.7 and higher
• ply

Flow

• JSlexer defines a debug instance and a lexer instance.
• parser defines a ST, TAC and parser instance.
• runTime define a RTC which uses all of the above.

Usage

• run make
• ./runTime.py