Analyzing and optimizing native code for portability to the Web using Emscripten, Native Client and ConConJS

Agenda

Glossary
Motivation
Previous Work
Methodology
Artifact — ConConJS
Future Work
Conclusion

Glossary

Native Code

Native Code or Machine code is a set of instructions executed directly by a computer's central processing unit (CPU).

Machine Code

W65C816S Machine Code

Assembly Code

An assembly language is a low-level programming language for a computer, or other programmable device, in which there is a very strong (generally one-to-one) correspondence between the language and the architecture's machine code instructions.

Assembly Code

"Hello world!" program for DOS in MASM style assembly

Unmanaged Code

Unmanaged code refers to code that does not need a runtime to execute. Often written in a programming language such as C or C++, which is compiled directly into machine code.

Managed Code

Managed code, refers to code which is written in programming languages like C#, VB.NET, Java, or similar, and executed in a virtual environment (such as the .NET CLR or the JVM) which “simulates” a CPU in software.

Motivation

How can we make our large native code based graphic accelerated applications portable to all modern devices at the same time?

Without:

Having to write platform specific code
Higher costs

Software Portability

Software portability is often cited as desirable, but rarely receives systematic attention.

"Most of its basis are anecdotes and case studies."

Why Portability

Platform agnostic code

Unified code base

Portable software is more robust
Portability expands your market
Portability provides freedom

"Write once, run everywhere"

Many programming languages and API's claim to be "portable"

We will focus in C, C++ and OpenGL

C and C++ are everywhere

C and C++ Relevance

Since it supports many target platforms from a single code base, nearly all professional game development middle-ware is written in C/C++
Good for large code-bases (static type system, compiled language, mature compilers and debuggers)

OpenGL is also everywhere (almost)

But writing code in these technologies does not ensure portability.

Regardless...

All modern devices can be a single target platform...

The Web

Biggest open & standardized platform
Great for reaching people
Has evolved organically in the digital age
Beaten all odds and outlasted all adversity
Has scaled successfully beyond all reason

Why not make our content available for everyone?

Web's Standardized Stack

Document Object Model

HTML 5
CSS 3.0
JavaScript (Ecmascript [ECMA-262 specification and ISO/IEC 16262] )

Rendering API's

CanvasRenderingContext2D
WebGL

BUT...

Game developers don't do Web Stuff.

"HTML is not even a programming language."

"JavaScript is slow."

"There is a large amount of tools built using established languages, such as C and C++, that need to be ported."

What then?

What if?

C/C++ => %$&# => Web

Almighty LLVM to the rescue.

LLVM Compilation Model

Also, other things had to happen...

JavaScript Engines

Late 2008/early 2009 the race for fast JavaScript starts

V8 (Google)
TraceMonkey (Mozilla)
and Nitro (Safari)

asm.js

Is a JavaScript specification
It's just (a subset of) JavaScript
Allows the Web to become a compilation target

SOLVED!

C/C++ => LLVM => Web

Previous Work

How to run native code in the Web

Plugins — Limited browser specific API

NPAPI
PPAPI
ActiveX

Plugins

Web browser

NPAPI

PPAPI

ActiveX

Internet Explorer

X

Chrome/Chromium

X

Firefox

X

Safari

X

Opera

X

Previous Work

How to run native code in the Web

Plugins — Limited browser specific API
Native Client — Sandbox for native code, only works in Chrome Web browsers

Native Client

Native Client Application

Typical Web Application

Native Client Tool-chain Workflow

Demo

Native Client

The Good

Performance is similar to native code. (5 - 15 percent slowdown)

C/C++ Standard Library support

Threading support

Dynamic Linking support (when using NaCl)

Limitations

Since I/O operations are sand boxed code needs to be adapted
Only works on Chrome
Only static linking support (when using PNaCl)

Previous Work

How to run native code in the Web

Plugins — Limited browser specific API
Native Client — Sandbox for native code, only works in Chrome Web browsers
JavaScript cross-compilation (Emscripten) — Works in all Web Browsers, performance hit

Emscripten

The Good

Runs in all browsers with JavaScript support

C/C++ Standard Library support

Regular C/C++ I/O support (emulated)

Limitations

No threading support (out of the box)
Performs slower than native code (50 - 100 percent slowdown)
Only static linking

Previous Work

JavaScript engines have gotten fast enough to run large compiled code bases

Compiled JavaScript can be faster than "regular" handwritten JavaScript

Cross-compiling to JavaScript is not new:

Google Web Toolkit (GWT) — 2006

http://www.gwtproject.org/

Pyjamas (PyJs) — 2007

https://github.com/pyjs/pyjs

Methodology

Intention

Evaluate the challenges of porting large graphics applications native code bases written in C and C++ to run on the Web, using Native Client and Emscripten.

How?

Analyze & diagnose existing native code bases

Summarize portability guidelines compliant with Web standards
Identify code style implementations that may affect performance of cross-compiled code

Resulting in:

Systematic approach for creating portable applications

ConConJS

Native Client / Emscripten build system

What is ConConJS?

ConConJS (IPA: /kənkəndʒeɪz/) is a diagnosis tool for multi-platform graphics applications.

Serves as a proxy for cross-compilers such as Native Client and Emscripten

ConConJS Pipeline Overview

ConConJS Phases

The parser, evaluates code against a given set of specification databases

The data extractor, retrieves relevant information about portability and performance

The cross-compiler, which produces, when possible, a resulting Web application from the given code base

The Parser

The Extractor

The cross-compiler

Performance

CPU Language Benchmarks

MFLOPS

CPP

JS

Ratio

Convolution 1

911

34

3.7%

Recursive Filter 1

1074

929

86.5%

Fourier Transform 1

1186

75

6.3%

Sinc Interpolation 1

391

28

7.2%

Higher 'ratio' is better

Future Work

ConConJS should be able to re-factor code (similar to what compiler optimizers attempt to do).
Add DirectX support.

Conclusion

The Web provides the means to distribute application to multiple platforms at the same time without friction for the consumers.
Running native code in the Web if not the present it is the future for software distribution.