Binaryen is a compiler and toolchain infrastructure library for WebAssembly, written in C++. It aims to make compiling to WebAssembly easy, fast, and effective:
Easy: Binaryen has a simple C API in a single header, and can also be used from JavaScript. It accepts input in WebAssembly-like form but also accepts a general control flow graph for compilers that prefer that.
Fast: Binaryen‘s internal IR uses compact data structures and is designed for completely parallel codegen and optimization, using all available CPU cores. Binaryen’s IR also compiles down to WebAssembly extremely easily and quickly because it is essentially a subset of WebAssembly.
Effective: Binaryen's optimizer has many passes that can improve code very significantly (e.g. local coloring to coalesce local variables; dead code elimination; precomputing expressions when possible at compile time; etc.). These optimizations aim to make Binaryen powerful enough to be used as a compiler backend by itself. One specific area of focus is on WebAssembly-specific optimizations (that general-purpose compilers might not do), which you can think of as wasm minification , similar to minification for JavaScript, CSS, etc., all of which are language-specific (an example of such an optimization is block return value generation in SimplifyLocals
).
Compilers built using Binaryen include
asm2wasm
which compiles asm.js to WebAssemblyAssemblyScript
which compiles TypeScript to Binaryen IRwasm2js
which compiles WebAssembly to JSAsterius
which compiles Haskell to WebAssemblyBinaryen also provides a set of toolchain utilities that can
Consult the contributing instructions if you're interested in participating.
Binaryen's internal IR is designed to be
There are a few differences between Binaryen IR and the WebAssembly language:
--generate-stack-ir --print-stack-ir
, which prints Stack IR, this is guaranteed to be valid for wasm parsers.)push
and pop
as mentioned earlier; another option is to add LLVM-like extractvalue/composevalue
instructions.As a result, you might notice that round-trip conversions (wasm => Binaryen IR => wasm) change code a little in some corner cases.
src/wasm-stack.h
). Stack IR allows a bunch of optimizations that are tailored for the stack machine form of WebAssembly‘s binary format (but Stack IR is less efficient for general optimizations than the main Binaryen IR). If you have a wasm file that has been particularly well-optimized, a simple round-trip conversion (just read and write, without optimization) may cause more noticeable differences, as Binaryen fits it into Binaryen IR’s more structured format. If you also optimize during the round-trip conversion then Stack IR opts will be run and the final wasm will be better optimized.Notes when working with Binaryen IR:
This repository contains code that builds the following tools in bin/
:
Usage instructions for each are below.
cmake . && make
A C++14 compiler is required. Note that you can also use ninja
as your generator: cmake -G Ninja . && ninja
.
Binaryen.js can be built using Emscripten, which can be installed via the SDK).
emcmake cmake . && emmake make binaryen_js
Using the Microsoft Visual Studio Installer, install the “Visual C++ tools for CMake” component.
Generate the projects:
mkdir build cd build "%VISUAL_STUDIO_ROOT%\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\cmake.exe" ..
Substitute VISUAL_STUDIO_ROOT with the path to your Visual Studio installation. In case you are using the Visual Studio Build Tools, the path will be “C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools”.
From the Developer Command Prompt, build the desired projects:
msbuild binaryen.vcxproj
CMake generates a project named “ALL_BUILD.vcxproj” for conveniently building all the projects.
Run
bin/wasm-opt [.wasm or .wat file] [options] [passes, see --help] [--help]
The wasm optimizer receives WebAssembly as input, and can run transformation passes on it, as well as print it (before and/or after the transformations). For example, try
bin/wasm-opt test/passes/lower-if-else.wat --print
That will pretty-print out one of the test cases in the test suite. To run a transformation pass on it, try
bin/wasm-opt test/passes/lower-if-else.wat --print --lower-if-else
The lower-if-else
pass lowers if-else into a block and a break. You can see the change the transformation causes by comparing the output of the two print commands.
It's easy to add your own transformation passes to the shell, just add .cpp
files into src/passes
, and rebuild the shell. For example code, take a look at the lower-if-else
pass.
Some more notes:
bin/wasm-opt --help
for the full list of options and passes.--debug
will emit some debugging info.Run
bin/wasm2js [input.wasm file]
This will print out JavaScript to the console.
For example, try
$ bin/wasm2js test/hello_world.wat
That output contains
function add(x, y) { x = x | 0; y = y | 0; return x + y | 0 | 0; }
as a translation of
(func $add (; 0 ;) (type $0) (param $x i32) (param $y i32) (result i32) (i32.add (local.get $x) (local.get $y) ) )
wasm2js‘s output is in ES6 module format - basically, it converts a wasm module into an ES6 module (to run on older browsers and Node.js versions you can use Babel etc. to convert it to ES5). Let’s look at a full example of calling that hello world wat; first, create the main JS file:
// main.mjs import { add } from "./hello_world.mjs"; console.log('the sum of 1 and 2 is:', add(1, 2));
The run this (note that you need a new enough Node.js with ES6 module support):
$ bin/wasm2js test/hello_world.wat -o hello_world.mjs $ node --experimental-modules main.mjs the sum of 1 and 2 is: 3
Things keep to in mind with wasm2js's output:
-O
or another optimization level. That will optimize along the entire pipeline (wasm and JS). It won't do everything a JS minifer would, though, like minify whitespace, so you should still run a normal JS minifer afterwards.Run
bin/asm2wasm [input.asm.js file]
This will print out a WebAssembly module in s-expression format to the console.
For example, try
$ bin/asm2wasm test/hello_world.asm.js
That input file contains
function () { "use asm"; function add(x, y) { x = x | 0; y = y | 0; return x + y | 0; } return { add: add }; }
You should see something like this:
By default you should see pretty colors as in that image. Set COLORS=0
in the env to disable colors if you prefer that. On Linux and Mac, you can set COLORS=1
in the env to force colors (useful when piping to more
, for example). For Windows, pretty colors are only available when stdout/stderr
are not redirected/piped.
Pass --debug
on the command line to see debug info, about asm.js functions as they are parsed, etc.
When using emcc
with the BINARYEN
option, it will use Binaryen to build to WebAssembly. This lets you compile C and C++ to WebAssembly, with emscripten using asm.js internally as a build step. Since emscripten's asm.js generation is very stable, and asm2wasm is a fairly simple process, this method of compiling C and C++ to WebAssembly is usable already. See the emscripten wiki for more details about how to use it.
./check.py
(or python check.py
) will run wasm-shell
, wasm-opt
, asm2wasm
, etc. on the testcases in test/
, and verify their outputs.
The check.py
script supports some options:
./check.py [--interpreter=/path/to/interpreter] [TEST1] [TEST2]..
./check.py --list-suites
.emcc
or nodejs
in the path. They will not run if the tool cannot be found, and you'll see a warning.tests/spec
, in git submodules. Running ./check.py
should update those.“Binaryen” is a combination of binary - since WebAssembly is a binary format for the web - and Emscripten - with which it can integrate in order to compile C and C++ all the way to WebAssembly, via asm.js. Binaryen began as Emscripten's WebAssembly processing library (wasm-emscripten
).
“Binaryen” is pronounced in the same manner as “Targaryen”: bi-NAIR-ee-in. Or something like that? Anyhow, however Targaryen is correctly pronounced, they should rhyme. Aside from pronunciation, the Targaryen house words, “Fire and Blood”, have also inspired Binaryen's: “Code and Bugs.”
Yes, it does. Here's a step-by-step tutorial on how to compile it under Windows 10 x64 with with CMake and Visual Studio 2015. Help would be appreciated on Windows and OS X as most of the core devs are on Linux.