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WebAssembly SIMD Example in C

128-bit packed Single Instruction Multiple Data (SIMD) instructions provide simultaneous computations over packed data in just one instruction. It's commonly used to improve performance for multimedia applications. With the SIMD proposal, the modules can benefit from using these commonly used instructions in modern hardware to gain more speedup.

If you are interested in enabling the SIMD proposal will improve how much performance of the applications, please refer to our wasm32-wasi benchmark for more information. The Mandelbrot Set application can have a 2.65x speedup in our benchmark.

We modified the Mandelbrot Set example from our wasm32-wasi benchmark project. We will use this as an example in this article.

Prerequisites​

Before we start, make sure you have installed the following software:

  1. Install WasmEdge

  2. Emscripten, a toolchain for compiling C/C++ to WebAssembly. Please refer to the emcc official repository for detailed instructions.

git clone --depth 1 https://github.com/emscripten-core/emsdk.git
cd emsdk
./emsdk install latest
./emsdk activate latest
source ./emsdk_env.sh

Compile the C-SIMD application to Wasm-SIMD binary with emcc​

emcc -g -Oz --llvm-lto 1 -s STANDALONE_WASM -s INITIAL_MEMORY=32MB -s MAXIMUM_MEMORY=4GB \
  -mmutable-globals \
  -mnontrapping-fptoint \
  -msign-ext \
  mandelbrot-simd.c -o mandelbrot-simd.wasm

Run with WasmEdge​

wasmedge mandelbrot-simd.wasm 15000

Ahead-of-Time mode​

With WasmEdge's AoT compiler, you will get higher performance.

# Compile wasm-simd with wasmedge aot compiler
$ wasmedge compile mandelbrot-simd.wasm mandelbrot-simd-out.wasm
# Run the native binary with wasmedge
$ wasmedge mandelbrot-simd-out.wasm 15000