How to use the command wasm-opt (with examples)
WebAssembly (Wasm) is a binary instruction format designed for efficient execution in web browsers. The wasm-opt command is part of the Binaryen toolkit and is used to optimize WebAssembly binary files. It applies various optimizations to improve the performance and size of the binary files.
Use case 1: Applying default optimizations and writing to a given file
Code:
wasm-opt -O input.wasm -o output.wasm
Motivation: By applying default optimizations, we can improve the performance and size of the WebAssembly binary file. This is useful when we want to enhance the execution speed and reduce the file size.
Explanation:
wasm-opt: The command itself.-O: Specifies the optimization level. In this case, it applies default optimizations.input.wasm: The input WebAssembly binary file.-o: Specifies the output file name.output.wasm: The name of the optimized output file.
Example output: The command will apply default optimizations to the input.wasm file and generate an optimized binary file named output.wasm.
Use case 2: Applying all optimizations and writing to a given file
Code:
wasm-opt -O4 input.wasm -o output.wasm
Motivation: Applying all optimizations takes more time but generates optimal code. This is useful when we want to achieve the best possible performance and size reduction for the WebAssembly binary file.
Explanation:
wasm-opt: The command itself.-O4: Specifies the highest optimization level (level 4). It applies all available optimizations.input.wasm: The input WebAssembly binary file.-o: Specifies the output file name.output.wasm: The name of the optimized output file.
Example output: The command will apply all available optimizations to the input.wasm file and generate an optimized binary file named output.wasm.
Use case 3: Optimizing a file for size
Code:
wasm-opt -Oz input.wasm -o output.wasm
Motivation: Sometimes, the size of the WebAssembly binary file is more important than its execution speed. By optimizing the file for size, we can significantly reduce its size. This is useful when bandwidth or storage constraints are important considerations.
Explanation:
wasm-opt: The command itself.-Oz: Specifies the optimization level for size. It applies size-specific optimizations.input.wasm: The input WebAssembly binary file.-o: Specifies the output file name.output.wasm: The name of the optimized output file.
Example output: The command will optimize the input.wasm file for size and generate an optimized binary file named output.wasm.
Use case 4: Printing the textual representation of the binary to console
Code:
wasm-opt input.wasm --print
Motivation: Sometimes, it’s helpful to view the textual representation of a WebAssembly binary file. This can aid in understanding and debugging the code.
Explanation:
wasm-opt: The command itself.input.wasm: The input WebAssembly binary file.--print: Instructs the command to print the textual representation of the binary to the console.
Example output: The command will print the textual representation of the input.wasm file to the console.
Conclusion:
The wasm-opt command is a powerful tool for optimizing WebAssembly binary files. It offers various optimization levels to improve performance and reduce the size of the files. Additionally, it provides the capability to print the textual representation of the binary, aiding in debugging and understanding the code. By utilizing the different use cases of this command, developers can achieve optimized WebAssembly binaries that meet the desired performance and size requirements.
