The Wasmer WebAssembly runtime provides various features for users and developers:
Compilers: Wasmer supports multiple compilers: Singlepass, Cranelift and LLVM. Each of these have different tradeoffs of compilation speed vs runtime speed;
Caching: compiled WebAssembly modules can be reused so subsequent runs of a Wasm file will have very little start up time;
Metering: computation time and other resources can be monitored and limits set to control how the Wasm code runs. This is also known as "gas metering";
WebAssembly Features:
Bulk-memory operations: e.g. instructions with behavior similar to C's memmove and memset in WebAssembly;
Multi-value return: return multiple values from functions making data transfer between host and guest simpler;
Import & export of mutable globals: adds ability to import and export mutable globals;
Non-trapping float-to-int conversions: this proposal would establish a convention for saturating operations, to avoid introducing trapping;
Sign-extension operations: adds five new integer instructions for sign-extending 8-bit, 16-bit, and 32-bit values;
Reference types: easier and more efficient interop with host environment;
SIMD: Single Instruction, Multiple data: do heavy number crunching more quickly and/or with lower power usage.
Threads: adds a new shared linear memory type and some new operations for atomic memory access;
ABIs: it allows running different types of programs compiled to WebAssembly, with ABIs such as:
Emscripten
WASI
Support of features by Compiler
Runtime features:
Singlepass
Cranelift
LLVM
Emscripten
✅
✅
✅
WASI
✅
✅
✅
WebAssembly features:
Singlepass
Cranelift
LLVM
Bulk memory operations
✅
✅
✅
Multi-value return
🔄
✅
✅
Import & export of mutable globals
✅
✅
✅
Non-trapping float-to-int conversions
✅
✅
✅
Sign-extension operations
✅
✅
✅
Reference types
🔄
✅
✅
SIMD (Phase 4)
✅
✅
✅
Threads (Phase 2)
✅
🔄
✅
Legend
✅ Supported
🔄 In the works
⬜ Not yet supported (please ping us if you need this feature!)
Support by Operating System
Linux
macOS
Windows
Cranelift
✅
✅
✅
LLVM
✅
✅
✅
Singlepass
✅
✅
✅
WASI
✅
✅
✅*
* poll_fd is not fully implemented for Windows yet
Compiler Support by Chipset
x86_64
arm64
x86
Cranelift
✅
✅
✅
LLVM
✅
✅
✅
Singlepass
✅
🔄
⬜
Language Embeddings
Wasmer enables WebAssembly usage in a lot of different languages. Here are some of the features in each of those: