Runtimes

Catalog of Wasm runtimes together with the corresponding tests and benchmarks. This catalog is specifically focused on the runtimes used or potentially useful for the blockchains.

Features

Runtime	Wasmer			Wasmtime		Wasmi
Backend	Singlepass	Cranelift	LLVM	Cranelift	Lightbeam
Type	Non-optimizing compiler	Optimizing compiler	Optimizing compiler	Optimizing compiler	Non-optimizing compiler	Interpreter
WASI	✅	✅	✅	✅	❓	❌
Metering*	✅	❌	✅	🔁6	❌	✅metered_wasmi
SIMD	❌	❌	✅	🔁	❓	❌
Multi-value return	🔁	🔁	🔁	✅	❓	❓

• ✅ -- yes
• 🔁 -- in progress
• ❓ -- unknown
• ❌ -- no

Metering

Currently there are three implementations of the metering:

• pwasm-utils by Parity, which is a code transformation tool that injects metering code into a Wasm file;
• Wasmer runtime is able to perform gas metering by injecting low-level metering code upon Wasm compilation;
• wasm-metering by Ewasm -- currently orphaned, gas metering injection.

Additionaly Wasmi has its own version with embedded metering functionality, see metered_wasmi.

Both pwasm-utils by Parity and wasm-metering by Ewasm are code transformation tools that can be combined with any Wasm runtime, e.g. someone can inject gas metering into the code before passing it to a runtime for execution.

OS Support

Runtime	Wasmer			Wasmtime		Wasmi
Backend	Singlepass	Cranelift	LLVM	Cranelift	Lightbeam
GNU Linux	✅	✅	✅	✅	❓	✅
MacOS	✅	✅	✅	✅	❓	✅
Windows NT	✅	✅	❌#347	✅	❓	❓

Testing

Runtime	Wasmer			Wasmtime		Wasmi
Backend	Singlepass	Cranelift	LLVM	Cranelift	Lightbeam
Spec tests	✅2	✅2	✅2	✅	❓	❓
cargo-fuzz (libfuzzer)	✅3	❌	✅3	✅	❓	✅4
honggfuzz	✅3	❌	✅3	❓	❓	✅4
aflfuzz	✅3	❌	✅3	❓	❓	❌

Note, additionally to fuzz tests provided by Wasmer Trail of Bits performed volatility study of Wasmer and have created afl test that you can find in wasmer-afl directory.

Spec tests

Both Wasmer and Wasmi use official test suite to verify compatibility with the Wasm spec.

Additional properties

Additionaly Wasmtime+Cranelift supports the following, according to @tschneidereit:

• Debugging in gdb/lldb
• Openly governed
• License gives a patent grant

Footnotes

1: Wasmer support of features by backend

2: Wasmer spec tests

3: Wasmer fuzz tests

4: Wasmi homepage

5: Wasm official test suite

6: There are rumors of metering projects for Cranelift/Wasmtime. They might not be public, according to @tschneidereit