wasm2llvm

Lift WASM to LLVM IR.

Example from testsuite/i32.wast

(module
  (func (export "add") (param $x i32) (param $y i32) (result i32) (i32.add (local.get $x) (local.get $y)))

wasm2llvm uses wabt to get module binary representation corresponding to text format to e.g.:

(func (export "add") (param $x i32) (param $y i32) (result i32) (i32.add (local.get $x) (local.get $y))

wasm2ll takes name of WebAssembly function definition e.g. add and corresponding WebAssembly bytecode and outputs LLVM IR e.g.:

define i32 @add(i32 %a, i32 %b) #0 {
  %1 = add nsw i32 %a, %b
  ret i32 %1
}

How to run sieve.wat

wat2wasm --enable-tail-call -v sieve.wat  -o sieve.wasm
wasm-interp --run-all-exports --enable-tail-call --host-print sieve.wasm 
called host host.print(i32:42) => i32:0
f() => i32:0

How wabt(-rs) works

ScriptParser::from_str takes wast input e.g. testsuite/i32.wast

ModuleBinary::into_vec returns module binary same as wast2json testsuite/i32.wast -o i32.json would return in i32.0.wasm

module binary comes from Script::write_binares which calls to foreign call to wabt_write_binary_spec_script

How to get module binary for test

wast2json testsuite/i32.wast -o i32.json

Module binary is i32.0.wasm

How to compile Rust to WebAssembly and get text representation

Install target for WebAssembly

rustup target add wasm32-unknown-unknown --toolchain nightly

Create a simple program that always returs 1.

echo "fn main(){1;}" > test.rs

Compile it to WebAssembly

rustup run nightly rustc --target=wasm32-unknown-unknown test.rs

Set up wabt.

Convert the assembly into the text representation.

wasm2wat test.wasm -o test.wat

Run it with wasmtime

wasmtime test.wasm