WebAssembly.jl

Author MikeInnes
Popularity
60 Stars
Updated Last
1 Year Ago
Started In
March 2018

WebAssembly

Build Status

Tools for working with the WebAssembly format in Julia. In particular, this package exposes the IR as simple Julia data structures, allowing parsers and code generators to convert to/from the IR, as well as allowing optimisation passes directly on the IR in the vein of binaryen.

Build IR for a x^n function:

using WebAssembly: i32, f64, irfunc
using IRTools.All

pow = let
  ir = IR()
  x = argument!(ir, f64)
  n = argument!(ir, i32)
  cond = block!(ir)
  body = block!(ir)
  ret  = block!(ir)
  n = argument!(cond, n, i32)
  r = argument!(cond, 1.0, f64)
  branch!(cond, ret, unless = push!(cond, stmt(xcall(i32.gt_s, n, Int32(0)), type = i32)))
  n = push!(body, stmt(xcall(i32.sub, n, Int32(1)), type = i32))
  r′ = push!(body, stmt(xcall(f64.mul, r, x), type = f64))
  branch!(body, cond, n, r′)
  return!(ret, r)
  ir
end
julia> pow
1: (%1 :: f64, %2 :: i32)
  br 2 (%2, 1.0)
2: (%3 :: i32, %4 :: f64)
  %5 = (i32.gt_s)(%3, 0) :: i32
  br 4 unless %5
3:
  %6 = (i32.sub)(%3, 1) :: i32
  %7 = (f64.mul)(%4, %1) :: f64
  br 2 (%6, %7)
4:
  return %4

Construct a wasm function and module:

func = irfunc(:pow, pow)

mod = WebAssembly.Module(funcs=[func],
   exports=[WebAssembly.Export(:pow, :pow, :func)])

WebAssembly.binary(mod, "test.wasm")

Disassemble the result with binaryen:

shell> wasm-dis test.wasm
(module
 (type $0 (func (param f64 i32) (result f64)))
 (export "pow" (func $0))
 (func $0 (; 0 ;) (type $0) (param $0 f64) (param $1 i32) (result f64)
  (local $2 f64)
  (local.set $2 (f64.const 1))
  (loop $label$1
   (if
    (i32.eqz (i32.le_s (local.get $1) (i32.const 0)))
    (block
     (local.set $1
      (i32.sub (local.get $1) (i32.const 1)))
     (local.set $2
      (f64.mul (local.get $2) (local.get $0)))
     (br $label$1))))
  (local.get $2)))

(If wasm-dis is not on your path you can use

julia> run(`$(WebAssembly.Binaryen.wasm_dis) test.wasm`);

to get syntax-highlighted WASM in a terminal).

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