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WAST

wasm-as

WAST to WASM

sum.wast

(module
  (export "sum" (func $s))
  (func $s (param $x i32) (param $y i32) (result i32)
    (return
      (i32.add
        (get_local $x)
        (get_local $y)
      )
    )
  )
)

wasm-as.exe sum.wast -o sum.wasm

sum.wasm (в hex редакторе)

00 61 73 6D 01 00 00 00 01 87 80 80 80 00 01 60 02 7F 7F 01 7F 03 82 80 80 80 00 01 00 07 87 80 80 80 00 01 03 73 75 6D 00 00 0A 8E 80 80 80 00 01 88 80 80 80 00 00 20 00 20 01 6A 0F 0B

Запуск в браузере

WebAssembly.compile(new Uint8Array(`
00 61 73 6D 01 00 00 00 01 87 80 80 80 00 01 60 02 7F 7F 01 7F 03 82 80 80 80 00 01 00 07 87 80 80 80 00 01 03 73 75 6D 00 00 0A 8E 80 80 80 00 01 88 80 80 80 00 00 20 00 20 01 6A 0F 0B
`.trim().split(/[\s\r\n]+/g).map(str => parseInt(str, 16))
)).then(module => {
  const instance = new WebAssembly.Instance(module);
  const sum = instance.exports.sum;
  console.log(sum(42, 37)); // 79
});

wasm-dis

WASM to WAST

wasm-dis.exe sum.wasm

(module
 (type $0 (func (param i32 i32) (result i32)))
 (memory $0 0)
 (export "sum" (func $0))
 (func $0 (type $0) (param $var$0 i32) (param $var$1 i32) (result i32)
  (return
   (i32.add
    (get_local $var$0)
    (get_local $var$1)
   )
  )
 )
)

.WAST, генерируемый emcc

sum.c

int sum(x, y){
	return x+y;
}

emcc -s SIDE_MODULE=1 -s WASM=1 -O3 sum.c -o sum_emcc.wasm

wasm-dis.exe sum_emcc.wasm

(module
 (type $0 (func (param i32 i32) (result i32)))
 (type $1 (func))
 (import "env" "memoryBase" (global $import$0 i32))
 (import "env" "memory" (memory $0 256))
 (import "env" "table" (table 0 anyfunc))
 (import "env" "tableBase" (global $import$3 i32))
 (global $global$0 (mut i32) (i32.const 0))
 (global $global$1 (mut i32) (i32.const 0))
 (export "__post_instantiate" (func $2))
 (export "_sum" (func $0))
 (export "runPostSets" (func $1))
 (func $0 (type $0) (param $var$0 i32) (param $var$1 i32) (result i32)
  (i32.add
   (get_local $var$1)
   (get_local $var$0)
  )
 )
 (func $1 (type $1)
  (nop)
 )
 (func $2 (type $1)
  (block $label$0
   (set_global $global$0
    (get_global $import$0)
   )
   (set_global $global$1
    (i32.add
     (get_global $global$0)
     (i32.const 5242880)
    )
   )
   (call $1)
  )
 )
 ;; custom section "dylink", size 5
)

.WASM, генерируемый wabt

https://github.com/WebAssembly/wabt

wast2wasm sum.wast -o sum.wasm

00 61 73 6D 01 00 00 00 01 07 01 60 02 7F 7F 01 7F 03 02 01 00 07 07 01 03 73 75 6D 00 00 0A 0A 01 08 00 20 00 20 01 6A 0F 0B

Разбор опкодов

https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md

wabt

00 61 73 6D
01 00 00 00
01 07 01 60 02 7F 7F 01 7F
03 02 01 00
07 07 01 03 73 75 6D 00 00
0A 0A 01 08 00 20 00 20 01 6A 0F 0B

00 61 73 6D - wasm magic word (.asm)

01 00 00 00 - wasm version (0x01)

Name Code Description
Type 0x01 Function signature declarations
Import 0x02 Import declarations
Function 0x03 Function declarations
Table 0x04 Indirect function table and other tables
Memory 0x05 Memory attributes
Global 0x06 Global declarations
Export 0x07 Exports
Start 0x08 Start function declaration
Element 0x09 Elements section
Code 0x0A Function bodies (code)
Data 0x0B Data segments

01 07 01 60 02 7F 7F 01 7F

01 - Section "Type"

07 - Section size

01 - Count of type entries to follow

60 - Function types are encoded by the byte 0x60 followed by the respective vectors of parameter and result types

Code Type
0x7F i32
0x7E i64
0x7D f32
0x7C f64

02 - Count of function inputs

7F - Input type (i32)

7F - Input type (i32)

01 - Count of function outputs

7F - Output type (i32)

(func $s (param $x i32) (param $y i32) (result i32)

03 02 01 00

03 - Section "Function"

02 - Section size

01 - Count of signature indices to follow

00 - Function "s" signature index

07 07 01 03 73 75 6D 00 00

07 - Section "Export"

07 - Section size

01 - Count of export entries

03 - Function name size

73 75 6D - "sum" (function name from export) (export "sum" (func $s))

Code Type
0x00 Function
0x01 Table
0x02 Memory
0x03 Global

00 - kind of definition being imported (0x00 - Function)

00 - export Function "s" signature index

0A 0A 01 08 00 20 00 20 01 6A 0F 0B

0A - Section "Code"

0A - Section size

01 - Count of functions

08 - Function size

00 - Number of local variables

20 - read a local variable or parameter param $x i32

00 - index of x

20 - read a local variable or parameter param $y i32

01 - index of y

6A - i32.add

0F - Return

0B - End