An incomplete v8 bytecode interpreter / virtual machine for a subset of instructions. Plus, a tiny playground for profiling javascript code and inspecting the corresponding bytecode.
This project's ambition is building an incomplete virtual machine capable of executing a subset of byte code supported by V8 JavaScript engine as pictured below. Largely as a challenge of building a register machine capable of executing different operations, highly practical, as well as to better understand the inner-workings of the most popular and battle-tested JavaScript engine and optimizations happening behind the scenes.
graph TD
JS[JavaScript]
BC[V8 Byte Code]
VM[Virtual Machine]
IO[Output]
V8[JavaScript<br> Engine]
JS-->BC
BC-->VM
VM-->IO
JS-->V8
V8-->IO
style VM fill:blue
Note: Does not currently parse .bytecode files, the VM is currently work in progress
$ make start |
|---|
Install dependencies with make install and execute
$ make test # or make tddRunning tests with high verbosity logs from executor
$ EXPLAIN=1 DEBUG=1 make test # or make tddGenerate .bytecode file for each javascript file in the examples/ directory
$ makeClean all .bytecode files in the examples/ directory
$ make clean$ make
✓ Generated examples/earlyReturn.bytecode$ cat examples/earlyReturn.bytecode | head -20
[generated bytecode for function: main (0x26a884854fb9 <SharedFunctionInfo main>)]
Bytecode length: 49
Parameter count 2
Register count 3
Frame size 24
OSR nesting level: 0
Bytecode Age: 0
71 S> 0x26a8848559ce @ 0 : 0c LdaZero
77 E> 0x26a8848559cf @ 1 : 6c 03 00 TestLessThan a0, [0]
0x26a8848559d2 @ 4 : 98 19 JumpIfFalse [25] (0x26a8848559eb @ 29)
88 S> 0x26a8848559d4 @ 6 : 21 00 01 LdaGlobal [0], [1]
0x26a8848559d7 @ 9 : c2 Star1
96 E> 0x26a8848559d8 @ 10 : 2d f9 01 03 LdaNamedProperty r1, [1], [3]
0x26a8848559dc @ 14 : c3 Star0
0x26a8848559dd @ 15 : 13 02 LdaConstant [2]
0x26a8848559df @ 17 : c1 Star2
96 E> 0x26a8848559e0 @ 18 : 5d fa f9 f8 05 CallProperty1 r0, r1, r2, [5]
123 S> 0x26a8848559e5 @ 23 : 0b 03 Ldar a0
132 E> 0x26a8848559e7 @ 25 : 46 ff 07 MulSmi [-1], [7]
137 S> 0x26a8848559ea @ 28 : a8 Return$ make start
[DEBUG] OP [ 'Jump', [ 3 ] ]
[DEBUG] OP [ 'LdaZero' ]
[DEBUG] OP [ 'LdaGlobal', [ 0 ], [ 1 ] ]
[DEBUG] OP [ 'Star0' ]
[DEBUG] OP [ 'LdaNamedProperty', 'r0', [ 1 ], [ 3 ] ]
[DEBUG] OP [ 'Star1' ]
[DEBUG] OP [ 'LdaConstant', [ 2 ] ]
[DEBUG] OP [ 'Star2' ]
[DEBUG] OP [ 'CallProperty1', 'r1', 'r0', 'r2', [ 5 ] ]
•• Hello World ••
[DEBUG] OP [ 'LdaSmi', [ 6 ] ]
[DEBUG] OP [ 'Star0' ]
[DEBUG] OP [ 'TestLessThan', 'r0', [ 0 ] ]
[DEBUG] OP [ 'MulSmi', [ 5 ], [ 0 ] ]
[DEBUG] OP [ 'Return' ]
[DEBUG] ST {
registers: {
accumulator: 30,
r0: 6,
r1: [Function: log],
r2: '•• Hello World ••',
a0: undefined,
a1: undefined,
a2: undefined
},
flags: { boolean: false },
constants: [ 'console', 'log', '•• Hello World ••', 1 ],
ip: 14,
return: 30
}- V8 / Interpreter / Ignition: Design Doc
- V8 / Interpreter / ByteCodes: Chromium, Node