Opcodes

Every instruction of the bytecode, generated from the ops! table in crates/djs-core/src/bytecode/ops.rs: the encoded byte, the immediates, the encoded size, the stack effect and the fuel cost class. The emitter, decoder, disassembler and the stack-depth checker are generated from the same table, so this page cannot disagree with them.

opcode	byte	immediates	size	pop → push	cost	description
`undefined`	0	–	1	0 → 1	Basic	`-> undefined`
`null`	1	–	1	0 → 1	Basic	`-> null`
`push_true`	2	–	1	0 → 1	Basic	`-> true`
`push_false`	3	–	1	0 → 1	Basic	`-> false`
`push_i8`	4	I8	2	0 → 1	Basic	`-> n`: a small integer constant.
`push_i32`	5	I32	5	0 → 1	Basic	`-> n`: an integer constant.
`push_const`	6	Const	5	0 → 1	Basic	`-> v`: a constant pool entry (non-int32 numbers, strings).
`push_atom`	7	Atom	5	0 → 1	Basic	`-> s`: the string of an atom.
`object`	8	–	1	0 → 1	Alloc	`-> {}`
`array_from`	9	Count	3	imm0 → 1	Alloc	`v1 .. vn -> array`: an array literal without holes or spread.
`array_push`	10	–	1	2 → 1	Basic	`array v -> array`
`array_hole`	11	–	1	1 → 1	Basic	`array -> array`: append a hole.
`array_spread`	12	–	1	2 → 1	Access	`array iterable -> array`: append the elements of an iterable (spread).
`fclosure`	13	Child	5	0 → 1	Alloc	`-> function`: create a closure of child template `child`.
`regexp`	14	–	1	2 → 1	Alloc	`pattern flags -> regexp`
`get_template_object`	15	Const	5	0 → 1	Alloc	`-> template object`: tagged templates. `CONSTS[idx]` is the site’s object once created; before that, the index of `n`, `n` cooked strings (or `undefined`) and `n` raw strings, from which the first run creates and caches it.
`special_object`	16	U8	2	0 → 1	Alloc	`-> v`: `arguments`, `new.target`, home object, … (function entry only).
`rest`	17	Arg	3	0 → 1	Alloc	`-> array`: the actual arguments from `index` on (a rest parameter).
`drop`	18	–	1	1 → 0	Basic	`a ->`
`dup`	19	–	1	1 → 2	Basic	`a -> a a`
`dup2`	20	–	1	2 → 4	Basic	`a b -> a b a b`
`swap`	21	–	1	2 → 2	Basic	`a b -> b a`
`nip`	22	–	1	2 → 1	Basic	`a b -> b`
`insert2`	23	–	1	2 → 3	Basic	`a b -> b a b`
`insert3`	24	–	1	3 → 4	Basic	`a b c -> c a b c`
`insert4`	25	–	1	4 → 5	Basic	`a b c d -> d a b c d`
`rot3l`	26	–	1	3 → 3	Basic	`x a b -> a b x`
`rot3r`	27	–	1	3 → 3	Basic	`a b x -> x a b`
`pick`	28	U8	2	1+imm0 → 2+imm0	Basic	`x a1 .. an -> x a1 .. an x`: copy the value under the top `n` (`pick 0` is `dup`). Destructuring reaches its iterator under assignment-target references.
`poke`	29	U8	2	2+imm0 → 1+imm0	Basic	`x a1 .. an v -> v a1 .. an`: overwrite the value under the top `n` + 1.
`name_get`	30	NameRef	5	0 → 1	Free	`-> v`: read a name.
`name_put`	31	NameRef	5	1 → 0	Free	`v ->`: assign a name.
`name_set`	32	NameRef	5	1 → 1	Free	`v -> v`: assign a name, keep the value.
`name_init`	33	NameRef	5	1 → 0	Free	`v ->`: initialize a declaration (no TDZ check, const allowed).
`name_typeof`	34	NameRef	5	0 → 1	Free	`-> v`: read a name for `typeof` (undeclared globals give `undefined`).
`enter_scope`	35	Scope	3	0 → 0	Free	Scope entry: TDZ setup, Boxes, hoisted block functions.
`leave_scope`	36	Scope	3	0 → 0	Free	Scope exit.
`iter_scope`	37	Scope	3	0 → 0	Free	Start of a `for (let ...)` iteration: fresh copies of the scope’s captured bindings (`rebox`, CreatePerIterationEnvironment).
`label`	38	LabelId	5	0 → 0	Free	A label position (symbolic labels).
`get_loc`	39	Loc	3	0 → 1	Basic	`-> v`
`put_loc`	40	Loc	3	1 → 0	Basic	`v ->`
`set_loc`	41	Loc	3	1 → 1	Basic	`v -> v`
`get_loc_chk`	42	Loc	3	0 → 1	Basic	`-> v`, ReferenceError if uninitialized (TDZ).
`put_loc_chk`	43	Loc	3	1 → 0	Basic	`v ->`, ReferenceError if uninitialized.
`set_loc_chk`	44	Loc	3	1 → 1	Basic	`v -> v`, ReferenceError if uninitialized.
`set_loc_uninit`	45	Loc	3	0 → 0	Basic	Store the uninitialized marker.
`inc_loc`	46	Loc	3	0 → 0	Basic	`loc = loc + 1` (`i++;`, `++i;` on an unchecked local): `inc` in place. An object takes `%ToNumeric` into the local first, then the instruction runs again.
`dec_loc`	47	Loc	3	0 → 0	Basic	`loc = loc - 1`, as `inc_loc`.
`get_arg`	48	Arg	3	0 → 1	Basic	`-> v`
`put_arg`	49	Arg	3	1 → 0	Basic	`v ->`
`set_arg`	50	Arg	3	1 → 1	Basic	`v -> v`
`get_box`	51	Loc	3	0 → 1	Basic	`-> v`: the value of the Box in local `loc`.
`put_box`	52	Loc	3	1 → 0	Basic	`v ->`
`set_box`	53	Loc	3	1 → 1	Basic	`v -> v`
`get_box_chk`	54	Loc	3	0 → 1	Basic	`-> v` with a TDZ check.
`put_box_chk`	55	Loc	3	1 → 0	Basic	`v ->` with a TDZ check.
`set_box_chk`	56	Loc	3	1 → 1	Basic	`v -> v` with a TDZ check.
`new_box`	57	Loc	3	0 → 0	Alloc	`loc = new Box(uninitialized)`
`new_box_init`	58	Loc	3	1 → 0	Alloc	`v ->`: `loc = new Box(v)`.
`rebox`	59	Loc	3	0 → 0	Alloc	`loc = new Box(current value)`: per-iteration bindings.
`get_cap`	60	Cap	3	0 → 1	Basic	`-> v`: the value of the closure’s capture `cap`.
`put_cap`	61	Cap	3	1 → 0	Basic	`v ->`
`set_cap`	62	Cap	3	1 → 1	Basic	`v -> v`
`get_cap_chk`	63	Cap	3	0 → 1	Basic	`-> v` with a TDZ check.
`put_cap_chk`	64	Cap	3	1 → 0	Basic	`v ->` with a TDZ check.
`set_cap_chk`	65	Cap	3	1 → 1	Basic	`v -> v` with a TDZ check.
`get_global`	66	Atom, Cache	7	0 → 1	Access	`-> v`: global lexical record, then the global object; ReferenceError if missing.
`get_global_typeof`	67	Atom, Cache	7	0 → 1	Access	`-> v`: like `get_global`, but `undefined` if missing (`typeof`).
`put_global`	68	Atom, Cache	7	1 → 0	Access	`v ->`: ReferenceError if missing, TypeError for a global const.
`init_global_lex`	69	Atom	5	1 → 0	Access	`v ->`: initialize a Script top-level let/const/class.
`global_decls`	70	Const	5	0 → 0	Access	Script GlobalDeclarationInstantiation from the declaration list in constant `idx`.
`throw_const_assign`	71	Atom	5	0 → 0	Basic	TypeError `'x' is read-only`.
`get_field`	72	Atom, Cache	7	1 → 1	Access	`obj -> v`
`get_method`	73	Atom, Cache	7	1 → 2	Access	`obj -> f obj`: callee and `this` for a method call.
`put_field`	74	Atom, Cache	7	2 → 0	Access	`obj v ->`
`get_elem`	75	–	1	2 → 1	Access	`obj key -> v`
`get_elem2`	76	–	1	2 → 3	Access	`obj key -> obj key' v`: `get_elem` keeping the reference for a compound assignment or update, with `key'` = ToPrimitive(key) (one conversion for the get and the put, after the RequireObjectCoercible of `obj`).
`to_propkey`	77	–	1	1 → 1	Basic	`key -> key'`: ToPrimitive(key, string) now, for a computed key whose definition comes after other code (`{ [k]: v }`: ToPropertyKey before `v`). Primitives stay.
`get_elem_method`	78	–	1	2 → 2	Access	`obj key -> f obj`
`put_elem`	79	–	1	3 → 0	Access	`obj key v ->`
`define_field`	80	Atom, Cache	7	2 → 1	Access	`obj v -> obj`: CreateDataProperty (literals).
`define_elem`	81	–	1	3 → 1	Access	`obj key v -> obj`: computed keys.
`define_getter`	82	Atom	5	2 → 1	Access	`obj f -> obj`
`define_setter`	83	Atom	5	2 → 1	Access	`obj f -> obj`
`define_getter_elem`	84	–	1	3 → 1	Access	`obj key f -> obj`
`define_setter_elem`	85	–	1	3 → 1	Access	`obj key f -> obj`
`define_method`	86	Atom	5	2 → 1	Access	`obj f -> obj`: also sets the home object.
`define_method_elem`	87	–	1	3 → 1	Access	`obj key f -> obj`
`set_proto`	88	–	1	2 → 1	Basic	`obj v -> obj`: a literal `__proto__: v` sets the prototype when `v` is an object or null (other values are ignored).
`set_function_name`	89	U8	2	2 → 2	Basic	`key f -> key f`: SetFunctionName(f, ToPropertyKey(key), prefix) for an anonymous function under a computed key (`prefix`: 0 none, 1 “get”, 2 “set”).
`copy_data_props`	90	U8	2	2 → 1	Access	`obj src -> obj`: object spread / rest (flags select the variant).
`delete`	91	–	1	2 → 1	Access	`obj key -> bool`
`in`	92	–	1	2 → 1	Access	`key obj -> bool`
`private_symbol`	93	Atom, U8	6	0 → 1	Alloc	`-> sym`: a new private name (a private symbol described `#x`). `flags`: `heap::cells::flags::SYM_PRIVATE_METHOD` (a method or accessor) and `SYM_PRIVATE_READONLY` (no setter).
`get_private_field`	94	–	1	2 → 1	Access	`obj sym -> v`: `obj.#x` (own properties only, never a proxy trap; a getter is called).
`put_private_field`	95	–	1	3 → 0	Access	`obj sym v ->`: `obj.#x = v` (a setter is called).
`define_private_field`	96	U8	2	3 → 1	Access	`obj sym v -> obj`: adds a private field (`kind` 0) or method (1), ignoring extensibility; TypeError if `obj` has it already.
`define_private_accessor`	97	–	1	4 → 1	Access	`obj sym getter setter -> obj`: adds a private accessor (`undefined` for a missing half).
`private_in`	98	–	1	2 → 1	Access	`sym obj -> bool`: `#x in obj`.
`get_super`	99	–	1	1 → 1	Access	`o -> o.[[GetPrototypeOf]]()`: the base of a super property (from the home object), or the super constructor (from the active function).
`get_super_field`	100	Atom	5	2 → 1	Access	`this base -> v`: `super.x`, base.[[Get]](x, this).
`put_super_field`	101	Atom	5	3 → 0	Access	`this base v ->`: `super.x = v`, base.[[Set]](x, v, this).
`get_super_elem`	102	–	1	3 → 1	Access	`this base key -> v`
`put_super_elem`	103	–	1	4 → 0	Access	`this base key v ->`
`set_home_object`	104	–	1	2 → 2	Basic	`home f -> home f`: sets the home object of `f` (class field initializers).
`define_class`	105	U8	2	3 → 2	Alloc	`parent protoParent ctor -> ctor proto`: ClassDefinitionEvaluation’s prototype and constructor setup. `flags` bit 0: there is a heritage (`parent` and `protoParent`, checked by %ClassHeritage, are used; otherwise ignored).
`define_class_method`	106	Atom, U8	6	2 → 1	Access	`obj f -> obj`: a class method (`kind` 0), getter (1) or setter (2): non-enumerable, and sets the home object.
`define_class_method_elem`	107	U8	2	3 → 1	Access	`obj key f -> obj`
`define_class_field`	108	–	1	3 → 1	Access	`obj key v -> obj`: a public class field (CreateDataPropertyOrThrow).
`require_object_coercible`	109	–	1	1 → 1	Basic	`v -> v`: TypeError for `null`/`undefined` (destructuring).
`neg`	110	–	1	1 → 1	Basic	`a -> -a`
`plus`	111	–	1	1 → 1	Basic	`a -> +a` (ToNumber)
`bnot`	112	–	1	1 → 1	Basic	`a -> ~a`
`not`	113	–	1	1 → 1	Basic	`a -> !a`
`typeof`	114	–	1	1 → 1	Basic	`a -> typeof a`
`inc`	115	–	1	1 → 1	Basic	`a -> a + 1` (numeric)
`dec`	116	–	1	1 → 1	Basic	`a -> a - 1` (numeric)
`to_numeric`	117	–	1	1 → 1	Basic	`a -> ToNumeric(a)` (postfix `++`/`--`)
`to_string`	118	–	1	1 → 1	Basic	`a -> ToString(a)` (template substitutions)
`add`	119	–	1	2 → 1	Basic	`a b -> a + b`
`sub`	120	–	1	2 → 1	Basic	`a b -> a - b`
`mul`	121	–	1	2 → 1	Basic	`a b -> a * b`
`div`	122	–	1	2 → 1	Basic	`a b -> a / b`
`mod`	123	–	1	2 → 1	Basic	`a b -> a % b`
`pow`	124	–	1	2 → 1	Basic	`a b -> a ** b`
`shl`	125	–	1	2 → 1	Basic	`a b -> a << b`
`sar`	126	–	1	2 → 1	Basic	`a b -> a >> b`
`shr`	127	–	1	2 → 1	Basic	`a b -> a >>> b`
`band`	128	–	1	2 → 1	Basic	`a b -> a & b`
`bor`	129	–	1	2 → 1	Basic	`a b -> a \| b`
`bxor`	130	–	1	2 → 1	Basic	`a b -> a ^ b`
`lt`	131	–	1	2 → 1	Basic	`a b -> a < b`
`le`	132	–	1	2 → 1	Basic	`a b -> a <= b`
`gt`	133	–	1	2 → 1	Basic	`a b -> a > b`
`ge`	134	–	1	2 → 1	Basic	`a b -> a >= b`
`eq`	135	–	1	2 → 1	Basic	`a b -> a == b`
`ne`	136	–	1	2 → 1	Basic	`a b -> a != b`
`strict_eq`	137	–	1	2 → 1	Basic	`a b -> a === b`
`strict_ne`	138	–	1	2 → 1	Basic	`a b -> a !== b`
`instanceof`	139	–	1	2 → 1	Access	`a b -> a instanceof b`
`is_nullish`	140	–	1	1 → 1	Basic	`v -> v is null or undefined`
`is_undefined`	141	–	1	1 → 1	Basic	`v -> v === undefined`
`concat`	142	Count	3	imm0 → 1	Alloc	`s1 .. sn -> s`: join template literal parts in one allocation.
`jump`	143	Target	5	0 → 0	Basic	Unconditional jump.
`jump_if_false`	144	Target	5	1 → 0	Basic	`v ->`: jump if ToBoolean(v) is false.
`jump_if_true`	145	Target	5	1 → 0	Basic	`v ->`: jump if ToBoolean(v) is true.
`gosub`	146	Target	5	0 → 1	Basic	`-> ret`: push the return address (an int32) and jump (enter a `finally`).
`ret`	147	–	1	1 → 0	Basic	`ret ->`: jump to the popped return address.
`throw`	148	–	1	1 → 0	Basic	`v ->`: throw `v`.
`return`	149	–	1	1 → 0	Basic	`v ->`: return `v`.
`return_undef`	150	–	1	0 → 0	Basic	Return `undefined`.
`call`	151	Argc	3	2+imm0 → 1	Call	`f this a1 .. an -> r`
`construct`	152	Argc	3	1+imm0 → 1	Call	`f a1 .. an -> r`: `new f(...)`, new.target = f.
`call_spread`	153	–	1	3 → 1	Call	`f this args -> r`: call with an argument array (spread).
`construct_spread`	154	–	1	2 → 1	Call	`f args -> r`
`super_call`	155	Argc	3	2+imm0 → 1	Call	`f a1 .. an newTarget -> r`: `super(...)` in a derived constructor: constructs `f` (the super constructor) with that new.target.
`super_call_spread`	156	–	1	3 → 1	Call	`f args newTarget -> r`: `super(...args)` with an argument array (spread).
`call_intrinsic`	157	Intrinsic, Argc	5	imm1 → 1	Call	`a1 .. an -> r`: privileged code only.
`generator_start`	158	Loc	3	0 → 0	Alloc	Generator function entry: creates the generator object, stores it in local `generator`, suspends the frame (to resume at the next instruction) and returns the object to the caller.
`yield`	159	Loc	3	1 → 2	Alloc	`v -> received isReturn`: suspends the generator in local `generator`, handing `v` to the resumer. Resumed by `next(x)`: `x false`; by `return(x)`: `x true` (the code returns `x`, running finally blocks); `throw(e)` throws `e` here.
`yield_star`	160	Loc	3	1 → 2	Alloc	`innerResult -> received isReturn`: `yield` for `yield*` in a sync generator: the resumer hands `innerResult` (the inner iterator’s result object) on as it is, without reading `value` or wrapping it (GeneratorYield ( innerResult )).
`async_start`	161	Loc	3	0 → 0	Alloc	Async function entry: creates the async state (with the result promise) in local `state`. The function runs on synchronously.
`await`	162	Loc	3	1 → 1	Alloc	`v -> result`: suspends the async function of local `state` until `v` settles, then pushes its value or throws its reason here. The first await returns the result promise to the caller.
`async_return`	163	Loc	3	1 → 0	Call	`v ->`: return from an async function: resolves the result promise with `v` and returns the promise.
`async_reject`	164	Loc	3	1 → 0	Call	`e ->`: an exception leaves an async function: rejects the result promise with `e` and returns the promise (the target of the body’s catch-all handler).
`get_iterator`	165	–	1	1 → 1	Access	`obj -> iterator`
`iter_next`	166	Target	5	2 → 1	Call	`it next -> r`: `r = next.call(it)`, an iterator result. When `next` is the original `next` of an Array or String Iterator and that step runs no user code, `r` is the next value itself and the instruction jumps (no result object, D1800).
`iter_check_object`	167	–	1	1 → 1	Basic	`v -> v`: TypeError if `v` is not an object (iterator results).
`iterator_close`	168	–	1	1 → 0	Access	`iterator ->`: call `iterator.return()` if present.
`for_in_start`	169	–	1	1 → 1	Alloc	`obj -> for-in iterator` (a snapshot of the enumerable keys)
`for_in_next`	170	–	1	1 → 3	Access	`it -> it key done`
`check_ctor`	171	–	1	0 → 0	Basic	TypeError if a class constructor is called without `new`.
`check_this`	172	–	1	1 → 1	Basic	`v -> v`: a derived constructor’s `this`: ReferenceError while uninitialized (`undefined`, before `super()`).
`check_this_uninit`	173	–	1	1 → 0	Basic	`v ->`: before `super()` binds `this`: ReferenceError if it is bound already.
`check_ctor_return`	174	–	1	1 → 1	Basic	`v -> v`: a derived constructor’s return value: TypeError unless an object or `undefined`.
`throw_error`	175	Atom, U8	6	0 → 0	Basic	Throws a new error with message `atom`; `kind` 0: TypeError, 1: ReferenceError.
`debugger`	176	–	1	0 → 0	Free	`debugger` (no effect).
`nop`	177	–	1	0 → 0	Free	No operation.