ByteCodeEngineering

The “byte-code” is a special representation that is executed by Emacs VM. The Emacs VM is a simple stack-machine interpreter. This page collects informations for byte-code and Emacs VM.

Documents

The byte-code is translated by the Emacs Lisp compiler. See the documentation for byte compiling: CompiledFile and Info (Elisp, Section 16, Byte Compilation).

Specs

See the emacs lisp and C sources for byte-code spec and VM details: bytecomp.el, disass.el and bytecode.c.

Instruction Table

Here is the Emacs VM instruction table for 23.3. (Collected from bytecomp.el and bytecode.c)

OPCODE	Instruction	Operands	Stack IN	Stack Out	Note
0	stack_ref				stack_ref+0 → dup.
+N	: stack_ref+0..5			var
+6	: stack_ref+6	index8		var
+7	: stack_ref+7	index16		var
010	varref
+N	: varref+0..5			var
+6	: varref+6	index8		var
+7	: varref+7	index16		var
020	varset
+N	: varset+0..5		var
+6	: varset+6	index8	var
+7	: varset+7	index16	var
030	varbind				let, specbind
+N	: varbind+0..5		var
+6	: varbind+6	index8	var
+7	: varbind+7	index16	var
040	call
+N	: call+0..5		func,args..	retval
+6	: call+6	num8	func,args..	retval
+7	: call+7	num16	func,args..	retval
050	unbind				unbind_to
+N	: unbind+0..5
+6	: unbind+6	num8
+7	: unbind+7	num16
070	nth		num, list	val
071	symbolp		val	result
072	consp		val	result
073	stringp		val	result
074	listp		val	result
075	eq		val1, val2	result
076	memq		list, elm	result
077	not		val	result
0100	car		cell	car
0101	cdr		cell	cdr
0102	cons		cdr,car	cons
0103	list1		elm	list
0104	list2		val2,val1	list
0105	list3		val3,2,1	list
0106	list4		val4,3,2,1	list
0107	length		list	length
0110	aref		array, num	val
0111	aset		array,num,val	val
0112	symbol_value		sym	val
0113	symbol_function		sym	val
0114	set		val, sym	val
0115	fset		val, sym	val
0116	get		prop, sym	val
0117	substring		to,from,str	result
0120	concat2		str2,1	result
0121	concat3		str3,2,1	result
0122	concat4		str4,3,2,1	result
0123	sub1		num	result
0124	add1		num	result
0125	eqlsign		num2,num1	result
0126	gtr		right,left	result
0127	lss		right,left	result
0130	leq		right,left	result
0131	geq		right,left	result
0132	diff		right,left	result
0133	negate		num	result
0134	plus		right,left	result
0135	max		num1,num2	result
0136	min		num1,num2	result
0137	mult		right,left	result
0140	point			point	Was Bmark in v17.
0141	save_current_buffer				Obsolete.
0142	goto_char		point	point
0143	insert		string	string
0144	point_max			point
0145	point_min			point
0146	char_after		point	result
0147	following_char			result
0150	preceding_char			result
0151	current_column			result
0152	indent_to		num	result
0153	scan_buffer			(error)	No longer generated as of v18
0154	eolp			result
0155	eobp			result
0156	bolp			result
0157	bobp			result
0160	current_buffer			buf
0161	set_buffer		buf	buf
0162	save_current_buffer_1				Replacing Bsave_current_buffer. record_unwind_protect
0162	read_char				No longer generated as of v19
0163	set_mark			(error)	this loser is no longer generated as of v18
0164	interactive_p			result	Obsolete.
0165	forward_char		num	nil
0166	forward_word		num	result
0167	skip_chars_forward		limit,string	result
0170	skip_chars_backward		limit,string	result
0171	forward_line		num	result
0172	char_syntax		char	result
0173	buffer_substring		end,start	result
0174	delete_region		end,start	nil
0175	narrow_to_region		end,start	nil
0176	widen			nil
0177	end_of_line		num	nil
0201	constant2	num16		value
0202	goto	dst16			quit
0203	gotoifnil	dst16	val
0204	gotoifnonnil	dst16	val
0205	gotoifnilelsepop	dst16	val
0206	gotoifnonnilelsepop	dst16	val
0207	return		result		goto exit
0210	discard		discard
0211	dup		val	val1,val2
0212	save_excursion				record_unwind_protect
0213	save_window_excursion			result	Obsolete. record_unwind_protect / progn
0214	save_restriction				record_unwind_protect / save_restriction_save
0215	catch		tag	result	internal_catch / eval_sub
0216	unwind_protect		finally		record_unwind_protect / progn
0217	condition_case		handlers,body	result
0220	temp_output_buffer_setup		bufname	buf	Obsolete.
0221	temp_output_buffer_show		val,buf	val	Obsolete. unbind_to
0222	unbind_all				Obsolete. unbind_to → count
0223	set_marker		buf,pos,marker	marker
0224	match_beginning		subexp	result
0225	match_end		subexp	result
0226	upcase		obj	result
0227	downcase		obj	result
0230	stringeqlsign		str2,str1	result
0231	stringlss		str2,str1	result
0232	equal		obj2,obj1	result
0233	nthcdr		list,num	result
0234	elt		num,seq	result
0235	member		list,elt	result
0236	assq		list,key	result
0237	nreverse		list	result
0240	setcar		val,cell	result
0241	setcdr		val,cell	result
0242	car_safe		obj	result
0243	cdr_safe		obj	result
0244	nconc		list2,list1	result
0245	quo		right,left	result	/
0246	rem		right,left	result	%
0247	numberp		obj	result
0250	integerp		obj	result
0252	Rgoto	raddr8			relative jump : raddr - 127
0253	Rgotoifnil	raddr8	var		relative jump : raddr - 127
0254	Rgotoifnonnil	raddr8	var		relative jump : raddr - 127
0255	Rgotoifnilelsepop	raddr8	var		relative jump : raddr - 127
0256	Rgotoifnonnilelsepop	raddr8	var		relative jump : raddr - 127
0257	listN	num8	values	list
0260	concatN	num8	values	result
0261	insertN	num8	values	nil
0262	stack_set	num8	value		stack_ref is code 0
0263	stack_set2	num16	value
0266	discardN	num8
0300	constant
+N	: constant			value

Tools

-Assembler for Emacs' bytecode interpreter