stackvm.txt

Instruction Set Architecture
============================
00	UNDEF		undefined
01	IGNORE		no-op
02	BREAK		debugger break
03	ENTER x		adjust call frame by x
04	LEAVE x		leave call frame
05	CALL		( a -- )
06	PUSH		push zero ( -- 0 )
07	POP		drop item ( n -- )
08	CONST x		push constant ( -- n )
09	LOCAL x		index local frame by x ( -- n )
0A	JUMP		( a -- )
0B	EQ j		integer equal ( a b -- )
0C	NE j		integer not equal ( a b -- )
0D	LTI j		integer less ( ai bi -- )
0E	LEI j		integer less or equal ( ai bi -- )
0F	GTI j		integer greater than ( ai bi -- )
10	GEI j		integer greater or equal ( ai bi -- )
11	LTU j		unsigned less than ( au bu -- )
12	LEU j		unsigned less equal ( au bu -- )
13	GTU j		unsigned greater than ( au bu -- )
14	GEU j		unsigned greater or equal ( au bu -- )
15	EQF j		float equal ( af bf -- )
16	NEF j		float not equal
17	LTF j		float less than
18	LEF j		float less or equal
19	GTF j		float greater than
1A	GEF j		float greater or equal
1B	LOAD1		read byte from memory ( a -- b )
1C	LOAD2		read short from memory ( a -- s )
1D	LOAD4		read word from memory ( a -- i )
1E	STORE1		store byte into memory ( a b -- )
1F	STORE2		store short into memory ( a s -- )
20	STORE4		store word info memory ( a i -- )
21	ARG b		store TOS into arg position ( n -- )
22	BLOCK_COPY x	( r2 r1 r0 -- )
23	SEX8		sign extend 8-bit ( b -- i )
24	SEX16		sign extend 16-bit ( s -- i )
25	NEGI		integer negate ( i -- i )
26	ADD		addition ( au bu -- u )
27	SUB		subtract ( au bu -- u )
28	DIVI		integer divide ( n d -- q )
29	DIVU		unsigned divide ( n d -- q )
2A	MODI		integer modulo ( n d -- m )
2B	MODU		unsigned modulo ( n d -- m )
2C	MULI		integer multiply ( a b -- i )
2D	MULU		unsigned multiply ( a b -- u )
2E	BAND		bitwise-AND ( a b -- u )
2F	BOR		bitwise-OR ( a b -- u )
30	BXOR		bitwise-XOR ( a b -- u )
31	BCOM		bitwise complement ( u -- u )
32	LSH		left shift ( n shft -- n )
33	RSHI		arithmetic right shift ( n shift -- n )
34	RSHU		bitwise right shift ( n shift -- n )
35	NEGF		float negate ( f -- f )
36	ADDF		float addition ( af bf -- f )
37	SUBF		float subtraction ( af bf -- f )
38	DIVF		float division ( n d -- q )
39	MULF		float multiplication ( a b -- f )
3A	CVIF		convert integer to float ( i -- f )
3B	CVFI		convert float to integer ( f -- i )


File Format
===========
len	field name
---	----------
4	magic 0x12721444 or 0x44147212
4	instruction count
4	CODE segment size
4	CODE segment offset
4	DATA segment size
4	DATA segment offset
4	LIT segment size
4	BSS segment size


Call Frame Format
=================
                         +---------------+ \
top of address space --> | arg...        |  \
                         | arg1          |   \
                         | arg0          |    \
                         +---------------+     \
                         | N/A           |      >-- vm entry call
SP at entry -----------> | saved PC (-1) |     /
                         +---------------+    /
                         | local...      |   /
                         | local1        |  /
SP after ENTER (????)--> | local0        | /
                         +---------------+ \
                         | arg...        |  \
                         | arg1          |   \
                         | arg0          |    \
                         +---------------+     \
                         | saved SP      |      >-- second function call
SP at entry -----------> | saved PC      |     /
                         +---------------+    /
                         | local...      |   /
                         | local1        |  /
SP after ENTER (????)--> | local0        | /
                         +---------------+


System Calls
============
The VM permits calling external (native) functions by doing a CALL to a negative
address. -1 is traditionally used to indicate an exit from the VM, -2 and beyond
are free to be used for any purposes.