ZHVM - is a registers based RISC virtual machine (Harvard memory organization) with 32-bit code length and 64-bit registers.
ZHVM based on standard C library and STL.
Assembler requires FLEX 2.6 to be installed in system.
ZHVM consists of two parts:
- libzhvm.a - library implements VM and assembler
- libzyaml.a - library implements JSON/YAML parsing
- repl - Read-Eval-Print-Loop application to work with ZHVM
- cmplv2 - Standalone ZHVM assembler
ZHVM project requires CMake 3.0 to be built.
There are some ZHVM code examples in ${SOURCE_DIRECTORY}/share.
- test-001.zsf - simple consters program
- test-002.zsf - fibbonachi numbers calculator
- test-003.zsf - simple function invocation
VM process 32-bit commands. Each command encodes operation code, two source registers, one destination register and 14-bit immediate constant.
VM has 15+1 general usage registers:
- RZ - Zero register. Always return zero, even if non-zero value was written
- RA - A(ccumulator) register.
- RB - B(ase) register.
- RC - C(ounter) register.
- R0-R8 - Argument registers.
- RS - S(tack) top register.
- RD - D(ata) register.
- RP - P(rogram) pointer. Incremented by 4 bytes each cycle.
Any register can be used in any operation, but RP and RZ have special meaning.
Initial registers state can be defined in assembler using following syntax:
!$R NUMBER # Set initial value of register R to NUMBER
!$R @LABEL # Set initial value of register R to value of label LABEL
Supports only already defined labels.
VM uses 6-bit operation code length, which can be used to code 64 commands.
Current VM version has several reserved for future use codes. If any of reserved codes are found, VM halts with error.
Valid operation codes:
- hlt - halt vm.
- add - add two numbers.
$d = $s0 + ($s1 + imm) - sub - substract two numbers.
$d = $s0 - ($s1 + imm) - mul - two numbers multiplications.
$d = $s0 * ($s1 + imm) - div - two numbers division.
$d = $s0 / ($s1 + imm) - mod - two numbers division remainder.
$d = $s0 % ($s1 + imm) - cmz - conditional move zero.
if ($s0 == 0) $d = ($s1 + imm) - cmn - conditional move non-zero. [if ($s0 != 0) $d = ($s1 + imm)`
- ldb - load 1-byte.
$d = mem[S0] + S1 + imm - lds - load 2-bytes.
$d = mem[S0] + S1 + imm - ldl - load 4-bytes.
$d = mem[S0] + S1 + imm - ldq - load 8-bytes.
$d = mem[S0] + S1 + imm - svb - store 1-byte.
mem[$d] = S0 + S1 + imm - svs - store 2-bytes.
mem[$d] = S0 + S1 + imm - svl - store 4-bytes.
mem[$d] = S0 + S1 + imm - svq - store 8-bytes.
mem[$d] = S0 + S1 + imm - and - bitwise and.
$d = $s0 & ($s1 + imm) - or - bitwise or.
$d = $s0 | ($s1 + imm) - xor - bitwise xor.
$d = $s0 ^ ($s1 + imm) - gr - is greater.
$d = $s0 > ($s1 + imm) - ls - is less.
$d = $s0 < ($s1 + imm) - gre - is greater or equal.
$d = $s0 >= ($s1 + imm) - lse - is less or equal.
$d = $s0 <= ($s1 + imm) - eq - is equal.
$d = $s0 == ($s1 + imm) - neq - is not equal.
$d = $s0 != ($s1 + imm) - ccl - call c-func.
cfuncs[$s0 + $s1 + imm]() - cpy - copy bytes.
memcpy($d, $s0, S1 + imm) - cmp - compare bytes.
$d = memcpy($d, $s0, S1 + imm) - zcl - call ZHVM function
($p = zcl($s, $a + @func)). Save old dest at $s and move it by 4 bytes, then load new $p = $a + @func - ret - return from ZHVM function
($p = ret($s)). Take new destination from $s and set it to $p. - nop - do nothing.
C functions can be called from VM. Current implementation expects that only 16 function available.
Standard functions:
- print RA to console.
ccl[,0] - scan from console to RA.
ccl[,1]
Assembler supports definition of labels with following syntax:
!LABEL_NAME # Define label with name LABEL_NAME
Labels can be used in code instead of immediate values in any command with @ (at) symbol preceding label name.
$p = add[,@LABEL_NAME] # Use defined label
VM uses Harvard architecture. Data and code memory segments pointers for labels
are switched by !code and !data words. After !code word labels are defined
in code segment, after !data in data segment. So, there can be no code or
data labels.
Labels can be used before actual label defined. But, all labels must be set before EOF.
ZHVM image starts with 16 bytes header:
- [4 bytes] Magic number. [0xD0FA5534]
- [4 bytes] VM version. [current and only version is 3]
- [4 bytes] VM code byte length. [actual VM code length]
- [4 bytes] VM data byte length. [actual VM data length]
- [120 bytes] Initial VM registers stage.
Immediatly after follows the very body of VM image.
After image body sdbm hash of header and body are saved.