GebvM is an 8-bit register-based virtual machine. GebVM has...
Registers There are 8 8-bit registers (R0-R7) that store unsigned values.
Memory There are 65,536 bytes of memory also storing unsigned values. The running program is loaded into memory starting at address 0x0000. A stack occupies the space from 0xFF00 to 0xFFFF.
Bytecode GebVM uses its own bytecode specification. A couple trivial compiled examples are included, and more interesting examples may be added if there is an assembler for the project in the future.
I/O Input, output, and errors are written from/to stdin, stdout, and stderr (respectively).
These commands and paths can vary with Go version and local settings. This was tested on v1.15.
> # Pull the code
> go get github.com/scottmcleodjr/gebvm
>
> # Run the tests
> go test github.com/scottmcleodjr/gebvm/...
? github.com/scottmcleodjr/gebvm [no test files]
ok github.com/scottmcleodjr/gebvm/memory 0.009s
ok github.com/scottmcleodjr/gebvm/processor 0.033s
>
> # Build the project
> go build github.com/scottmcleodjr/gebvm
>
> # Run hellow_world.geb
> ./gebvm ~/go/src/github.com/scottmcleodjr/gebvm/examples/hello_world.geb
Hello, World!
| Instruction | Code | Arguments | Description |
|---|---|---|---|
| No Operation | 0x00 | Do nothing and continue execution | |
| Move Lit Reg | 0x01 | Literal, Register | Copy literal value to register |
| Move Reg Reg | 0x02 | Source Register, Destination Register | Copy value from source to destination register |
| Move Lit Memory | 0x03 | Literal, Pointer Register | Copy literal value to address at pointer register |
| Move Reg Memory | 0x04 | Register, Pointer Register | Copy value from register to address at pointer register |
| Move Memory Reg | 0x05 | Pointer Register, Register | Copy value from address at pointer register to register |
| Logical And | 0x20 | Left Register, Right Register | Set R0 to logical and of values in left and right registers |
| Logical Or | 0x21 | Left Register, Right Register | Set R0 to logical or of values in left and right registers |
| Logical Xor | 0x22 | Left Register, Right Register | Set R0 to logical xor of values in left and right registers |
| Logical Bit Clear | 0x23 | Left Register, Right Register | Set R0 to logical bit clear of values in left and right registers |
| Logical Shift Left | 0x24 | Register, Shift Distance | Logical shift left value in register by distance bytes |
| Logical Shift Right | 0x25 | Register, Shift Distance | Logical shift right value in register by distance bytes |
| Inc | 0x40 | Register | Increment value in register by 1 |
| Dec | 0x41 | Register | Decrement value in register by 1 |
| Add | 0x42 | Left Register, Right Register | Set R0 to sum of values in left and right registers |
| Subtract | 0x43 | Left Register, Right Register | Set R0 to difference of values in left and right registers |
| Multiply | 0x44 | Left Register, Right Register | Set R0 to product of values in left and right registers |
| Divide | 0x45 | Left Register, Right Register | Set R0 to quotient of values in left and right registers |
| Jump | 0x60 | Address (High Byte, Low Byte) | Set IP to address |
| JumpEqual | 0x61 | Register, Address (High Byte, Low Byte) | Set IP to address if values in R0 and register are equal |
| JumpNotEqual | 0x62 | Register, Address (High Byte, Low Byte) | Set IP to address if values in R0 and register are not equal |
| StackPushLit | 0x80 | Literal | Push literal value onto the stack |
| StackPushReg | 0x81 | Register | Push value from register onto the stack |
| StackPop | 0x82 | Register | Pop the top value from the stack and store at register |
| Call | 0x83 | Address (High Byte, Low Byte) | Function call |
| Return | 0x84 | Function return | |
| 0xE0 | Address (High Byte, Low Byte), Length | Output length chars beginning at address to the writer | |
| ReadInput | 0xE1 | Register | Store a single char from the reader to register |
| Halt | 0xFF | Halt execution |
- A pointer register holds the high byte of the address. The sequential next register holds the low byte. R7 cannot be used as a pointer register.
- Registers are represented by the numbers 0x00 (R0) through 0x07 (R7).