7 KiB
SuperVM
SuperVM is a stack machine with a simple, but flexible command set.
The Stack
The virtual machine utilizes a stack to provide operands to instructions. This stack stores temporary values the program is working with.
Registers and Flags
The SuperVM virtual machine is a stack machine, but has also some control registers that can be set with special instructions. The registers mainly control stack access or control flow.
| Mnemonic | Register | Function |
|---|---|---|
| SP | Stack Pointer | Stores the current 'top' position of the stack. |
| BP | Base Pointer | Stores the current stack frame position. |
| CP | Code Pointer | Stores the instruction which is executed next. |
| FG | Flag Register | Stores the state of the flags. |
Stack Pointer
The stack pointer points to the top of the stack. Each push operation increases
the stack pointer by one, each pop operation reduces it by one.
Base Pointer
The base pointer is a pointer that can be set to access the stack relative to it. The indended use is to create a stack frame with the base pointer by pushing the previous base pointer to the stack and setting the new base pointer to the current stack pointer.
Returning a function with this mechanism is moving the stack pointer to the current base pointer, then popping the previous base pointer from the stack.
Flag Register
| Bit | Flag | Option |
|---|---|---|
| 0 | Zero | Is set when the output is zero. |
| 1 | Negative | Is set when the MSB is set. |
Instructions
An SuperVM instruction is composed of multiple components:
| Component | Range | Size | Function |
|---|---|---|---|
| execution | See below. | 4 | When is the instruction executed. |
| input0 | Zero/Pop/Peek/Arg | 2 | Where does input0 come from? |
| input1 | Zero/Pop | 1 | Where does input1 come from? |
| command | [6bit] | 6 | Which command is executed? |
| cmdinfo | [16bit] | 16 | Parameter value for the command. |
| flagmod | yes/no | 1 | Does this command modifies flags? |
| output | Discard/Push/Jump | 2 | What is done with the output? |
| argument | [32bit] | 32 | Some commands can take extra information |
Execution Modes
The execution mode checks whether the instruction will be execution or not. The execution
depends on the state of the flags. An X means "Don't care", a 0 means the flag must be
cleared and a 1 means the flag must be set.
An instruction is only executed when all conditions are met.
| Flag | Range |
|---|---|
| Zero | X/0/1 |
| Negative | X/0/1 |
Commands
| ID | Command | Action |
|---|---|---|
| 0 | COPY | output = input0 |
| 1 | STORE | output = MEMORY[input0] = input1 |
| 2 | LOAD | output = MEMORY[input0] |
| 3 | GET | output = STACK[BP + input0] |
| 4 | SET | output = STACK[BP + input0] = input1 |
| 5 | BPGET | output = BP |
| 6 | BPSET | output = BP = input0 |
| 7 | RSTSTACK | output = SP = BP |
| 8 | MATH | output = input0 OP[info] input1 |
| 9 | spget | output = SP + input0 |
| 10 | spset | output = SP + input0 = input1 |
| 11 | ||
| 12 | ||
| 13 | ||
| 14 | ||
| 15 |
Math
The math operator is a compound operator that contains all
arithmetic operations. The arithmetic operation is selected
by the cmdinfo.
| cmdinfo | Operation |
|---|---|
| 0 | Addition |
| 1 | Subtraction |
| 2 | Multiplication |
| 3 | Division |
| 4 | Euclidean Division / Modulo |
| 5 | Bitwise Logic And |
| 6 | Bitwise Logic Or |
| 7 | Bitwise Logic Xor |
| 8 | Bitwise Logic Not |
| 9 | Rotating Bit Shift Left |
| 10 | Rotating Bit Shift Right |
| 11 | Arithmetic Bit Shift Left |
| 12 | Arithmetic Bit Shift Right |
| 13 | Logic Bit Shift Left |
| 14 | Logic Bit Shift Right |
Assembler Mnemonics
| Mnemonic | Arg? | i0 | i1 | Cmd | CmdInfo | Output |
|---|---|---|---|---|---|---|
| nop | no | zero | zero | copy | 0 | discard |
| push | yes | arg | zero | copy | 0 | push |
| drop | no | pop | zero | copy | 0 | discard |
| dup | no | peek | zero | copy | 0 | push |
| jmp | yes | arg | zero | copy | 0 | jump |
| jmpi | no | pop | zero | copy | 0 | jump |
| ret | no | pop | zero | copy | 0 | jump |
| load | yes | arg | zero | load | 0 | push |
| loadi | no | pop | zero | load | 0 | push |
| store | yes | arg | pop | store | 0 | discard |
| storei | no | pop | pop | store | 0 | discard |
| get | yes | arg | zero | get | 0 | push |
| geti | no | pop | zero | get | 0 | push |
| set | yes | arg | pop | set | 0 | discard |
| seti | no | pop | pop | set | 0 | discard |
| bpget | no | zero | zero | bpget | 0 | push |
| bpset | no | pop | zero | bpset | 0 | discard |
| add | no | pop | pop | math | 0 | push |
| sub | no | pop | pop | math | 1 | push |
| mul | no | pop | pop | math | 2 | push |
| div | no | pop | pop | math | 3 | push |
| mod | no | pop | pop | math | 4 | push |
| and | no | pop | pop | math | 5 | push |
| or | no | pop | pop | math | 6 | push |
| xor | no | pop | pop | math | 7 | push |
| not | no | pop | zero | math | 8 | push |
| rol | no | pop | pop | math | 9 | push |
| ror | no | pop | pop | math | 10 | push |
| asl | no | pop | pop | math | 11 | push |
| asr | no | pop | pop | math | 12 | push |
| shl | no | pop | pop | math | 13 | push |
| shr | no | pop | pop | math | 14 | push |