CarpVM

This is a project I've been slowly working on for about half a year now. The goal is to try and build a small (and decently reliable) VM from the ground up, learning more and more C as I go.

Right now there are instructions, registers, a stack, data memory, and the most basic of gotos.

Installation

1. make
2. make install

Use

NOTE: See carp -h for help with command-line options.

Interpreter

1. Write a Carp file - see SYNTAX.md. More formal spec coming.
2. Run ./carp.out -f your_file.carp.

API

1. Include carp/carp.h in your program.
2. Run gcc program.c /usr/local/lib/libcarp.a -o program.out.

Instruction set

Defined as such: NAME (args): Description

• HALT (code): Halts and attempts to clean up stack, data memory, and label memory before exiting with given exit code.
• NOP (): Does nothing. Seriously.
• LOAD (reg, val): Loads given integer value into given register.
• MOV (dst, src): Copies contents of src register into dst register.
• ADD (): Pops the top two integers from the stack and pushes their sum.
• SUB (): Pops the top two integers from the stack and pushes the difference (lower minus upper).
• MUL (): Pops the top two integers from the stack and pushes their product.
• MOD (rega, regb): Computes rega % regb and stores in ERX.
• NOT (reg): Computes bitwise NOT of reg and stores in reg.
• XOR (): Pops the top two integers from the stack and XORs them.
• OR (): Pops the top two integers from the stack and ORs them.
• AND (): Pops the top two integers from the stack and ANDs them.
• INCR (reg): Increments value in given register.
• DECR (reg): Decrements value in given register.
• INC (): Increments the value at the top of the stack.
• DEC (): Decrements the value at the top of the stack.
• PUSHR (reg): Pushes value in given register.
• PUSH (val): Pushes given value.
• POP (val): Pops an integer from the stack and dumps it into GBG.
• CMP (): Pops the top two integers from the stack and checks if equal. 0 means equal. Result will be pushed onto the stack.
• MOV (rega, regb): Move value in rega to regb.
• JZ (addr): Jumps to given absolute address if top of the stack is 0.
• RJZ (diff): Adds differential to current EIP (relative jump) if top of the stack is 0.
• JNZ (addr): Jumps to given absolute address if top of the stack is not 0.
• RJNZ (diff): Adds differential to current EIP (relative jump) if top of the stack is not 0.
• JMP (addr): Jumps to given absolute address.
• RJMP (diff): Adds differential to current EIP (relative jump).
• DBS (key, val): Sets data memory at key (string pointer) to given value.
• DBG (key, reg): Gets value from data memory at key (string pointer) and dumps it into given register.
• CALL (key, nargs): Save state and set EIP to value in data memory at key.
• RET (val): Push return value and load state.
• PREG (reg): Prints contents of given register.
• PTOP (): Peeks top of stack and prints top value.

Registers

• REG0 ... REG9: General purpose.
• EAX, EBX, ECX, EDX: Used for ... something in the future. Just taking up space for now.
• ERX: Used for remainder/mod.
• EIP: Instruction pointer. Used for keeping place in code, gotos, calling, etc.
• ESP: Stack pointer. Not currently in use; stack implementation is separate.
• GBG: Garbage register mainly used for popping.

How to contribute

One way:

1. Check out the TODO.md file to see if anything needs doing.
2. Write some code (following existing implicit style) and submit a pull request.

Another way:

1. Write some code for a feature you want to exist and submit a pull request.

License

GPLv3. See LICENSE.txt.

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