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About the developer

tekknolagi
977 Stars 83 Forks GNU General Public License v3.0 473 Commits 6 Opened issues

Description

"interesting" VM in C. Let's see how this goes.

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THIS PROJECT IS UNSTABLE AND DEPRECATED

I have since started slow work on a more stable, better thought-out project called RabbitVM. It doesn't quite have the same level of documentation but it should work much better.

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 calls. Not sure if recursion works... it should in theory. Haven't tested.

CONSIDER THIS PRE-ALPHA SOFTWARE. Things change more than they do in Rust!

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Installation

Getting Carp

If you already have a local copy (cloned before submodule was added)

  • git fetch
  • git rebase
  • git submodule init
  • git submodule update

If you don't already have a local copy

  • git clone --recursive

NOTE: If

git submodule status
doesn't return a SHA1 hash and repository name, you have a problem. NOTE: Recursive clone is for testing library. If not included, tests will not build.

Building Carp

  1. make
  2. make test
    (optional)
  3. make install
  4. make clean
    (optional)

Tested Machines

Arch (bit)

OS (with version, name) Compiler (with version)
64-bit Ubuntu 12.04 (precise) gcc 4.6.3
64-bit Ubuntu 14.04 (trusty) gcc 4.8.2
32-bit Ubuntu 14.04 (trusty) gcc 4.8.2
64-bit OS X 10.9.4 (Mavericks) clang 3.2
32-bit OS X 10.9.4 (Mavericks) gcc 4.2.1
64-bit Arch Linux 3.13.6-1 clang 3.4.2
64-bit? Arch Linux 3.13.6-1 gcc 4.9.0 20140604

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

Instruction set

Opcode

Arguments Description
HALT exit code Sets

ext
to given code, halts, and attempts to clean up stack, data memory, and label memory.
NOP Does nothing. Seriously.
LOADR reg, val Loads given integer value into given register.
LOAD diff Loads value at location
fp
+ diff in the stack.
STORE diff, val Stores value at location
fp
+ diff.
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 Pops the top two integers from the stack and pushes lower % upper.
SHR Pops the top two integers from the stack and pushes lower >> upper.
SHL Pops the top two integers from the stack and pushes lower << upper.
NOT Pops top integer from stack and pushes bitwise NOT of that integer.
XOR Pops the top two integers from the stack and pushes bitwise XOR..
OR Pops the top two integers from the stack and pushes bitwise OR.
AND Pops the top two integers from the stack and pushes bitwise AND.
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 reg Pops an integer from the stack and dumps it into given register.
CMP Pops the top two integers from the stack and checks if equal. 0 means equal. Pushes result.
LT Pops the top two integers from the stack and checks if lower < upper. Pushes result.
GT Pops the top two integers from the stack and checks if lower > upper. Pushes result.
JZ addr Jumps to given absolute address if top of the stack is 0.
RJZ diff Adds differential to
ip
(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
ip
(relative jump) if top of the stack is not 0.
JMP addr Jumps to given absolute address unconditionally.
RJMP diff Adds differential to
ip
(relative jump) unconditionally.
CALL key/addr Save state and set IP to value in data memory at key. Function may return value in
ax
.
RET Put top of the stack into
ax
and load previous state.
PREG reg Prints contents of given register.
PTOP Peeks top of stack and prints top value.

Registers

Name

Purpose

r0
...
r9
| General purpose.
ax
| Return value for user-defined function.
bx
,
cx
,
dx
,
rx
| ... something in the future. Just taking up space for now.
ip
| Instruction pointer. Used for keeping place in code, gotos, calling, etc.
sp
| Stack pointer.
fp
| Frame pointer. Used to keep state for function calls.
gbg
| Garbage register mainly used for popping.
run
| Boolean - is machine running?
ext
| Exit code.

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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