VNVM

Tiny Von Neumann VM with custom assembly

Registers:

• r0-r9 - general purpose
• sp - StackPointer
• lr - LinkRegister (return address)
• pc - ProcessCounter (current instruction)

"Headers"

• .stack (n) - size of a stack, allocated when program image is loaded
• .entry (label) - entry point
• .ascii "(some str)" - static const string
• .number #some_n - static const integer
• (label): - label

Instruction

• mov (reg), (reg/#some_n) - move from -> to
• push { (reg/reg1, reg2/reg1 - reg2) } - push register/pair of registers/all registers in segment to stack
• pop { (reg/reg1, reg2/reg1 - reg2) } - pop register/pair of registers/all registers in segment from stack
• add (reg), (reg/$some_n) - addition (+=)
• sub (reg), (reg/$some_n) - subtraction (-=)
• inc (reg) - increment
• dec (reg) - decrement
• cmp (regA), (regB/#some_n) - compare, write value to r0: 0 - regA==regB, >0 - regA > regB, <0 - regA < regB
• jeq (label) - jump to label if r0 == 0
• bl (label) - call label (write return address and jump)
• printf - print zero-terminated string with address [r0]
• printn - print number stored in r0
• scann - read number to r0

Additional comments

In case if pc == 0, the program is in terminal state, the execution is finished

VNVM/VNAsm/VNDasm tools

VNVM - Virtual Machine with pseudo-debugger

Starting VM

./VNVM #Start VM
./VNVM <binary file> #Load program image and start VM

VM Commands

• run - begin the execution of loaded image of a program to the terminal state
• load <path (.bin)> - load an image from binary file
• step - one step of execution
• regs - print register values
• stack - show last n values on stack
• dump <path (.bin)> - save current VM image to binary file
• exit - leave VM

VNAsm - assembly translator

./VNAsm <assembly (.vn) path> #translate to binary file <assembly path>.bin
./VNAsm <assembly (.vn) path> <image (.bin) path> #Translate to bin image

VNDasm - disassembly translator

./VNDasm <image (.bin) path> #Translate to assembly language <image path>.vn
./VNDasm <image (.bin) path> <assembly (.vn) path> #Translate to assembly