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hellerve 74e9c43403 updated readme for new version
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Veits Virtual Machine

A virtual machine that executes assembler-like code.

Performance

Performance is pretty okay on basic, small programs. The included factorial function takes 0.1 second on 100000 iterations. As a scale, a Python 3.3 program on the same machine using the code:

def fac(n): if n < 2: return 1 else: return n * fac(n-1) fac(12)

takes about 3.7 seconds on 100000 iterations.

This does not say anything about overall performance though and I am not sure whether this small, funny test has any real value in measuring performance. Also, Python is much more feature-rich, so you cannot compare the two at all.

DISCLAIMER: Parsing takes quite a long time, so try to write your programs as concise as possible.

Instruction set

Up until now, all the operations are executed on integers.

Operations overview:

  • ENTRY - Specifies an entry point for the routine by its index.

  • ADD - Adds the two items to each other that are on top of the stack and stores the result on top of the stack.

  • SUB - Subtracts the two items from each other that are on top of the stack and stores the result on top of the stack.

  • MULT - Multiplies the two items to each other that are on top of the stack and stores the result on top of the stack.

  • DIV - Performs a division operation to the two items that are on top of the stack and stores the result on top of the stack.

  • MOD - Performs a modulo operation to the two items that are on top of the stack and stores the result on top of the stack.

  • LT - Checks whether the item on top of the stack is greater than the item below it and stores a boolean on top of the stack.

  • EQ - Checks whether the item on top of the stack is equal to the item below it and stores a boolean on top of the stack.

  • GT - Checks whether the item on top of the stack is smaller than the item below it and stores a boolean on top of the stack.

  • LEQ - Checks whether the item on top of the stack is smaller than or equal to the item below it and stores a boolean on top of the stack.

  • GEQ - Checks whether the item on top of the stack is greater than or equal to the item below it and stores a boolean on top of the stack.

  • BR - Jumps to the instruction that is provided as an argument.

  • BRT - Jumps to the instruction that is provided as an argument if the value on top of the stack is TRUE.

  • BRF - Jumps to the instruction that is provided as an argument if the value on top of the stack is FALSE.

  • CONST - Puts the argument provided to the operation on top of the stack.

  • LOAD - Loads an element from any position on the stack on top of the stack(usually used to get function arguments like this: LOAD -3).

  • GLOAD - Loads an element from any position on the data segment on top of the stack.

  • STORE - Stores an element on the stack.

  • GSTORE - Stores an element in the data segment.

  • PRINT - Prints the element on top of the stack as character.

  • IPRINT - Prints the element on top of the stack as integer.

  • POP - Pops the element on top of the stack.

  • HALT - Ends the program.

  • CALL - calls a subroutine with a number of arguments.

  • RET - Returns from a subroutine with a return value.

  • FETCH - Fetches a value.

  • INC -Increments the value on top of the stack by one(equal to ++).

  • DEC -Decrements the value on top of the stack by one(equal to --).