goto-model

It is a model of some abstract assembly language. Key feature of the model is work with conditional jumps instead of structured approach.

Current model

There is a machine that operates using only n registers.

Each register contains a typed value. The types can be I (Natural numbers) or B (Boolean).

Allowed operations:

• I
  • Add r0 r1 r2 - r0 = r1 + r2
• B
  • And r0 r1 r2 - r0 = r1 & r2
  • Or r0 r1 r2 - r0 = r1 | r2

The language consists of the following instructions:

• exit - finishes the program execution
• <expr> - expression
• label_name: - puts a label label_name into the program
• jmp label_name; - unconditional jump to the label label_name
• condjmp label_name <cond>; - conditional jump to the label label_name. Condition may take the following forms (<const> - compile-time known constant value):
  • r ? <const> where ? is one of <, >, <=, >=, ==, !=

Specified model restrictions

• A program may have unreachable code due to logical implications. High-level example:

if (x > 10) {
  if (x < 10) {
    // unreachable code
  }
}

• A program does not provide certain conditions for condjmps.