Yet Another Virtual Machine - Comparison Instructions

OPCODE: 11101

• If the flag has operand is set:
  • read two times X byte(s) following the instruction
  • increment the value of the IP register by 2 * X
• Else:
  • read two times X byte(s) at the address SB + SP - 2 * X
  • decrement the value of the SP register by 2 * X
• if value1 is less than value2:
  • write the byte -1 at the address SB + SP where
• if value1 is greater than value2:
  • write the byte 1 at the address SB + SP where
• if value1 is equal to value2:
  • write the byte 0 at the address SB + SP where
SB is the address of the stack base, and SP the stack pointer register
• increment the value of the SP register by X

Instruction	Value for X
CMP8	1
CMP16	2
CMP32	4
CMP64	8

CMP8 4 5
CMP8 5 4
CMP8 5 5

⇩

CMP8 (1 11101 00)	4	5
CMP8 (1 11101 00)	5	4
CMP8 (1 11101 00)	5	5

⇩

STACK HEAD (SP = 3)
0
1
-1
STACK BASE