# vim: set filetype=ruby:

# Multiplication: C = A * B, A >= 0 and B >= 0
register.A = 3
register.B = 7

# Save A in T
label(SaveA)  { decrement A, MoveS1, IncT }
label(IncT) { increment T, IncS1 }
label(IncS1) { increment S, SaveA }

label(MoveS1) { decrement S, SaveB, IncA1 }
label(IncA1) { increment A, MoveS1 }

# Save B in U
label(SaveB)  { decrement B, MoveS2, IncU }
label(IncU) { increment U, IncS2 }
label(IncS2) { increment S, SaveB }

label(MoveS2) { decrement S, Mul, IncB1 }
label(IncB1) { increment B, MoveS2 }

# Multiply A * B
label(Mul) { decrement A, MoveT, DecB }

# Add B to C
label(DecB) { decrement B, MoveU, IncC }
label(IncC) { increment C, DecB }

# Move U back to B
label(MoveU) { decrement U, SaveB, IncB2 }
label(IncB2) { increment B, MoveU }

# Move T back to A
label(MoveT) { decrement T, ClearU, IncA2 }
label(IncA2) { increment A, MoveT }

# Clear U
label(ClearU) { decrement U, Stop, ClearU }

# Stop
label(Stop)   { halt }