No subf surprise here
Remember how integer subtraction uses subf and reverses its operands? The floating-point unit has a real fsubs that computes fD = fA - fB in natural order:
fsubs f1, f1, f2 # f1 = a - b
blr
Destination, then operands left-to-right, exactly as in C. The floating-point instruction set is generally more regular than the integer one — one fewer idiom to memorize.
Your task
Write func_80189700 to compile to the fsubs above.