Reason: Saving SI and DI on the stack way too late. Just because ZUN
absolutely *had* to move the clipping condition before these two PUSH
instructions… Was it really necessary to save a total of 4 instructions
for an unlikely worst case in a function that's maybe called like 10-20
times per frame *at worst*?
Part of P0192, funded by [Anonymous], nrook, and -Tom-.
motion_t is also used for certain animations in MAINE.EXE, so not all
instances refer to entities in playfield space. Explicitly specifying
the latter now allows us to gain…
Part of P0149, funded by Blue Bolt, Ember2528, and -Tom-.
Well, we *could* pointlessly decompile this function into an unreadable
mess, but only if we throw away the semantics of the return value, and
replace its type with `void` or `uint32_t`.
(Turbo C++ can't cast registers to a struct value, and adding a
constructor to SPPoint would break everything else, if it even works.)
ZUN's original usage code doesn't care either way, because it only ever
accesses the returned value directly through DX:AX.
Part of P0148, funded by [Anonymous].
Adding op/, main/, and end/ directories does nicely cover a great
majority of the "not really further classifiable slices" implied in
d56bd45.
Part of P0086, funded by [Anonymous] and Blue Bolt.
nmlgc