Reason: Pascal calling convention with function parameters but no stack
frame. Theoretically we can __emit__() everything inside this function,
but there's no way we can get a `RETN 8` this way. Oh, and it also
accesses SI and DI without backing them up to the stack.
And thanks to TLINK apparently not reporting fixup overflows when
segments are small enough (?), it took quite a while to get that CALL
correct and not weirdly offset by 32 bytes. 😕
Part of P0134, funded by [Anonymous].
> assigning to the DI register immediately before a CALL
Yeah, no amount of comma operator trickery can get *that* out of this
compiler. Also, these TH05 .PI functions are the only place in PC-98
Touhou with a `IMUL DI, imm8` instruction, which is impossible to get
out of Turbo C++'s built-in assembler.
Well, at least the `if` branches decompile somewhat nicely.
Part of P0134, funded by [Anonymous].
Well, it *would* have been decompilable, but that ridiculous placement
of the nullptr assignment would have forced the entire function call to
be spelled out in inline ASM, verbatim. No amount of comma operator
trickery would have generated the same instructions either. And for a
function this small and obvious in what its decompilation *should* be,
it really defeated the purpose of adding a separate translation unit…
Part of P0134, funded by [Anonymous].
The TH02 version is a piece of cake…
… but TH04 starts turning it into this un-decompilable piece of
unnecessarily micro-optimized ZUN code. Couldn't have chosen anything
better for the first separate ASM translation unit.
Aside from now having to convert names of exported *variables* to
uppercase for visibility in ASM translation units, the most notable
lesson in this was the one about avoiding fixup overflows. From the
Borland C++ Version 4.0 User's Guide:
"In an assembly language program, a fixup overflow frequently
occurs if you have declared an external variable within a
segment definition, but this variable actually exists in a
different segment."
Can't be restated often enough.
Completes P0032, funded by zorg.
nmlgc