So, we have a problem. The ridiculously optimized graph_putsa_fx() used
in TH04 and TH05 swaps out the target of two CALL instructions at
run-time… because there *really* wasn't any free register left for an
indirect CALL, eh? Therefore, the necessary relative addresses have to
be calculated at assembly time, by subtracting the target function
label from the call site label.
Unfortunately, the resulting values are stored in the .DATA segment,
which we can't move out right now. Declaring the labels as EXTERN
wouldn't work either, since the linker can't do fancy arithmetic and is
limited to simply replacing address placeholders with one single
address. This is explained pretty well at:
http://computer-programming-forum.com/46-asm/48f3d4a463bb38d1.htm
Which means we're stuck, and can't separate out this function for the
foreseeable future.
So, time to approach the SHARED segment from the top instead, to at
least get everything around graph_putsa_fx() done now. 🤷
vram_planes_set() is the first common function there. But since it was
introduced in TH01, we've got some maintenance to do for that game
first…
Part of P0138, funded by [Anonymous] and Blue Bolt.
Whoops, turns out that the build has been broken on TASM32 version 5.3
(the one in the DevKit) ever since 7897bf1. In contrast to version 5.0
(which I use for my development), 5.3 actually defines 32-bit segments
if you specify a .386 CPU before using .MODEL.
That might have been the reason for the .286 workaround all along?
Turns out there's the USE16 modifier, which makes this much more
explicit than switching CPUs.
Since I'd still prefer to not use include guards *and* to have that
standalone .GRZ viewer, these would have actually caused somewhat of
an issue with the upcoming final stretch of the master.hpp transition.
Part of P0133, funded by [Anonymous].
Which gets rid of 13 redundant translation units. Definitely a good
start, before I figure out how to best handle the more complicated
cases.
(Maintenance mode commit)
And get rid of the constraining FX() macro, with its spacing parameter
that we haven't even seen used so far.
Part of P0124, funded by [Anonymous] and Blue Bolt.
By now, it's become obvious where it has to be. Apparently, the order
of translation units inside ZUN's modified master.lib did somehow
change with TH02?
(Maintenance mode commit)
ZUN might have gotten the impression that the EGC can *only* work with
multiples of 16 pixels per load or store? Which might explain why…
Part of P0102, funded by Yanga.
100% PI for both! Now, where are all the modders who wanted to replace
MDRV2 with PMD… because you can now prototype that, without worring
about x86 instruction lengths, at least inside the main menu.
Part of P0095, funded by Yanga.
> "Sure, this is a PI push, but this second-to-last set of PI false
positives so small, let's immediately decompile it ^.^"
> Time taken: 22 minutes
Nice when this works out!
Part of P0095, funded by Yanga.
Starting with the odd one out, the one that doesn't use master.lib and
has two input sense functions: one for the main menu, and one for the
option window.
Both of which also immediately perform the ring arithmetic on the menu
cursor variable… because there's nothing else to be done with these
inputs in OP.EXE? Separating input sensing from processing apparently
wasn't all too obvious of a thought, and it's only truly done in TH02
and later.
Part of P0090, funded by Yanga.
That's… pretty specific. The only thing on the main menu with this
color is the "1996 ZUN" text at the bottom… probably part of an
effect that we never got to see. Every other idea would be baseless
speculation, given that the snapped buffer isn't used anywhere else.
Part of P0090, funded by Yanga.
Also something that any future ReC project should be doing right at the
start. Finally, it made sense to do it here as well, because…
Part of P0084, funded by Yanga.
Which repurpose the .PTN image slots to store the background of
frequently updated VRAM sections, like all the numbers in the HUD.
Future games would simply use the text RAM and gaiji for numbers. Which
would have worked just fine for TH01 as well (especially since all the
functions we've seen so far are aligned to the 8-pixel byte grid), but
it looks as if ZUN simply wasn't aware of gaiji during the development
of TH01.
Part of P0083, funded by Yanga.
Mangled C++ function names would *not* have been a mistake if I hadn't
made the other mistake of restricting parts of the code to C…
Part of P0083, funded by Yanga.
All the weird double returns in FUUIN.EXE just magically appear with
-O-! 😮
And yeah, it's a bowl of global state spaghetti once again. 🍝 Named
the functions in a way that would make sense to a user of the API, who
should be aware of typical side effects, like, y'know, a changed
hardware palette… That's how you end up with the supposed "main"
function getting a "_palette_show" suffix.
Completes P0082, funded by Ember2528.
Since we not only have the .PTN sub-image count array in the middle of
all those .GRP flags, but the .PTN loading code also reusing the
palette set flag…
Part of P0082, funded by Ember2528.
Yet another run-length encoded graphics format, this one being
exclusively used to wastefully store Konngara's sword slash and kuji-in
kill "animation".
But for once, the terrible code generated by inline functions with
non-literal parameters perfectly matches what ZUN wrote here.
Part of P0081, funded by Ember2528.
Just like with the z_text_*() functions, master.lib doesn't already
have graph_init() and graph_exit() either, and once again, ZUN's code
here doesn't fully correspond to any master.lib function. Unlike the
z_text_*() functions though, those names aren't really the best
descriptions for these rather random combinations of BIOS calls and I/O
port writes…
Anyway, that's the entire segment!
Part of P0080, funded by Ember2528 and Splashman.
No macros for the port numbers here! Anyone who will try to read and
understand this code will probably want to look those up in PC-98
hardware documentation, and macros would just be an annoying layer of
indirection then.
Part of P0080, funded by Ember2528 and Splashman.
Page… 2? On a system with only page 0 and 1? Had to get out my real
PC-98 to double-check that I wasn't missing anything here, since
every emulator only looks at the bottom bit of the page number. But
real hardware seems to do the same, and there really is nothing special
to it semantically, being equivalent to page 0. 🤷
Part of P0080, funded by Ember2528 and Splashman.
And with all possible .COM executables decompiled, this set of changes
reaches an acceptable scope, allowing us to *finally*…
Part of P0077, funded by Splashman and -Tom-.
In which our typedefs mercilessly reveal ZUN's original sloppiness, and
the unncessary sign extension taking place here. Also, ❎ unused…
Completes P0069, funded by [Anonymous] and Yanga.
Yes, when clipping the start and end points to the screen area, ZUN
uses an integer division to calculate the line slopes, rather than a
floating-point one. Doesn't seem like it actually causes any incorrect
lines to be drawn, though; that case is only hit in the Mima boss
fight, which draws a few lines with a bottom coordinate of 400 rather
than 399. It *might* also restore the wrong pixels at parts of the
YuugenMagan fight, causing weird flickering, but seriously, that's an
issue everywhere you look in this game.
Part of P0069, funded by [Anonymous] and Yanga.
TH01's (original) version also replicates the PC-98 text RAM's reverse
and underline attributes. Which was removed in later games,
interestingly and inconsistently enough.
Part of P0068, funded by Yanga.
Including the longest function present in more than one game among all
of PC-98 Touhou, and #23 on the list of longest functions overall,
which draws a 1-pixel line between two arbitrary pixels.
Completes P0067, funded by Splashman.
Semi-unused, that is, the one use of this function doesn't actually
move the rectangle to a different position. Ironically, the non-moving
back-to-front function immediately above *is* unused…
Also, too bad that stack order is the only reason we can't use structs
to combine all plane variables into a single object.
Part of P0067, funded by Splashman.
Previously sloppily mis-RE'd as "some page variable, idk", back in
2015…
Now also with a page number typedef. And yeah, restricting bool to C++
has now proven to be stupid after all.
Part of P0067, funded by Splashman.
Which store colors as GRB, as suggested by the structure's ID string.
Even master.lib's own functions add an additional XCHG AH, AL
instruction to get colors into and out of this format. MASTER.MAN
suggests that it's some sort of standard on PC-98. It does match the
order of ths hardware's palette register ports, after all.
(0AAh = green, 0ACh = red, 0AEh = blue)
Now we also know why __seg* wasn't used more commonly, as lamented in
c8e8e98. Turbo C++ simply doesn't support a lot of arithmetic on
segment pointers.
And then that undecompilable far call to a function within the same
segment, but inside a different translation unit…
Also, thanks again to Egor for the SCOPY@ hack that debuted in 0460072.
Would have probably struggled with this a lot more without that.
And *then* you realize that TH01 effectively doesn't even use the
resident palette. 😐
And yes, we're procrastinating the whole issue of potentially using
a single translation unit for all three binaries by using a common
segment name, because it *really* isn't that easy.
Completes P0066, funded by Keyblade Wiedling Neko and Splashman.
The TH04/TH05 BGM/SE mode setup is a good example for code where
different structure field offsets will vanish completely upon reverse-
engineering. If we continued to use the per-game ID string as the
variable name, we'd only have another game-specific "difference" there.
Part of P0065, funded by Touhou Patch Center.
Waiting with the `fx` parameter in TH01's calls for the decompilation
of this game's version of this function…
Part of P0062, funded by Touhou Patch Center.
nmlgc