* addHL and subHL affect flags, and are smaller
Most importantly, addHL and subHL now affect the flags as you would expect from a 16 bit addition/subtraction. This seems like it'd be preferred behaviour, however I realise any code relying on it not affecting flags would break. One byte saved in addHL, and two bytes saved in subHL. Due to the branching nature of the original code, it's difficult to compare speeds, subHL is either 1 or 6 cycles faster depending on branching, and addHL is between -1 and 3 cycles faster. If the chance of a carry is 50%, addHL is expected to be a cycle faster, but for a chance of carry below 25% (so a < 0x40) this will be up to a cycle slower.
* Update core.asm
* Reworked one use of addHL
By essentially inlining both addHL and cpHLDE, 100 cycles are saved, but due to the registers not needing preserving, a byte is saved too.
* Corrected spelling error in comment
* Reworked second use of addHL
43 cycles saved, and no more addHL in critical loops. No bytes saved or used.
* Fixed tabs and spacing, and made a comment clearer.
* Clearer comments
* Adopted push/pop notation
Pretty major improvements to both of these, cpHLDE is now 5 bytes shorter and between 9 and 12 cycles faster due to branching, and writeHLinDE is now 2 bytes shorter and 21 cycles faster.
* Optimised intoXX functions
Rewrote intoXX functions to mainly rely on intoHL, as the HL instructions are smaller and faster. Also removed some redundant push and pop instructions. I edited the given unit tests to test these, and they seem to work as expected.
* Doesn't use self-modifying code
The number of bytes is the same as my previous attempt, with 11 more cycles in intoHL, so although I don't feel as clever this time it's still a good optimisation. I found an equivalent method for intoDE, however relying on intoHL still allows for `ex (sp), hl` to be used in intoIX, which is smaller and faster.
* Update core.asm
* Tried harder to follow coding convention
Added tabs between mnemonics and operands, and replaced a new line I accidentally removed.
Sure, it's a bit slower, but it prevents a lot of hard to debug
problems. I don't have to want to remember "don't use IX if you
have any blk* calls". Let's optimize I/O later.
When there's a mismatch, retry up to a certain number of times.
This makes random problem related to assembling big kernels go away! But
it also make SD card reading much slower...
For now, this achieves nothing else than wasting cycles, but this is the
first step in enabling CRC verifications (CMD59).
I think that this is where my random problems with assembling large
kernels from SDC come from: bad data that isn't detected. If that
happens when PGM loads programs in memory, then anything can happen.
`sdct`, when ran often enough, will error out or corrupt away (go
crazy)...
That was an interesting bug. It didn't cause a problem in emulation, but
in an RC2014 on an SD card, an include that didn't end with two newlines
would cause an infinite loop.
Needed if we want to compile the kernel and zasm from within a SD card.
I didn't go straight for 32-bit because it was significantly more
complex and 24-bit give us 16M. Enough to go on for a while...
A new app to stress test the SD card driver. Also, accompanying this
commit, changes solidifying the SD card driver so that stress tests
actually pass :)
With fsGetC becoming a "random address" API, it broke pgm. This commit
fixes it. To avoid adding the weight of a blkdev in pgm, I manage the
read offset directly in pgm.
This huge refactoring remove the Seek and Tell routine from blockdev
implementation requirements and change GetC and PutC's API so that they
take an address to read and write (through HL/DE) at each call.
The "PTR" approach in blockdev implementation was very redundant from
device to device and it made more sense to generalize. It's possible
that future device aren't "random access", but we'll be able to add more
device types later.
Another important change in this commit is that the "blockdev handle" is
now opaque. Previously, consumers of the API would happily call routines
directly from one of the 4 offsets. We can't do that any more. This
makes the API more solid for future improvements.
This change forced me to change a lot of things in fs, but overall,
things are now simpler. No more `FS_PTR`: the "device handle" now holds
the active pointer.
Lots, lots of changes, but it also feels a lot cleaner and solid.
The ability to specify "0" routines in blkdev table is not used anymore
now that stdio is a separate subsystem.
Also, I'm preparing a blockdev refactoring and this complicates my work.
Move load/save to blkdev_cmds and add a new "poke" builtin shell cmd
that is the mirror of "peek" and strictly uses stdio (no blkdev
involved).
This allows us to slim the minimal OS size but, more importantly, change
the behavior of "load" so that we don't expect GetC to block until Z is
set. This way, using "load X" with X being larger than the blkdev size
won't block forever.
This also brings our RC2014 minimal kernel below the 1K mark again.
The pgm module implements a shell hook so that when an unknown command
is typed, we look into the mounted filesystem and look for a file with
the same name as the command. If we find one, we load it in memory and
run it.
It would previously only work when GetC-ing our way into a new sector.
Seeking into one would not work. Now it's much more robust and this
paves the way for write support.
This allows us to break through the 64K limit for includes CFS in zasm,
a limit we were dangerously close to breaking. In fact, this commit
makes us go over that limit. Right in time!
It was a bad idea to remove it. Now that I'm introducing the concept of
a per-app glue file, it becomes much easier to build emulated zasm as a
userspace app.
