mirror of
https://github.com/bsnes-emu/bsnes.git
synced 2025-01-17 20:58:28 +01:00
c9f7c6c4be
byuu says:
I added some useful new functions to nall/primitives:
auto Natural<T>::integer() const -> Integer<T>;
auto Integer<T>::natural() const -> Natural<T>;
These let you cast between signed and unsigned representation without
having to care about the value of T (eg if you take a Natural<T> as a
template parameter.) So for instance when you're given an unsigned type
but it's supposed to be a sign-extended type (example: signed
multiplication), eg Natural<T> → Integer<T>, you can just say:
x = y.integer() * z.integer();
The TLCS900H core gained some more pesky instructions such as DAA, BS1F,
BS1B.
I stole an optimization from RACE for calculating the overflow flag on
addition. Assuming: z = x + y + c;
Before: ~(x ^ y) & (x ^ z) & signBit;
After: (x ^ z) & (y ^ z) & signBit;
Subtraction stays the same. Assuming: z = x - y - c;
Same: (x ^ y) & (x ^ z) & signBit;
However, taking a speed penalty, I've implemented the carry computation
in a way that doesn't require an extra bit.
Adding before:
uint9 z = x + y + c;
c = z & 0x100;
Subtracting before:
uint9 z = x - y - c;
c = z & 0x100;
Adding after:
uint8 z = x + y + c;
c = z < x || z == x && c;
Subtracting after:
uint8 z = x - y - c;
c = z > x || z == x && c;
I haven't been able to code golf the new carry computation to be any
shorter, unless I include an extra bit, eg for adding:
c = z < x + c;
But that defeats the entire point of the change. I want the computation
to work even when T is uintmax_t.
If anyone can come up with a faster method, please let me know.
Anyway ... I also had to split off INC and DEC because they compute
flags differently (word and long modes don't set flags at all, byte mode
doesn't set carry at all.)
I also added division by zero support, although I don't know if it's
actually hardware accurate. It's what other emulators do, though.
The unofficial higan repository
higan emulates a number of classic video-game consoles of the 1980s and 1990s, allowing you to play classic games on a modern general-purpose computer.
This repository includes the source-code for stable and WIP releases of higan, starting during the development of v068. It also includes community-maintained documentation.
Basically,
apart from .gitignore files,
anything in the
higan,
hiro,
icarus,
libco,
nall,
ruby,
or shaders
directories should be exactly as it appeared in official releases.
Everything else has been added for various reasons.
Official higan resources
Unofficial higan resources
- Unofficial forum
- Documentation for the current stable version
- Source code repository archives official higan releases and WIP snapshots since approximately v067r21
- Latest WIP build for Windows
- Documentation for the latest WIP version