mirror of https://github.com/bsnes-emu/bsnes.git
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.
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| .. | ||
| arithmetic | ||
| beat | ||
| cipher | ||
| database | ||
| decode | ||
| dsp | ||
| elliptic-curve | ||
| emulation | ||
| encode | ||
| hash | ||
| http | ||
| image | ||
| mac | ||
| macos | ||
| posix | ||
| string | ||
| vector | ||
| vfs | ||
| windows | ||
| xorg | ||
| GNUmakefile | ||
| adaptive-array.hpp | ||
| algorithm.hpp | ||
| any.hpp | ||
| arguments.hpp | ||
| arithmetic.hpp | ||
| array-span.hpp | ||
| array-view.hpp | ||
| array.hpp | ||
| atoi.hpp | ||
| bit-field.hpp | ||
| bit-vector.hpp | ||
| bit.hpp | ||
| chrono.hpp | ||
| counting-sort.hpp | ||
| directory.hpp | ||
| dl.hpp | ||
| endian.hpp | ||
| file-buffer.hpp | ||
| file-map.hpp | ||
| file.hpp | ||
| function.hpp | ||
| hashset.hpp | ||
| hid.hpp | ||
| image.hpp | ||
| induced-sort.hpp | ||
| inode.hpp | ||
| interpolation.hpp | ||
| intrinsics.hpp | ||
| iterator.hpp | ||
| locale.hpp | ||
| location.hpp | ||
| main.hpp | ||
| map.hpp | ||
| matrix.hpp | ||
| maybe.hpp | ||
| memory.hpp | ||
| merge-sort.hpp | ||
| nall.hpp | ||
| path.hpp | ||
| platform.hpp | ||
| pointer.hpp | ||
| primitives.hpp | ||
| property.hpp | ||
| queue.hpp | ||
| random.hpp | ||
| range.hpp | ||
| run.hpp | ||
| serial.hpp | ||
| serializer.hpp | ||
| service.hpp | ||
| set.hpp | ||
| shared-memory.hpp | ||
| shared-pointer.hpp | ||
| simd.hpp | ||
| smtp.hpp | ||
| stdint.hpp | ||
| string.hpp | ||
| suffix-array.hpp | ||
| terminal.hpp | ||
| thread.hpp | ||
| traits.hpp | ||
| unique-pointer.hpp | ||
| utility.hpp | ||
| varint.hpp | ||
| vector.hpp | ||
| vfs.hpp | ||
| view.hpp | ||