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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