dingusppc/core/mathutils.h
joevt 6f0d3b48ba Fix TBR range
Fixed an issue where TBR doesn't have full 64-bit range. The original calculation was 64 bit and ended with a ÷ 10^9. This means the max for the upper 32 bits is 2^32/10^9 = 4. The solution is to use a multiplication method that supports a 96 bit product. core/mathutils.h contains functions for that. TBR driving frequency is assumed to be less than 1 GHz. Some minor modification is required for future > 1 GHz support.
2022-09-15 21:22:37 -07:00

50 lines
1.5 KiB
C

/*
DingusPPC - The Experimental PowerPC Macintosh emulator
Copyright (C) 2018-22 divingkatae and maximum
(theweirdo) spatium
(Contact divingkatae#1017 or powermax#2286 on Discord for more info)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef MATH_UTILS_H
#define MATH_UTILS_H
inline void _u32xu64(uint32_t a, uint64_t b, uint32_t &hi, uint64_t &lo)
{
uint64_t p0 = (b & 0xffffffff) * a;
uint64_t p1 = (b >> 32) * a;
lo = p0 + (p1 << 32);
hi = (p1 >> 32) + (lo < p0);
}
inline void _u32xu64(uint32_t a, uint64_t b, uint64_t &hi, uint32_t &lo)
{
uint64_t p0 = (b & 0xffffffff) * a;
uint64_t p1 = (b >> 32) * a;
lo = p0;
hi = (p0 >> 32) + p1;
}
inline void _u64xu64(uint64_t a, uint64_t b, uint64_t &hi, uint64_t &lo)
{
uint32_t p0h; uint64_t p0l; _u32xu64(b, a, p0h, p0l);
uint64_t p1h; uint32_t p1l; _u32xu64(b >> 32, a, p1h, p1l);
lo = p0l + ((uint64_t)p1l << 32);
hi = p0h + p1h + (lo < p0l);
}
#endif // MATH_UTILS_H