PS math accuracy (#654)

* math accuracy

* submodule

* Update aurora

---------

Co-authored-by: Luke Street <luke@street.dev>
This commit is contained in:
qwertyquerty
2026-05-06 20:22:59 -07:00
committed by GitHub
parent 7c7c8b228e
commit 9aee2e9cfe
3 changed files with 4 additions and 138 deletions
+1 -1
+2
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@@ -1,5 +1,7 @@
#pragma once
#include <array>
struct RoomEntry {
u8 roomNo;
std::vector<s16> roomPoints = {};
+1 -137
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@@ -2,9 +2,6 @@
#define _SRC_DUSK_MATH_H_
#include <cmath>
#include <array>
#include <limits>
#include <bit>
#ifndef M_PI
#define M_PI 3.14159265358979323846f
@@ -19,139 +16,6 @@ inline float i_cosf(float x) { return cos(x); }
inline float i_tanf(float x) { return tan(x); }
inline float i_acosf(float x) { return acos(x); }
// frsqrte matching courtesy of Geotale, with reference to https://achurch.org/cpu-tests/ppc750cl.s
struct BaseAndDec32 {
uint32_t base;
int32_t dec;
};
struct BaseAndDec64 {
uint64_t base;
int64_t dec;
};
union c32 {
constexpr c32(const float p) {
f = p;
}
constexpr c32(const uint32_t p) {
u = p;
}
uint32_t u;
float f;
};
union c64 {
constexpr c64(const double p) {
f = p;
}
constexpr c64(const uint64_t p) {
u = p;
}
uint64_t u;
double f;
};
static constexpr uint64_t EXPONENT_SHIFT_F64 = 52;
static constexpr uint64_t MANTISSA_MASK_F64 = 0x000fffffffffffffULL;
static constexpr uint64_t EXPONENT_MASK_F64 = 0x7ff0000000000000ULL;
static constexpr uint64_t SIGN_MASK_F64 = 0x8000000000000000ULL;
static constexpr std::array<BaseAndDec64, 32> RSQRTE_TABLE = {{
{0x69fa000000000ULL, -0x15a0000000LL},
{0x5f2e000000000ULL, -0x13cc000000LL},
{0x554a000000000ULL, -0x1234000000LL},
{0x4c30000000000ULL, -0x10d4000000LL},
{0x43c8000000000ULL, -0x0f9c000000LL},
{0x3bfc000000000ULL, -0x0e88000000LL},
{0x34b8000000000ULL, -0x0d94000000LL},
{0x2df0000000000ULL, -0x0cb8000000LL},
{0x2794000000000ULL, -0x0bf0000000LL},
{0x219c000000000ULL, -0x0b40000000LL},
{0x1bfc000000000ULL, -0x0aa0000000LL},
{0x16ae000000000ULL, -0x0a0c000000LL},
{0x11a8000000000ULL, -0x0984000000LL},
{0x0ce6000000000ULL, -0x090c000000LL},
{0x0862000000000ULL, -0x0898000000LL},
{0x0416000000000ULL, -0x082c000000LL},
{0xffe8000000000ULL, -0x1e90000000LL},
{0xf0a4000000000ULL, -0x1c00000000LL},
{0xe2a8000000000ULL, -0x19c0000000LL},
{0xd5c8000000000ULL, -0x17c8000000LL},
{0xc9e4000000000ULL, -0x1610000000LL},
{0xbedc000000000ULL, -0x1490000000LL},
{0xb498000000000ULL, -0x1330000000LL},
{0xab00000000000ULL, -0x11f8000000LL},
{0xa204000000000ULL, -0x10e8000000LL},
{0x9994000000000ULL, -0x0fe8000000LL},
{0x91a0000000000ULL, -0x0f08000000LL},
{0x8a1c000000000ULL, -0x0e38000000LL},
{0x8304000000000ULL, -0x0d78000000LL},
{0x7c48000000000ULL, -0x0cc8000000LL},
{0x75e4000000000ULL, -0x0c28000000LL},
{0x6fd0000000000ULL, -0x0b98000000LL},
}};
[[nodiscard]] static inline double frsqrte(const double val) {
c64 bits(val);
uint64_t mantissa = bits.u & MANTISSA_MASK_F64;
int64_t exponent = bits.u & EXPONENT_MASK_F64;
bool sign = (bits.u & SIGN_MASK_F64) != 0;
// Handle 0 case
if (mantissa == 0 && exponent == 0) {
return std::copysign(std::numeric_limits<double>::infinity(), bits.f);
}
// Handle NaN-like
if (exponent == EXPONENT_MASK_F64) {
if (mantissa == 0) {
return sign ? std::numeric_limits<double>::quiet_NaN() : 0.0;
}
return val;
}
// Handle negative inputs
if (sign) {
return std::numeric_limits<double>::quiet_NaN();
}
if (exponent == 0) {
// Shift so one bit goes to where the exponent would be,
// then clear that bit to mimic a not-subnormal number!
// Aka, if there are 12 leading zeroes, shift left once
uint32_t shift = std::countl_zero(mantissa) - static_cast<uint32_t>(63 - EXPONENT_SHIFT_F64);
mantissa <<= shift;
mantissa &= MANTISSA_MASK_F64;
// The shift is subtracted by 1 because denormals by default
// are offset by 1 (exponent 0 doesn't have implied 1 bit)
exponent -= static_cast<int64_t>(shift - 1) << EXPONENT_SHIFT_F64;
}
// In reality this doesn't get the full exponent -- Only the least significant bit
// Only that's needed because square roots of higher exponent bits simply multiply the
// result by 2!!
uint32_t key = static_cast<uint32_t>((static_cast<uint64_t>(exponent) | mantissa) >> 37);
uint64_t new_exp =
(static_cast<uint64_t>((0xbfcLL << EXPONENT_SHIFT_F64) - exponent) >> 1) & EXPONENT_MASK_F64;
// Remove the bits relating to anything higher than the LSB of the exponent
const auto &entry = RSQRTE_TABLE[0x1f & (key >> 11)];
// The result is given by an estimate then an adjustment based on the original
// key that was computed
uint64_t new_mantissa = static_cast<uint64_t>(entry.base + entry.dec * static_cast<int64_t>(key & 0x7ff));
return c64(new_exp | new_mantissa).f;
}
#include <dolphin/ppc_math.h>
#endif // _SRC_DUSK_MATH_H_