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GBA BIOS: Use custom ArcTan, not relying on OS

This commit is contained in:
Jeffrey Pfau 2016-08-13 14:10:51 -07:00
parent 7401371016
commit 6867400ca8
2 changed files with 50 additions and 1 deletions
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1
CHANGES
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@ -51,6 +51,7 @@ Misc:
- PSP2: Add fit-to-height screen mode
- GBA Video: Remove old slow path fallback
- GBA Video: Optimize sprite drawing
- GBA BIOS: Use custom ArcTan, not relying on OS
0.4.1: (2016-07-11)
Bugfixes:

50
src/gba/bios.c
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@ -265,6 +265,52 @@ static void _Div(struct GBA* gba, int32_t num, int32_t denom) {
}
}
static int16_t _ArcTan(int16_t i) {
int32_t a = -((i * i) >> 14);
int32_t b = ((0xA9 * a) >> 14) + 0x390;
b = ((b * a) >> 14) + 0x91C;
b = ((b * a) >> 14) + 0xFB6;
b = ((b * a) >> 14) + 0x16AA;
b = ((b * a) >> 14) + 0x2081;
b = ((b * a) >> 14) + 0x3651;
b = ((b * a) >> 14) + 0xA2F9;
return (i * b) >> 16;
}
static int16_t _ArcTan2(int16_t x, int16_t y) {
if (!y) {
if (x >= 0) {
return 0;
}
return 0x8000;
}
if (!x) {
if (y >= 0) {
return 0x4000;
}
return 0xC000;
}
if (y >= 0) {
if (x >= 0) {
if (x >= y) {
return _ArcTan((y << 14)/ x);
}
} else if (-x >= y) {
return _ArcTan((y << 14) / x) + 0x8000;
}
return 0x4000 - _ArcTan((x << 14) / y);
} else {
if (x <= 0) {
if (-x > -y) {
return _ArcTan((y << 14) / x) + 0x8000;
}
} else if (x >= -y) {
return _ArcTan((y << 14) / x) + 0x10000;
}
return 0xC000 - _ArcTan((x << 14 / y));
}
}
void GBASwi16(struct ARMCore* cpu, int immediate) {
struct GBA* gba = (struct GBA*) cpu->master;
mLOG(GBA_BIOS, DEBUG, "SWI: %02X r0: %08X r1: %08X r2: %08X r3: %08X",
@ -303,8 +349,10 @@ void GBASwi16(struct ARMCore* cpu, int immediate) {
case 0x8:
cpu->gprs[0] = sqrt((uint32_t) cpu->gprs[0]);
break;
case 0x9:
cpu->gprs[0] = _ArcTan(cpu->gprs[0]);
case 0xA:
cpu->gprs[0] = (uint16_t) (atan2f(cpu->gprs[1] / 16384.f, cpu->gprs[0] / 16384.f) / (2 * M_PI) * 0x10001);
cpu->gprs[0] = _ArcTan2(cpu->gprs[0], cpu->gprs[1]);
break;
case 0xB:
case 0xC: