drc: add a timing hack for Internal Section

[pcsx_rearmed.git] / libpcsxcore / gte_divider.c

/*
 * PlayStation Geometry Transformation Engine emulator
 *
 * Originally written by smf for MAME
 * Imported to PCSX with just some cosmetic changes
 *
 * Copyright 2003-2013 smf
 *
 * Licensed under the BSD-3-Clause
 */

#include "gte.h"
#include "gte_divider.h"

static const u8 table[] =
{
	0xff, 0xfd, 0xfb, 0xf9, 0xf7, 0xf5, 0xf3, 0xf1, 0xef, 0xee, 0xec, 0xea, 0xe8, 0xe6, 0xe4, 0xe3,
	0xe1, 0xdf, 0xdd, 0xdc, 0xda, 0xd8, 0xd6, 0xd5, 0xd3, 0xd1, 0xd0, 0xce, 0xcd, 0xcb, 0xc9, 0xc8,
	0xc6, 0xc5, 0xc3, 0xc1, 0xc0, 0xbe, 0xbd, 0xbb, 0xba, 0xb8, 0xb7, 0xb5, 0xb4, 0xb2, 0xb1, 0xb0,
	0xae, 0xad, 0xab, 0xaa, 0xa9, 0xa7, 0xa6, 0xa4, 0xa3, 0xa2, 0xa0, 0x9f, 0x9e, 0x9c, 0x9b, 0x9a,
	0x99, 0x97, 0x96, 0x95, 0x94, 0x92, 0x91, 0x90, 0x8f, 0x8d, 0x8c, 0x8b, 0x8a, 0x89, 0x87, 0x86,
	0x85, 0x84, 0x83, 0x82, 0x81, 0x7f, 0x7e, 0x7d, 0x7c, 0x7b, 0x7a, 0x79, 0x78, 0x77, 0x75, 0x74,
	0x73, 0x72, 0x71, 0x70, 0x6f, 0x6e, 0x6d, 0x6c, 0x6b, 0x6a, 0x69, 0x68, 0x67, 0x66, 0x65, 0x64,
	0x63, 0x62, 0x61, 0x60, 0x5f, 0x5e, 0x5d, 0x5d, 0x5c, 0x5b, 0x5a, 0x59, 0x58, 0x57, 0x56, 0x55,
	0x54, 0x53, 0x53, 0x52, 0x51, 0x50, 0x4f, 0x4e, 0x4d, 0x4d, 0x4c, 0x4b, 0x4a, 0x49, 0x48, 0x48,
	0x47, 0x46, 0x45, 0x44, 0x43, 0x43, 0x42, 0x41, 0x40, 0x3f, 0x3f, 0x3e, 0x3d, 0x3c, 0x3c, 0x3b,
	0x3a, 0x39, 0x39, 0x38, 0x37, 0x36, 0x36, 0x35, 0x34, 0x33, 0x33, 0x32, 0x31, 0x31, 0x30, 0x2f,
	0x2e, 0x2e, 0x2d, 0x2c, 0x2c, 0x2b, 0x2a, 0x2a, 0x29, 0x28, 0x28, 0x27, 0x26, 0x26, 0x25, 0x24,
	0x24, 0x23, 0x22, 0x22, 0x21, 0x20, 0x20, 0x1f, 0x1e, 0x1e, 0x1d, 0x1d, 0x1c, 0x1b, 0x1b, 0x1a,
	0x19, 0x19, 0x18, 0x18, 0x17, 0x16, 0x16, 0x15, 0x15, 0x14, 0x14, 0x13, 0x12, 0x12, 0x11, 0x11,
	0x10, 0x0f, 0x0f, 0x0e, 0x0e, 0x0d, 0x0d, 0x0c, 0x0c, 0x0b, 0x0a, 0x0a, 0x09, 0x09, 0x08, 0x08,
	0x07, 0x07, 0x06, 0x06, 0x05, 0x05, 0x04, 0x04, 0x03, 0x03, 0x02, 0x02, 0x01, 0x01, 0x00, 0x00,
	0x00
};

u32 DIVIDE(u16 numerator, u16 denominator)
{
	if (numerator < (denominator * 2)) {
		int shift = __builtin_clz(denominator) - 16;

		int r1 = (denominator << shift) & 0x7fff;
		int r2 = table[(r1 + 0x40) >> 7] + 0x101;
		int r3 = ((0x80 - r2 * (r1 + 0x8000)) >> 8) & 0x1ffff;
		u32 reciprocal = (r2 * r3 + 0x80) >> 8;

		return ((u64)reciprocal * (numerator << shift) + 0x8000) >> 16;
	}

	return 0xffffffff;
}