static uint8_t __attribute__((aligned(64))) ppu_bitreverse_lut[256] = { 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0, 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8, 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4, 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc, 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2, 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa, 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6, 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe, 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1, 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9, 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5, 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd, 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3, 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb, 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7, 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff }; static void ppu_reset(struct nes_state *state) { struct ppu_state *restrict ppu = &state->ppu; memset(ppu, 0, sizeof(struct ppu_state)); } __attribute__((hot, flatten, optimize("unroll-loops"))) static inline void ppu_evaluate_sprites(struct nes_state *state, uint32_t scanline) { struct ppu_state *restrict ppu = &state->ppu; uint8_t sprite_height = (ppu->reg_ctrl & PPU_CTRL_SPRITE_HEIGHT) ? 16 : 8; uint8_t n = 0; uint8_t sprite_zero_found = 0; uint8_t * restrict src = ppu->oam; uint8_t * restrict dst = ppu->secondary_oam; for(uint8_t i = 0; i < 64; i++, src += 4) { uint32_t row = scanline - src[0]; if(row < sprite_height) { if(n < 8) { dst[0] = src[0]; dst[1] = src[1]; dst[2] = src[2]; dst[3] = src[3]; dst += 4; sprite_zero_found |= (i == 0); n++; } else { ppu->reg_status |= PPU_STATUS_SPRITE_OVERFLOW; break; } } } ppu->sprite_zero_in_range = sprite_zero_found; ppu->sprite_count = n; } __attribute__((hot)) static inline void ppu_fetch_sprite_patterns(struct nes_state * restrict state, uint32_t scanline) { struct ppu_state *restrict ppu = &state->ppu; uint8_t * restrict sec_oam = ppu->secondary_oam; uint8_t ctrl = ppu->reg_ctrl; uint8_t sprite_height = (ctrl & PPU_CTRL_SPRITE_HEIGHT) ? 16 : 8; uint32_t sprite_pattern_table_base = (ctrl & PPU_CTRL_SPRITE_TILE) << 9; for(uint8_t i = 0; i < ppu->sprite_count; i++, sec_oam += 4) { uint8_t y = sec_oam[0]; uint8_t tile = sec_oam[1]; uint8_t attr = sec_oam[2]; uint8_t x = sec_oam[3]; uint32_t row = scanline - y; row = (attr & SPRITE_ATTR_FLIP_VERTICAL) ? sprite_height - 1 - row : row; uint32_t bank; uint32_t addr; if(sprite_height == 16) { // For 8x16 sprites: // - Bank comes from tile bit 0 (bits 1-7 are the tile index) // - Row 0-7 uses base tile, row 8-15 uses base tile + 1 // - Row offset wraps to 0-7 within each 8-pixel half // // Original logic: // bank = (tile & 1) << 12; // tile &= 0xfe; // if(row >= 8) { tile++; row -= 8; } // addr = bank + tile * 16 + row; addr = ((tile & 1) << 12) + ((tile & 0xfe) + (row >> 3)) * 16 + (row & 7); } else { addr = sprite_pattern_table_base + tile * 16 + row; } uint8_t val_lo = state->mapper_function.chr_read(state, addr); uint8_t val_hi = state->mapper_function.chr_read(state, addr + 8); uint8_t rev = -(!!(attr & SPRITE_ATTR_FLIP_HORIZONTAL)); uint8_t lsb = (rev & ppu_bitreverse_lut[val_lo]) | (~rev & val_lo); uint8_t msb = (rev & ppu_bitreverse_lut[val_hi]) | (~rev & val_hi); ppu->sprites[i].shift_lo = lsb; ppu->sprites[i].shift_hi = msb; ppu->sprites[i].position = x; ppu->sprites[i].priority = attr & SPRITE_ATTR_PRIORITY; ppu->sprites[i].palette = attr & SPRITE_ATTR_PALETTE_MASK; } } __attribute__((always_inline, hot, optimize("no-jump-tables", "no-unroll-loops"))) static inline void ppu_render_pixel(struct nes_state * restrict state, uint32_t x, uint32_t y, uint8_t mask_reg) { struct ppu_state *restrict ppu = &state->ppu; uint16_t bit = 0x8000 >> ppu->fine_x; uint8_t sp_pixel = 0; uint8_t sp_palette = 0; uint8_t sp_prio = 0; uint8_t sp_zero = 0; // uint8_t mask_reg = ppu->reg_mask; // Single load uint8_t show_bg = mask_reg & PPU_MASK_SHOW_BG; uint8_t show_sprites = mask_reg & PPU_MASK_SHOW_SPRITES; uint8_t left_bg = mask_reg & 0x02; uint8_t left_sp = mask_reg & 0x04; uint8_t bg_mask = (show_bg && (left_bg || x & ~7)) ? 0xff : 0x00; uint8_t sp_mask = (show_sprites && (left_sp || x & ~7)); // Background uint8_t p0 = !!(ppu->bg_shift_pattern_low & bit); uint8_t p1 = !!(ppu->bg_shift_pattern_high & bit); uint8_t a0 = !!(ppu->bg_shift_attrib_low & bit); uint8_t a1 = !!(ppu->bg_shift_attrib_high & bit); uint8_t bg_pixel = ((p1 << 1) | p0) & bg_mask; uint8_t bg_palette = ((a1 << 1) | a0) & bg_mask; // Sprites - evaluate in forward order (0 has highest priority) if(sp_mask) { uint8_t found_sprite = 0xff; for(uint8_t i = 0; i < ppu->sprite_count; i++) { if(!ppu->sprites[i].position) { sp_pixel = (((ppu->sprites[i].shift_hi & 0x80) >> 6) | ((ppu->sprites[i].shift_lo & 0x80) >> 7)); if(sp_pixel) { found_sprite = i; goto sprite_found; } } } goto no_sprite; sprite_found: sp_prio = ppu->sprites[found_sprite].priority; sp_palette = ppu->sprites[found_sprite].palette; sp_zero = ppu->sprite_zero_in_range & !(found_sprite); } no_sprite: // Final pixel composition uint8_t bg_index = (bg_palette << 2) + bg_pixel; uint8_t sp_index = (sp_palette << 2) + sp_pixel; uint8_t selector = (bg_pixel ? 2 : 0) | (sp_pixel ? 1 : 0); uint8_t palette_index = 0; if(selector == 1) { palette_index = 0x10 | sp_index; } else if(selector == 2) { palette_index = bg_index; } else if(selector == 3) { palette_index = (sp_prio) ? bg_index : (0x10 | sp_index); if (sp_zero && x <= 254) ppu->reg_status |= PPU_STATUS_SPRITE_ZERO_HIT; } state->pixels[y * 256 + x] = ppu->palette[palette_index]; // NOTE(peter): Add color_emphasis bits (expand palette to 8x). } __attribute__((noinline, hot, optimize("no-jump-tables", "unroll-loops"))) static void ppu_tick(struct nes_state *state) { struct ppu_state *restrict ppu = &state->ppu; uint32_t dot = ppu->dot; uint32_t scanline = ppu->scanline; uint8_t reg_mask = ppu->reg_mask; uint8_t rendering = (reg_mask & (PPU_MASK_SHOW_SPRITES | PPU_MASK_SHOW_BG)); for(uint8_t ppu_loops = 0; ppu_loops < 3; ++ppu_loops) { if(rendering) { if(scanline <= 239) { if(dot >= 1 && dot < 256) { // NOTE(peter): dot 256 will be done in the next else in the chain ppu_render_pixel(state, dot - 1, scanline, reg_mask); goto shift_and_fetch; } else if(dot == 256) { if((ppu->vram_addr & 0x7000) != 0x7000) { ppu->vram_addr += 0x1000; } else { ppu->vram_addr &= ~0x7000; uint32_t y = (ppu->vram_addr & 0x03e0) >> 5; if(y == 29) { y = 0; ppu->vram_addr ^= 0x0800; } else if(y == 31) { y = 0; } else { y++; } ppu->vram_addr = (ppu->vram_addr & ~0x03e0) | (y << 5); } ppu_render_pixel(state, dot - 1, scanline, reg_mask); goto shift_and_fetch; } else if(dot == 257) { ppu->vram_addr = (ppu->vram_addr & ~0x041f) | (ppu->temp_addr & 0x041f); ppu_evaluate_sprites(state, scanline); } else if(dot >= 321 && dot <= 336) { goto shift_and_fetch; } else if(dot == 340) { ppu_fetch_sprite_patterns(state, scanline); } } if(scanline == 261) { if(dot >= 1 && dot < 256) { // NOTE(peter): dot 256 will be done in the next else in the chain goto shift_and_fetch; } else if(dot == 256) { if((ppu->vram_addr & 0x7000) != 0x7000) { ppu->vram_addr += 0x1000; } else { ppu->vram_addr &= ~0x7000; uint32_t y = (ppu->vram_addr & 0x03e0) >> 5; if(y == 29) { y = 0; ppu->vram_addr ^= 0x0800; } else if(y == 31) { y = 0; } else { y++; } ppu->vram_addr = (ppu->vram_addr & ~0x03e0) | (y << 5); } goto shift_and_fetch; } else if(dot == 257) { ppu->vram_addr = (ppu->vram_addr & ~0x041f) | (ppu->temp_addr & 0x041f); } else if(dot >= 280 && dot <= 304) { ppu->vram_addr = (ppu->vram_addr & ~0x7be0) | (ppu->temp_addr & 0x7be0); } else if(dot >= 321 && dot <= 336) { shift_and_fetch: if(reg_mask & PPU_MASK_SHOW_SPRITES) { for(uint32_t i = 0; i < ppu->sprite_count; i++) { if(ppu->sprites[i].position > 0) { ppu->sprites[i].position--; } else { ppu->sprites[i].shift_lo <<= 1; ppu->sprites[i].shift_hi <<= 1; } } } ppu->bg_shift_pattern_low <<= 1; ppu->bg_shift_pattern_high <<= 1; ppu->bg_shift_attrib_low <<= 1; ppu->bg_shift_attrib_high <<= 1; switch(dot % 8) { case 1: { uint32_t nt_addr = 0x2000 | (ppu->vram_addr & 0x0fff); ppu->bg_next_tile_id = state->mapper_function.ciram_read(state, nt_addr); } break; case 3: { uint32_t attr_addr = 0x23c0 | (ppu->vram_addr & 0x0c00) | ((ppu->vram_addr >> 4) & 0x38) | ((ppu->vram_addr >> 2) & 0x07); uint8_t attr = state->mapper_function.ciram_read(state, attr_addr & 0x0fff); uint8_t shift = ((ppu->vram_addr >> 4) & 4) | (ppu->vram_addr & 2); ppu->bg_next_tile_attrib = (attr >> shift) & 3; } break; case 5: { uint32_t base = (ppu->reg_ctrl & PPU_CTRL_BG_TILE_SELECT) << 8; uint32_t tile = ppu->bg_next_tile_id; uint32_t fine_y = (ppu->vram_addr >> 12) & 7; uint32_t addr_lsb = (base + tile * 16 + fine_y) & 0x1fff; ppu->bg_next_tile_lsb = state->mapper_function.chr_read(state, addr_lsb); } break; case 7: { uint32_t base = (ppu->reg_ctrl & PPU_CTRL_BG_TILE_SELECT) << 8; uint32_t tile = ppu->bg_next_tile_id; uint32_t fine_y = (ppu->vram_addr >> 12) & 7; uint32_t addr_msb = (base + tile * 16 + fine_y + 8) & 0x1fff; ppu->bg_next_tile_msb = state->mapper_function.chr_read(state, addr_msb); } break; case 0: { ppu->bg_shift_pattern_low = (ppu->bg_shift_pattern_low) | ppu->bg_next_tile_lsb; ppu->bg_shift_pattern_high = (ppu->bg_shift_pattern_high) | ppu->bg_next_tile_msb; uint8_t a = ppu->bg_next_tile_attrib; ppu->bg_shift_attrib_low = (ppu->bg_shift_attrib_low) | ((a & 1) ? 0xff : 0x00); ppu->bg_shift_attrib_high = (ppu->bg_shift_attrib_high) | ((a & 2) ? 0xff : 0x00); if((ppu->vram_addr & 0x001f) == 31) { ppu->vram_addr &= ~0x001f; ppu->vram_addr ^= 0x0400; } else { ppu->vram_addr++; } } break; } } } } if(dot == 1) { switch(scanline) { case 241: { ppu->reg_status |= PPU_STATUS_VBLANK; state->cpu.nmi_pending = (ppu->reg_ctrl & PPU_CTRL_NMI); } break; case 261: { ppu->reg_status &= ~PPU_STATUS_VBLANK; ppu->reg_status &= ~PPU_STATUS_SPRITE_ZERO_HIT; ppu->reg_status &= ~PPU_STATUS_SPRITE_OVERFLOW; } break; } } dot++; if(dot > 340) { dot = 0; scanline++; if(scanline == 261 && !ppu->even_frame && rendering) { dot = 1; } if(scanline > 261) { scanline = 0; ppu->frame_ready = 1; ppu->even_frame = !ppu->even_frame; } } if(state->mapper_function.tick) { state->mapper_function.tick(state); // TODO(peter): This signature has to be changed to supply dot and scanline! } } ppu->dot = dot; ppu->scanline = scanline; }