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-rw-r--r--mknes_ppu.c520
1 files changed, 520 insertions, 0 deletions
diff --git a/mknes_ppu.c b/mknes_ppu.c
new file mode 100644
index 0000000..64d6821
--- /dev/null
+++ b/mknes_ppu.c
@@ -0,0 +1,520 @@
+
+
+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))
+static inline void ppu_evaluate_sprites(struct nes_state *state) {
+ struct ppu_state *restrict ppu = &state->ppu;
+ uint8_t sprite_height = (ppu->reg_ctrl & 0x20) ? 16 : 8;
+ uint8_t n = 0;
+ uint8_t sprite_zero_found = 0;
+
+ uint8_t * restrict src = ppu->oam;
+ uint8_t * restrict dst = ppu->temp_secondary_oam; // Write to temp buffer
+
+ for(uint8_t i = 0; i < 64; i++, src += 4) {
+ uint8_t y = src[0];
+ int32_t row = (int32_t)ppu->scanline - y;
+
+ if(row >= 0 && row < sprite_height) {
+ if(n < 8) {
+ dst[0] = src[0];
+ dst[1] = src[1];
+ dst[2] = src[2];
+ dst[3] = src[3];
+
+ if(i == 0) {
+ sprite_zero_found = 1; // Sprite 0 is in range, will be in slot 0
+ }
+
+ dst += 4;
+ n++;
+
+ } else {
+ ppu->reg_status |= 0x20; // Set overflow immediately
+ break;
+ }
+ }
+ }
+ ppu->sprite_zero_in_range = sprite_zero_found;
+ ppu->sprite_count_next = n;
+}
+
+__attribute__((hot))
+static inline void ppu_fetch_sprite_patterns(struct nes_state *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 & 0x20) ? 16 : 8;
+ uint32_t sprite_pattern_table_base = (ctrl & 0x08) << 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 & 0x80) ? sprite_height - 1 - row : row;
+
+ uint32_t bank, addr;
+ if(sprite_height == 16) {
+ bank = (tile & 1) << 12;
+ tile &= 0xfe;
+ if(row >= 8) {
+ tile++;
+ row -= 8;
+ }
+ addr = bank + tile * 16 + row;
+
+ } 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 & 0x40));
+ 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 & 0x20;
+ ppu->sprites[i].palette = attr & 0x3;
+ }
+}
+
+
+__attribute__((always_inline, hot))
+static inline void ppu_render_pixel(struct nes_state *state, uint32_t x, uint32_t y) {
+ 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 show_bg = ppu->reg_mask & 0x08;
+ uint8_t show_sprites = ppu->reg_mask & 0x10;
+ uint8_t left_bg = ppu->reg_mask & 0x02;
+ uint8_t left_sp = ppu->reg_mask & 0x04;
+
+ uint8_t bg_mask = (show_bg && (left_bg || x & ~7)) ? 0xff : 0x00;
+ uint8_t sp_mask = (show_sprites && (left_sp || x & ~7));// ? 0xff : 0x00;
+
+ // 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;
+
+ // Sprite
+
+ if(sp_mask && ppu->sprite_count) {
+ switch(ppu->sprite_count) {
+ case 8: {
+ if(!ppu->sprites[7].position) {
+ sp_pixel = (((ppu->sprites[7].shift_hi & 0x80) >> 6) | ((ppu->sprites[7].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[7].priority;
+ sp_palette = ppu->sprites[7].palette;
+ break;
+ }
+ }
+ } __attribute__((fallthrough));
+
+ case 7: {
+ if(!ppu->sprites[6].position) {
+ sp_pixel = (((ppu->sprites[6].shift_hi & 0x80) >> 6) | ((ppu->sprites[6].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[6].priority;
+ sp_palette = ppu->sprites[6].palette;
+ break;
+ }
+ }
+ } __attribute__((fallthrough));
+
+ case 6: {
+ if(!ppu->sprites[5].position) {
+ sp_pixel = (((ppu->sprites[5].shift_hi & 0x80) >> 6) | ((ppu->sprites[5].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[5].priority;
+ sp_palette = ppu->sprites[5].palette;
+ break;
+ }
+ }
+ } __attribute__((fallthrough));
+
+ case 5: {
+ if(!ppu->sprites[4].position) {
+ sp_pixel = (((ppu->sprites[4].shift_hi & 0x80) >> 6) | ((ppu->sprites[4].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[4].priority;
+ sp_palette = ppu->sprites[4].palette;
+ break;
+ }
+ }
+ } __attribute__((fallthrough));
+
+ case 4: {
+ if(!ppu->sprites[3].position) {
+ sp_pixel = (((ppu->sprites[3].shift_hi & 0x80) >> 6) | ((ppu->sprites[3].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[3].priority;
+ sp_palette = ppu->sprites[3].palette;
+ break;
+ }
+ }
+ } __attribute__((fallthrough));
+
+ case 3: {
+ if(!ppu->sprites[2].position) {
+ sp_pixel = (((ppu->sprites[2].shift_hi & 0x80) >> 6) | ((ppu->sprites[2].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[2].priority;
+ sp_palette = ppu->sprites[2].palette;
+ break;
+ }
+ }
+ } __attribute__((fallthrough));
+
+ case 2: {
+ if(!ppu->sprites[1].position) {
+ sp_pixel = (((ppu->sprites[1].shift_hi & 0x80) >> 6) | ((ppu->sprites[1].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[1].priority;
+ sp_palette = ppu->sprites[1].palette;
+ break;
+ }
+ }
+ } __attribute__((fallthrough));
+
+ case 1: {
+ if(!ppu->sprites[0].position) {
+ sp_pixel = (((ppu->sprites[0].shift_hi & 0x80) >> 6) | ((ppu->sprites[0].shift_lo & 0x80) >> 7));
+ if(sp_pixel) {
+ sp_prio = ppu->sprites[0].priority;
+ sp_palette = ppu->sprites[0].palette;
+ sp_zero = ppu->sprite_zero_in_range; // Only slot 0 can be sprite 0
+ break;
+ }
+ }
+ }
+ }
+ }
+
+ // 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);
+
+ // NOTE(peter): It's actually faster to preset case3 version of palette_index than to start from zero
+ uint8_t palette_index = (sp_prio) ? bg_index : 0x10 | sp_index;
+
+ switch(selector) {
+ case 0: { palette_index = 0; } break;
+ case 1: { palette_index = 0x10 | sp_index; } break;
+ case 2: { palette_index = bg_index; } break;
+ case 3: { ppu->reg_status |= (sp_zero && x < 255) ? 0x40 : 0; } break; // NOTE(peter): Sprite zero hit!
+ }
+
+ state->pixels[y * 256 + x] = ppu->palette[palette_index]; // NOTE(peter): Add color_emphasis bits (expand palette to 8x).
+}
+
+__attribute__((hot, optimize("no-jump-tables")))
+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 rendering = (ppu->reg_mask & 0x18);
+
+ for(uint8_t ppu_loops = 0; ppu_loops < 3; ++ppu_loops) {
+
+ if(rendering) {
+
+ if(scanline <= 239) {
+
+ if(dot == 65) {
+ ppu_evaluate_sprites(state); // Evaluate sprites early, sets overflow immediately
+ }
+
+ if(dot >= 1 && dot <= 256) {
+ 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);
+ goto stupid;
+ }
+
+ if(dot == 257) {
+ ppu->vram_addr = (ppu->vram_addr & ~0x041f) | (ppu->temp_addr & 0x041f);
+ memcpy(ppu->secondary_oam, ppu->temp_secondary_oam, 32);
+ ppu->sprite_count = ppu->sprite_count_next;
+ }
+
+ if(dot >= 321 && dot <= 336) {
+stupid: if(ppu->reg_mask & 0x10) {
+ 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 & 0x10) << 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 & 0x10) << 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 == 340) {
+ ppu_fetch_sprite_patterns(state, scanline);
+ }
+
+ }
+
+ if(scanline == 261) {
+ if(dot == 65) {
+ ppu_evaluate_sprites(state); // Evaluate sprites early
+ }
+
+ if(dot >= 1 && dot <= 256) {
+ 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 stupid2;
+ }
+
+ if(dot == 257) {
+ ppu->vram_addr = (ppu->vram_addr & ~0x041f) | (ppu->temp_addr & 0x041f);
+ memcpy(ppu->secondary_oam, ppu->temp_secondary_oam, 32);
+ ppu->sprite_count = ppu->sprite_count_next;
+ }
+
+ if(dot >= 280 && dot <= 304) {
+ ppu->vram_addr = (ppu->vram_addr & ~0x7be0) | (ppu->temp_addr & 0x7be0);
+ }
+
+ if(dot >= 321 && dot <= 336) {
+stupid2: if(ppu->reg_mask & 0x10) {
+ 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 & 0x10) << 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 & 0x10) << 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 == 340) {
+ ppu_fetch_sprite_patterns(state, scanline);
+ }
+ }
+
+ }
+
+ if(dot == 1) {
+ switch(scanline) {
+ case 241: {
+ ppu->reg_status |= 0x80;
+ state->cpu.nmi_pending = (ppu->reg_ctrl & 0x80);
+ } break;
+
+ case 261: {
+ ppu->reg_status &= ~0x80;
+ ppu->reg_status &= ~0x40;
+ } break;
+ }
+ }
+
+ dot++;
+ if(dot > 340) {
+ dot = 0;
+ scanline++;
+
+ if(scanline == 261 && !ppu->even_frame && (ppu->reg_mask & 0x18)) {
+ 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);
+ }
+
+ ppu->dot = dot;
+ ppu->scanline = scanline;
+
+ }
+}
generated by cgit v1.2.3 (git 2.46.0) at 2026-01-25 13:14:35 +0000