Simplified FIFO logic
This commit is contained in:
Lior Halphon
parent
cb01259073
commit
0461fb5b2a
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@ -8,7 +8,7 @@
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static inline unsigned fifo_size(GB_fifo_t *fifo)
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{
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return (fifo->write_end - fifo->read_end) & 0xF;
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return (fifo->write_end - fifo->read_end) & (GB_FIFO_LENGTH - 1);
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}
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static void fifo_clear(GB_fifo_t *fifo)
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@ -20,7 +20,7 @@ static GB_fifo_item_t *fifo_pop(GB_fifo_t *fifo)
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{
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GB_fifo_item_t *ret = &fifo->fifo[fifo->read_end];
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fifo->read_end++;
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fifo->read_end &= 0xF;
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fifo->read_end &= (GB_FIFO_LENGTH - 1);
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return ret;
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}
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@ -38,7 +38,7 @@ static void fifo_push_bg_row(GB_fifo_t *fifo, uint8_t lower, uint8_t upper, uint
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upper <<= 1;
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fifo->write_end++;
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fifo->write_end &= 0xF;
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fifo->write_end &= (GB_FIFO_LENGTH - 1);
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}
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}
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else {
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@ -53,7 +53,7 @@ static void fifo_push_bg_row(GB_fifo_t *fifo, uint8_t lower, uint8_t upper, uint
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upper >>= 1;
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fifo->write_end++;
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fifo->write_end &= 0xF;
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fifo->write_end &= (GB_FIFO_LENGTH - 1);
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}
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}
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}
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@ -63,14 +63,14 @@ static void fifo_overlay_object_row(GB_fifo_t *fifo, uint8_t lower, uint8_t uppe
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while (fifo_size(fifo) < 8) {
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fifo->fifo[fifo->write_end] = (GB_fifo_item_t) {0,};
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fifo->write_end++;
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fifo->write_end &= 0xF;
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fifo->write_end &= (GB_FIFO_LENGTH - 1);
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}
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uint8_t flip_xor = flip_x? 0: 0x7;
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for (unsigned i = 8; i--;) {
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uint8_t pixel = (lower >> 7) | ((upper >> 7) << 1);
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GB_fifo_item_t *target = &fifo->fifo[(fifo->read_end + (i ^ flip_xor)) & 0xF];
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GB_fifo_item_t *target = &fifo->fifo[(fifo->read_end + (i ^ flip_xor)) & (GB_FIFO_LENGTH - 1)];
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if (pixel != 0 && (target->pixel == 0 || target->priority > priority)) {
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target->pixel = pixel;
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target->palette = palette;
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@ -329,7 +329,7 @@ static void render_pixel_if_possible(GB_gameboy_t *gb)
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GB_fifo_item_t *oam_fifo_item = NULL;
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bool draw_oam = false;
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bool bg_enabled = true, bg_priority = false;
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if (!gb->bg_fifo_paused) {
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fifo_item = fifo_pop(&gb->bg_fifo);
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bg_priority = fifo_item->bg_priority;
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@ -556,6 +556,8 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
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gb->cycles_for_line = MODE2_LENGTH + 4;
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fifo_clear(&gb->bg_fifo);
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fifo_clear(&gb->oam_fifo);
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/* Fill the FIFO with 8 pixels of "junk", it's going to be dropped anyway. */
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fifo_push_bg_row(&gb->bg_fifo, 0, 0, 0, false, false);
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/* Todo: find out actual access time of SCX */
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gb->position_in_line = - (gb->io_registers[GB_IO_SCX] & 7) - 8;
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gb->fetcher_x = ((gb->io_registers[GB_IO_SCX]) / 8) & 0x1f;
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@ -567,7 +569,7 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
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/* The actual rendering cycle */
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gb->fetcher_divisor = false;
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gb->fetcher_state = GB_FETCHER_GET_TILE;
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gb->bg_fifo_paused = true;
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gb->bg_fifo_paused = false;
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gb->oam_fifo_paused = false;
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gb->in_window = false;
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while (true) {
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@ -636,7 +638,7 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
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gb->fetcher_x = 0;
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gb->fetcher_state = GB_FETCHER_GET_TILE;
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}
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bool push = false;
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if (gb->fetcher_divisor) {
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switch (gb->fetcher_state) {
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@ -720,8 +722,16 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
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}
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break;
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case GB_FETCHER_SLEEP:
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push = true;
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case GB_FETCHER_SLEEP: {
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gb->cycles_for_line += gb->fetcher_stop_penalty;
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GB_SLEEP(gb, display, 19, gb->fetcher_stop_penalty);
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gb->fetcher_stop_penalty = 0;
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fifo_push_bg_row(&gb->bg_fifo, gb->current_tile_data[0], gb->current_tile_data[1],
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gb->current_tile_attributes & 7, gb->current_tile_attributes & 0x80, gb->current_tile_attributes & 0x20);
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gb->bg_fifo_paused = false;
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gb->oam_fifo_paused = false;
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}
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break;
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}
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gb->fetcher_state++;
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@ -730,16 +740,6 @@ void GB_display_run(GB_gameboy_t *gb, uint8_t cycles)
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gb->fetcher_divisor ^= true;
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render_pixel_if_possible(gb);
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if (push) {
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gb->cycles_for_line += gb->fetcher_stop_penalty;
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GB_SLEEP(gb, display, 19, gb->fetcher_stop_penalty);
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gb->fetcher_stop_penalty = 0;
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fifo_push_bg_row(&gb->bg_fifo, gb->current_tile_data[0], gb->current_tile_data[1],
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gb->current_tile_attributes & 7, gb->current_tile_attributes & 0x80, gb->current_tile_attributes & 0x20);
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gb->bg_fifo_paused = false;
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gb->oam_fifo_paused = false;
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}
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if (gb->position_in_line == 160) break;
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gb->cycles_for_line++;
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GB_SLEEP(gb, display, 21, 1);
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@ -195,8 +195,9 @@ typedef struct {
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bool bg_priority; // For sprite FIFO – the BG priority bit. For the BG FIFO – the CGB attributes priority bit
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} GB_fifo_item_t;
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#define GB_FIFO_LENGTH 16
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typedef struct {
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GB_fifo_item_t fifo[16];
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GB_fifo_item_t fifo[GB_FIFO_LENGTH];
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uint8_t read_end;
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uint8_t write_end;
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} GB_fifo_t;
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@ -430,6 +431,7 @@ struct GB_gameboy_internal_s {
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uint8_t extra_penalty_for_sprite_at_0;
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bool is_first_line_mode2;
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bool oam_interrupt_line;
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bool ready_to_push;
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);
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/* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */
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