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https://github.com/TomHarte/CLK.git
synced 2024-11-25 16:31:42 +00:00
Made an attempt to make execution flow through this loop more straightforward for a branch predictor.
This commit is contained in:
Thomas Harte
parent
7843a244b0
commit
1ff9b474bf
@ -54,126 +54,151 @@ void VideoOutput::run_for_cycles(int number_of_cycles)
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// Vertical: 0–39: pixels; otherwise blank; 48–53 sync, 54–56 colour burst
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// Horizontal: 0–223: pixels; otherwise blank; 256–259 sync
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while(number_of_cycles--)
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while(number_of_cycles)
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{
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_counter = (_counter + 1)%_counter_period;
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int h_counter =_counter & 63;
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int cycles_run_for = 0;
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if(!h_counter)
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if(_counter >= _v_sync_start_position && _counter <= _v_sync_end_position)
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{
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_ink = 0xff;
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_paper = 0x00;
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_use_alternative_character_set = _use_double_height_characters = _blink_text = false;
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set_character_set_base_address();
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_phase += 64;
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if(!_counter)
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// this is a sync line
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cycles_run_for = std::min(64 - h_counter, number_of_cycles);
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_crt->output_sync((unsigned int)cycles_run_for * 6);
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}
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else if(_counter < 224*64 && h_counter < 40)
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{
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// this is a pixel line
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if(!h_counter)
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{
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_phase += 128;
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_frame_counter++;
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_ink = 0xff;
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_paper = 0x00;
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_use_alternative_character_set = _use_double_height_characters = _blink_text = false;
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set_character_set_base_address();
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_phase += 64;
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_pixel_target = _crt->allocate_write_area(120);
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_v_sync_start_position = _next_frame_is_sixty_hertz ? PAL60VSyncStartPosition : PAL50VSyncStartPosition;
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_v_sync_end_position = _next_frame_is_sixty_hertz ? PAL60VSyncEndPosition : PAL50VSyncEndPosition;
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_counter_period = _next_frame_is_sixty_hertz ? PAL60Period : PAL50Period;
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if(!_counter)
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{
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_phase += 128; // TODO: incorporate all the lines that were missed
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_frame_counter++;
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_v_sync_start_position = _next_frame_is_sixty_hertz ? PAL60VSyncStartPosition : PAL50VSyncStartPosition;
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_v_sync_end_position = _next_frame_is_sixty_hertz ? PAL60VSyncEndPosition : PAL50VSyncEndPosition;
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_counter_period = _next_frame_is_sixty_hertz ? PAL60Period : PAL50Period;
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}
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}
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cycles_run_for = std::min(40 - h_counter, number_of_cycles);
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int columns = cycles_run_for;
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while(columns--)
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{
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uint8_t pixels, control_byte;
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if(_is_graphics_mode && _counter < 200*64)
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{
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control_byte = pixels = _ram[0xa000 + (_counter >> 6) * 40 + h_counter];
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}
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else
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{
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int address = 0xbb80 + (_counter >> 9) * 40 + h_counter;
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control_byte = _ram[address];
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int line = _use_double_height_characters ? ((_counter >> 7) & 7) : ((_counter >> 6) & 7);
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pixels = _ram[_character_set_base_address + (control_byte&127) * 8 + line];
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}
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uint8_t inverse_mask = (control_byte & 0x80) ? 0x77 : 0x00;
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if(_blink_text && (_frame_counter&32)) pixels = 0;
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if(control_byte & 0x60)
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{
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if(_pixel_target)
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{
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uint8_t colours[2] = {
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(uint8_t)(_paper ^ inverse_mask),
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(uint8_t)(_ink ^ inverse_mask),
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};
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_pixel_target[0] = (colours[(pixels >> 4)&1] & 0x0f) | (colours[(pixels >> 5)&1] & 0xf0);
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_pixel_target[1] = (colours[(pixels >> 2)&1] & 0x0f) | (colours[(pixels >> 3)&1] & 0xf0);
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_pixel_target[2] = (colours[(pixels >> 0)&1] & 0x0f) | (colours[(pixels >> 1)&1] & 0xf0);
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}
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}
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else
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{
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switch(control_byte & 0x1f)
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{
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case 0x00: _ink = 0x00; break;
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case 0x01: _ink = 0x44; break;
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case 0x02: _ink = 0x22; break;
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case 0x03: _ink = 0x66; break;
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case 0x04: _ink = 0x11; break;
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case 0x05: _ink = 0x55; break;
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case 0x06: _ink = 0x33; break;
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case 0x07: _ink = 0x77; break;
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case 0x08: case 0x09: case 0x0a: case 0x0b:
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case 0x0c: case 0x0d: case 0x0e: case 0x0f:
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_use_alternative_character_set = (control_byte&1);
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_use_double_height_characters = (control_byte&2);
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_blink_text = (control_byte&4);
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set_character_set_base_address();
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break;
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case 0x10: _paper = 0x00; break;
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case 0x11: _paper = 0x44; break;
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case 0x12: _paper = 0x22; break;
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case 0x13: _paper = 0x66; break;
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case 0x14: _paper = 0x11; break;
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case 0x15: _paper = 0x55; break;
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case 0x16: _paper = 0x33; break;
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case 0x17: _paper = 0x77; break;
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case 0x18: case 0x19: case 0x1a: case 0x1b:
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case 0x1c: case 0x1d: case 0x1e: case 0x1f:
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_is_graphics_mode = (control_byte & 4);
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_next_frame_is_sixty_hertz = !(control_byte & 2);
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break;
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default: break;
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}
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if(_pixel_target) _pixel_target[0] = _pixel_target[1] = _pixel_target[2] = (uint8_t)(_paper ^ inverse_mask);
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}
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if(_pixel_target) _pixel_target += 3;
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h_counter++;
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}
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if(h_counter == 40)
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{
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_crt->output_data(40 * 6, 2);
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}
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}
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State new_state = Blank;
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if(
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(h_counter >= 48 && h_counter <= 53) ||
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(_counter >= _v_sync_start_position && _counter <= _v_sync_end_position)) new_state = Sync;
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else if(h_counter >= 54 && h_counter <= 56) new_state = ColourBurst;
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else if(_counter < 224*64 && h_counter < 40) new_state = Pixels;
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if(_state != new_state)
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else
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{
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switch(_state)
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// this is a blank line (or the equivalent part of a pixel line)
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if(h_counter < 48)
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{
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case ColourBurst: _crt->output_colour_burst(_cycles_in_state * 6, _phase, 128); break;
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case Sync: _crt->output_sync(_cycles_in_state * 6); break;
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case Blank: _crt->output_blank(_cycles_in_state * 6); break;
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case Pixels: _crt->output_data(_cycles_in_state * 6, 2); break;
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cycles_run_for = std::min(48 - h_counter, number_of_cycles);
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_crt->output_blank((unsigned int)cycles_run_for * 6);
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}
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_state = new_state;
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_cycles_in_state = 0;
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if(_state == Pixels) _pixel_target = _crt->allocate_write_area(120);
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}
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_cycles_in_state++;
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if(new_state == Pixels) {
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uint8_t pixels, control_byte;
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if(_is_graphics_mode && _counter < 200*64)
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else if(h_counter < 54)
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{
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control_byte = pixels = _ram[0xa000 + (_counter >> 6) * 40 + h_counter];
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cycles_run_for = std::min(54 - h_counter, number_of_cycles);
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_crt->output_sync((unsigned int)cycles_run_for * 6);
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}
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else if(h_counter < 56)
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{
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cycles_run_for = std::min(56 - h_counter, number_of_cycles);
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_crt->output_colour_burst((unsigned int)cycles_run_for * 6, _phase, 128);
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}
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else
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{
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int address = 0xbb80 + (_counter >> 9) * 40 + h_counter;
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control_byte = _ram[address];
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int line = _use_double_height_characters ? ((_counter >> 7) & 7) : ((_counter >> 6) & 7);
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pixels = _ram[_character_set_base_address + (control_byte&127) * 8 + line];
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cycles_run_for = std::min(64 - h_counter, number_of_cycles);
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_crt->output_blank((unsigned int)cycles_run_for * 6);
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}
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uint8_t inverse_mask = (control_byte & 0x80) ? 0x77 : 0x00;
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if(_blink_text && (_frame_counter&32)) pixels = 0;
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if(control_byte & 0x60)
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{
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if(_pixel_target)
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{
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uint8_t colours[2] = {
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(uint8_t)(_paper ^ inverse_mask),
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(uint8_t)(_ink ^ inverse_mask),
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};
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_pixel_target[0] = (colours[(pixels >> 4)&1] & 0x0f) | (colours[(pixels >> 5)&1] & 0xf0);
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_pixel_target[1] = (colours[(pixels >> 2)&1] & 0x0f) | (colours[(pixels >> 3)&1] & 0xf0);
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_pixel_target[2] = (colours[(pixels >> 0)&1] & 0x0f) | (colours[(pixels >> 1)&1] & 0xf0);
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}
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}
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else
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{
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switch(control_byte & 0x1f)
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{
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case 0x00: _ink = 0x00; break;
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case 0x01: _ink = 0x44; break;
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case 0x02: _ink = 0x22; break;
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case 0x03: _ink = 0x66; break;
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case 0x04: _ink = 0x11; break;
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case 0x05: _ink = 0x55; break;
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case 0x06: _ink = 0x33; break;
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case 0x07: _ink = 0x77; break;
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case 0x08: case 0x09: case 0x0a: case 0x0b:
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case 0x0c: case 0x0d: case 0x0e: case 0x0f:
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_use_alternative_character_set = (control_byte&1);
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_use_double_height_characters = (control_byte&2);
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_blink_text = (control_byte&4);
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set_character_set_base_address();
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break;
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case 0x10: _paper = 0x00; break;
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case 0x11: _paper = 0x44; break;
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case 0x12: _paper = 0x22; break;
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case 0x13: _paper = 0x66; break;
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case 0x14: _paper = 0x11; break;
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case 0x15: _paper = 0x55; break;
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case 0x16: _paper = 0x33; break;
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case 0x17: _paper = 0x77; break;
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case 0x18: case 0x19: case 0x1a: case 0x1b:
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case 0x1c: case 0x1d: case 0x1e: case 0x1f:
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_is_graphics_mode = (control_byte & 4);
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_next_frame_is_sixty_hertz = !(control_byte & 2);
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break;
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default: break;
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}
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if(_pixel_target) _pixel_target[0] = _pixel_target[1] = _pixel_target[2] = (uint8_t)(_paper ^ inverse_mask);
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}
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if(_pixel_target) _pixel_target += 3;
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}
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_counter = (_counter + cycles_run_for)%_counter_period;
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number_of_cycles -= cycles_run_for;
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}
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}
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