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gbdb,cpu,video: reduce number of calls to cycle functions

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Instead of calling cpu_cycle() and video_cycle() once per emulated
cycle, call cpu_cycle() once per emulated instruction. This should not
have any obvious effects on the emulation (as currently written),
because all of the memory reads and writes are done in the first
"cycle" of the instruction.

This patch results in a substantial performance gain (>100%, if I
recall correctly).
This commit is contained in:
Max Regan
2018-07-02 00:12:07 -07:00
parent 447276d029
commit ea2ea1e293
5 changed files with 17 additions and 19 deletions
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9
src/gbemu/video.c
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@@ -12,12 +12,11 @@ void gb_video_init(struct gb_video *video)
memset(video, 0, sizeof(*video));
}
void gb_video_cycle(struct gb_video *video)
void gb_video_cycle(struct gb_video *video, int cycles)
{
if (video->line_counter < CYCLES_PER_LINE - 1) {
video->line_counter++;
} else {
video->line_counter = 0;
video->line_counter += cycles;
if (video->line_counter >= CYCLES_PER_LINE) {
video->line_counter -= CYCLES_PER_LINE;
video->curline += 1;
if (video->curline > LCD_Y_MAX) {
video->curline = 0;