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Eliminate branch conditionals in scanner address calculation

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This commit is contained in:
Aaron Culliney 2018-11-10 09:33:25 -08:00
parent 18d831b04c
commit ed37c18ec5
2 changed files with 6 additions and 9 deletions
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3
src/display.h
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@ -156,9 +156,8 @@ typedef enum font_mode_t {
* Graphics mode
*/
typedef enum drawpage_mode_t {
DRAWPAGE_TEXT = 1,
DRAWPAGE_TEXT = 0,
DRAWPAGE_HIRES,
DRAWPAGE_MODE_CHANGE,
NUM_DRAWPAGE_MODES,
} drawpage_mode_t;

12
src/video/video.c
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@ -87,6 +87,8 @@ static uint16_t vert_offset_hgr[SCANLINES_FRAME] = {
0x0B80,0x0F80,0x1380,0x1780,0x1B80,0x1F80, // 256,257,258,259,260,261
};
static uint16_t *vert_offset[NUM_DRAWPAGE_MODES] = { &vert_offset_txt[0], &vert_offset_hgr[0] };
// scanline horizontal offsets (UtAIIe 5-12, 5-15+)
static uint8_t scan_offset[5][CYCLES_SCANLINE] =
{
@ -212,13 +214,9 @@ unsigned long video_clearDirty(unsigned long flags) {
// video scanner & generator routines
static inline uint16_t _getScannerAddress(drawpage_mode_t mode, int page, unsigned int vCount, unsigned int hCount) {
uint16_t a = 0;
if (mode == DRAWPAGE_TEXT) {
a = (page ? 0x800 : 0x400) + vert_offset_txt[vCount>>3] + scan_offset[vCount>>6][hCount];
} else {
a = (page ? 0x4000 : 0x2000) + vert_offset_hgr[vCount] + scan_offset[vCount>>6][hCount];
}
return a;
uint16_t baseOff = (0x1 << 10) << (mode * 3) << page; // 0x400 or 0x2000 + page
unsigned int vCount3 = vCount >> ((1 - (mode & 0x1)) * 3); // TEXT:vCount>>3 GRAPHICS:vCount
return baseOff + vert_offset[mode][vCount3] + scan_offset[vCount>>6][hCount];
}
static drawpage_mode_t _currentMode(unsigned int vCount) {