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[sw] Speed up Draw_FadeScreen

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It now processes 4 pixels at a time and uses a bit mask instead of a
conditional to set 3 of the 4 pixels to black. On top of the 4:1 pixel
processing and avoiding inner-loop conditional jumps, gcc unrolls the
loop, so Draw_FadeScreen itself is more than 4x as fast as it was. The
end result is about 5% (3fps) speedup to timedemo demo1 on my 900MHz
EEE Pc when nq has been hacked to always draw the fade-screen.
This commit is contained in:
Bill Currie 2021-07-08 14:18:06 +09:00
parent ef6dd422e5
commit 4b1eb0d760
1 changed files with 9 additions and 8 deletions
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17
libs/video/renderer/sw/draw.c
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@ -777,21 +777,22 @@ void
Draw_FadeScreen (void)
{
int x, y;
byte *pbuf;
int height = vid.conheight;
int width = vid.conwidth / 4;
uint32_t *pbuf;
VID_UnlockBuffer ();
S_ExtraUpdate ();
VID_LockBuffer ();
for (y = 0; y < vid.conheight; y++) {
unsigned int t;
for (y = 0; y < height; y++) {
uint32_t mask;
pbuf = ((byte *)vid.buffer) + vid.rowbytes * y;
t = (y & 1) << 1;
pbuf = (uint32_t *) ((byte *)vid.buffer + vid.rowbytes * y);
mask = 0xff << ((y & 1) << 4);
for (x = 0; x < vid.conwidth; x++) {
if ((x & 3) != t)
pbuf[x] = 0;
for (x = 0; x < width; x++) {
*pbuf++ &= mask;
}
}
vr_data.scr_copyeverything = 1;