From ddac85e5a041fd8f41f4874de9808152c9979f22 Mon Sep 17 00:00:00 2001 From: Bruce Evans Date: Fri, 14 Apr 2017 12:03:34 +0000 Subject: [PATCH] Further unobfuscate the method of drawing the mouse cursor in vga planar mode. Don't manually unroll the 2 inner loops. On Haswell, doing so gave a speedup of about 0.5% (about 4 cycles per iteration out of 1400), but hard-coded a limit of width 9 and made better better optimizations harder to see. gcc-4.2.1 -O does the unrolling anyway, unless tricked with a volatile hack. gcc's unrolling is not very good and gives a a speedup of about half as much (about 2 cycles per iteration). (All timing on i386.) Manual unrolling was only feasible because the inner loop only iterates once or twice. Usually twice, but a dynamic check is needed to decide, and was not moved from the second-innermost loop manually or by gcc. This commit basically adds another dynamic check in the inner loop. Cursor widths of 10-17 require 3 iterations in the inner loop and this is not so easy to unroll -- even gcc stops at 2. --- sys/dev/syscons/scvgarndr.c | 49 +++++++++++++------------------------ 1 file changed, 17 insertions(+), 32 deletions(-) diff --git a/sys/dev/syscons/scvgarndr.c b/sys/dev/syscons/scvgarndr.c index 2ec06a514b6..8450deb74c9 100644 --- a/sys/dev/syscons/scvgarndr.c +++ b/sys/dev/syscons/scvgarndr.c @@ -1031,7 +1031,7 @@ draw_pxlmouse_planar(scr_stat *scp, int x, int y) int xoff, yoff; int ymax; u_short m; - int i, j; + int i, j, k; line_width = scp->sc->adp->va_line_width; xoff = (x - scp->xoff*8)%8; @@ -1043,42 +1043,27 @@ draw_pxlmouse_planar(scr_stat *scp, int x, int y) outw(GDCIDX, 0xff08); /* bit mask */ outw(GDCIDX, 0x0803); /* data rotate/function select (and) */ p = scp->sc->adp->va_window + line_width*y + x/8; - if (x < scp->xpixel - 8) { - for (i = y, j = 0; i < ymax; ++i, ++j) { - m = ~((mouse_and_mask[j] & ~mouse_or_mask[j]) >> xoff); - readb(p); - writeb(p, m >> 8); - readb(p + 1); - writeb(p + 1, m); - p += line_width; - } - } else { - xoff += 8; - for (i = y, j = 0; i < ymax; ++i, ++j) { - m = ~((mouse_and_mask[j] & ~mouse_or_mask[j]) >> xoff); - readb(p); - writeb(p, m); - p += line_width; + for (i = y, j = 0; i < ymax; ++i, ++j) { + m = ~((mouse_and_mask[j] & ~mouse_or_mask[j]) >> xoff); + for (k = 0; k < 2; ++k) { + if (x + 8 * k < scp->xpixel) { + readb(p + k); + writeb(p + k, m >> (8 * (1 - k))); + } } + p += line_width; } outw(GDCIDX, 0x1003); /* data rotate/function select (or) */ p = scp->sc->adp->va_window + line_width*y + x/8; - if (x < scp->xpixel - 8) { - for (i = y, j = 0; i < ymax; ++i, ++j) { - m = mouse_or_mask[j] >> xoff; - readb(p); - writeb(p, m >> 8); - readb(p + 1); - writeb(p + 1, m); - p += line_width; - } - } else { - for (i = y, j = 0; i < ymax; ++i, ++j) { - m = mouse_or_mask[j] >> xoff; - readb(p); - writeb(p, m); - p += line_width; + for (i = y, j = 0; i < ymax; ++i, ++j) { + m = mouse_or_mask[j] >> xoff; + for (k = 0; k < 2; ++k) { + if (x + 8 * k < scp->xpixel) { + readb(p + k); + writeb(p + k, m >> (8 * (1 - k))); + } } + p += line_width; } outw(GDCIDX, 0x0003); /* data rotate/function select */ }