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vga: optimize horizontal pel panning in 256-color modes

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Do not go through the panning buffer unless the address wraps in the middle
of the line.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-12-29 14:46:59 +01:00
parent 973a724eb0
commit 4d6c310502
1 changed files with 12 additions and 0 deletions
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12
hw/display/vga-helpers.h
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@ -265,6 +265,18 @@ static void *vga_draw_line8d2(VGACommonState *vga, uint8_t *d,
palette = vga->last_palette;
hpel = (hpel >> 1) & 3;
/* For 256 color modes, we can adjust the source address and write directly
* to the destination, even if horizontal pel panning is active. However,
* the loop below assumes that the address does not wrap in the middle of a
* plane. If that happens...
*/
if (addr + (width >> 3) * 4 < VGA_VRAM_SIZE) {
addr += hpel * 4;
hpel = 0;
}
/* ... use the panning buffer as in planar modes. */
if (hpel) {
width += 8;
d = vga->panning_buf;