Commit a0f42610 authored by Avi Kivity's avatar Avi Kivity Committed by Anthony Liguori
Browse files

vga: optimize ppm_save() divisions 



ppm_save() spends upwards of 50% of its time doing divisions. Replace them
with shifts.

Reviewed-by: default avatarAlon Levy <alevy@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 19bf7c87

hw/vga.c

+4 −6
Original line number Diff line number Diff line
@@ -2373,12 +2373,10 @@ int ppm_save(const char *filename, struct DisplaySurface *ds) 
                v = *(uint32_t *)d;

            else

                v = (uint32_t) (*(uint16_t *)d);

            r = ((v >> ds->pf.rshift) & ds->pf.rmax) * 256 /

                (ds->pf.rmax + 1);

            g = ((v >> ds->pf.gshift) & ds->pf.gmax) * 256 /

                (ds->pf.gmax + 1);

            b = ((v >> ds->pf.bshift) & ds->pf.bmax) * 256 /

                (ds->pf.bmax + 1);

            /* Limited to 8 or fewer bits per channel: */

            r = ((v >> ds->pf.rshift) & ds->pf.rmax) << (8 - ds->pf.rbits);

            g = ((v >> ds->pf.gshift) & ds->pf.gmax) << (8 - ds->pf.gbits);

            b = ((v >> ds->pf.bshift) & ds->pf.bmax) << (8 - ds->pf.bbits);

            *pbuf++ = r;

            *pbuf++ = g;

            *pbuf++ = b;