From a0f426109e17d579c2712f5b96a50215e6cc06a4 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Tue, 3 Jan 2012 15:32:57 +0200 Subject: [PATCH] vga: optimize ppm_save() divisions ppm_save() spends upwards of 50% of its time doing divisions. Replace them with shifts. Reviewed-by: Alon Levy Signed-off-by: Avi Kivity Signed-off-by: Anthony Liguori --- hw/vga.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/hw/vga.c b/hw/vga.c index 4878fbcbb..950f97e44 100644 --- a/hw/vga.c +++ b/hw/vga.c @@ -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;