| Message ID | 1325597577-29385-1-git-send-email-avi@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 01/03/2012 03:32 PM, Avi Kivity wrote: > ppm_save() spends upwards of 50% of its time doing divisions. Replace them > with shifts. > > Pings.
On Tue, Jan 03, 2012 at 03:32:57PM +0200, Avi Kivity wrote: > ppm_save() spends upwards of 50% of its time doing divisions. Replace them > with shifts. > Reviewed-by: Alon Levy <alevy@redhat.com> rmax/bmax/gmax are all uint8_t atm, could add a compilation error if sizeof(bmax)!=1 ever. > Signed-off-by: Avi Kivity <avi@redhat.com> > --- > hw/vga.c | 10 ++++------ > 1 files changed, 4 insertions(+), 6 deletions(-) > > diff --git a/hw/vga.c b/hw/vga.c > index ca79aa1..a228cde 100644 > --- a/hw/vga.c > +++ b/hw/vga.c > @@ -2370,12 +2370,10 @@ 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; > -- > 1.7.7.1 > >
On Thu, Jan 12, 2012 at 05:16:03PM +0200, Alon Levy wrote: > On Tue, Jan 03, 2012 at 03:32:57PM +0200, Avi Kivity wrote: > > ppm_save() spends upwards of 50% of its time doing divisions. Replace them > > with shifts. > > > > Reviewed-by: Alon Levy <alevy@redhat.com> > > rmax/bmax/gmax are all uint8_t atm, could add a compilation error if > sizeof(bmax)!=1 ever. meant {r,g,b}bits. > > > Signed-off-by: Avi Kivity <avi@redhat.com> > > --- > > hw/vga.c | 10 ++++------ > > 1 files changed, 4 insertions(+), 6 deletions(-) > > > > diff --git a/hw/vga.c b/hw/vga.c > > index ca79aa1..a228cde 100644 > > --- a/hw/vga.c > > +++ b/hw/vga.c > > @@ -2370,12 +2370,10 @@ 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; > > -- > > 1.7.7.1 > > > > >
On 01/03/2012 07:32 AM, Avi Kivity wrote: > ppm_save() spends upwards of 50% of its time doing divisions. Replace them > with shifts. > > Signed-off-by: Avi Kivity<avi@redhat.com> Applied. Thanks. Regards, Anthony Liguori > --- > hw/vga.c | 10 ++++------ > 1 files changed, 4 insertions(+), 6 deletions(-) > > diff --git a/hw/vga.c b/hw/vga.c > index ca79aa1..a228cde 100644 > --- a/hw/vga.c > +++ b/hw/vga.c > @@ -2370,12 +2370,10 @@ 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;
diff --git a/hw/vga.c b/hw/vga.c index ca79aa1..a228cde 100644 --- a/hw/vga.c +++ b/hw/vga.c @@ -2370,12 +2370,10 @@ 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;
ppm_save() spends upwards of 50% of its time doing divisions. Replace them with shifts. Signed-off-by: Avi Kivity <avi@redhat.com> --- hw/vga.c | 10 ++++------ 1 files changed, 4 insertions(+), 6 deletions(-)