Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions

2012-01-12 Thread Anthony Liguori 

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


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;

Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions

2012-01-12 Thread Alon Levy 
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 
> 
> 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 
> > ---
> >  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
> > 
> > 
>

Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions

2012-01-12 Thread Alon Levy 
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 

rmax/bmax/gmax are all uint8_t atm, could add a compilation error if
sizeof(bmax)!=1 ever.

> Signed-off-by: Avi Kivity 
> ---
>  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
> 
>

Re: [Qemu-devel] [PATCH] vga: optimize ppm_save() divisions

2012-01-12 Thread Avi Kivity 
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.

-- 
error compiling committee.c: too many arguments to function

[Qemu-devel] [PATCH] vga: optimize ppm_save() divisions

2012-01-03 Thread Avi Kivity 
ppm_save() spends upwards of 50% of its time doing divisions. Replace them
with shifts.

Signed-off-by: Avi Kivity 
---
 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