[FFmpeg-devel] pre discussion around Blackfin dct_quantize_bfin routine

[Marc Hoffman]

On 6/12/07, Guillaume Poirier <gpoirier at mplayerhq.hu> wrote:
> Hi,
> Reimar Doeffinger wrote:
> > Hello,
> > On Mon, Jun 11, 2007 at 10:58:00PM -0400, Marc Hoffman wrote:
> >> This is my rough draft it works well with the small precision errors
> >> due to 16bit arithmetic, actually its the same (as far as I can tell)
> >> as the MMX quantizer. I ran my reference fixpoint against the mmx and
> >> it seems to work on the cases I tried, its 1 bit off which seems
> >> about right considering the truncation of the coeffs from 22 to
> >> 16bits.  Can someone look over my shoulder and give a peak. I know I
> >> have to clean up the codes a bit but I wanted to get someone else to
> >> review my work up until now.  I have used inline asm, Michael this
> >> should be pretty straight forward for you to get your head around.
> >> This doubles the performance roughly.
> >
> > Hmm. Ok, most is cleanup suggestions so I might be telling you things
> > you already know, still...
> >
> >> #define clock()      ({ int _t; asm volatile ("%0=cycles;" : "=d" (_t)); _t; })
> >
> > If you leave that in the final version you should probably use a less
> > collision-freindly name like bfin_clock or so.
> > Also that ({ }) construction is a nasty gcc-ism, you could avoid it by
> > making it a static always_inline fuction, though that increases the risk
> > of the compiler messing up...
> > And actually, maybe you could just implement START_TIMER and STOP_TIMER
> > in libavutil (or does that do something else)?
> > If not, maybe naming it START_PROF and END_PROF is at least more
> > consistent, and least the EPROF name is not quite obvious in its meaning
>
>
> In case you didn't know Marc (I'm sure you do though), you only need
> to implement BlackFin version of read_time(void) as found in
> libavutil/common.h to get a working support of START_TIMER and
> STOP_TIMER on you plateform.
>
> Guillaume


So this is all I need to do....  Thanks :)

yoda:~/ffmpeg-svn mmh$ svn diff libavutil/common.h
Index: libavutil/common.h
===================================================================
--- libavutil/common.h  (revision 9231)
+++ libavutil/common.h  (working copy)
@@ -267,7 +267,7 @@
         }\
     }

-#if defined(ARCH_X86) || defined(ARCH_POWERPC)
+#if defined(ARCH_X86) || defined(ARCH_POWERPC) || defined(ARCH_BFIN)
 #if defined(ARCH_X86_64)
 static inline uint64_t read_time(void)
 {
@@ -286,6 +286,19 @@
         );
         return l;
 }
+#elif ARCH_BFIN
+static inline uint64_t read_time(void)
+{
+    union {
+        struct {
+            unsigned lo;
+            unsigned hi;
+        } p;
+        unsigned long long c;
+    } t;
+    asm volatile ("%0=cycles; %1=cycles2;" : "=d" (t.p.lo), "=d" (t.p.hi));
+    return t.c;
+}
 #else //FIXME check ppc64
 static inline uint64_t read_time(void)
 {