Blackfin - read_time primitive

note this primitive currently uses a union to concatenate 2x32bit registers because of poor compiler support
around DImode and asm.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@9302 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavutil/common.h

@@ -267,7 +267,7 @@ static inline int ff_get_fourcc(const char *s){
         }\
     }
 
-#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 @@ static inline long long read_time(void)
         );
         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)
 {