Move av_log2 function and asociated table to the codec lib, remove 3 identical implementations, always have LUT in iram (gives a *tiny* speedup on coldfire), make the clz based function return the same value as the non clz based function for 0 input to be safe (slows down flac ~2% on the gigabeat S)

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@23858 a1c6a512-1295-4272-9138-f99709370657

2 files changed, 48 insertions, 0 deletions

diff --git a/apps/codecs/lib/codeclib.c b/apps/codecs/lib/codeclib.c
index 8cc40894e3..1c624e0f8c 100644
--- a/apps/codecs/lib/codeclib.c
+++ b/apps/codecs/lib/codeclib.c
@@ -138,6 +138,18 @@ void qsort(void *base, size_t nmemb, size_t size,
     ci->qsort(base,nmemb,size,compar);
 }
 
+/* From ffmpeg - libavutil/common.h */
+const uint8_t ff_log2_tab[256] ICONST_ATTR = {
+    0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
+    5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+    6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+    6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
+};
+
 #ifdef RB_PROFILE
 void __cyg_profile_func_enter(void *this_fn, void *call_site) {
 #ifdef CPU_COLDFIRE
diff --git a/apps/codecs/lib/codeclib.h b/apps/codecs/lib/codeclib.h
index e7f45d3572..bf7b41775a 100644
--- a/apps/codecs/lib/codeclib.h
+++ b/apps/codecs/lib/codeclib.h
@@ -19,6 +19,9 @@
  *
  ****************************************************************************/
 
+#ifndef __CODECLIB_H__
+#define __CODECLIB_H__
+
 #include "config.h"
 #include "codecs.h"
 #include <sys/types.h>
@@ -71,6 +74,37 @@ unsigned udiv32_arm(unsigned a, unsigned b);
 #define UDIV32(a, b) (a / b)
 #endif
 
+/* TODO figure out if we really need to care about calculating
+   av_log2(0) */
+#if (defined(CPU_ARM) && (ARM_ARCH > 4))
+static inline unsigned int av_log2(uint32_t v)
+{
+    unsigned int lz = __builtin_clz(v);
+    return 31 - lz + (lz >> 5); /* make sure av_log2(0) returns 0 */
+}
+#else
+/* From libavutil/common.h */
+extern const uint8_t ff_log2_tab[256] ICONST_ATTR;
+
+static inline unsigned int av_log2(unsigned int v)
+{
+    int n;
+
+    n = 0;
+    if (v & 0xffff0000) {
+        v >>= 16;
+        n += 16;
+    }
+    if (v & 0xff00) {
+        v >>= 8;
+        n += 8;
+    }
+    n += ff_log2_tab[v];
+
+    return n;
+}
+#endif
+
 /* Various codec helper functions */
 
 int codec_init(void);
@@ -82,3 +116,5 @@ void __cyg_profile_func_enter(void *this_fn, void *call_site)
 void __cyg_profile_func_exit(void *this_fn, void *call_site)
     NO_PROF_ATTR ICODE_ATTR;
 #endif
+
+#endif /* __CODECLIB_H__ */