From 727984b4ff75df5729e5b34af20e04b2c90d19c1 Mon Sep 17 00:00:00 2001
From: Nils Wallménius <nils@rockbox.org>
Date: Sun, 29 Nov 2009 10:57:21 +0000
Subject: Use clz instruction to count leading zeroes on armv5+, gives about 2%
 speedup with one sample on the Gigabeat S

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@23781 a1c6a512-1295-4272-9138-f99709370657
---
 apps/codecs/libalac/alac.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

(limited to 'apps/codecs/libalac/alac.c')

diff --git a/apps/codecs/libalac/alac.c b/apps/codecs/libalac/alac.c
index 112ad20bad..f94ff0fa9d 100644
--- a/apps/codecs/libalac/alac.c
+++ b/apps/codecs/libalac/alac.c
@@ -166,6 +166,15 @@ static inline void unreadbits(alac_file *alac, int bits)
         alac->input_buffer_bitaccumulator *= -1;
 }
 
+/* ARMv5+ has a clz instruction equivalent to our function.
+ */
+#if (defined(CPU_ARM) && (ARM_ARCH > 4))
+static inline int count_leading_zeros(uint32_t v)
+{
+    return __builtin_clz(v);
+}
+#else
+
 static const unsigned char bittab[16] ICONST_ATTR = {
     0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4
 };
@@ -196,9 +205,7 @@ static inline int count_leading_zeros(int input)
     output -= bittab[input];
     return output;
 }
-
-
-
+#endif
 
 void basterdised_rice_decompress(alac_file *alac,
                                  int32_t *output_buffer,
-- 
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