From df2c71ea5ad313e16c73e7eeaf42bbfa826866e3 Mon Sep 17 00:00:00 2001
From: "Timothy B. Terriberry" <tterribe@xiph.org>
Date: Thu, 23 Dec 2010 08:06:48 -0800
Subject: [PATCH] Use _BitScanReverse for EC_ILOG with MSVC.
Also updates the TI dsplib macros to use the same EC_CLZ mechanism
as everything else.
---
libcelt/ecintrin.h | 34 ++++++++++++++++++++++------------
1 file changed, 22 insertions(+), 12 deletions(-)
diff --git a/libcelt/ecintrin.h b/libcelt/ecintrin.h
index 54ae90a17..e6e0f9b0c 100644
--- a/libcelt/ecintrin.h
+++ b/libcelt/ecintrin.h
@@ -83,17 +83,30 @@
/*Count leading zeros.
This macro should only be used for implementing ec_ilog(), if it is defined.
All other code should use EC_ILOG() instead.*/
-#ifdef __GNUC_PREREQ
-#if __GNUC_PREREQ(3,4)
-# if INT_MAX>=2147483647
-# define EC_CLZ0 sizeof(unsigned)*CHAR_BIT
-# define EC_CLZ(_x) (__builtin_clz(_x))
-# elif LONG_MAX>=2147483647L
-# define EC_CLZ0 sizeof(unsigned long)*CHAR_BIT
-# define EC_CLZ(_x) (__builtin_clzl(_x))
+#if defined(_MSC_VER)
+# include <intrin.h>
+static __inline int ec_bsr(unsigned long _x){
+ unsigned long ret;
+ _BitScanReverse(&ret,_x);
+ return (int)ret;
+}
+# define EC_CLZ0 (1)
+# define EC_CLZ(_x) (-ec_bsr(_x))
+#elif defined(ENABLE_TI_DSPLIB)
+# include "dsplib.h"
+# define EC_CLZ0 (31)
+# define EC_CLZ(_x) (_lnorm(x))
+#elif defined(__GNUC_PREREQ)
+# if __GNUC_PREREQ(3,4)
+# if INT_MAX>=2147483647
+# define EC_CLZ0 ((int)sizeof(unsigned)*CHAR_BIT)
+# define EC_CLZ(_x) (__builtin_clz(_x))
+# elif LONG_MAX>=2147483647L
+# define EC_CLZ0 ((int)sizeof(unsigned long)*CHAR_BIT)
+# define EC_CLZ(_x) (__builtin_clzl(_x))
+# endif
# endif
#endif
-#endif
#if defined(EC_CLZ)
/*Note that __builtin_clz is not defined when _x==0, according to the gcc
@@ -101,9 +114,6 @@
The majority of the time we can never pass it zero.
When we need to, it can be special cased.*/
# define EC_ILOG(_x) (EC_CLZ0-EC_CLZ(_x))
-#elif defined(ENABLE_TI_DSPLIB)
-#include "dsplib.h"
-#define EC_ILOG(x) (31 - _lnorm(x))
#else
# define EC_ILOG(_x) (ec_ilog(_x))
#endif
--
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