shithub: libvpx

Info  •  Files  •  Log  •  Branches

Merge "Add a C fallback for get_msb() and change inline to INLINE."

--- a/vp9/common/vp9_systemdependent.h

+++ b/vp9/common/vp9_systemdependent.h

@@ -12,7 +12,6 @@

 #define VP9_COMMON_VP9_SYSTEMDEPENDENT_H_

 #ifdef _MSC_VER

-#include <intrin.h>

 #include <math.h>

 #define snprintf _snprintf

 #endif

@@ -35,15 +34,40 @@

 }

 #endif

-static const inline int get_msb(int x) {

-#ifdef _MSC_VER

-int r = 0;

-_BitScanReverse(&r, x);

-return r;

+// use GNU builtins where available.

+#if defined(__GNUC__) && \

+    ((__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || __GNUC__ >= 4)

+static INLINE int get_msb(unsigned int n) {

+  return 31 ^ __builtin_clz(n);

+}

+#elif defined(_MSC_VER) && _MSC_VER > 1310 && \

+      (defined(_M_X64) || defined(_M_IX86))

+#include <intrin.h>

+#pragma intrinsic(_BitScanReverse)

+

+static INLINE int get_msb(unsigned int n) {

+  unsigned long first_set_bit;

+  _BitScanReverse(&first_set_bit, n);

+  return first_set_bit;

+}

 #else

-return 31 ^ __builtin_clz(x);

-#endif

+// Returns (int)floor(log2(n)). n must be > 0.

+static INLINE int get_msb(unsigned int n) {

+  int log = 0;

+  unsigned int value = n;

+  int i;

+

+  for (i = 4; i >= 0; --i) {

+    const int shift = (1 << i);

+    const unsigned int x = value >> shift;

+    if (x != 0) {

+      value = x;

+      log += shift;

+    }

+  }

+  return log;

 }

+#endif

 struct VP9Common;

 void vp9_machine_specific_config(struct VP9Common *cm);