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

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For systems without __builtin_clz() or _BitScanReverse(), taken from libwep

Change-Id: Iead257efc1772c466c79e1dc0356ed571d38d43e
This commit is contained in:
Alex Converse 2014-01-08 12:25:47 -08:00
parent af72081818
commit ce7ff3b63d
1 changed files with 33 additions and 9 deletions
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42
vp9/common/vp9_systemdependent.h
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@ -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 @@ static int round(double x) {
}
#endif
static const inline int get_msb(int x) {
#ifdef _MSC_VER
int r = 0;
_BitScanReverse(&r, x);
return r;
#else
return 31 ^ __builtin_clz(x);
#endif
// 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
// 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);