bluelib/core/sys/windows/bitop.c

#include <blue/core/bitop.h>
#include <intrin.h>
#include <assert.h>

#define CPU_FEATURE_YES		1
#define CPU_FEATURE_NO		-1
#define CPU_FEATURE_UNKNOWN	0

static int cpu_supports_popcnt = CPU_FEATURE_UNKNOWN;

static int check_popcnt_support()
{
	int d[4];
	__cpuid(d, 0x00000001);

	return (d[2] & 0x800000) ? CPU_FEATURE_YES : CPU_FEATURE_NO;
}

int b_popcountl(long v)
{
	if (cpu_supports_popcnt == CPU_FEATURE_UNKNOWN) {
		cpu_supports_popcnt = check_popcnt_support();
	}

	if (cpu_supports_popcnt == CPU_FEATURE_YES) {
#if _M_AMD64 == 100
		return __popcnt64(v);
#else
		return __popcnt(v);
#endif
	}
	
	assert(0 && "CPU does not support popcount!");
	return 0;
}

int b_ctzl(long v)
{
	unsigned long trailing_zero = 0;

#if _M_AMD64 == 100
	int x = _BitScanForward64(&trailing_zero, v);
#else
	int x = _BitScanForward(&trailing_zero, v);
#endif

	if (x) {
		return trailing_zero;
	} else {
		return 64;
	}
}

int b_clzl(long v)
{
	unsigned long leading_zero = 0;

#if _M_AMD64 == 100
	int x = _BitScanReverse64(&leading_zero, v);
#else
	int x = _BitScanReverse(&leading_zero, v);
#endif

	if (x) {
		return 64 - leading_zero;
	} else {
		// Same remarks as above
		return 64;
	}
}