Using the compiler intrinsic shows approximately around 25% speed
up with some classifier specific unit tests.
Signed-off-by: Gurucharan Shetty <gshe...@nicira.com>
---
lib/util.c | 2 +-
lib/util.h | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/lib/util.c b/lib/util.c
index f3e47b1..01fe7dc 100644
--- a/lib/util.c
+++ b/lib/util.c
@@ -949,7 +949,7 @@ english_list_delimiter(size_t index, size_t total)
}
/* Returns the number of trailing 0-bits in 'n'. Undefined if 'n' == 0. */
-#if __GNUC__ >= 4
+#if __GNUC__ >= 4 || _MSC_VER
/* Defined inline in util.h. */
#else
/* Returns the number of trailing 0-bits in 'n'. Undefined if 'n' == 0. */
diff --git a/lib/util.h b/lib/util.h
index 7da7aa8..1e0b94e 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -354,6 +354,42 @@ raw_clz64(uint64_t n)
{
return __builtin_clzll(n);
}
+#elif _MSC_VER
+static inline int
+raw_ctz(uint64_t n)
+{
+#ifdef _WIN64
+ uint32_t r = 0;
+ _BitScanForward64(&r, n);
+ return r;
+#else
+ uint32_t low = n & 0x00000000FFFFFFFF, high, r = 0;
+ if (_BitScanForward(&r, low)) {
+ return r;
+ }
+ high = n >> 32;
+ _BitScanForward(&r, high);
+ return r + 32;
+#endif
+}
+
+static inline int
+raw_clz64(uint64_t n)
+{
+#ifdef _WIN64
+ uint32_t r = 0;
+ _BitScanReverse64(&r, n);
+ return 63 - r;
+#else
+ uint32_t low, high = n >> 32, r = 0;
+ if (_BitScanReverse(&r, high)) {
+ return 31 - r;
+ }
+ low = n & 0x00000000FFFFFFFF;
+ _BitScanReverse(&r, low);
+ return 63 - r;
+#endif
+}
#else
/* Defined in util.c. */
int raw_ctz(uint64_t n);
--
1.7.9.5
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