Implement missing functions for 32-bit safe bsf, as well as 64-bit
fls and log2.
Signed-off-by: Anatoly Burakov <anatoly.bura...@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitre...@intel.com>
---
Notes:
v3:
- Added clarification that pos is not checked
lib/librte_eal/common/include/rte_common.h | 64 +++++++++++++++++++++-
1 file changed, 63 insertions(+), 1 deletion(-)
diff --git a/lib/librte_eal/common/include/rte_common.h
b/lib/librte_eal/common/include/rte_common.h
index d115b175c..6883e5c3b 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -456,6 +456,30 @@ rte_bsf32(uint32_t v)
return (uint32_t)__builtin_ctz(v);
}
+/**
+ * Searches the input parameter for the least significant set bit
+ * (starting from zero). Safe version (checks for input parameter being zero).
+ *
+ * @warning ``pos`` must be a valid pointer. It is not checked!
+ *
+ * @param v
+ * The input parameter.
+ * @param pos
+ * If ``v`` was not 0, this value will contain position of least
significant
+ * bit within the input parameter.
+ * @return
+ * Returns 0 if ``v`` was 0, otherwise returns 1.
+ */
+static inline int
+rte_bsf32_safe(uint64_t v, uint32_t *pos)
+{
+ if (v == 0)
+ return 0;
+
+ *pos = rte_bsf32(v);
+ return 1;
+}
+
/**
* Return the rounded-up log2 of a integer.
*
@@ -473,7 +497,6 @@ rte_log2_u32(uint32_t v)
return rte_bsf32(v);
}
-
/**
* Return the last (most-significant) bit set.
*
@@ -515,6 +538,45 @@ rte_bsf64_safe(uint64_t v, uint32_t *pos)
return 1;
}
+/**
+ * Return the last (most-significant) bit set.
+ *
+ * @note The last (most significant) bit is at position 32.
+ * @note rte_fls_u32(0) = 0, rte_fls_u32(1) = 1, rte_fls_u32(0x80000000) = 32
+ *
+ * @param x
+ * The input parameter.
+ * @return
+ * The last (most-significant) bit set, or 0 if the input is 0.
+ */
+static inline int
+rte_fls_u64(uint64_t x)
+{
+ return (x == 0) ? 0 : 64 - __builtin_clzll(x);
+}
+
+/**
+ * Return the rounded-up log2 of a integer.
+ *
+ * @param v
+ * The input parameter.
+ * @return
+ * The rounded-up log2 of the input, or 0 if the input is 0.
+ */
+static inline uint32_t
+rte_log2_u64(uint64_t v)
+{
+ uint32_t pos = 0;
+ if (v == 0)
+ return 0;
+ v = rte_align64pow2(v);
+ /* TODO: replace with rte_bsf64 when that lands */
+ /* we checked for v being 0 already, so pos is always valid */
+ rte_bsf64_safe(v, &pos);
+ return pos;
+}
+
+
#ifndef offsetof
/** Return the offset of a field in a structure. */
#define offsetof(TYPE, MEMBER) __builtin_offsetof (TYPE, MEMBER)
--
2.17.1
