Add 32b and 64b API's to align the given integer to the previous power
of 2.
Signed-off-by: Pavan Nikhilesh <pbhagavat...@caviumnetworks.com>
---
v3 Changes:
- Move commonly used code to rte_combine(32/64)ms1b so that it can be reused.
v2 Changes:
- Modified api name to `rte_align(32/64)prevpow2` from
`rte_align(32/64)lowpow2`.
- corrected fuction to return if the integer is already aligned to
power of 2.
lib/librte_eal/common/include/rte_common.h | 92 ++++++++++++++++++++++++++----
1 file changed, 81 insertions(+), 11 deletions(-)
diff --git a/lib/librte_eal/common/include/rte_common.h
b/lib/librte_eal/common/include/rte_common.h
index c7803e41c..7e147dcf2 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -223,6 +223,51 @@ extern int RTE_BUILD_BUG_ON_detected_error;
} while(0)
#endif
+/**
+ * Combines 32b inputs most significant set bits into the least
+ * significant bits to construct a value with the same MSBs as x
+ * but all 1's under it.
+ *
+ * @param x
+ * The integer whose MSBs need to be combined with its LSBs
+ * @return
+ * The combined value.
+ */
+static inline uint32_t
+rte_combine32ms1b(register uint32_t x)
+{
+ x |= x >> 1;
+ x |= x >> 2;
+ x |= x >> 4;
+ x |= x >> 8;
+ x |= x >> 16;
+
+ return x;
+}
+
+/**
+ * Combines 64b inputs most significant set bits into the least
+ * significant bits to construct a value with the same MSBs as x
+ * but all 1's under it.
+ *
+ * @param v
+ * The integer whose MSBs need to be combined with its LSBs
+ * @return
+ * The combined value.
+ */
+static inline uint64_t
+rte_combine64ms1b(register uint64_t v)
+{
+ v |= v >> 1;
+ v |= v >> 2;
+ v |= v >> 4;
+ v |= v >> 8;
+ v |= v >> 16;
+ v |= v >> 32;
+
+ return v;
+}
+
/*********** Macros to work with powers of 2 ********/
/**
@@ -250,15 +295,28 @@ static inline uint32_t
rte_align32pow2(uint32_t x)
{
x--;
- x |= x >> 1;
- x |= x >> 2;
- x |= x >> 4;
- x |= x >> 8;
- x |= x >> 16;
+ x = rte_combine32ms1b(x);
return x + 1;
}
+/**
+ * Aligns input parameter to the previous power of 2
+ *
+ * @param x
+ * The integer value to algin
+ *
+ * @return
+ * Input parameter aligned to the previous power of 2
+ */
+static inline uint32_t
+rte_align32prevpow2(uint32_t x)
+{
+ x = rte_combine32ms1b(x);
+
+ return x - (x >> 1);
+}
+
/**
* Aligns 64b input parameter to the next power of 2
*
@@ -272,16 +330,28 @@ static inline uint64_t
rte_align64pow2(uint64_t v)
{
v--;
- v |= v >> 1;
- v |= v >> 2;
- v |= v >> 4;
- v |= v >> 8;
- v |= v >> 16;
- v |= v >> 32;
+ v = rte_combine64ms1b(v);
return v + 1;
}
+/**
+ * Aligns 64b input parameter to the previous power of 2
+ *
+ * @param v
+ * The 64b value to align
+ *
+ * @return
+ * Input parameter aligned to the previous power of 2
+ */
+static inline uint64_t
+rte_align64prevpow2(uint64_t v)
+{
+ v = rte_combine64ms1b(v);
+
+ return v - (v >> 1);
+}
+
/*********** Macros for calculating min and max **********/
/**
--
2.16.3
