[v3,3/5] common: add missing implementations
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Commit Message
Implement missing functions for 32-bit safe bsf, as well as 64-bit
fls and log2.
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@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(-)
Comments
-----Original Message-----
> Date: Wed, 14 Nov 2018 16:47:08 +0000
> From: Anatoly Burakov <anatoly.burakov@intel.com>
> To: dev@dpdk.org
> CC: cristian.dumitrescu@intel.com, thomas@monjalon.net,
> bruce.richardson@intel.com, ferruh.yigit@intel.com,
> jasvinder.singh@intel.com
> Subject: [dpdk-dev] [PATCH v3 3/5] common: add missing implementations
> X-Mailer: git-send-email 1.7.0.7
>
> External Email
>
> Implement missing functions for 32-bit safe bsf, as well as 64-bit
> fls and log2.
>
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
> ---
> +/**
> + * Return the last (most-significant) bit set.
> + *
> + * @note The last (most significant) bit is at position 32.
s/position 32/position 64
> + * @note rte_fls_u32(0) = 0, rte_fls_u32(1) = 1, rte_fls_u32(0x80000000) = 32
Fix here too
IMO, it is better to add unit test case for newly added common functions
in test/test/test_common.c
> + *
> + * @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);
> +}
> +
On 15-Nov-18 8:40 AM, Jerin Jacob wrote:
> -----Original Message-----
>> Date: Wed, 14 Nov 2018 16:47:08 +0000
>> From: Anatoly Burakov <anatoly.burakov@intel.com>
>> To: dev@dpdk.org
>> CC: cristian.dumitrescu@intel.com, thomas@monjalon.net,
>> bruce.richardson@intel.com, ferruh.yigit@intel.com,
>> jasvinder.singh@intel.com
>> Subject: [dpdk-dev] [PATCH v3 3/5] common: add missing implementations
>> X-Mailer: git-send-email 1.7.0.7
>>
>> External Email
>>
>> Implement missing functions for 32-bit safe bsf, as well as 64-bit
>> fls and log2.
>>
>> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
>> Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
>> ---
>
>> +/**
>> + * Return the last (most-significant) bit set.
>> + *
>> + * @note The last (most significant) bit is at position 32.
>
> s/position 32/position 64
>
>> + * @note rte_fls_u32(0) = 0, rte_fls_u32(1) = 1, rte_fls_u32(0x80000000) = 32
>
> Fix here too
>
> IMO, it is better to add unit test case for newly added common functions
> in test/test/test_common.c
Good catches and good ideas, thanks!
>
>> + *
>> + * @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);
>> +}
>> +
>
@@ -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)