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* [dpdk-dev] [PATCH] Fix rte_is_power_of_2() function since it returns true for zero and zero is not a power of 2. Avoid branching in RTE_MIN and RTE_MAX when calculating minimum and maximum of two numbers.
@ 2014-12-10 16:46 r k
  0 siblings, 0 replies; only message in thread
From: r k @ 2014-12-10 16:46 UTC (permalink / raw)
  To: dev

Subject: [PATCH] Fix rte_is_power_of_2() function since it returns
true for zero and zero is not a power of 2. Avoid branching in RTE_MIN
and RTE_MAX when calculating minimum and maximum of two numbers.

Signed-off-by: Ravi Kerur <rkerur@gmail.com>
---
 lib/librte_eal/common/include/rte_common.h | 6 +++---
 lib/librte_pmd_e1000/igb_pf.c              | 4 ++--
 lib/librte_pmd_ixgbe/ixgbe_pf.c            | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/lib/librte_eal/common/include/rte_common.h
b/lib/librte_eal/common/include/rte_common.h
index 921b91f..21b17ad 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -203,7 +203,7 @@ extern int RTE_BUILD_BUG_ON_detected_error;
static inline int  rte_is_power_of_2(uint32_t n)  {
-       return ((n-1) & n) == 0;
+       return n && !(n & (n - 1));
 }

 /**
@@ -259,7 +259,7 @@ rte_align64pow2(uint64_t v)  #define RTE_MIN(a, b) ({ \
                typeof (a) _a = (a); \
                typeof (b) _b = (b); \
-               _a < _b ? _a : _b; \
+                _b ^ ((_a ^ _b) & -(_a < _b)); \
        })

 /**
@@ -268,7 +268,7 @@ rte_align64pow2(uint64_t v)  #define RTE_MAX(a, b) ({ \
                typeof (a) _a = (a); \
                typeof (b) _b = (b); \
-               _a > _b ? _a : _b; \
+                _a ^ ((_a ^ _b) & -(_a < _b)); \
        })

 /*********** Other general functions / macros ********/ diff --git
a/lib/librte_pmd_e1000/igb_pf.c b/lib/librte_pmd_e1000/igb_pf.c index
bc3816a..546499c 100644
--- a/lib/librte_pmd_e1000/igb_pf.c
+++ b/lib/librte_pmd_e1000/igb_pf.c
@@ -321,11 +321,11 @@ igb_vf_set_mac_addr(struct rte_eth_dev *dev,
uint32_t vf, uint32_t *msgbuf)  static int
igb_vf_set_multicast(struct rte_eth_dev *dev, __rte_unused uint32_t
vf, uint32_t *msgbuf)  {
-       int i;
+       int16_t i;
        uint32_t vector_bit;
        uint32_t vector_reg;
        uint32_t mta_reg;
-       int entries = (msgbuf[0] & E1000_VT_MSGINFO_MASK) >>
+       int32_t entries = (msgbuf[0] & E1000_VT_MSGINFO_MASK) >>
                E1000_VT_MSGINFO_SHIFT;
        uint16_t *hash_list = (uint16_t *)&msgbuf[1];
        struct e1000_hw *hw = E1000_DEV_PRIVATE_TO_HW(dev->data->dev_private);
diff --git a/lib/librte_pmd_ixgbe/ixgbe_pf.c
b/lib/librte_pmd_ixgbe/ixgbe_pf.c index 51da1fd..426caf9 100644
--- a/lib/librte_pmd_ixgbe/ixgbe_pf.c
+++ b/lib/librte_pmd_ixgbe/ixgbe_pf.c
@@ -390,7 +390,7 @@ ixgbe_vf_set_multicast(struct rte_eth_dev *dev,
__rte_unused uint32_t vf, uint32
        struct ixgbe_hw *hw = IXGBE_DEV_PRIVATE_TO_HW(dev->data->dev_private);
        struct ixgbe_vf_info *vfinfo =
                *(IXGBE_DEV_PRIVATE_TO_P_VFDATA(dev->data->dev_private));
-       int nb_entries = (msgbuf[0] & IXGBE_VT_MSGINFO_MASK) >>
+       int32_t nb_entries = (msgbuf[0] & IXGBE_VT_MSGINFO_MASK) >>
                IXGBE_VT_MSGINFO_SHIFT;
        uint16_t *hash_list = (uint16_t *)&msgbuf[1];
        uint32_t mta_idx;
@@ -399,7 +399,7 @@ ixgbe_vf_set_multicast(struct rte_eth_dev *dev,
__rte_unused uint32_t vf, uint32
        const uint32_t IXGBE_MTA_BIT_SHIFT = 5;
        const uint32_t IXGBE_MTA_BIT_MASK = (0x1 << IXGBE_MTA_BIT_SHIFT) - 1;
        uint32_t reg_val;
-       int i;
+       int16_t i;

        /* only so many hash values supported */
        nb_entries = RTE_MIN(nb_entries, IXGBE_MAX_VF_MC_ENTRIES);
--
1.9.1

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2014-12-10 16:46 [dpdk-dev] [PATCH] Fix rte_is_power_of_2() function since it returns true for zero and zero is not a power of 2. Avoid branching in RTE_MIN and RTE_MAX when calculating minimum and maximum of two numbers r k

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