[dpdk-dev] [PATCH v2 3/4] common: add 64-bit fls function

[Anatoly Burakov]

Add missing implementation for 64-bit fls function, and extend
unit test to test the new function as well.

Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
---
 lib/librte_eal/common/include/rte_common.h | 18 ++++++++++++++++++
 test/test/test_common.c                    | 21 +++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
index d102f2cec..7b50b8479 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -547,6 +547,24 @@ 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 64.
+ * @note rte_fls_u64(0) = 0, rte_fls_u64(1) = 1,
+ *       rte_fls_u64(0x8000000000000000) = 64
+ *
+ * @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);
+}
+
 #ifndef offsetof
 /** Return the offset of a field in a structure. */
 #define offsetof(TYPE, MEMBER)  __builtin_offsetof (TYPE, MEMBER)
diff --git a/test/test/test_common.c b/test/test/test_common.c
index 4a42aaed8..f6dd4c18d 100644
--- a/test/test/test_common.c
+++ b/test/test/test_common.c
@@ -242,6 +242,8 @@ test_fls(void)
 	};
 
 	for (i = 0; i < RTE_DIM(test); i++) {
+		uint64_t arg64;
+
 		arg = test[i].arg;
 		rc = rte_fls_u32(arg);
 		expected = test[i].rc;
@@ -250,6 +252,25 @@ test_fls(void)
 				arg, rc, expected);
 			return TEST_FAILED;
 		}
+		/* 64-bit version */
+		arg = test[i].arg;
+		rc = rte_fls_u64(arg);
+		expected = test[i].rc;
+		if (rc != expected) {
+			printf("Wrong rte_fls_u64(0x%x) rc=%d, expected=%d\n",
+				arg, rc, expected);
+			return TEST_FAILED;
+		}
+		/* 64-bit version shifted by 32 bits */
+		arg64 = (uint64_t)test[i].arg << 32;
+		rc = rte_fls_u64(arg64);
+		/* don't shift zero */
+		expected = test[i].rc == 0 ? 0 : test[i].rc + 32;
+		if (rc != expected) {
+			printf("Wrong rte_fls_u64(0x%" PRIx64 ") rc=%d, expected=%d\n",
+				arg64, rc, expected);
+			return TEST_FAILED;
+		}
 	}
 
 	return 0;
-- 
2.17.1