[dpdk-dev] [PATCH v2] common: add 64-bit log2 function

[Anatoly Burakov]

Add missing implementation for 64-bit log2 function, and extend
the unit test to test this new function. Also, remove duplicate
reimplementation of this function from testpmd and memalloc.

Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
---
 app/test-pmd/testpmd.c                     | 17 +----------------
 lib/librte_eal/common/include/rte_common.h | 18 ++++++++++++++++++
 lib/librte_eal/linuxapp/eal/eal_memalloc.c | 17 +----------------
 test/test/test_common.c                    | 20 +++++++++++++++++++-
 4 files changed, 39 insertions(+), 33 deletions(-)

diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
index a10bc40bb..8d584b008 100644
--- a/app/test-pmd/testpmd.c
+++ b/app/test-pmd/testpmd.c
@@ -649,28 +649,13 @@ calc_mem_size(uint32_t nb_mbufs, uint32_t mbuf_sz, size_t pgsz, size_t *out)
 	return 0;
 }
 
-static inline uint32_t
-bsf64(uint64_t v)
-{
-	return (uint32_t)__builtin_ctzll(v);
-}
-
-static inline uint32_t
-log2_u64(uint64_t v)
-{
-	if (v == 0)
-		return 0;
-	v = rte_align64pow2(v);
-	return bsf64(v);
-}
-
 static int
 pagesz_flags(uint64_t page_sz)
 {
 	/* as per mmap() manpage, all page sizes are log2 of page size
 	 * shifted by MAP_HUGE_SHIFT
 	 */
-	int log2 = log2_u64(page_sz);
+	int log2 = rte_log2_u64(page_sz);
 
 	return (log2 << HUGE_SHIFT);
 }
diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
index 7b50b8479..7178ba1e9 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -565,6 +565,24 @@ rte_fls_u64(uint64_t x)
 	return (x == 0) ? 0 : 64 - __builtin_clzll(x);
 }
 
+/**
+ * Return the rounded-up log2 of a 64-bit 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)
+{
+	if (v == 0)
+		return 0;
+	v = rte_align64pow2(v);
+	/* we checked for v being 0 already, so no undefined behavior */
+	return rte_bsf64(v);
+}
+
 #ifndef offsetof
 /** Return the offset of a field in a structure. */
 #define offsetof(TYPE, MEMBER)  __builtin_offsetof (TYPE, MEMBER)
diff --git a/lib/librte_eal/linuxapp/eal/eal_memalloc.c b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
index 784939566..6e6af5b06 100644
--- a/lib/librte_eal/linuxapp/eal/eal_memalloc.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
@@ -208,28 +208,13 @@ get_file_size(int fd)
 	return st.st_size;
 }
 
-static inline uint32_t
-bsf64(uint64_t v)
-{
-	return (uint32_t)__builtin_ctzll(v);
-}
-
-static inline uint32_t
-log2_u64(uint64_t v)
-{
-	if (v == 0)
-		return 0;
-	v = rte_align64pow2(v);
-	return bsf64(v);
-}
-
 static int
 pagesz_flags(uint64_t page_sz)
 {
 	/* as per mmap() manpage, all page sizes are log2 of page size
 	 * shifted by MAP_HUGE_SHIFT
 	 */
-	int log2 = log2_u64(page_sz);
+	int log2 = rte_log2_u64(page_sz);
 	return log2 << RTE_MAP_HUGE_SHIFT;
 }
 
diff --git a/test/test/test_common.c b/test/test/test_common.c
index f6dd4c18d..94d367471 100644
--- a/test/test/test_common.c
+++ b/test/test/test_common.c
@@ -213,13 +213,31 @@ test_log2(void)
 	const uint32_t step = 1;
 
 	for (i = 0; i < max; i = i + step) {
+		uint64_t i64;
+
+		/* extend range for 64-bit */
+		i64 = (uint64_t)i << 32;
+		base = (uint32_t)ceilf(log2(i64));
+		compare = rte_log2_u64(i64);
+		if (base != compare) {
+			printf("Wrong rte_log2_u64(%" PRIx64 ") val %x, expected %x\n",
+				i64, compare, base);
+			return TEST_FAILED;
+		}
+
 		base = (uint32_t)ceilf(log2((uint32_t)i));
-		compare = rte_log2_u32(i);
+		compare = rte_log2_u32((uint32_t)i);
 		if (base != compare) {
 			printf("Wrong rte_log2_u32(%x) val %x, expected %x\n",
 				i, compare, base);
 			return TEST_FAILED;
 		}
+		compare = rte_log2_u64((uint64_t)i);
+		if (base != compare) {
+			printf("Wrong rte_log2_u64(%x) val %x, expected %x\n",
+				i, compare, base);
+			return TEST_FAILED;
+		}
 	}
 	return 0;
 }
-- 
2.17.1