[dpdk-dev] [PATCH v2 2/4] common: add bsf64 and bsf32_safe functions

[Anatoly Burakov <anatoly.burakov@intel.com>]

Add an rte_bsf64 function that follows the convention of existing
rte_bsf32 function. Also, add missing implementation for safe
version of rte_bsf32, and implement unit tests for all recently
added bsf varieties.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 doc/guides/rel_notes/release_19_02.rst     |  4 +-
 lib/librte_eal/common/include/rte_common.h | 43 +++++++++++++++++++++-
 test/test/test_common.c                    | 41 ++++++++++++++++++++-
 3 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/doc/guides/rel_notes/release_19_02.rst b/doc/guides/rel_notes/release_19_02.rst
index c4cce4c98..0f446ed74 100644
--- a/doc/guides/rel_notes/release_19_02.rst
+++ b/doc/guides/rel_notes/release_19_02.rst
@@ -100,7 +100,9 @@ API Changes
 
 
 * eal: function ``rte_bsf64`` in ``rte_bitmap.h`` has been renamed to
-  ``rte_bsf64_safe`` and moved to ``rte_common.h``.
+  ``rte_bsf64_safe`` and moved to ``rte_common.h``. A new ``rte_bsf64`` function
+  has been added in ``rte_common.h`` that follows convention set by existing
+  ``rte_bsf32`` function.
 
 
 ABI Changes
diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
index 66cdf60b2..d102f2cec 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -447,6 +447,30 @@ 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.
  *
@@ -482,6 +506,23 @@ rte_fls_u32(uint32_t x)
 	return (x == 0) ? 0 : 32 - __builtin_clz(x);
 }
 
+/**
+ * Searches the input parameter for the least significant set bit
+ * (starting from zero).
+ * If a least significant 1 bit is found, its bit index is returned.
+ * If the content of the input parameter is zero, then the content of the return
+ * value is undefined.
+ * @param v
+ *     input parameter, should not be zero.
+ * @return
+ *     least significant set bit in the input parameter.
+ */
+static inline int
+rte_bsf64(uint64_t v)
+{
+	return (uint32_t)__builtin_ctzll(v);
+}
+
 /**
  * Searches the input parameter for the least significant set bit
  * (starting from zero). Safe version (checks for input parameter being zero).
@@ -502,7 +543,7 @@ rte_bsf64_safe(uint64_t v, uint32_t *pos)
 	if (v == 0)
 		return 0;
 
-	*pos = __builtin_ctzll(v);
+	*pos = rte_bsf64(v);
 	return 1;
 }
 
diff --git a/test/test/test_common.c b/test/test/test_common.c
index c6d17baae..4a42aaed8 100644
--- a/test/test/test_common.c
+++ b/test/test/test_common.c
@@ -50,12 +50,48 @@ test_macros(int __rte_unused unused_parm)
 	return 0;
 }
 
+static int
+test_bsf(void)
+{
+	uint32_t shift, pos;
+
+	/* safe versions should be able to handle 0 */
+	if (rte_bsf32_safe(0, &pos) != 0)
+		FAIL("rte_bsf32_safe");
+	if (rte_bsf64_safe(0, &pos) != 0)
+		FAIL("rte_bsf64_safe");
+
+	for (shift = 0; shift < 63; shift++) {
+		uint32_t val32;
+		uint64_t val64;
+
+		val64 = 1ULL << shift;
+		if ((uint32_t)rte_bsf64(val64) != shift)
+			FAIL("rte_bsf64");
+		if (rte_bsf64_safe(val64, &pos) != 1)
+			FAIL("rte_bsf64_safe");
+		if (pos != shift)
+			FAIL("rte_bsf64_safe");
+
+		if (shift > 31)
+			continue;
+
+		val32 = 1U << shift;
+		if ((uint32_t)rte_bsf32(val32) != shift)
+			FAIL("rte_bsf32");
+		if (rte_bsf32_safe(val32, &pos) != 1)
+			FAIL("rte_bsf32_safe");
+		if (pos != shift)
+			FAIL("rte_bsf32_safe");
+	}
+
+	return 0;
+}
+
 static int
 test_misc(void)
 {
 	char memdump[] = "memdump_test";
-	if (rte_bsf32(129))
-		FAIL("rte_bsf32");
 
 	rte_memdump(stdout, "test", memdump, sizeof(memdump));
 	rte_hexdump(stdout, "test", memdump, sizeof(memdump));
@@ -226,6 +262,7 @@ test_common(void)
 	ret |= test_align();
 	ret |= test_macros(0);
 	ret |= test_misc();
+	ret |= test_bsf();
 	ret |= test_log2();
 	ret |= test_fls();
 
-- 
2.17.1