[PATCH v3 2/3] eal: add rte ffs32 and rte ffs64 inline functions

[Andre Muezerie]

From: Tyler Retzlaff <roretzla at linux.microsoft.com>

Provide toolchain abstraction for __builtin_ffs{,l,ll} gcc built-in
intrinsics.

Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
---
 lib/eal/include/rte_bitops.h | 74 ++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/lib/eal/include/rte_bitops.h b/lib/eal/include/rte_bitops.h
index deb1fd43f2..0862fd4008 100644
--- a/lib/eal/include/rte_bitops.h
+++ b/lib/eal/include/rte_bitops.h
@@ -958,6 +958,48 @@ rte_popcount64(uint64_t v)
 	return (unsigned int)__popcnt64(v);
 }
 
+/**
+ * Search v from least significant bit (LSB) to the most
+ * significant bit (MSB) for a set bit (1).
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   Bit index + 1 if a set bit is found, zero otherwise.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ffs32(uint32_t v)
+{
+	unsigned long rv;
+
+	if (_BitScanForward(&rv, v) == 0)
+		return 0;
+
+	return (unsigned int)rv + 1;
+}
+
+/**
+ * Search v from least significant bit (LSB) to the most
+ * significant bit (MSB) for a set bit (1).
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   Bit index + 1 if a set bit is found, zero otherwise.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ffs64(uint64_t v)
+{
+	unsigned long rv;
+
+	if (_BitScanForward64(&rv, v) == 0)
+		return 0;
+
+	return (unsigned int)rv + 1;
+}
+
 #else
 
 /**
@@ -1044,6 +1086,38 @@ rte_popcount64(uint64_t v)
 	return (unsigned int)__builtin_popcountll(v);
 }
 
+/**
+ * Search v from least significant bit (LSB) to the most
+ * significant bit (MSB) for a set bit (1).
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   Bit index + 1 if a set bit is found, zero otherwise.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ffs32(uint32_t v)
+{
+	return (unsigned int)__builtin_ffs(v);
+}
+
+/**
+ * Search v from least significant bit (LSB) to the most
+ * significant bit (MSB) for a set bit (1).
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   Bit index + 1 if a set bit is found, zero otherwise.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ffs64(uint64_t v)
+{
+	return (unsigned int)__builtin_ffsll(v);
+}
+
 #endif
 
 /**
-- 
2.47.2.vfs.0.1