[PATCH v3 2/3] eal: provide leading and trailing zero bit count abstraction

[Tyler Retzlaff]

From: Tyler Retzlaff <roretzla at microsoft.com>

Provide an abstraction for leading and trailing zero bit counting
functions to hide compiler specific intrinsics and builtins.

Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
---
 lib/eal/include/rte_bitops.h | 168 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 168 insertions(+)

diff --git a/lib/eal/include/rte_bitops.h b/lib/eal/include/rte_bitops.h
index 531479e..387d7aa 100644
--- a/lib/eal/include/rte_bitops.h
+++ b/lib/eal/include/rte_bitops.h
@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: BSD-3-Clause
  * Copyright(c) 2020 Arm Limited
+ * Copyright(c) 2010-2019 Intel Corporation
+ * Copyright(c) 2023 Microsoft Corporation
  */
 
 #ifndef _RTE_BITOPS_H_
@@ -275,6 +277,172 @@
 	return val & mask;
 }
 
+#ifdef RTE_TOOLCHAIN_MSVC
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of leading 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of leading zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_clz32(uint32_t v)
+{
+	unsigned long rv;
+
+	(void)_BitScanReverse(&rv, v);
+
+	return (unsigned int)rv;
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of leading 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of leading zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_clz64(uint64_t v)
+{
+	unsigned long rv;
+
+	(void)_BitScanReverse64(&rv, v);
+
+	return (unsigned int)rv;
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of trailing 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of trailing zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ctz32(uint32_t v)
+{
+	unsigned long rv;
+
+	(void)_BitScanForward(&rv, v);
+
+	return (unsigned int)rv;
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of trailing 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of trailing zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ctz64(uint64_t v)
+{
+	unsigned long rv;
+
+	(void)_BitScanForward64(&rv, v);
+
+	return (unsigned int)rv;
+}
+
+#else
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of leading 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of leading zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_clz32(uint32_t v)
+{
+	return (unsigned int)__builtin_clz(v);
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of leading 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of leading zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_clz64(uint64_t v)
+{
+	return (unsigned int)__builtin_clzll(v);
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of trailing 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of trailing zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ctz32(uint32_t v)
+{
+	return (unsigned int)__builtin_ctz(v);
+}
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
+ *
+ * Get the count of trailing 0-bits in v.
+ *
+ * @param v
+ *   The value.
+ * @return
+ *   The count of trailing zero bits.
+ */
+__rte_experimental
+static inline unsigned int
+rte_ctz64(uint64_t v)
+{
+	return (unsigned int)__builtin_ctzll(v);
+}
+
+#endif
+
 /**
  * Combines 32b inputs most significant set bits into the least
  * significant bits to construct a value with the same MSBs as x
-- 
1.8.3.1