[PATCH v2 1/2] eal: provide leading and trailing zero bit count abstraction

[Tyler Retzlaff]

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/meson.build    |   1 +
 lib/eal/include/rte_bitcount.h | 265 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 266 insertions(+)
 create mode 100644 lib/eal/include/rte_bitcount.h

diff --git a/lib/eal/include/meson.build b/lib/eal/include/meson.build
index cfcd40a..8ff1d65 100644
--- a/lib/eal/include/meson.build
+++ b/lib/eal/include/meson.build
@@ -5,6 +5,7 @@ includes += include_directories('.')
 
 headers += files(
         'rte_alarm.h',
+        'rte_bitcount.h',
         'rte_bitmap.h',
         'rte_bitops.h',
         'rte_branch_prediction.h',
diff --git a/lib/eal/include/rte_bitcount.h b/lib/eal/include/rte_bitcount.h
new file mode 100644
index 0000000..587de52
--- /dev/null
+++ b/lib/eal/include/rte_bitcount.h
@@ -0,0 +1,265 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (C) 2022 Microsoft Corporation
+ */
+
+#ifndef _RTE_BITCOUNT_H_
+#define _RTE_BITCOUNT_H_
+
+#include <rte_compat.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#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_clz(unsigned int 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_clzl(unsigned long 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_clzll(unsigned long long 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_ctz(unsigned int 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_ctzl(unsigned long 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_ctzll(unsigned long long 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_clz(unsigned int 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_clzl(unsigned long v)
+{
+	return (unsigned int)__builtin_clzl(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_clzll(unsigned long 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_ctz(unsigned int 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_ctzl(unsigned long v)
+{
+	return (unsigned int)__builtin_ctzl(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_ctzll(unsigned long v)
+{
+	return (unsigned int)__builtin_ctzll(v);
+}
+
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_BITCOUNT_H_ */
+
-- 
1.8.3.1