[Minios-devel] [UNIKRAFT PATCHv6 01/37] uk/arch: Implement ukarch_ffsl for Arm64

[Wei Chen <wei.chen@xxxxxxx>]

From: Wei Chen <Wei.Chen@xxxxxxx>

This function is ported from Arm32 and is modified to work
on Arm64.

Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
---
 include/uk/arch/arm/arm64/atomic.h | 70 ++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 include/uk/arch/arm/arm64/atomic.h

diff --git a/include/uk/arch/arm/arm64/atomic.h 
b/include/uk/arch/arm/arm64/atomic.h
new file mode 100644
index 0000000..7ee6667
--- /dev/null
+++ b/include/uk/arch/arm/arm64/atomic.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Port from Mini-OS: include/arm/os.h
+ */
+/*
+ * Authors: Karim Allah Ahmed <karim.allah.ahmed@xxxxxxxxx>
+ *          Thomas Leonard <talex5@xxxxxxxxx>
+ *          Wei Chen <Wei.Chen@xxxxxxx>
+ *
+ * Copyright (c) 2014 Karim Allah Ahmed
+ * Copyright (c) 2014 Thomas Leonard
+ * Copyright (c) 2018, Arm Ltd., All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef __UKARCH_ATOMIC_H__
+#error Do not include this header directly
+#endif
+
+/**
+ * ukarch_ffsl - find first (lowest) set bit in word.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+static inline unsigned long ukarch_ffsl(unsigned long word)
+{
+       int clz;
+
+       /* xxxxx10000 = word
+        * xxxxx01111 = word - 1
+        * 0000011111 = word ^ (word - 1)
+        *      4     = 63 - clz(word ^ (word - 1))
+        */
+
+       __asm__("sub x0, %[word], #1\n"
+               "eor x0, x0, %[word]\n"
+               "clz %[clz], x0\n"
+               :
+               /* Outputs: */
+               [clz] "=r"(clz)
+               :
+               /* Inputs: */
+               [word] "r"(word)
+               :
+               /* Clobbers: */
+               "x0");
+
+       return 63 - clz;
+}
-- 
2.17.1


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