benchmarks/lockhammer/include/cpu_relax.h

Implements the __cpu_relax() macro whose behavior can be modified using
the USE_RELAX makefile variable.

Change-Id: Ic3dbf09bdf6c852a1d94af909c2de7c158741db2

Author: jty2

benchmarks/lockhammer/include/cpu_relax.h

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2017-2025, The Linux Foundation. All rights reserved.
+ *
+ * SPDX-License-Identifier:    BSD-3-Clause
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of The Linux Foundation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER 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 CPU_RELAX_H
+#define CPU_RELAX_H
+
+
+#ifndef CPU_RELAX_ITERATIONS
+#define CPU_RELAX_ITERATIONS 1
+#endif
+
+static inline void __cpu_relax(void) {
+    for (unsigned long i = 0; i < CPU_RELAX_ITERATIONS; i++) {
+#ifdef __aarch64__
+#if defined(RELAX_IS_ISB)
+        asm volatile ("isb" : : : "memory" );
+#elif defined(RELAX_IS_NOP)
+        asm volatile ("nop" : : : "memory");
+#elif defined(RELAX_IS_EMPTY)
+        asm volatile ("" : : : "memory");
+#elif defined(RELAX_IS_NOTHING)
+
+#endif
+#endif // __aarch64__
+
+#ifdef __x86_64__
+
+#if defined(RELAX_IS_PAUSE)
+    // RELAX_IS_PAUSE is the implementation for x86 in jdk-9
+    asm volatile ("rep; nop"); // aka pause
+#elif defined(RELAX_IS_EMPTY)
+    asm volatile ("" : : : "memory");
+#elif defined(RELAX_IS_NOTHING)
+
+#endif
+#endif // __x86_64__
+
+    }
+}
+
+#endif // CPU_RELAX_H
+
+/* vim: set tabstop=4 shiftwidth=4 softtabstop=4 expandtab: */