From a7bcb7e62d8bc4026ad6442410a74cdb1eb86761 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Mon, 31 Jan 2022 02:50:27 +0000
Subject: [PATCH] Implement ottd_rdtsc for AARCH64 on GCC/clang

---
 src/cpu.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/cpu.cpp b/src/cpu.cpp
index d95c704e2a..d9d7ac2377 100644
--- a/src/cpu.cpp
+++ b/src/cpu.cpp
@@ -50,6 +50,17 @@ uint64 ottd_rdtsc()
 # define RDTSC_AVAILABLE
 #endif
 
+/* rdtsc for AARCH64. Use GCC syntax */
+#if defined(__aarch64__) && !defined(RDTSC_AVAILABLE)
+uint64 ottd_rdtsc()
+{
+	uint64 val;
+	asm volatile("mrs %0, cntvct_el0" : "=r" (val));
+	return val;
+}
+# define RDTSC_AVAILABLE
+#endif
+
 /* rdtsc for PPC which has this not */
 #if (defined(__POWERPC__) || defined(__powerpc__)) && !defined(RDTSC_AVAILABLE)
 uint64 ottd_rdtsc()