From 0aaa5ac087896901d4eb75f50e2f1d3d7d9e1dc5 Mon Sep 17 00:00:00 2001
From: Johnnie Birch <45402135+jlb6740@users.noreply.github.com>
Date: Sat, 25 Jul 2020 19:44:21 -0700
Subject: [PATCH 1/2] Update inline assembly for x86 to support new syntax

https://github.com/rust-lang/rfcs/blob/master/text/2843-llvm-asm.md
https://github.com/rust-lang/rfcs/pull/2873
---
 src/cpucounter.c  | 5 ++++-
 src/cpucounter.rs | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/cpucounter.c b/src/cpucounter.c
index a77ee25..bc052a3 100644
--- a/src/cpucounter.c
+++ b/src/cpucounter.c
@@ -3,6 +3,9 @@
 uint64_t cpucounter(void)
 {
     uint64_t low, high;
-    __asm__ __volatile__ ("rdtscp" : "=a" (low), "=d" (high) : : "%ecx");
+    __asm__ __volatile__("rdtscp"
+                         : "=a"(low), "=d"(high)
+                         :
+                         : "%ecx");
     return (high << 32) | low;
 }
diff --git a/src/cpucounter.rs b/src/cpucounter.rs
index 5c9e41a..8517769 100644
--- a/src/cpucounter.rs
+++ b/src/cpucounter.rs
@@ -8,7 +8,7 @@ pub(crate) struct CPUCounter;
 #[inline]
 unsafe fn cpucounter() -> u64 {
     let (low, high): (u64, u64);
-    llvm_asm!("rdtscp" :  "={eax}" (low), "={edx}" (high) : : "ecx");
+    asm!("rdtscp", out("eax") low, out("edx") high, out("ecx") _);
     (high << 32) | low
 }
 

From 7030f5af0b616725b2c837be289b6a879735e02b Mon Sep 17 00:00:00 2001
From: Johnnie Birch <45402135+jlb6740@users.noreply.github.com>
Date: Sat, 25 Jul 2020 19:59:26 -0700
Subject: [PATCH 2/2] Add support for Arm

---
 src/cpucounter.c  | 10 ++++++++++
 src/cpucounter.rs | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/cpucounter.c b/src/cpucounter.c
index bc052a3..c62aa1b 100644
--- a/src/cpucounter.c
+++ b/src/cpucounter.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 
+#if defined(__x86_64__) || defined(__amd64__)
 uint64_t cpucounter(void)
 {
     uint64_t low, high;
@@ -9,3 +10,12 @@ uint64_t cpucounter(void)
                          : "%ecx");
     return (high << 32) | low;
 }
+#elif defined(__aarch64__)
+uint64_t cpucounter(void)
+{
+    uint64_t virtual_timer_value;
+    __asm__ __volatile__("mrs %0, cntvct_el0"
+                         : "=r"(virtual_timer_value));
+    return virtual_timer_value;
+}
+#endif
diff --git a/src/cpucounter.rs b/src/cpucounter.rs
index 8517769..a8b5d06 100644
--- a/src/cpucounter.rs
+++ b/src/cpucounter.rs
@@ -6,12 +6,22 @@ pub(crate) struct CPUCounter;
 
 #[cfg(asm)]
 #[inline]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 unsafe fn cpucounter() -> u64 {
     let (low, high): (u64, u64);
     asm!("rdtscp", out("eax") low, out("edx") high, out("ecx") _);
     (high << 32) | low
 }
 
+#[cfg(asm)]
+#[inline]
+#[cfg(any(target_arch = "aarch64"))]
+unsafe fn cpucounter() -> u64 {
+    let (vtm): (u64);
+    asm!("mrs {}, cntvct_el0", out(reg) vtm);
+    vtm
+}
+
 #[cfg(not(asm))]
 extern "C" {
     fn cpucounter() -> u64;