From 295fc7d0f8f0b6158307c5c9b11a60516f9eb221 Mon Sep 17 00:00:00 2001
From: Morph <39850852+Morph1984@users.noreply.github.com>
Date: Wed, 28 Jun 2023 01:35:16 -0400
Subject: [PATCH] x64: cpu_wait: Implement MWAITX for non-MSVC compilers

---
 src/common/x64/cpu_wait.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/common/x64/cpu_wait.cpp b/src/common/x64/cpu_wait.cpp
index ea16c8490..41d385f59 100644
--- a/src/common/x64/cpu_wait.cpp
+++ b/src/common/x64/cpu_wait.cpp
@@ -47,6 +47,16 @@ static void TPAUSE() {
     const auto edx = static_cast<u32>(tsc >> 32);
     asm volatile("tpause %0" : : "r"(RequestC02State), "d"(edx), "a"(eax));
 }
+
+static void MWAITX() {
+    static constexpr auto EnableWaitTimeFlag = 1U << 1;
+    static constexpr auto RequestC1State = 0U;
+
+    // monitor_var should be aligned to a cache line.
+    alignas(64) u64 monitor_var{};
+    asm volatile("monitorx" : : "a"(&monitor_var), "c"(0), "d"(0));
+    asm volatile("mwaitx" : : "a"(RequestC1State), "b"(PauseCycles), "c"(EnableWaitTimeFlag));
+}
 #endif
 
 void MicroSleep() {