From f946118c057ed51dcc324e5b64edfe29644ed316 Mon Sep 17 00:00:00 2001
From: lizzie <lizzie@eden-emu.dev>
Date: Tue, 19 May 2026 07:46:59 +0000
Subject: [PATCH] [core/core_timing] better MWAITX and WAITPKG delays

Signed-off-by: lizzie <lizzie@eden-emu.dev>
---
 src/common/x64/cpu_wait.cpp | 81 +++++++++++++------------------------
 src/common/x64/cpu_wait.h   |  4 +-
 src/core/core_timing.cpp    |  2 +-
 3 files changed, 32 insertions(+), 55 deletions(-)

diff --git a/src/common/x64/cpu_wait.cpp b/src/common/x64/cpu_wait.cpp
index 85d27161ba..78a2d2d921 100644
--- a/src/common/x64/cpu_wait.cpp
+++ b/src/common/x64/cpu_wait.cpp
@@ -5,6 +5,8 @@
 
 #ifdef _MSC_VER
 #include <intrin.h>
+#else
+#include <x86intrin.h>
 #endif
 
 #include "common/x64/cpu_detect.h"
@@ -13,60 +15,33 @@
 
 namespace Common::X64 {
 
-namespace {
-
-// 100,000 cycles is a reasonable amount of time to wait to save on CPU resources.
-// For reference:
-// At 1 GHz, 100K cycles is 100us
-// At 2 GHz, 100K cycles is 50us
-// At 4 GHz, 100K cycles is 25us
-constexpr auto PauseCycles = 100'000U;
-
-} // Anonymous namespace
-
-#if defined(_MSC_VER) && !defined(__clang__)
-__forceinline static void TPAUSE() {
-    static constexpr auto RequestC02State = 0U;
-    _tpause(RequestC02State, FencedRDTSC() + PauseCycles);
-}
-
-__forceinline 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{};
-    _mm_monitorx(&monitor_var, 0, 0);
-    _mm_mwaitx(EnableWaitTimeFlag, RequestC1State, PauseCycles);
-}
-#else
-static void TPAUSE() {
-    static constexpr auto RequestC02State = 0U;
-    const auto tsc = FencedRDTSC() + PauseCycles;
-    const auto eax = static_cast<u32>(tsc & 0xFFFFFFFF);
-    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));
-}
+#ifdef __clang__
+__attribute__((target("waitpkg")))
+__attribute__((target("mwaitx")))
+#elif defined(__GNUC__)
+#pragma GCC target("waitpkg")
+#pragma GCC target("mwaitx")
 #endif
-
-void MicroSleep() {
-    static const bool has_waitpkg = GetCPUCaps().waitpkg;
-    static const bool has_monitorx = GetCPUCaps().monitorx;
-
-    if (has_waitpkg) {
-        TPAUSE();
-    } else if (has_monitorx) {
-        MWAITX();
+void MicroSleep(u64 rem) {
+    // 100,000 cycles is a reasonable amount of time to wait to save on CPU resources.
+    // For reference:
+    // At 1 GHz, 100K cycles is 100us
+    // At 2 GHz, 100K cycles is 50us
+    // At 4 GHz, 100K cycles is 25us
+    auto& caps = GetCPUCaps();
+    u32 cycles = caps.invariant_tsc
+        ? 1'000'000U
+        : rem * (caps.tsc_frequency / 1000000ULL);
+    if (caps.waitpkg) {
+        constexpr auto RequestC02State = 0U;
+        _tpause(RequestC02State, FencedRDTSC() + cycles);
+    } else if (caps.monitorx) {
+        constexpr auto EnableWaitTimeFlag = 1U << 1;
+        constexpr auto RequestC1State = 0U;
+        // monitor_var should be aligned to a cache line.
+        alignas(64) u64 monitor_var{};
+        _mm_monitorx(&monitor_var, 0, 0);
+        _mm_mwaitx(EnableWaitTimeFlag, RequestC1State, cycles);
     } else {
         std::this_thread::yield();
     }
diff --git a/src/common/x64/cpu_wait.h b/src/common/x64/cpu_wait.h
index 472ddca815..8bf47783ec 100644
--- a/src/common/x64/cpu_wait.h
+++ b/src/common/x64/cpu_wait.h
@@ -3,8 +3,10 @@
 
 #pragma once
 
+#include "common/common_types.h"
+
 namespace Common::X64 {
 
-void MicroSleep();
+void MicroSleep(u64 rem);
 
 } // namespace Common::X64
diff --git a/src/core/core_timing.cpp b/src/core/core_timing.cpp
index 6738a0d73d..d91361f2e7 100644
--- a/src/core/core_timing.cpp
+++ b/src/core/core_timing.cpp
@@ -78,7 +78,7 @@ void CoreTiming::Initialize(std::function<void()>&& on_thread_init_) {
                                     Common::Windows::SleepForOneTick();
                                 } else {
 #ifdef ARCHITECTURE_x86_64
-                                    Common::X64::MicroSleep();
+                                    Common::X64::MicroSleep(wait_time);
 #else
                                     std::this_thread::yield();
 #endif