From d54fb0ba78ce2ffac3caa399414af19ec1016f05 Mon Sep 17 00:00:00 2001
From: SamoZ256 <96914946+SamoZ256@users.noreply.github.com>
Date: Sat, 27 Sep 2025 00:41:17 +0200
Subject: [PATCH] arm: flush denormals to zero (#1696)

---
 src/Cafe/OS/libs/coreinit/coreinit_Thread.cpp | 36 +++++++++++++++----
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/src/Cafe/OS/libs/coreinit/coreinit_Thread.cpp b/src/Cafe/OS/libs/coreinit/coreinit_Thread.cpp
index 2f89000b..19391bbd 100644
--- a/src/Cafe/OS/libs/coreinit/coreinit_Thread.cpp
+++ b/src/Cafe/OS/libs/coreinit/coreinit_Thread.cpp
@@ -15,6 +15,33 @@
 
 #include "util/helpers/helpers.h"
 
+#ifdef __arm64__
+#if defined(__clang__)
+#include <arm_acle.h>
+#elif defined(_MSC_VER)
+#include <intrin.h>
+#endif
+#endif
+
+namespace {
+
+void enableFlushDenormalsToZero()
+{
+#if defined(ARCH_X86_64)
+	_mm_setcsr(_mm_getcsr() | 0x8000);
+#elif defined(__arm64__)
+#if defined(__clang__)
+	__arm_wsr64("fpcr", __arm_rsr64("fpcr") | (1 << 24));
+#elif defined(__GNUC__)
+	__builtin_aarch64_set_fpcr(__builtin_aarch64_get_fpcr() | (1 << 24));
+#elif defined(_MSC_VER)
+	_WriteStatusReg(ARM64_FPCR, _ReadStatusReg(ARM64_FPCR) | (1 << 24));
+#endif
+#endif
+}
+
+}
+
 SlimRWLock srwlock_activeThreadList;
 
 // public list of active threads
@@ -1321,9 +1348,7 @@ namespace coreinit
 #endif
 		OSHostThread* hostThread = (OSHostThread*)_thread;
 
-        #if defined(ARCH_X86_64)
-		_mm_setcsr(_mm_getcsr() | 0x8000); // flush denormals to zero
-        #endif
+		enableFlushDenormalsToZero();
 
 		PPCInterpreter_t* hCPU = &hostThread->ppcInstance;
 		__OSLoadThread(hostThread->m_thread, hCPU, hostThread->selectedCore);
@@ -1369,9 +1394,8 @@ namespace coreinit
 	{
 		SetThreadName(fmt::format("OSSched[core={}]", (uintptr_t)_assignedCoreIndex).c_str());
 		t_assignedCoreIndex = (sint32)(uintptr_t)_assignedCoreIndex;
-        #if defined(ARCH_X86_64)
-		_mm_setcsr(_mm_getcsr() | 0x8000); // flush denormals to zero
-        #endif
+
+		enableFlushDenormalsToZero();
 
 #if BOOST_OS_LINUX
 		if (g_gdbstub)