Rename system::initCpuFlags() to system::resetFpuFlags(). Implement it on ARM64.

adapters/standalone.cpp

@@ -129,7 +129,7 @@ int main(int argc, char* argv[]) {
 
 	// Initialize environment
 	system::init();
-	system::initCpuFlags();
+	system::resetFpuFlags();
 	asset::init();
 	if (!settings::devMode) {
 		logger::logPath = asset::user("log.txt");

include/system.hpp

@@ -195,10 +195,16 @@ The launched process will continue running if the current process is closed.
 */
 void runProcessDetached(const std::string& path);
 
-PRIVATE void init();
-/** Sets Rack-recommended CPU flags for the current thread.
+/** Returns the CPU's floating point unit control flags.
+MXCSR register on x64, and the FPCR register on ARM64.
+*/
+uint32_t getFpuFlags();
+void setFpuFlags(uint32_t flags);
+/** Sets Rack-recommended FPU flags for the current thread.
 */
-void initCpuFlags();
+void resetFpuFlags();
+
+PRIVATE void init();
 
 
 } // namespace system

src/engine/Engine.cpp

@@ -476,7 +476,7 @@ void Engine::stepBlock(int frames) {
 	std::lock_guard<std::mutex> stepLock(internal->blockMutex);
 	SharedLock<SharedMutex> lock(internal->mutex);
 	// Configure thread
-	system::initCpuFlags();
+	system::resetFpuFlags();
 	random::init();
 
 	internal->blockFrame = internal->frame;
@@ -1267,7 +1267,7 @@ void EngineWorker::run() {
 	// Configure thread
 	contextSet(engine->internal->context);
 	system::setThreadName(string::f("Worker %d", id));
-	system::initCpuFlags();
+	system::resetFpuFlags();
 	random::init();
 
 	while (true) {

src/system.cpp

@@ -39,7 +39,6 @@
 
 #include <system.hpp>
 #include <string.hpp>
-#include <simd/common.hpp>
 
 
 /*
@@ -952,23 +951,49 @@ void runProcessDetached(const std::string& path) {
 }
 
 
-void init() {
-	initTime();
+uint32_t getFpuFlags() {
+#if defined ARCH_X64
+	return _mm_getcsr();
+#elif defined ARCH_ARM64
+	uint64_t fpcr;
+	__asm__ volatile("mrs %0, fpcr" : "=r" (fpcr));
+	return fpcr;
+#endif
+}
+
+void setFpuFlags(uint32_t flags) {
+#if defined ARCH_X64
+	_mm_setcsr(flags);
+#elif defined ARCH_ARM64
+	uint64_t fpcr = flags;
+	__asm__ volatile("msr fpcr, %0" :: "r" (fpcr));
+#endif
 }
 
+void resetFpuFlags() {
+	uint32_t flags = 0;
 
-void initCpuFlags() {
+#if defined ARCH_X64
 	// Set CPU to flush-to-zero (FTZ) and denormals-are-zero (DAZ) mode
 	// https://software.intel.com/en-us/node/682949
-	// On ARM64, this is a SIMDe function.
-	_MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);
+	// _MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);
+	flags |= 0x8000;
+	// _MM_SET_DENORMALS_ZERO_MODE(_MM_DENORMALS_ZERO_ON);
+	flags |= 0x0040;
+	// Round-to-nearest is default
+#elif defined ARCH_ARM64
+	// Set Flush-to-Zero
+	flags |= 1 << 24;
 	// ARM64 always uses DAZ
-#if defined ARCH_X64
-	_MM_SET_DENORMALS_ZERO_MODE(_MM_DENORMALS_ZERO_ON);
+	// Round-to-nearest is default
 #endif
 
-	// Reset rounding mode to default (nearest)
-	std::fesetround(FE_TONEAREST);
+	setFpuFlags(flags);
+}
+
+
+void init() {
+	initTime();
 }