Properly handle move semantics in the scoped FTZ

src/common/utils.cpp

@@ -54,5 +54,19 @@ ScopedFlushToZero::ScopedFlushToZero() {
 }
 
 ScopedFlushToZero::~ScopedFlushToZero() {
-    _MM_SET_FLUSH_ZERO_MODE(old_ftz_mode);
+    if (old_ftz_mode) {
+        _MM_SET_FLUSH_ZERO_MODE(*old_ftz_mode);
+    }
+}
+
+ScopedFlushToZero::ScopedFlushToZero(ScopedFlushToZero&& o)
+    : old_ftz_mode(std::move(o.old_ftz_mode)) {
+    o.old_ftz_mode.reset();
+}
+
+ScopedFlushToZero& ScopedFlushToZero::operator=(ScopedFlushToZero&& o) {
+    old_ftz_mode = std::move(o.old_ftz_mode);
+    o.old_ftz_mode.reset();
+
+    return *this;
 }

src/common/utils.h

@@ -97,6 +97,9 @@ class ScopedFlushToZero {
     ScopedFlushToZero(const ScopedFlushToZero&) = delete;
     ScopedFlushToZero& operator=(const ScopedFlushToZero&) = delete;
 
+    ScopedFlushToZero(ScopedFlushToZero&&);
+    ScopedFlushToZero& operator=(ScopedFlushToZero&&);
+
    private:
     /**
      * The previous FTZ mode. When we use this on the Wine side, this should
@@ -104,5 +107,5 @@ class ScopedFlushToZero {
      * don't accidentally end up disabling FTZ somewhere where it should be
      * enabled.
      */
-    unsigned int old_ftz_mode;
+    std::optional<unsigned int> old_ftz_mode;
 };