Merge pull request #1654 from Unity-Technologies/unity-main-optimize-preemptive-suspend

Avoid coop suspend overhead if not enabled.

Author: joncham

mono/utils/mono-threads-api.h

@@ -102,6 +102,9 @@ This will put the current thread in GC Unsafe mode.
 For further explanation of what can and can't be done in GC unsafe mode:
 http://www.mono-project.com/docs/advanced/runtime/docs/coop-suspend/#gc-unsafe-mode
 */
+
+#if defined(ENABLE_HYBRID_SUSPEND) || defined(ENABLE_COOP_SUSPEND)
+
 #define MONO_ENTER_GC_UNSAFE\
 do {	\
 MONO_STACKDATA (__gc_unsafe_dummy); \
@@ -133,6 +136,24 @@ For further explanation of what can and can't be done in GC unsafe mode:
 MONO_STACKDATA (__gc_safe_unbalanced_dummy); \
 mono_threads_enter_gc_safe_region_unbalanced_internal (&__gc_safe_unbalanced_dummy)
 
+#else
+
+#define MONO_ENTER_GC_UNSAFE do {
+
+#define MONO_EXIT_GC_UNSAFE ; } while (0)
+
+#define MONO_ENTER_GC_UNSAFE_UNBALANCED do {
+
+#define MONO_EXIT_GC_UNSAFE_UNBALANCED ; } while (0)
+
+#define MONO_ENTER_GC_SAFE do {
+
+#define MONO_EXIT_GC_SAFE ; } while (0)
+
+#define MONO_ENTER_GC_SAFE_UNBALANCED
+
+#endif
+
 void
 mono_threads_enter_no_safepoints_region (const char *func);