8361376: Regressions 1-6% in several Renaissance in 26-b4 only MacOSX aarch64

Author: TheRealMDoerr

src/hotspot/share/gc/shared/barrierSetNMethod.cpp

@@ -179,10 +179,6 @@ void BarrierSetNMethod::arm_all_nmethods() {
 }
 
 int BarrierSetNMethod::nmethod_stub_entry_barrier(address* return_address_ptr) {
-  // Enable WXWrite: the function is called directly from nmethod_entry_barrier
-  // stub.
-  MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, Thread::current()));
-
   address return_address = *return_address_ptr;
   AARCH64_PORT_ONLY(return_address = pauth_strip_pointer(return_address));
   CodeBlob* cb = CodeCache::find_blob(return_address);
@@ -191,25 +187,33 @@ int BarrierSetNMethod::nmethod_stub_entry_barrier(address* return_address_ptr) {
   nmethod* nm = cb->as_nmethod();
   BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
 
-  // Called upon first entry after being armed
-  bool may_enter = !bs_nm->is_not_entrant(nm) && bs_nm->nmethod_entry_barrier(nm);
-  assert(!nm->is_osr_method() || may_enter, "OSR nmethods should always be entrant after migration");
+  bool may_enter = !bs_nm->is_not_entrant(nm);
 
   if (may_enter) {
-    // In case a concurrent thread disarmed the nmethod, we need to ensure the new instructions
-    // are made visible, by using a cross modify fence. Note that this is synchronous cross modifying
-    // code, where the existence of new instructions is communicated via data (the guard value).
-    // This cross modify fence is only needed when the nmethod entry barrier modifies the
-    // instructions. Not all platforms currently do that, so if this check becomes expensive,
-    // it can be made conditional on the nmethod_patching_type.
-    OrderAccess::cross_modify_fence();
-
-    // Diagnostic option to force deoptimization 1 in 10 times. It is otherwise
-    // a very rare event.
-    if (DeoptimizeNMethodBarriersALot && !nm->is_osr_method()) {
-      static volatile uint32_t counter=0;
-      if (Atomic::add(&counter, 1u) % 10 == 0) {
-        may_enter = false;
+    // Enable WXWrite: the function is called directly from nmethod_entry_barrier
+    // stub.
+    MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, Thread::current()));
+
+    // Called upon first entry after being armed
+    may_enter = bs_nm->nmethod_entry_barrier(nm);
+    assert(!nm->is_osr_method() || may_enter, "OSR nmethods should always be entrant after migration");
+
+    if (may_enter) {
+      // In case a concurrent thread disarmed the nmethod, we need to ensure the new instructions
+      // are made visible, by using a cross modify fence. Note that this is synchronous cross modifying
+      // code, where the existence of new instructions is communicated via data (the guard value).
+      // This cross modify fence is only needed when the nmethod entry barrier modifies the
+      // instructions. Not all platforms currently do that, so if this check becomes expensive,
+      // it can be made conditional on the nmethod_patching_type.
+      OrderAccess::cross_modify_fence();
+
+      // Diagnostic option to force deoptimization 1 in 10 times. It is otherwise
+      // a very rare event.
+      if (DeoptimizeNMethodBarriersALot && !nm->is_osr_method()) {
+        static volatile uint32_t counter=0;
+        if (Atomic::add(&counter, 1u) % 10 == 0) {
+          may_enter = false;
+        }
       }
     }
   }