8266497: Remove unnecessary EMCP liveness indication

Reviewed-by: iklam, dholmes, sspitsyn

src/hotspot/share/oops/instanceKlass.cpp

@@ -3989,30 +3989,6 @@ void InstanceKlass::purge_previous_version_list() {
       _has_previous_versions = true;
     }
 
-    // At least one method is live in this previous version.
-    // Reset dead EMCP methods not to get breakpoints.
-    // All methods are deallocated when all of the methods for this class are no
-    // longer running.
-    Array<Method*>* method_refs = pv_node->methods();
-    if (method_refs != NULL) {
-      log_trace(redefine, class, iklass, purge)("previous methods length=%d", method_refs->length());
-      for (int j = 0; j < method_refs->length(); j++) {
-        Method* method = method_refs->at(j);
-
-        if (!method->on_stack()) {
-          // no breakpoints for non-running methods
-          if (method->is_running_emcp()) {
-            method->set_running_emcp(false);
-          }
-        } else {
-          assert (method->is_obsolete() || method->is_running_emcp(),
-                  "emcp method cannot run after emcp bit is cleared");
-          log_trace(redefine, class, iklass, purge)
-            ("purge: %s(%s): prev method @%d in version @%d is alive",
-             method->name()->as_C_string(), method->signature()->as_C_string(), j, version);
-        }
-      }
-    }
     // next previous version
     last = pv_node;
     pv_node = pv_node->previous_versions();
@@ -4112,29 +4088,6 @@ void InstanceKlass::add_previous_version(InstanceKlass* scratch_class,
     return;
   }
 
-  if (emcp_method_count != 0) {
-    // At least one method is still running, check for EMCP methods
-    for (int i = 0; i < old_methods->length(); i++) {
-      Method* old_method = old_methods->at(i);
-      if (!old_method->is_obsolete() && old_method->on_stack()) {
-        // if EMCP method (not obsolete) is on the stack, mark as EMCP so that
-        // we can add breakpoints for it.
-
-        // We set the method->on_stack bit during safepoints for class redefinition
-        // and use this bit to set the is_running_emcp bit.
-        // After the safepoint, the on_stack bit is cleared and the running emcp
-        // method may exit.   If so, we would set a breakpoint in a method that
-        // is never reached, but this won't be noticeable to the programmer.
-        old_method->set_running_emcp(true);
-        log_trace(redefine, class, iklass, add)
-          ("EMCP method %s is on_stack " INTPTR_FORMAT, old_method->name_and_sig_as_C_string(), p2i(old_method));
-      } else if (!old_method->is_obsolete()) {
-        log_trace(redefine, class, iklass, add)
-          ("EMCP method %s is NOT on_stack " INTPTR_FORMAT, old_method->name_and_sig_as_C_string(), p2i(old_method));
-      }
-    }
-  }
-
   // Add previous version if any methods are still running.
   // Set has_previous_version flag for processing during class unloading.
   _has_previous_versions = true;

src/hotspot/share/oops/method.cpp

@@ -2230,8 +2230,6 @@ void Method::set_on_stack(const bool value) {
   if (value && !already_set) {
     MetadataOnStackMark::record(this);
   }
-  assert(!value || !is_old() || is_obsolete() || is_running_emcp(),
-         "emcp methods cannot run after emcp bit is cleared");
 }
 
 // Called when the class loader is unloaded to make all methods weak.

src/hotspot/share/oops/method.hpp

@@ -88,10 +88,9 @@ class Method : public Metadata {
     _dont_inline           = 1 << 2,
     _hidden                = 1 << 3,
     _has_injected_profile  = 1 << 4,
-    _running_emcp          = 1 << 5,
-    _intrinsic_candidate   = 1 << 6,
-    _reserved_stack_access = 1 << 7,
-    _scoped                = 1 << 8
+    _intrinsic_candidate   = 1 << 5,
+    _reserved_stack_access = 1 << 6,
+    _scoped                = 1 << 7
   };
   mutable u2 _flags;
 
@@ -743,20 +742,6 @@ class Method : public Metadata {
   bool is_deleted() const                           { return access_flags().is_deleted(); }
   void set_is_deleted()                             { _access_flags.set_is_deleted(); }
 
-  bool is_running_emcp() const {
-    // EMCP methods are old but not obsolete or deleted. Equivalent
-    // Modulo Constant Pool means the method is equivalent except
-    // the constant pool and instructions that access the constant
-    // pool might be different.
-    // If a breakpoint is set in a redefined method, its EMCP methods that are
-    // still running must have a breakpoint also.
-    return (_flags & _running_emcp) != 0;
-  }
-
-  void set_running_emcp(bool x) {
-    _flags = x ? (_flags | _running_emcp) : (_flags & ~_running_emcp);
-  }
-
   bool on_stack() const                             { return access_flags().on_stack(); }
   void set_on_stack(const bool value);
 

src/hotspot/share/prims/jvmtiImpl.cpp

@@ -243,8 +243,17 @@ void JvmtiBreakpoint::each_method_version_do(method_action meth_act) {
 
     for (int i = methods->length() - 1; i >= 0; i--) {
       Method* method = methods->at(i);
-      // Only set breakpoints in running EMCP methods.
-      if (method->is_running_emcp() &&
+      // Only set breakpoints in EMCP methods.
+      // EMCP methods are old but not obsolete. Equivalent
+      // Modulo Constant Pool means the method is equivalent except
+      // the constant pool and instructions that access the constant
+      // pool might be different.
+      // If a breakpoint is set in a redefined method, its EMCP methods
+      // must have a breakpoint also.
+      // None of the methods are deleted until none are running.
+      // This code could set a breakpoint in a method that
+      // is never reached, but this won't be noticeable to the programmer.
+      if (!method->is_obsolete() &&
           method->name() == m_name &&
           method->signature() == m_signature) {
         ResourceMark rm;