8034839: jvm hangs with gc/gctests/LoadUnloadGC test

Provide fast lookup of checked dependencies via hashmap

Reviewed-by: kvn, roland

hotspot/src/share/vm/code/codeCache.cpp

@@ -595,11 +595,8 @@ void CodeCache::clear_inline_caches() {
   }
 }
 
-#ifndef PRODUCT
 // Keeps track of time spent for checking dependencies
-static elapsedTimer dependentCheckTime;
-#endif
-
+NOT_PRODUCT(static elapsedTimer dependentCheckTime;)
 
 int CodeCache::mark_for_deoptimization(DepChange& changes) {
   MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

hotspot/src/share/vm/code/dependencies.cpp

@@ -725,56 +725,19 @@ Klass* Dependencies::DepStream::context_type() {
 }
 
 // ----------------- DependencySignature --------------------------------------
-bool DependencySignature::equals(const DependencySignature& sig) const {
-  if (type() != sig.type()) {
+bool DependencySignature::equals(DependencySignature* sig) const {
+  if ((type() != sig->type()) || (args_count() != sig->args_count())) {
     return false;
   }
 
-  if (args_count() != sig.args_count()) {
-    return false;
-  }
-
-  for (int i = 0; i < sig.args_count(); i++) {
-    if (arg(i) != sig.arg(i)) {
+  for (int i = 0; i < sig->args_count(); i++) {
+    if (arg(i) != sig->arg(i)) {
       return false;
     }
   }
   return true;
 }
 
-
-// ----------------- DependencySignatureBuffer --------------------------------------
-DependencySignatureBuffer::DependencySignatureBuffer() {
-  _signatures = NEW_RESOURCE_ARRAY(GrowableArray<DependencySignature*>*, Dependencies::TYPE_LIMIT);
-  memset(_signatures, 0, sizeof(DependencySignature*) * Dependencies::TYPE_LIMIT);
-}
-
-/* Check if arguments are identical. Two dependency signatures are considered
- * identical, if the type as well as all argument identifiers are identical.
- * If the dependency has not already been checked, the dependency signature is
- * added to the checked dependencies of the same type. The function returns
- * false, which causes the dependency to be checked in the caller.
- */
-bool DependencySignatureBuffer::add_if_missing(const DependencySignature& sig) {
-  const int index = sig.type();
-  GrowableArray<DependencySignature*>* buffer = _signatures[index];
-  if (buffer == NULL) {
-    buffer = new GrowableArray<DependencySignature*>();
-    _signatures[index] = buffer;
-  }
-
-  // Check if we have already checked the dependency
-  for (int i = 0; i < buffer->length(); i++) {
-    DependencySignature* checked_signature = buffer->at(i);
-    if (checked_signature->equals(sig)) {
-      return true;
-    }
-  }
-  buffer->append((DependencySignature*)&sig);
-  return false;
-}
-
-
 /// Checking dependencies:
 
 // This hierarchy walker inspects subtypes of a given type,

hotspot/src/share/vm/code/dependencies.hpp

@@ -32,6 +32,7 @@
 #include "code/compressedStream.hpp"
 #include "code/nmethod.hpp"
 #include "utilities/growableArray.hpp"
+#include "utilities/hashtable.hpp"
 
 //** Dependencies represent assertions (approximate invariants) within
 // the runtime system, e.g. class hierarchy changes.  An example is an
@@ -526,13 +527,12 @@ class Dependencies: public ResourceObj {
 };
 
 
-class DependencySignature : public ResourceObj {
+class DependencySignature : public GenericHashtableEntry<DependencySignature, ResourceObj> {
  private:
   int                   _args_count;
   uintptr_t             _argument_hash[Dependencies::max_arg_count];
   Dependencies::DepType _type;
 
-
  public:
   DependencySignature(Dependencies::DepStream& dep) {
     _args_count = dep.argument_count();
@@ -542,21 +542,14 @@ class DependencySignature : public ResourceObj {
     }
   }
 
-  bool equals(const DependencySignature& sig) const;
+  bool equals(DependencySignature* sig) const;
+  uintptr_t key() const { return _argument_hash[0] >> 2; }
 
   int args_count()             const { return _args_count; }
   uintptr_t arg(int idx)       const { return _argument_hash[idx]; }
   Dependencies::DepType type() const { return _type; }
 };
 
-class DependencySignatureBuffer : public StackObj {
- private:
-  GrowableArray<DependencySignature*>**  _signatures;
-
- public:
-  DependencySignatureBuffer();
-  bool add_if_missing(const DependencySignature& sig);
-};
 
 // Every particular DepChange is a sub-class of this class.
 class DepChange : public StackObj {

hotspot/src/share/vm/code/nmethod.cpp

@@ -2168,25 +2168,21 @@ void nmethod::check_all_dependencies(DepChange& changes) {
   // Turn off dependency tracing while actually testing dependencies.
   NOT_PRODUCT( FlagSetting fs(TraceDependencies, false) );
 
-  // 'dep_signature_buffers' caches already checked dependencies.
-  DependencySignatureBuffer dep_signature_buffers;
-
+ GenericHashtable<DependencySignature, ResourceObj>* table = new GenericHashtable<DependencySignature, ResourceObj>(11027);
   // Iterate over live nmethods and check dependencies of all nmethods that are not
   // marked for deoptimization. A particular dependency is only checked once.
   for(nmethod* nm = CodeCache::alive_nmethod(CodeCache::first()); nm != NULL; nm = CodeCache::alive_nmethod(CodeCache::next(nm))) {
     if (!nm->is_marked_for_deoptimization()) {
       for (Dependencies::DepStream deps(nm); deps.next(); ) {
         // Construct abstraction of a dependency.
-        const DependencySignature* current_sig = new DependencySignature(deps);
-        // Determine if 'deps' is already checked. If it is not checked,
-        // 'add_if_missing()' adds the dependency signature and returns
-        // false.
-        if (!dep_signature_buffers.add_if_missing(*current_sig)) {
+        DependencySignature* current_sig = new DependencySignature(deps);
+        // Determine if 'deps' is already checked. table->add() returns
+        // 'true' if the dependency was added (i.e., was not in the hashtable).
+        if (table->add(current_sig)) {
           if (deps.check_dependency() != NULL) {
             // Dependency checking failed. Print out information about the failed
             // dependency and finally fail with an assert. We can fail here, since
             // dependency checking is never done in a product build.
-            ResourceMark rm;
             changes.print();
             nm->print();
             nm->print_dependencies();