Merge pull request #18374 from nbhuiyan/hidden-cls

Correct the handling of hidden class field comparisions
eclipse-openj9 · Nov 8, 2023 · 406c9da · 406c9da
2 parents 0a0620e + a6584f8
commit 406c9da
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Showing 4 changed files with 46 additions and 1 deletion.
diff --git a/runtime/compiler/env/VMJ9.cpp b/runtime/compiler/env/VMJ9.cpp
@@ -6988,6 +6988,17 @@ TR_J9VMBase::jitFieldsAreSame(TR_ResolvedMethod * method1, I_32 cpIndex1, TR_Res
    TR::VMAccessCriticalSection jitFieldsAreSame(this);
    bool result = false;
 
+   // Hidden classes generated within the same host class do not have distinct class names,
+   // but share the same field names with different field data types and offsets. Therefore,
+   // name-based check for whether fields are same can result in false positives when it comes
+   // to hidden classes unless the fields are from the same j9class objects.
+   if (method1->classOfMethod()
+       && method2->classOfMethod()
+       && (isHiddenClass(method1->classOfMethod())
+          || isHiddenClass(method2->classOfMethod()))
+       && method1->classOfMethod() != method2->classOfMethod())
+      return false;
+
    bool sigSame = true;
    if (method1->fieldsAreSame(cpIndex1, method2, cpIndex2, sigSame))
       result = true;

diff --git a/runtime/compiler/env/VMJ9.h b/runtime/compiler/env/VMJ9.h
@@ -1295,6 +1295,15 @@ class TR_J9VMBase : public TR_FrontEnd
 
    virtual bool isAnonymousClass(TR_OpaqueClassBlock *j9clazz) { return (J9_ARE_ALL_BITS_SET(((J9Class*)j9clazz)->romClass->extraModifiers, J9AccClassAnonClass)); }
    virtual bool isAnonymousClass(J9ROMClass *romClass) { return (J9_ARE_ALL_BITS_SET(romClass->extraModifiers, J9AccClassAnonClass)); }
+
+   /**
+    * \brief Check whether or not the class object is a hidden class
+    *
+    * \param j9clazz the class location
+    * \return true if class is hidden class, false otherwise
+    */
+   virtual bool isHiddenClass(TR_OpaqueClassBlock *j9clazz) { return (J9_ARE_ALL_BITS_SET(((J9Class*)j9clazz)->romClass->extraModifiers, J9AccClassHidden)); }
+
    virtual int64_t getCpuTimeSpentInCompThread(TR::Compilation * comp); // resolution is 0.5 sec or worse. Returns -1 if unavailable
 
    virtual void * getClassLoader(TR_OpaqueClassBlock * classPointer);

diff --git a/runtime/compiler/env/VMJ9Server.cpp b/runtime/compiler/env/VMJ9Server.cpp
@@ -468,7 +468,21 @@ TR_J9ServerVM::jitFieldsAreSame(TR_ResolvedMethod * method1, I_32 cpIndex1, TR_R
    {
    bool result = false;
    bool sigSame = true;
-   if (method1->fieldsAreSame(cpIndex1, method2, cpIndex2, sigSame))
+   TR_OpaqueClassBlock * classOfMethod1 = static_cast<TR_ResolvedJ9JITServerMethod *>(method1)->classOfMethod();
+   TR_OpaqueClassBlock * classOfMethod2 = static_cast<TR_ResolvedJ9JITServerMethod *>(method2)->classOfMethod();
+   // Hidden classes generated within the same host class do not have distinct class names,
+   // but share the same field names with different field data types and offsets. Therefore,
+   // name-based check for whether fields are same can result in false positives when it comes
+   // to hidden classes unless the fields are from the same j9class objects.
+   if (classOfMethod1
+       && classOfMethod2
+       && (isHiddenClass(classOfMethod1)
+          || isHiddenClass(classOfMethod2))
+       && classOfMethod1 != classOfMethod2)
+      {
+      result = false;
+      }
+   else if (method1->fieldsAreSame(cpIndex1, method2, cpIndex2, sigSame))
       {
       result = true;
       }
@@ -1943,6 +1957,16 @@ TR_J9ServerVM::isAnonymousClass(TR_OpaqueClassBlock *j9clazz)
    return (J9_ARE_ALL_BITS_SET(extraModifiers, J9AccClassAnonClass));
    }
 
+bool
+TR_J9ServerVM::isHiddenClass(TR_OpaqueClassBlock *j9clazz)
+   {
+   uintptr_t extraModifiers = 0;
+   JITServer::ServerStream *stream = _compInfoPT->getMethodBeingCompiled()->_stream;
+   JITServerHelpers::getAndCacheRAMClassInfo((J9Class *)j9clazz, _compInfoPT->getClientData(), stream, JITServerHelpers::CLASSINFO_ROMCLASS_EXTRAMODIFIERS, (void *)&extraModifiers);
+
+   return (J9_ARE_ALL_BITS_SET(extraModifiers, J9AccClassHidden));
+   }
+
 TR_IProfiler *
 TR_J9ServerVM::getIProfiler()
    {

diff --git a/runtime/compiler/env/VMJ9Server.hpp b/runtime/compiler/env/VMJ9Server.hpp
@@ -203,6 +203,7 @@ class TR_J9ServerVM: public TR_J9VM
    virtual bool transformJlrMethodInvoke(J9Method *callerMethod, J9Class *callerClass) override;
    using TR_J9VM :: isAnonymousClass;
    virtual bool isAnonymousClass(TR_OpaqueClassBlock *j9clazz) override;
+   virtual bool isHiddenClass(TR_OpaqueClassBlock *j9clazz) override;
    virtual TR_IProfiler *getIProfiler() override;
    virtual TR_StaticFinalData dereferenceStaticFinalAddress(void *staticAddress, TR::DataType addressType) override;
    virtual void reserveTrampolineIfNecessary( TR::Compilation *, TR::SymbolReference *symRef, bool inBinaryEncoding) override;