Adjust how we assign vtable indexes during class loading.

Only populate the super vtable set in the edge case of a super class
overriding a method from a new interface.

Test: test.py
Bug: 211854716
Bug: 233545487
Change-Id: I350f545df1cb193cd50a76e85b582c5bff9c15cc

2 files changed, 108 insertions, 102 deletions

diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index c8dbc75e61..a598d27ea2 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -37,6 +37,7 @@
 #include "art_method-inl.h"
 #include "barrier.h"
 #include "base/arena_allocator.h"
+#include "base/arena_bit_vector.h"
 #include "base/casts.h"
 #include "base/file_utils.h"
 #include "base/hash_map.h"
@@ -7976,40 +7977,7 @@ size_t ClassLinker::LinkMethodsHelper<kPointerSize>::AssignVTableIndexes(
       super_vtable_buffer_ptr,
       super_vtable_buffer_size,
       allocator_.Adapter());
-  ArrayRef<uint32_t> same_signature_vtable_lists;
-  // Insert the first `mirror::Object::kVTableLength` indexes with pre-calculated hashes.
-  DCHECK_GE(super_vtable_length, mirror::Object::kVTableLength);
-  for (uint32_t i = 0; i != mirror::Object::kVTableLength; ++i) {
-    size_t hash = class_linker_->object_virtual_method_hashes_[i];
-    // There are no duplicate signatures in `java.lang.Object`, so use `HashSet<>::PutWithHash()`.
-    // This avoids equality comparison for the three `java.lang.Object.wait()` overloads.
-    super_vtable_signatures.PutWithHash(i, hash);
-  }
-  // Insert the remaining indexes, check for duplicate signatures.
-  if (super_vtable_length > mirror::Object::kVTableLength) {
-    for (size_t i = mirror::Object::kVTableLength; i < super_vtable_length; ++i) {
-      // Use `super_vtable_accessor` for getting the method for hash calculation.
-      // Letting `HashSet<>::insert()` use the internal accessor copy in the hash
-      // function prevents the compiler from optimizing this properly because the
-      // compiler cannot prove that the accessor copy is immutable.
-      size_t hash = ComputeMethodHash(super_vtable_accessor.GetVTableEntry(i));
-      auto [it, inserted] = super_vtable_signatures.InsertWithHash(i, hash);
-      if (UNLIKELY(!inserted)) {
-        if (same_signature_vtable_lists.empty()) {
-          same_signature_vtable_lists = ArrayRef<uint32_t>(
-              allocator_.AllocArray<uint32_t>(super_vtable_length), super_vtable_length);
-          std::fill_n(same_signature_vtable_lists.data(), super_vtable_length, dex::kDexNoIndex);
-          same_signature_vtable_lists_ = same_signature_vtable_lists;
-        }
-        DCHECK_LT(*it, i);
-        same_signature_vtable_lists[i] = *it;
-        *it = i;
-      }
-    }
-  }
 
-  // For each declared virtual method, look for a superclass virtual method
-  // to override and assign a new vtable index if no method was overridden.
   DeclaredVirtualSignatureSet declared_virtual_signatures(
       kMinLoadFactor,
       kMaxLoadFactor,
@@ -8018,8 +7986,22 @@ size_t ClassLinker::LinkMethodsHelper<kPointerSize>::AssignVTableIndexes(
       declared_virtuals_buffer_ptr,
       declared_virtuals_buffer_size,
       allocator_.Adapter());
+
+  ArrayRef<uint32_t> same_signature_vtable_lists;
   const bool is_proxy_class = klass->IsProxyClass();
   size_t vtable_length = super_vtable_length;
+
+  // Record which declared methods are overriding a super method.
+  ArenaBitVector initialized_methods(&allocator_, num_virtual_methods, /* expandable= */ false);
+
+  // Note: our sets hash on the method name, and therefore we pay a high
+  // performance price when a class has many overloads.
+  //
+  // We populate the declared_virtual_signatures instead of the
+  // super_vtable_signatures (which is only lazy populated in case of interface
+  // overriding, see below). This makes sure that we pay the performance price
+  // only on that class, and not on its subclasses (except in the case of
+  // interface overriding, see below).
   for (size_t i = 0; i != num_virtual_methods; ++i) {
     ArtMethod* virtual_method = klass->GetVirtualMethodDuringLinking(i, kPointerSize);
     DCHECK(!virtual_method->IsStatic()) << virtual_method->PrettyMethod();
@@ -8028,57 +8010,65 @@ size_t ClassLinker::LinkMethodsHelper<kPointerSize>::AssignVTableIndexes(
         : virtual_method;
     size_t hash = ComputeMethodHash(signature_method);
     declared_virtual_signatures.PutWithHash(i, hash);
-    auto it = super_vtable_signatures.FindWithHash(signature_method, hash);
-    if (it != super_vtable_signatures.end()) {
-      size_t super_index = *it;
-      DCHECK_LT(super_index, super_vtable_length);
-      ArtMethod* super_method = super_vtable_accessor.GetVTableEntry(super_index);
-      // Historical note: Before Android 4.1, an inaccessible package-private
-      // superclass method would have been incorrectly overridden.
-      bool overrides = klass->CanAccessMember(super_method->GetDeclaringClass(),
-                                              super_method->GetAccessFlags());
-      if (overrides && super_method->IsFinal()) {
-        sants.reset();
-        ThrowLinkageError(klass, "Method %s overrides final method in class %s",
-                          virtual_method->PrettyMethod().c_str(),
-                          super_method->GetDeclaringClassDescriptor());
-        return 0u;
-      }
-      if (UNLIKELY(!same_signature_vtable_lists.empty())) {
-        // We may override more than one method according to JLS, see b/211854716 .
-        // We record the highest overridden vtable index here so that we can walk
-        // the list to find other overridden methods when constructing the vtable.
-        // However, we walk all the methods to check for final method overriding.
-        size_t current_index = super_index;
-        while (same_signature_vtable_lists[current_index] != dex::kDexNoIndex) {
-          DCHECK_LT(same_signature_vtable_lists[current_index], current_index);
-          current_index = same_signature_vtable_lists[current_index];
-          ArtMethod* current_method = super_vtable_accessor.GetVTableEntry(current_index);
-          if (klass->CanAccessMember(current_method->GetDeclaringClass(),
-                                     current_method->GetAccessFlags())) {
-            if (current_method->IsFinal()) {
-              sants.reset();
-              ThrowLinkageError(klass, "Method %s overrides final method in class %s",
-                                virtual_method->PrettyMethod().c_str(),
-                                current_method->GetDeclaringClassDescriptor());
-              return 0u;
-            }
-            if (!overrides) {
-              overrides = true;
-              super_index = current_index;
-              super_method = current_method;
-            }
-          }
-        }
-      }
-      if (overrides) {
-        virtual_method->SetMethodIndex(super_index);
-        continue;
-      }
+  }
+
+  // Loop through each super vtable method and see if they are overridden by a method we added to
+  // the hash table.
+  for (size_t j = 0; j < super_vtable_length; ++j) {
+    // Search the hash table to see if we are overridden by any method.
+    ArtMethod* super_method = super_vtable_accessor.GetVTableEntry(j);
+    if (!klass->CanAccessMember(super_method->GetDeclaringClass(),
+                                super_method->GetAccessFlags())) {
+      // Continue on to the next method since this one is package private and cannot be overridden.
+      // Before Android 4.1, the package-private method super_method might have been incorrectly
+      // overridden.
+      continue;
+    }
+    size_t hash = (j < mirror::Object::kVTableLength)
+        ? class_linker_->object_virtual_method_hashes_[j]
+        : ComputeMethodHash(super_method);
+    auto it = declared_virtual_signatures.FindWithHash(super_method, hash);
+    if (it == declared_virtual_signatures.end()) {
+      continue;
+    }
+    ArtMethod* virtual_method = klass->GetVirtualMethodDuringLinking(*it, kPointerSize);
+    if (super_method->IsFinal()) {
+      sants.reset();
+      ThrowLinkageError(klass, "Method %s overrides final method in class %s",
+                        virtual_method->PrettyMethod().c_str(),
+                        super_method->GetDeclaringClassDescriptor());
+      return 0u;
+    }
+    if (initialized_methods.IsBitSet(*it)) {
+      // The method is overriding two methods: one public, and one package private.
+      // We record that information to later set the method in the vtable
+      // location that isn't the method index.
+      if (same_signature_vtable_lists.empty()) {
+        same_signature_vtable_lists = ArrayRef<uint32_t>(
+            allocator_.AllocArray<uint32_t>(super_vtable_length), super_vtable_length);
+        std::fill_n(same_signature_vtable_lists.data(), super_vtable_length, dex::kDexNoIndex);
+        same_signature_vtable_lists_ = same_signature_vtable_lists;
+      }
+      same_signature_vtable_lists[j] = virtual_method->GetMethodIndexDuringLinking();
+    } else {
+      initialized_methods.SetBit(*it);
+    }
+    // Make sure the vtable index of the method is the vtable index of the overridden
+    // method that is public. We know that index is the largest one, a we can
+    // only start with a package private in the superclass hierarchy, and then have a new
+    // index in a closer superclass.
+    // This makes sure we find the public version when looking for interface
+    // (see code below).
+    virtual_method->SetMethodIndex(j);
+  }
+
+  // Add the non-overridden methods at the end.
+  for (size_t i = 0; i < num_virtual_methods; ++i) {
+    if (!initialized_methods.IsBitSet(i)) {
+      ArtMethod* local_method = klass->GetVirtualMethodDuringLinking(i, kPointerSize);
+      local_method->SetMethodIndex(vtable_length);
+      vtable_length++;
     }
-    // The method does not override any method from superclass, so it needs a new vtable index.
-    virtual_method->SetMethodIndex(vtable_length);
-    ++vtable_length;
   }
 
   // Assign vtable indexes for interface methods in new interfaces and store them
@@ -8105,24 +8095,34 @@ size_t ClassLinker::LinkMethodsHelper<kPointerSize>::AssignVTableIndexes(
         vtable_method = klass->GetVirtualMethodDuringLinking(*it1, kPointerSize);
         found = true;
       } else {
+        // This situation should be rare (a superclass implements a method
+        // declared in an interface this class is inheriting). Only in this case
+        // do we lazily populate the super_vtable_signatures.
+        if (super_vtable_signatures.empty()) {
+          for (size_t k = 0; k < super_vtable_length; ++k) {
+            ArtMethod* super_method = super_vtable_accessor.GetVTableEntry(k);
+            if (!klass->CanAccessMember(super_method->GetDeclaringClass(),
+                                        super_method->GetAccessFlags())) {
+                continue;
+            }
+            size_t super_hash = (k < mirror::Object::kVTableLength)
+                ? class_linker_->object_virtual_method_hashes_[k]
+                : ComputeMethodHash(super_method);
+            auto [it, inserted] = super_vtable_signatures.InsertWithHash(k, super_hash);
+            if (UNLIKELY(!inserted)) {
+              // If there is an existing method with the same name and
+              // signature, this means we have a package-private version and a
+              // public version. When setting up vtable indexes, we make sure
+              // the public version has the highest index, and therefore we only
+              // record the public version here. This makes sure we don't get
+              // the package-private version in the lookup below.
+              *it = k;
+            }
+          }
+        }
         auto it2 = super_vtable_signatures.FindWithHash(interface_method, hash);
         if (it2 != super_vtable_signatures.end()) {
-          // If there are multiple vtable methods with the same signature, the one with
-          // the highest vtable index is not nessarily the one in most-derived class.
-          // Find the most-derived method. See b/211854716 .
           vtable_method = super_vtable_accessor.GetVTableEntry(*it2);
-          if (UNLIKELY(!same_signature_vtable_lists.empty())) {
-            size_t current_index = *it2;
-            while (same_signature_vtable_lists[current_index] != dex::kDexNoIndex) {
-              DCHECK_LT(same_signature_vtable_lists[current_index], current_index);
-              current_index = same_signature_vtable_lists[current_index];
-              ArtMethod* current_method = super_vtable_accessor.GetVTableEntry(current_index);
-              ObjPtr<mirror::Class> current_class = current_method->GetDeclaringClass();
-              if (current_class->IsSubClass(vtable_method->GetDeclaringClass())) {
-                vtable_method = current_method;
-              }
-            }
-          }
           found = true;
         }
       }
@@ -8484,8 +8484,15 @@ bool ClassLinker::LinkMethodsHelper<kPointerSize>::LinkMethods(
       uint32_t vtable_index = virtual_method.GetMethodIndexDuringLinking();
       vtable->SetElementPtrSize(vtable_index, &virtual_method, kPointerSize);
       if (UNLIKELY(vtable_index < same_signature_vtable_lists.size())) {
-        // We may override more than one method according to JLS, see b/211854716 .
-        // If we do, arbitrarily update the method index to the lowest overridden vtable index.
+        // We may override more than one method according to JLS, see b/211854716.
+        // We really only expect one or two methods overridden, not more: one for
+        // package-private visibility, and one for public visibility.
+        // In AssignVTableIndexes, we make sure the vtable index of a method that
+        // overrides two methods is the same vtable index as the public one.
+        // This makes sure we find the public version when looking for interface
+        // method overriding.
+        // FIXME: Change this while loop into code that only expects two
+        // entries.
         while (same_signature_vtable_lists[vtable_index] != dex::kDexNoIndex) {
           DCHECK_LT(same_signature_vtable_lists[vtable_index], vtable_index);
           vtable_index = same_signature_vtable_lists[vtable_index];
@@ -8494,7 +8501,6 @@ bool ClassLinker::LinkMethodsHelper<kPointerSize>::LinkMethods(
                                      current_method->GetAccessFlags())) {
             DCHECK(!current_method->IsFinal());
             vtable->SetElementPtrSize(vtable_index, &virtual_method, kPointerSize);
-            virtual_method.SetMethodIndex(vtable_index);
           }
         }
       }
diff --git a/runtime/mirror/array-inl.h b/runtime/mirror/array-inl.h
index b0e77b45a6..b7a8a8ce49 100644
--- a/runtime/mirror/array-inl.h
+++ b/runtime/mirror/array-inl.h
@@ -98,7 +98,7 @@ inline void PrimitiveArray<T>::SetWithoutChecks(int32_t i, T value) {
   if (kTransactionActive) {
     Runtime::Current()->RecordWriteArray(this, i, GetWithoutChecks(i));
   }
-  DCHECK(CheckIsValidIndex<kVerifyFlags>(i));
+  DCHECK(CheckIsValidIndex<kVerifyFlags>(i)) << i << " " << GetLength<kVerifyFlags>();
   GetData()[i] = value;
 }
 // Backward copy where elements are of aligned appropriately for T. Count is in T sized units.