Avoid std::string allocations for finding an array class.

Introduce ClassLinker::FindArrayClass which performs an array class lookup
given the element/component class. This has a 16 element cache of recently
looked up arrays.
Pass the current thread to ClassLinker Find .. Class routines to avoid calls
to Thread::Current().
Avoid some uses of FindClass in the debugger where WellKnownClasses is a
faster and more compacting GC friendly alternative.

Change-Id: I60e231820b349543a7edb3ceb9cf1ce92db3c843
diff --git a/runtime/verifier/method_verifier.cc b/runtime/verifier/method_verifier.cc
index ab943a6..ffa8b9e 100644
--- a/runtime/verifier/method_verifier.cc
+++ b/runtime/verifier/method_verifier.cc
@@ -3129,14 +3129,15 @@
     this_class = actual_arg_type.GetClass();
   } else {
     const std::string& descriptor(actual_arg_type.GetDescriptor());
+    Thread* self = Thread::Current();
     ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
-    this_class = class_linker->FindClass(descriptor.c_str(), *class_loader_);
+    this_class = class_linker->FindClass(self, descriptor.c_str(), *class_loader_);
     if (this_class == NULL) {
       Thread* self = Thread::Current();
       self->ClearException();
       // Look for a system class
       SirtRef<mirror::ClassLoader> null_class_loader(self, nullptr);
-      this_class = class_linker->FindClass(descriptor.c_str(), null_class_loader);
+      this_class = class_linker->FindClass(self, descriptor.c_str(), null_class_loader);
     }
   }
   if (this_class == NULL) {
@@ -3638,7 +3639,7 @@
 // Returns the access field of a quick field access (iget/iput-quick) or NULL
 // if it cannot be found.
 mirror::ArtField* MethodVerifier::GetQuickFieldAccess(const Instruction* inst,
-                                                   RegisterLine* reg_line) {
+                                                      RegisterLine* reg_line) {
   DCHECK(inst->Opcode() == Instruction::IGET_QUICK ||
          inst->Opcode() == Instruction::IGET_WIDE_QUICK ||
          inst->Opcode() == Instruction::IGET_OBJECT_QUICK ||
@@ -3654,12 +3655,12 @@
     const std::string& descriptor(object_type.GetDescriptor());
     ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
     Thread* self = Thread::Current();
-    object_class = class_linker->FindClass(descriptor.c_str(), *class_loader_);
+    object_class = class_linker->FindClass(self, descriptor.c_str(), *class_loader_);
     if (object_class == NULL) {
       self->ClearException();
       // Look for a system class
       SirtRef<mirror::ClassLoader> null_class_loader(self, nullptr);
-      object_class = class_linker->FindClass(descriptor.c_str(), null_class_loader);
+      object_class = class_linker->FindClass(self, descriptor.c_str(), null_class_loader);
     }
   }
   if (object_class == NULL) {
diff --git a/runtime/verifier/method_verifier_test.cc b/runtime/verifier/method_verifier_test.cc
index a56abba..ffa2455 100644
--- a/runtime/verifier/method_verifier_test.cc
+++ b/runtime/verifier/method_verifier_test.cc
@@ -30,7 +30,7 @@
   void VerifyClass(const std::string& descriptor)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     ASSERT_TRUE(descriptor != NULL);
-    mirror::Class* klass = class_linker_->FindSystemClass(descriptor.c_str());
+    mirror::Class* klass = class_linker_->FindSystemClass(Thread::Current(), descriptor.c_str());
 
     // Verify the class
     std::string error_msg;
diff --git a/runtime/verifier/reg_type.cc b/runtime/verifier/reg_type.cc
index 630ef8a..63f0ff4 100644
--- a/runtime/verifier/reg_type.cc
+++ b/runtime/verifier/reg_type.cc
@@ -18,6 +18,7 @@
 
 
 #include "base/casts.h"
+#include "class_linker-inl.h"
 #include "dex_file-inl.h"
 #include "mirror/class.h"
 #include "mirror/class-inl.h"
@@ -928,11 +929,7 @@
     }
     mirror::Class* common_elem = ClassJoin(s_ct, t_ct);
     ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
-    Thread* self = Thread::Current();
-    SirtRef<mirror::ClassLoader> class_loader(self, s->GetClassLoader());
-    std::string descriptor("[");
-    descriptor += ClassHelper(common_elem).GetDescriptor();
-    mirror::Class* array_class = class_linker->FindClass(descriptor.c_str(), class_loader);
+    mirror::Class* array_class = class_linker->FindArrayClass(Thread::Current(), common_elem);
     DCHECK(array_class != NULL);
     return array_class;
   } else {
diff --git a/runtime/verifier/reg_type_cache.cc b/runtime/verifier/reg_type_cache.cc
index 5e894ed..9dd57b8 100644
--- a/runtime/verifier/reg_type_cache.cc
+++ b/runtime/verifier/reg_type_cache.cc
@@ -17,6 +17,7 @@
 #include "reg_type_cache-inl.h"
 
 #include "base/casts.h"
+#include "class_linker-inl.h"
 #include "dex_file-inl.h"
 #include "mirror/class-inl.h"
 #include "mirror/object-inl.h"
@@ -140,10 +141,11 @@
   // Class was not found, must create new type.
   // Try resolving class
   ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
-  SirtRef<mirror::ClassLoader> class_loader(Thread::Current(), loader);
+  Thread* self = Thread::Current();
+  SirtRef<mirror::ClassLoader> class_loader(self, loader);
   mirror::Class* klass = NULL;
   if (can_load_classes_) {
-    klass = class_linker->FindClass(descriptor, class_loader);
+    klass = class_linker->FindClass(self, descriptor, class_loader);
   } else {
     klass = class_linker->LookupClass(descriptor, loader);
     if (klass != NULL && !klass->IsLoaded()) {
@@ -277,7 +279,8 @@
   mirror::Class* klass = NULL;
   // Try loading the class from linker.
   if (!descriptor.empty()) {
-    klass = art::Runtime::Current()->GetClassLinker()->FindSystemClass(descriptor.c_str());
+    klass = art::Runtime::Current()->GetClassLinker()->FindSystemClass(Thread::Current(),
+                                                                       descriptor.c_str());
   }
   Type* entry = Type::CreateInstance(klass, descriptor, RegTypeCache::primitive_count_);
   RegTypeCache::primitive_count_++;