Use string length from DEX instead of recomputing

This gives around a 2% improvement in startup time overall. Here are results from a selection of
apps:

com.android.gallery3d/.app.GalleryActivity: 203.2ms → 197.7ms (change: -5.4ms, -2.7%)
com.android.messaging/.ui.conversationlist.ConversationListActivity:
  202.1ms → 199.1ms (change: -3.0ms, -1.5%)
com.android.contacts/.activities.PeopleActivity: 277.3ms → 270.7ms (change: -6.6ms, -2.4%)
com.android.camera2/com.android.camera.CameraLauncher:
  351.7ms → 344.1ms (change: -7.7ms, -2.2%)
com.android.dialer/.main.impl.MainActivity: 259.5ms → 254.2ms (change: -5.3ms, -2.0%)
com.android.settings/.Settings: 189.0ms → 186.5ms (change: -2.4ms, -1.3%)
com.android.email/.activity.Welcome: 222.8ms → 219.3ms (change: -3.6ms, -1.6%)
org.mozilla.firefox/.App: 370.2ms → 358.3ms (change: -11.9ms, -3.2%)

This is the average of 100 runs on a Pixel 2 XL.

Bug: 132691958
Test: device boots, start app many times
Change-Id: I93b6eb5105e32788cfc8159c6c21b400a161f86c

4 files changed, 44 insertions, 23 deletions

diff --git a/runtime/art_method-inl.h b/runtime/art_method-inl.h
index 61c261c52c..6bbccb8c4d 100644
--- a/runtime/art_method-inl.h
+++ b/runtime/art_method-inl.h
@@ -200,26 +200,19 @@ inline const char* ArtMethod::GetName() {
     const DexFile* dex_file = GetDexFile();
     return dex_file->GetMethodName(dex_file->GetMethodId(dex_method_idx));
   }
-  Runtime* const runtime = Runtime::Current();
-  if (this == runtime->GetResolutionMethod()) {
-    return "<runtime internal resolution method>";
-  } else if (this == runtime->GetImtConflictMethod()) {
-    return "<runtime internal imt conflict method>";
-  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveAllCalleeSaves)) {
-    return "<runtime internal callee-save all registers method>";
-  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveRefsOnly)) {
-    return "<runtime internal callee-save reference registers method>";
-  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveRefsAndArgs)) {
-    return "<runtime internal callee-save reference and argument registers method>";
-  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveEverything)) {
-    return "<runtime internal save-every-register method>";
-  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveEverythingForClinit)) {
-    return "<runtime internal save-every-register method for clinit>";
-  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveEverythingForSuspendCheck)) {
-    return "<runtime internal save-every-register method for suspend check>";
-  } else {
-    return "<unknown runtime internal method>";
+  return GetRuntimeMethodName();
+}
+
+inline std::string_view ArtMethod::GetNameView() {
+  uint32_t dex_method_idx = GetDexMethodIndex();
+  if (LIKELY(dex_method_idx != dex::kDexNoIndex)) {
+    DCHECK(!IsProxyMethod());
+    const DexFile* dex_file = GetDexFile();
+    uint32_t length = 0;
+    const char* name = dex_file->GetMethodName(dex_file->GetMethodId(dex_method_idx), &length);
+    return StringViewFromUtf16Length(name, length);
   }
+  return GetRuntimeMethodName();
 }
 
 inline ObjPtr<mirror::String> ArtMethod::ResolveNameString() {
diff --git a/runtime/art_method.cc b/runtime/art_method.cc
index 18fcfb2eab..0890da8c83 100644
--- a/runtime/art_method.cc
+++ b/runtime/art_method.cc
@@ -839,6 +839,29 @@ std::string ArtMethod::JniLongName() {
   return long_name;
 }
 
+const char* ArtMethod::GetRuntimeMethodName() {
+  Runtime* const runtime = Runtime::Current();
+  if (this == runtime->GetResolutionMethod()) {
+    return "<runtime internal resolution method>";
+  } else if (this == runtime->GetImtConflictMethod()) {
+    return "<runtime internal imt conflict method>";
+  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveAllCalleeSaves)) {
+    return "<runtime internal callee-save all registers method>";
+  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveRefsOnly)) {
+    return "<runtime internal callee-save reference registers method>";
+  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveRefsAndArgs)) {
+    return "<runtime internal callee-save reference and argument registers method>";
+  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveEverything)) {
+    return "<runtime internal save-every-register method>";
+  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveEverythingForClinit)) {
+    return "<runtime internal save-every-register method for clinit>";
+  } else if (this == runtime->GetCalleeSaveMethod(CalleeSaveType::kSaveEverythingForSuspendCheck)) {
+    return "<runtime internal save-every-register method for suspend check>";
+  } else {
+    return "<unknown runtime internal method>";
+  }
+}
+
 // AssertSharedHeld doesn't work in GetAccessFlags, so use a NO_THREAD_SAFETY_ANALYSIS helper.
 // TODO: Figure out why ASSERT_SHARED_CAPABILITY doesn't work.
 template <ReadBarrierOption kReadBarrierOption>
diff --git a/runtime/art_method.h b/runtime/art_method.h
index 23c1fe9493..5dc43a31e1 100644
--- a/runtime/art_method.h
+++ b/runtime/art_method.h
@@ -586,6 +586,8 @@ class ArtMethod final {
 
   ALWAYS_INLINE const char* GetName() REQUIRES_SHARED(Locks::mutator_lock_);
 
+  ALWAYS_INLINE std::string_view GetNameView() REQUIRES_SHARED(Locks::mutator_lock_);
+
   ObjPtr<mirror::String> ResolveNameString() REQUIRES_SHARED(Locks::mutator_lock_);
 
   const dex::CodeItem* GetCodeItem() REQUIRES_SHARED(Locks::mutator_lock_);
@@ -855,6 +857,9 @@ class ArtMethod final {
     } while (!access_flags_.compare_exchange_weak(old_access_flags, new_access_flags));
   }
 
+  // Used by GetName and GetNameView to share common code.
+  const char* GetRuntimeMethodName() REQUIRES_SHARED(Locks::mutator_lock_);
+
   DISALLOW_COPY_AND_ASSIGN(ArtMethod);  // Need to use CopyFrom to deal with 32 vs 64 bits.
 };
 
diff --git a/runtime/mirror/class.cc b/runtime/mirror/class.cc
index 5025c0295c..ec07a50b0e 100644
--- a/runtime/mirror/class.cc
+++ b/runtime/mirror/class.cc
@@ -446,7 +446,7 @@ static inline ArtMethod* FindInterfaceMethodWithSignature(ObjPtr<Class> klass,
     // Search declared methods, both direct and virtual.
     // (This lookup is used also for invoke-static on interface classes.)
     for (ArtMethod& method : klass->GetDeclaredMethodsSlice(pointer_size)) {
-      if (method.GetName() == name && method.GetSignature() == signature) {
+      if (method.GetNameView() == name && method.GetSignature() == signature) {
         return &method;
       }
     }
@@ -458,7 +458,7 @@ static inline ArtMethod* FindInterfaceMethodWithSignature(ObjPtr<Class> klass,
   for (int32_t i = 0, iftable_count = iftable->Count(); i < iftable_count; ++i) {
     ObjPtr<Class> iface = iftable->GetInterface(i);
     for (ArtMethod& method : iface->GetVirtualMethodsSlice(pointer_size)) {
-      if (method.GetName() == name && method.GetSignature() == signature) {
+      if (method.GetNameView() == name && method.GetSignature() == signature) {
         return &method;
       }
     }
@@ -470,7 +470,7 @@ static inline ArtMethod* FindInterfaceMethodWithSignature(ObjPtr<Class> klass,
     DCHECK(object_class->IsObjectClass());
     for (ArtMethod& method : object_class->GetDeclaredMethodsSlice(pointer_size)) {
       if (method.IsPublic() && !method.IsStatic() &&
-          method.GetName() == name && method.GetSignature() == signature) {
+          method.GetNameView() == name && method.GetSignature() == signature) {
         return &method;
       }
     }
@@ -496,7 +496,7 @@ ArtMethod* Class::FindInterfaceMethod(ObjPtr<DexCache> dex_cache,
   // We always search by name and signature, ignoring the type index in the MethodId.
   const DexFile& dex_file = *dex_cache->GetDexFile();
   const dex::MethodId& method_id = dex_file.GetMethodId(dex_method_idx);
-  std::string_view name = dex_file.StringDataByIdx(method_id.name_idx_);
+  std::string_view name = dex_file.StringViewByIdx(method_id.name_idx_);
   const Signature signature = dex_file.GetMethodSignature(method_id);
   return FindInterfaceMethod(name, signature, pointer_size);
 }