Avoid unnecessary read barriers in `ImageWriter`.

Also avoid visiting native roots during the same stages,
namely layout and writing (including copy-and-fixup).

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 181943478
Change-Id: I0d62d67556109dbcbd8a04fd0e8408733dacce33

1 files changed, 6 insertions, 5 deletions

diff --git a/runtime/jni/java_vm_ext.h b/runtime/jni/java_vm_ext.h
index 50e84142d6..8fa716e0ae 100644
--- a/runtime/jni/java_vm_ext.h
+++ b/runtime/jni/java_vm_ext.h
@@ -27,6 +27,10 @@
 
 namespace art {
 
+namespace linker {
+class ImageWriter;
+}  // namespace linker
+
 namespace mirror {
 class Array;
 }  // namespace mirror
@@ -219,10 +223,7 @@ class JavaVMExt : public JavaVM {
   JavaVMExt(Runtime* runtime, const RuntimeArgumentMap& runtime_options, std::string* error_msg);
 
   // Return true if self can currently access weak globals.
-  bool MayAccessWeakGlobalsUnlocked(Thread* self) const REQUIRES_SHARED(Locks::mutator_lock_);
-  bool MayAccessWeakGlobals(Thread* self) const
-      REQUIRES_SHARED(Locks::mutator_lock_)
-      REQUIRES(Locks::jni_weak_globals_lock_);
+  bool MayAccessWeakGlobals(Thread* self) const REQUIRES_SHARED(Locks::mutator_lock_);
 
   void WaitForWeakGlobalsAccess(Thread* self)
       REQUIRES_SHARED(Locks::mutator_lock_)
@@ -281,7 +282,7 @@ class JavaVMExt : public JavaVM {
   uint32_t global_ref_report_counter_ GUARDED_BY(Locks::jni_globals_lock_)
       = kGlobalRefReportInterval;
 
-
+  friend class linker::ImageWriter;  // Uses `globals_` and `weak_globals_` without read barrier.
   friend IndirectReferenceTable* GetIndirectReferenceTable(ScopedObjectAccess& soa,
                                                            IndirectRefKind kind);