Add read barrier support to the entrypoints.

Also remove "THIS_LOAD_REQUIRES_READ_BARRIER" since reading
an ArtMethod* no longer needs read barrier.

stub_test should also work with read barriers now.

Change-Id: I3fba18042de2f867a18dbdc38519986212bd9769
diff --git a/runtime/entrypoints/quick/quick_entrypoints.h b/runtime/entrypoints/quick/quick_entrypoints.h
index cef2510..3d3f7a1 100644
--- a/runtime/entrypoints/quick/quick_entrypoints.h
+++ b/runtime/entrypoints/quick/quick_entrypoints.h
@@ -20,6 +20,7 @@
 #include <jni.h>
 
 #include "base/macros.h"
+#include "base/mutex.h"
 #include "offsets.h"
 
 #define QUICK_ENTRYPOINT_OFFSET(ptr_size, x) \
@@ -71,6 +72,16 @@
                            Thread* self)
     NO_THREAD_SAFETY_ANALYSIS HOT_ATTR;
 
+// Read barrier entrypoints.
+// Compilers for ARM, ARM64, MIPS, MIPS64 can insert a call to this function directly.
+// For x86 and x86_64, compilers need a wrapper assembly function, to handle mismatch in ABI.
+// This is the read barrier slow path for instance and static fields and reference-type arrays.
+// TODO: Currently the read barrier does not have a fast path for compilers to directly generate.
+// Ideally the slow path should only take one parameter "ref".
+extern "C" mirror::Object* artReadBarrierSlow(mirror::Object* ref, mirror::Object* obj,
+                                              uint32_t offset)
+    SHARED_REQUIRES(Locks::mutator_lock_) HOT_ATTR;
+
 }  // namespace art
 
 #endif  // ART_RUNTIME_ENTRYPOINTS_QUICK_QUICK_ENTRYPOINTS_H_