Clean up the runtime read barrier and fix fake address dependency.

- Rename GetReadBarrierPointer to GetReadBarrierState.
- Change its return type to uint32_t.
- Fix the runtime fake address dependency for arm/arm64 using inline
  asm.
- Drop ReadBarrier::black_ptr_ and some brooks code.

Bug: 12687968
Test: test-art with CC, Ritz EAAC, libartd boot on N9.
Change-Id: I595970db825db5be2e98ee1fcbd7696d5501af55
diff --git a/compiler/optimizing/intrinsics_arm64.cc b/compiler/optimizing/intrinsics_arm64.cc
index db1c022..47e6d96 100644
--- a/compiler/optimizing/intrinsics_arm64.cc
+++ b/compiler/optimizing/intrinsics_arm64.cc
@@ -2659,7 +2659,7 @@
       //   if (src_ptr != end_ptr) {
       //     uint32_t rb_state = Lockword(src->monitor_).ReadBarrierState();
       //     lfence;  // Load fence or artificial data dependency to prevent load-load reordering
-      //     bool is_gray = (rb_state == ReadBarrier::gray_ptr_);
+      //     bool is_gray = (rb_state == ReadBarrier::GrayState());
       //     if (is_gray) {
       //       // Slow-path copy.
       //       do {
@@ -2704,9 +2704,8 @@
       codegen_->AddSlowPath(read_barrier_slow_path);
 
       // Given the numeric representation, it's enough to check the low bit of the rb_state.
-      static_assert(ReadBarrier::white_ptr_ == 0, "Expecting white to have value 0");
-      static_assert(ReadBarrier::gray_ptr_ == 1, "Expecting gray to have value 1");
-      static_assert(ReadBarrier::black_ptr_ == 2, "Expecting black to have value 2");
+      static_assert(ReadBarrier::WhiteState() == 0, "Expecting white to have value 0");
+      static_assert(ReadBarrier::GrayState() == 1, "Expecting gray to have value 1");
       __ Tbnz(tmp, LockWord::kReadBarrierStateShift, read_barrier_slow_path->GetEntryLabel());
 
       // Fast-path copy.