Use enum for read barrier options in compiler

Enums are just phenomenal. Also fixed a double load error in x86
interface check cast fast path.

Test: test-art-host

Change-Id: Iea403ce579145b6a294073f3900ad6921c1a0d53
diff --git a/compiler/optimizing/code_generator_x86.h b/compiler/optimizing/code_generator_x86.h
index 87295a4..164231b 100644
--- a/compiler/optimizing/code_generator_x86.h
+++ b/compiler/optimizing/code_generator_x86.h
@@ -241,7 +241,7 @@
                                         Location out,
                                         uint32_t offset,
                                         Location maybe_temp,
-                                        bool emit_read_barrier);
+                                        ReadBarrierOption read_barrier_option);
   // Generate a heap reference load using two different registers
   // `out` and `obj`:
   //
@@ -256,17 +256,17 @@
                                          Location out,
                                          Location obj,
                                          uint32_t offset,
-                                         bool emit_read_barrier);
+                                         ReadBarrierOption read_barrier_option);
   // Generate a GC root reference load:
   //
   //   root <- *address
   //
-  // while honoring read barriers if `requires_read_barrier` is true.
+  // while honoring read barriers based on read_barrier_option.
   void GenerateGcRootFieldLoad(HInstruction* instruction,
                                Location root,
                                const Address& address,
                                Label* fixup_label,
-                               bool requires_read_barrier);
+                               ReadBarrierOption read_barrier_option);
 
   // Push value to FPU stack. `is_fp` specifies whether the value is floating point or not.
   // `is_wide` specifies whether it is long/double or not.