x86/x86-64: Avoid temporary for read barrier field load.

Add TEST instructions for memory and immediate. Use the byte
version to avoid a temporary in read barrier field load.

Test: Tested with ART_USE_READ_BARRIER=true on host.
Test: Tested with ART_USE_READ_BARRIER=true ART_HEAP_POISONING=true on host.
Bug: 29966877
Bug: 12687968
Change-Id: Ia415d3c2e1ae1ff6dff11d72bbb7d96d5deed6ee
diff --git a/compiler/optimizing/code_generator_x86.h b/compiler/optimizing/code_generator_x86.h
index 894f2e8..c644e40 100644
--- a/compiler/optimizing/code_generator_x86.h
+++ b/compiler/optimizing/code_generator_x86.h
@@ -254,8 +254,7 @@
   void GenerateReferenceLoadTwoRegisters(HInstruction* instruction,
                                          Location out,
                                          Location obj,
-                                         uint32_t offset,
-                                         Location maybe_temp);
+                                         uint32_t offset);
   // Generate a GC root reference load:
   //
   //   root <- *address
@@ -487,7 +486,6 @@
                                              Location ref,
                                              Register obj,
                                              uint32_t offset,
-                                             Location temp,
                                              bool needs_null_check);
   // Fast path implementation of ReadBarrier::Barrier for a heap
   // reference array load when Baker's read barriers are used.
@@ -496,7 +494,6 @@
                                              Register obj,
                                              uint32_t data_offset,
                                              Location index,
-                                             Location temp,
                                              bool needs_null_check);
   // Factored implementation used by GenerateFieldLoadWithBakerReadBarrier
   // and GenerateArrayLoadWithBakerReadBarrier.
@@ -504,7 +501,6 @@
                                                  Location ref,
                                                  Register obj,
                                                  const Address& src,
-                                                 Location temp,
                                                  bool needs_null_check);
 
   // Generate a read barrier for a heap reference within `instruction`