Fix x86 & x86-64 UnsafeGetObject intrinsics with read barriers.

The implementation was incorrectly interpreting the 'offset'
input as an index in a (4-byte) object reference array,
whereas it is a (1-byte) offset to an object reference field
within the 'base' (object) input.

Bug: 29516905
Change-Id: Idfbead8289222b55069816a81284401eff791e85
Test: Covered by test/004-UnsafeTest.
diff --git a/compiler/optimizing/intrinsics_x86_64.cc b/compiler/optimizing/intrinsics_x86_64.cc
index 67c2f3a..504e746 100644
--- a/compiler/optimizing/intrinsics_x86_64.cc
+++ b/compiler/optimizing/intrinsics_x86_64.cc
@@ -1953,8 +1953,9 @@
       if (kEmitCompilerReadBarrier) {
         if (kUseBakerReadBarrier) {
           Location temp = locations->GetTemp(0);
-          codegen->GenerateArrayLoadWithBakerReadBarrier(
-              invoke, output_loc, base, 0U, offset_loc, temp, /* needs_null_check */ false);
+          Address src(base, offset, ScaleFactor::TIMES_1, 0);
+          codegen->GenerateReferenceLoadWithBakerReadBarrier(
+              invoke, output_loc, base, src, temp, /* needs_null_check */ false);
         } else {
           __ movl(output, Address(base, offset, ScaleFactor::TIMES_1, 0));
           codegen->GenerateReadBarrierSlow(
@@ -1994,7 +1995,7 @@
   locations->SetOut(Location::RequiresRegister());
   if (type == Primitive::kPrimNot && kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
     // We need a temporary register for the read barrier marking slow
-    // path in InstructionCodeGeneratorX86_64::GenerateArrayLoadWithBakerReadBarrier.
+    // path in InstructionCodeGeneratorX86_64::GenerateReferenceLoadWithBakerReadBarrier.
     locations->AddTemp(Location::RequiresRegister());
   }
 }