diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 404f044..6d9c55c 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -6377,7 +6377,7 @@
                     "art::mirror::CompressedReference<mirror::Object> and int32_t "
                     "have different sizes.");
 
-      // Slow path used to mark the GC root `root`.
+      // Slow path marking the GC root `root`.
       SlowPathCode* slow_path =
           new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM(instruction, root);
       codegen_->AddSlowPath(slow_path);
@@ -6518,7 +6518,7 @@
   // Object* ref = ref_addr->AsMirrorPtr()
   __ MaybeUnpoisonHeapReference(ref_reg);
 
-  // Slow path used to mark the object `ref` when it is gray.
+  // Slow path marking the object `ref` when it is gray.
   SlowPathCode* slow_path =
       new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM(instruction, ref);
   AddSlowPath(slow_path);
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index 122c174..cc8985d 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -5041,7 +5041,7 @@
                     "art::mirror::CompressedReference<mirror::Object> and int32_t "
                     "have different sizes.");
 
-      // Slow path used to mark the GC root `root`.
+      // Slow path marking the GC root `root`.
       SlowPathCodeARM64* slow_path =
           new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, root);
       codegen_->AddSlowPath(slow_path);
@@ -5239,7 +5239,7 @@
   // Object* ref = ref_addr->AsMirrorPtr()
   GetAssembler()->MaybeUnpoisonHeapReference(ref_reg);
 
-  // Slow path used to mark the object `ref` when it is gray.
+  // Slow path marking the object `ref` when it is gray.
   SlowPathCodeARM64* slow_path =
       new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, ref);
   AddSlowPath(slow_path);
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 7aca16f..f50eb5c 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -445,8 +445,8 @@
 // Slow path marking an object during a read barrier.
 class ReadBarrierMarkSlowPathX86 : public SlowPathCode {
  public:
-  ReadBarrierMarkSlowPathX86(HInstruction* instruction, Location obj)
-      : SlowPathCode(instruction), obj_(obj) {
+  ReadBarrierMarkSlowPathX86(HInstruction* instruction, Location obj, bool unpoison)
+      : SlowPathCode(instruction), obj_(obj), unpoison_(unpoison) {
     DCHECK(kEmitCompilerReadBarrier);
   }
 
@@ -470,6 +470,10 @@
         << instruction_->DebugName();
 
     __ Bind(GetEntryLabel());
+    if (unpoison_) {
+      // Object* ref = ref_addr->AsMirrorPtr()
+      __ MaybeUnpoisonHeapReference(reg);
+    }
     // No need to save live registers; it's taken care of by the
     // entrypoint. Also, there is no need to update the stack mask,
     // as this runtime call will not trigger a garbage collection.
@@ -499,6 +503,7 @@
 
  private:
   const Location obj_;
+  const bool unpoison_;
 
   DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkSlowPathX86);
 };
@@ -4631,10 +4636,6 @@
     // load the temp into the XMM and then copy the XMM into the
     // output, 32 bits at a time).
     locations->AddTemp(Location::RequiresFpuRegister());
-  } else if (object_field_get_with_read_barrier && kUseBakerReadBarrier) {
-    // We need a temporary register for the read barrier marking slow
-    // path in CodeGeneratorX86::GenerateFieldLoadWithBakerReadBarrier.
-    locations->AddTemp(Location::RequiresRegister());
   }
 }
 
@@ -4678,11 +4679,10 @@
     case Primitive::kPrimNot: {
       // /* HeapReference<Object> */ out = *(base + offset)
       if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
-        Location temp_loc = locations->GetTemp(0);
         // Note that a potential implicit null check is handled in this
         // CodeGeneratorX86::GenerateFieldLoadWithBakerReadBarrier call.
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            instruction, out, base, offset, temp_loc, /* needs_null_check */ true);
+            instruction, out, base, offset, /* needs_null_check */ true);
         if (is_volatile) {
           codegen_->GenerateMemoryBarrier(MemBarrierKind::kLoadAny);
         }
@@ -5093,11 +5093,6 @@
             Location::kOutputOverlap :
             Location::kNoOutputOverlap);
   }
-  // We need a temporary register for the read barrier marking slow
-  // path in CodeGeneratorX86::GenerateArrayLoadWithBakerReadBarrier.
-  if (object_array_get_with_read_barrier && kUseBakerReadBarrier) {
-    locations->AddTemp(Location::RequiresRegister());
-  }
 }
 
 void InstructionCodeGeneratorX86::VisitArrayGet(HArrayGet* instruction) {
@@ -5172,11 +5167,10 @@
       // /* HeapReference<Object> */ out =
       //     *(obj + data_offset + index * sizeof(HeapReference<Object>))
       if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
-        Location temp = locations->GetTemp(0);
         // Note that a potential implicit null check is handled in this
         // CodeGeneratorX86::GenerateArrayLoadWithBakerReadBarrier call.
         codegen_->GenerateArrayLoadWithBakerReadBarrier(
-            instruction, out_loc, obj, data_offset, index, temp, /* needs_null_check */ true);
+            instruction, out_loc, obj, data_offset, index, /* needs_null_check */ true);
       } else {
         Register out = out_loc.AsRegister<Register>();
         if (index.IsConstant()) {
@@ -6281,8 +6275,8 @@
 
 static bool TypeCheckNeedsATemporary(TypeCheckKind type_check_kind) {
   return kEmitCompilerReadBarrier &&
-      (kUseBakerReadBarrier ||
-       type_check_kind == TypeCheckKind::kAbstractClassCheck ||
+      !kUseBakerReadBarrier &&
+      (type_check_kind == TypeCheckKind::kAbstractClassCheck ||
        type_check_kind == TypeCheckKind::kClassHierarchyCheck ||
        type_check_kind == TypeCheckKind::kArrayObjectCheck);
 }
@@ -6343,7 +6337,7 @@
   }
 
   // /* HeapReference<Class> */ out = obj->klass_
-  GenerateReferenceLoadTwoRegisters(instruction, out_loc, obj_loc, class_offset, maybe_temp_loc);
+  GenerateReferenceLoadTwoRegisters(instruction, out_loc, obj_loc, class_offset);
 
   switch (type_check_kind) {
     case TypeCheckKind::kExactCheck: {
@@ -6565,7 +6559,7 @@
   }
 
   // /* HeapReference<Class> */ temp = obj->klass_
-  GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+  GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
 
   switch (type_check_kind) {
     case TypeCheckKind::kExactCheck:
@@ -6601,8 +6595,7 @@
       // going into the slow path, as it has been overwritten in the
       // meantime.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
 
       __ Bind(&compare_classes);
@@ -6641,8 +6634,7 @@
       // going into the slow path, as it has been overwritten in the
       // meantime.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
       break;
     }
@@ -6674,8 +6666,7 @@
       // going into the slow path, as it has been overwritten in the
       // meantime.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
 
       __ Bind(&check_non_primitive_component_type);
@@ -6683,8 +6674,7 @@
       __ j(kEqual, &done);
       // Same comment as above regarding `temp` and the slow path.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
       break;
     }
@@ -6875,17 +6865,17 @@
                                                                    Location maybe_temp) {
   Register out_reg = out.AsRegister<Register>();
   if (kEmitCompilerReadBarrier) {
-    DCHECK(maybe_temp.IsRegister()) << maybe_temp;
     if (kUseBakerReadBarrier) {
       // Load with fast path based Baker's read barrier.
       // /* HeapReference<Object> */ out = *(out + offset)
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          instruction, out, out_reg, offset, maybe_temp, /* needs_null_check */ false);
+          instruction, out, out_reg, offset, /* needs_null_check */ false);
     } else {
       // Load with slow path based read barrier.
       // Save the value of `out` into `maybe_temp` before overwriting it
       // in the following move operation, as we will need it for the
       // read barrier below.
+      DCHECK(maybe_temp.IsRegister()) << maybe_temp;
       __ movl(maybe_temp.AsRegister<Register>(), out_reg);
       // /* HeapReference<Object> */ out = *(out + offset)
       __ movl(out_reg, Address(out_reg, offset));
@@ -6902,17 +6892,15 @@
 void InstructionCodeGeneratorX86::GenerateReferenceLoadTwoRegisters(HInstruction* instruction,
                                                                     Location out,
                                                                     Location obj,
-                                                                    uint32_t offset,
-                                                                    Location maybe_temp) {
+                                                                    uint32_t offset) {
   Register out_reg = out.AsRegister<Register>();
   Register obj_reg = obj.AsRegister<Register>();
   if (kEmitCompilerReadBarrier) {
     if (kUseBakerReadBarrier) {
-      DCHECK(maybe_temp.IsRegister()) << maybe_temp;
       // Load with fast path based Baker's read barrier.
       // /* HeapReference<Object> */ out = *(obj + offset)
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          instruction, out, obj_reg, offset, maybe_temp, /* needs_null_check */ false);
+          instruction, out, obj_reg, offset, /* needs_null_check */ false);
     } else {
       // Load with slow path based read barrier.
       // /* HeapReference<Object> */ out = *(obj + offset)
@@ -6955,9 +6943,9 @@
                     "art::mirror::CompressedReference<mirror::Object> and int32_t "
                     "have different sizes.");
 
-      // Slow path used to mark the GC root `root`.
-      SlowPathCode* slow_path =
-          new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86(instruction, root);
+      // Slow path marking the GC root `root`.
+      SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86(
+          instruction, root, /* unpoison */ false);
       codegen_->AddSlowPath(slow_path);
 
       __ fs()->cmpl(Address::Absolute(Thread::IsGcMarkingOffset<kX86PointerSize>().Int32Value()),
@@ -6991,14 +6979,13 @@
                                                              Location ref,
                                                              Register obj,
                                                              uint32_t offset,
-                                                             Location temp,
                                                              bool needs_null_check) {
   DCHECK(kEmitCompilerReadBarrier);
   DCHECK(kUseBakerReadBarrier);
 
   // /* HeapReference<Object> */ ref = *(obj + offset)
   Address src(obj, offset);
-  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, temp, needs_null_check);
+  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, needs_null_check);
 }
 
 void CodeGeneratorX86::GenerateArrayLoadWithBakerReadBarrier(HInstruction* instruction,
@@ -7006,7 +6993,6 @@
                                                              Register obj,
                                                              uint32_t data_offset,
                                                              Location index,
-                                                             Location temp,
                                                              bool needs_null_check) {
   DCHECK(kEmitCompilerReadBarrier);
   DCHECK(kUseBakerReadBarrier);
@@ -7019,14 +7005,13 @@
   Address src = index.IsConstant() ?
       Address(obj, (index.GetConstant()->AsIntConstant()->GetValue() << TIMES_4) + data_offset) :
       Address(obj, index.AsRegister<Register>(), TIMES_4, data_offset);
-  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, temp, needs_null_check);
+  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, needs_null_check);
 }
 
 void CodeGeneratorX86::GenerateReferenceLoadWithBakerReadBarrier(HInstruction* instruction,
                                                                  Location ref,
                                                                  Register obj,
                                                                  const Address& src,
-                                                                 Location temp,
                                                                  bool needs_null_check) {
   DCHECK(kEmitCompilerReadBarrier);
   DCHECK(kUseBakerReadBarrier);
@@ -7056,17 +7041,23 @@
   //   performance reasons.
 
   Register ref_reg = ref.AsRegister<Register>();
-  Register temp_reg = temp.AsRegister<Register>();
   uint32_t monitor_offset = mirror::Object::MonitorOffset().Int32Value();
 
-  // /* int32_t */ monitor = obj->monitor_
-  __ movl(temp_reg, Address(obj, monitor_offset));
+  // 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");
+  constexpr uint32_t gray_byte_position = LockWord::kReadBarrierStateShift / kBitsPerByte;
+  constexpr uint32_t gray_bit_position = LockWord::kReadBarrierStateShift % kBitsPerByte;
+  constexpr int32_t test_value = static_cast<int8_t>(1 << gray_bit_position);
+
+  // if (rb_state == ReadBarrier::gray_ptr_)
+  //   ref = ReadBarrier::Mark(ref);
+  // At this point, just do the "if" and make sure that flags are preserved until the branch.
+  __ testb(Address(obj, monitor_offset + gray_byte_position), Immediate(test_value));
   if (needs_null_check) {
     MaybeRecordImplicitNullCheck(instruction);
   }
-  // /* LockWord */ lock_word = LockWord(monitor)
-  static_assert(sizeof(LockWord) == sizeof(int32_t),
-                "art::LockWord and int32_t have different sizes.");
 
   // Load fence to prevent load-load reordering.
   // Note that this is a no-op, thanks to the x86 memory model.
@@ -7074,25 +7065,20 @@
 
   // The actual reference load.
   // /* HeapReference<Object> */ ref = *src
-  __ movl(ref_reg, src);
+  __ movl(ref_reg, src);  // Flags are unaffected.
+
+  // Note: Reference unpoisoning modifies the flags, so we need to delay it after the branch.
+  // Slow path marking the object `ref` when it is gray.
+  SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86(
+      instruction, ref, /* unpoison */ true);
+  AddSlowPath(slow_path);
+
+  // We have done the "if" of the gray bit check above, now branch based on the flags.
+  __ j(kNotZero, slow_path->GetEntryLabel());
 
   // Object* ref = ref_addr->AsMirrorPtr()
   __ MaybeUnpoisonHeapReference(ref_reg);
 
-  // Slow path used to mark the object `ref` when it is gray.
-  SlowPathCode* slow_path =
-      new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86(instruction, ref);
-  AddSlowPath(slow_path);
-
-  // if (rb_state == ReadBarrier::gray_ptr_)
-  //   ref = ReadBarrier::Mark(ref);
-  // Given the numeric representation, it's enough to check the low bit of the
-  // rb_state. We do that by shifting the bit out of the lock word with SHR.
-  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");
-  __ shrl(temp_reg, Immediate(LockWord::kReadBarrierStateShift + 1));
-  __ j(kCarrySet, slow_path->GetEntryLabel());
   __ Bind(slow_path->GetExitLabel());
 }
 
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`
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 0c55ae4..ec37e5d 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -466,8 +466,8 @@
 // Slow path marking an object during a read barrier.
 class ReadBarrierMarkSlowPathX86_64 : public SlowPathCode {
  public:
-  ReadBarrierMarkSlowPathX86_64(HInstruction* instruction, Location obj)
-      : SlowPathCode(instruction), obj_(obj) {
+  ReadBarrierMarkSlowPathX86_64(HInstruction* instruction, Location obj, bool unpoison)
+      : SlowPathCode(instruction), obj_(obj), unpoison_(unpoison) {
     DCHECK(kEmitCompilerReadBarrier);
   }
 
@@ -491,6 +491,10 @@
         << instruction_->DebugName();
 
     __ Bind(GetEntryLabel());
+    if (unpoison_) {
+      // Object* ref = ref_addr->AsMirrorPtr()
+      __ MaybeUnpoisonHeapReference(obj_.AsRegister<CpuRegister>());
+    }
     // No need to save live registers; it's taken care of by the
     // entrypoint. Also, there is no need to update the stack mask,
     // as this runtime call will not trigger a garbage collection.
@@ -520,6 +524,7 @@
 
  private:
   const Location obj_;
+  const bool unpoison_;
 
   DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkSlowPathX86_64);
 };
@@ -4152,11 +4157,6 @@
         Location::RequiresRegister(),
         object_field_get_with_read_barrier ? Location::kOutputOverlap : Location::kNoOutputOverlap);
   }
-  if (object_field_get_with_read_barrier && kUseBakerReadBarrier) {
-    // We need a temporary register for the read barrier marking slow
-    // path in CodeGeneratorX86_64::GenerateFieldLoadWithBakerReadBarrier.
-    locations->AddTemp(Location::RequiresRegister());
-  }
 }
 
 void InstructionCodeGeneratorX86_64::HandleFieldGet(HInstruction* instruction,
@@ -4200,11 +4200,10 @@
     case Primitive::kPrimNot: {
       // /* HeapReference<Object> */ out = *(base + offset)
       if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
-        Location temp_loc = locations->GetTemp(0);
         // Note that a potential implicit null check is handled in this
         // CodeGeneratorX86::GenerateFieldLoadWithBakerReadBarrier call.
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            instruction, out, base, offset, temp_loc, /* needs_null_check */ true);
+            instruction, out, base, offset, /* needs_null_check */ true);
         if (is_volatile) {
           codegen_->GenerateMemoryBarrier(MemBarrierKind::kLoadAny);
         }
@@ -4588,11 +4587,6 @@
         Location::RequiresRegister(),
         object_array_get_with_read_barrier ? Location::kOutputOverlap : Location::kNoOutputOverlap);
   }
-  // We need a temporary register for the read barrier marking slow
-  // path in CodeGeneratorX86_64::GenerateArrayLoadWithBakerReadBarrier.
-  if (object_array_get_with_read_barrier && kUseBakerReadBarrier) {
-    locations->AddTemp(Location::RequiresRegister());
-  }
 }
 
 void InstructionCodeGeneratorX86_64::VisitArrayGet(HArrayGet* instruction) {
@@ -4667,11 +4661,10 @@
       // /* HeapReference<Object> */ out =
       //     *(obj + data_offset + index * sizeof(HeapReference<Object>))
       if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
-        Location temp = locations->GetTemp(0);
         // Note that a potential implicit null check is handled in this
         // CodeGeneratorX86::GenerateArrayLoadWithBakerReadBarrier call.
         codegen_->GenerateArrayLoadWithBakerReadBarrier(
-            instruction, out_loc, obj, data_offset, index, temp, /* needs_null_check */ true);
+            instruction, out_loc, obj, data_offset, index, /* needs_null_check */ true);
       } else {
         CpuRegister out = out_loc.AsRegister<CpuRegister>();
         if (index.IsConstant()) {
@@ -5687,8 +5680,8 @@
 
 static bool TypeCheckNeedsATemporary(TypeCheckKind type_check_kind) {
   return kEmitCompilerReadBarrier &&
-      (kUseBakerReadBarrier ||
-       type_check_kind == TypeCheckKind::kAbstractClassCheck ||
+      !kUseBakerReadBarrier &&
+      (type_check_kind == TypeCheckKind::kAbstractClassCheck ||
        type_check_kind == TypeCheckKind::kClassHierarchyCheck ||
        type_check_kind == TypeCheckKind::kArrayObjectCheck);
 }
@@ -5749,7 +5742,7 @@
   }
 
   // /* HeapReference<Class> */ out = obj->klass_
-  GenerateReferenceLoadTwoRegisters(instruction, out_loc, obj_loc, class_offset, maybe_temp_loc);
+  GenerateReferenceLoadTwoRegisters(instruction, out_loc, obj_loc, class_offset);
 
   switch (type_check_kind) {
     case TypeCheckKind::kExactCheck: {
@@ -5979,8 +5972,7 @@
       }
 
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
 
       if (cls.IsRegister()) {
         __ cmpl(temp, cls.AsRegister<CpuRegister>());
@@ -6004,8 +5996,7 @@
       }
 
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
 
       // If the class is abstract, we eagerly fetch the super class of the
       // object to avoid doing a comparison we know will fail.
@@ -6025,8 +6016,7 @@
       // going into the slow path, as it has been overwritten in the
       // meantime.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
 
       __ Bind(&compare_classes);
@@ -6050,8 +6040,7 @@
       }
 
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
 
       // Walk over the class hierarchy to find a match.
       NearLabel loop;
@@ -6077,8 +6066,7 @@
       // going into the slow path, as it has been overwritten in the
       // meantime.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
       __ Bind(&done);
       break;
@@ -6097,8 +6085,7 @@
       }
 
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
 
       // Do an exact check.
       NearLabel check_non_primitive_component_type;
@@ -6126,8 +6113,7 @@
       // going into the slow path, as it has been overwritten in the
       // meantime.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
 
       __ Bind(&check_non_primitive_component_type);
@@ -6135,8 +6121,7 @@
       __ j(kEqual, &done);
       // Same comment as above regarding `temp` and the slow path.
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
       __ jmp(type_check_slow_path->GetEntryLabel());
       __ Bind(&done);
       break;
@@ -6152,8 +6137,7 @@
       }
 
       // /* HeapReference<Class> */ temp = obj->klass_
-      GenerateReferenceLoadTwoRegisters(
-          instruction, temp_loc, obj_loc, class_offset, maybe_temp2_loc);
+      GenerateReferenceLoadTwoRegisters(instruction, temp_loc, obj_loc, class_offset);
 
       // We always go into the type check slow path for the unresolved
       // and interface check cases.
@@ -6321,17 +6305,17 @@
                                                                       Location maybe_temp) {
   CpuRegister out_reg = out.AsRegister<CpuRegister>();
   if (kEmitCompilerReadBarrier) {
-    DCHECK(maybe_temp.IsRegister()) << maybe_temp;
     if (kUseBakerReadBarrier) {
       // Load with fast path based Baker's read barrier.
       // /* HeapReference<Object> */ out = *(out + offset)
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          instruction, out, out_reg, offset, maybe_temp, /* needs_null_check */ false);
+          instruction, out, out_reg, offset, /* needs_null_check */ false);
     } else {
       // Load with slow path based read barrier.
       // Save the value of `out` into `maybe_temp` before overwriting it
       // in the following move operation, as we will need it for the
       // read barrier below.
+      DCHECK(maybe_temp.IsRegister()) << maybe_temp;
       __ movl(maybe_temp.AsRegister<CpuRegister>(), out_reg);
       // /* HeapReference<Object> */ out = *(out + offset)
       __ movl(out_reg, Address(out_reg, offset));
@@ -6348,17 +6332,15 @@
 void InstructionCodeGeneratorX86_64::GenerateReferenceLoadTwoRegisters(HInstruction* instruction,
                                                                        Location out,
                                                                        Location obj,
-                                                                       uint32_t offset,
-                                                                       Location maybe_temp) {
+                                                                       uint32_t offset) {
   CpuRegister out_reg = out.AsRegister<CpuRegister>();
   CpuRegister obj_reg = obj.AsRegister<CpuRegister>();
   if (kEmitCompilerReadBarrier) {
     if (kUseBakerReadBarrier) {
-      DCHECK(maybe_temp.IsRegister()) << maybe_temp;
       // Load with fast path based Baker's read barrier.
       // /* HeapReference<Object> */ out = *(obj + offset)
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          instruction, out, obj_reg, offset, maybe_temp, /* needs_null_check */ false);
+          instruction, out, obj_reg, offset, /* needs_null_check */ false);
     } else {
       // Load with slow path based read barrier.
       // /* HeapReference<Object> */ out = *(obj + offset)
@@ -6401,9 +6383,9 @@
                     "art::mirror::CompressedReference<mirror::Object> and int32_t "
                     "have different sizes.");
 
-      // Slow path used to mark the GC root `root`.
-      SlowPathCode* slow_path =
-          new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86_64(instruction, root);
+      // Slow path marking the GC root `root`.
+      SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86_64(
+          instruction, root, /* unpoison */ false);
       codegen_->AddSlowPath(slow_path);
 
       __ gs()->cmpl(Address::Absolute(Thread::IsGcMarkingOffset<kX86_64PointerSize>().Int32Value(),
@@ -6438,14 +6420,13 @@
                                                                 Location ref,
                                                                 CpuRegister obj,
                                                                 uint32_t offset,
-                                                                Location temp,
                                                                 bool needs_null_check) {
   DCHECK(kEmitCompilerReadBarrier);
   DCHECK(kUseBakerReadBarrier);
 
   // /* HeapReference<Object> */ ref = *(obj + offset)
   Address src(obj, offset);
-  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, temp, needs_null_check);
+  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, needs_null_check);
 }
 
 void CodeGeneratorX86_64::GenerateArrayLoadWithBakerReadBarrier(HInstruction* instruction,
@@ -6453,7 +6434,6 @@
                                                                 CpuRegister obj,
                                                                 uint32_t data_offset,
                                                                 Location index,
-                                                                Location temp,
                                                                 bool needs_null_check) {
   DCHECK(kEmitCompilerReadBarrier);
   DCHECK(kUseBakerReadBarrier);
@@ -6466,14 +6446,13 @@
   Address src = index.IsConstant() ?
       Address(obj, (index.GetConstant()->AsIntConstant()->GetValue() << TIMES_4) + data_offset) :
       Address(obj, index.AsRegister<CpuRegister>(), TIMES_4, data_offset);
-  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, temp, needs_null_check);
+  GenerateReferenceLoadWithBakerReadBarrier(instruction, ref, obj, src, needs_null_check);
 }
 
 void CodeGeneratorX86_64::GenerateReferenceLoadWithBakerReadBarrier(HInstruction* instruction,
                                                                     Location ref,
                                                                     CpuRegister obj,
                                                                     const Address& src,
-                                                                    Location temp,
                                                                     bool needs_null_check) {
   DCHECK(kEmitCompilerReadBarrier);
   DCHECK(kUseBakerReadBarrier);
@@ -6503,17 +6482,23 @@
   //   performance reasons.
 
   CpuRegister ref_reg = ref.AsRegister<CpuRegister>();
-  CpuRegister temp_reg = temp.AsRegister<CpuRegister>();
   uint32_t monitor_offset = mirror::Object::MonitorOffset().Int32Value();
 
-  // /* int32_t */ monitor = obj->monitor_
-  __ movl(temp_reg, Address(obj, monitor_offset));
+  // 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");
+  constexpr uint32_t gray_byte_position = LockWord::kReadBarrierStateShift / kBitsPerByte;
+  constexpr uint32_t gray_bit_position = LockWord::kReadBarrierStateShift % kBitsPerByte;
+  constexpr int32_t test_value = static_cast<int8_t>(1 << gray_bit_position);
+
+  // if (rb_state == ReadBarrier::gray_ptr_)
+  //   ref = ReadBarrier::Mark(ref);
+  // At this point, just do the "if" and make sure that flags are preserved until the branch.
+  __ testb(Address(obj, monitor_offset + gray_byte_position), Immediate(test_value));
   if (needs_null_check) {
     MaybeRecordImplicitNullCheck(instruction);
   }
-  // /* LockWord */ lock_word = LockWord(monitor)
-  static_assert(sizeof(LockWord) == sizeof(int32_t),
-                "art::LockWord and int32_t have different sizes.");
 
   // Load fence to prevent load-load reordering.
   // Note that this is a no-op, thanks to the x86-64 memory model.
@@ -6521,25 +6506,20 @@
 
   // The actual reference load.
   // /* HeapReference<Object> */ ref = *src
-  __ movl(ref_reg, src);
+  __ movl(ref_reg, src);  // Flags are unaffected.
+
+  // Note: Reference unpoisoning modifies the flags, so we need to delay it after the branch.
+  // Slow path marking the object `ref` when it is gray.
+  SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86_64(
+      instruction, ref, /* unpoison */ true);
+  AddSlowPath(slow_path);
+
+  // We have done the "if" of the gray bit check above, now branch based on the flags.
+  __ j(kNotZero, slow_path->GetEntryLabel());
 
   // Object* ref = ref_addr->AsMirrorPtr()
   __ MaybeUnpoisonHeapReference(ref_reg);
 
-  // Slow path used to mark the object `ref` when it is gray.
-  SlowPathCode* slow_path =
-      new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86_64(instruction, ref);
-  AddSlowPath(slow_path);
-
-  // if (rb_state == ReadBarrier::gray_ptr_)
-  //   ref = ReadBarrier::Mark(ref);
-  // Given the numeric representation, it's enough to check the low bit of the
-  // rb_state. We do that by shifting the bit out of the lock word with SHR.
-  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");
-  __ shrl(temp_reg, Immediate(LockWord::kReadBarrierStateShift + 1));
-  __ j(kCarrySet, slow_path->GetEntryLabel());
   __ Bind(slow_path->GetExitLabel());
 }
 
diff --git a/compiler/optimizing/code_generator_x86_64.h b/compiler/optimizing/code_generator_x86_64.h
index 4e0e34c..44844ac 100644
--- a/compiler/optimizing/code_generator_x86_64.h
+++ b/compiler/optimizing/code_generator_x86_64.h
@@ -248,8 +248,7 @@
   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
@@ -427,7 +426,6 @@
                                              Location ref,
                                              CpuRegister 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.
@@ -436,7 +434,6 @@
                                              CpuRegister obj,
                                              uint32_t data_offset,
                                              Location index,
-                                             Location temp,
                                              bool needs_null_check);
   // Factored implementation used by GenerateFieldLoadWithBakerReadBarrier
   // and GenerateArrayLoadWithBakerReadBarrier.
@@ -444,7 +441,6 @@
                                                  Location ref,
                                                  CpuRegister obj,
                                                  const Address& src,
-                                                 Location temp,
                                                  bool needs_null_check);
 
   // Generate a read barrier for a heap reference within `instruction`
diff --git a/compiler/optimizing/intrinsics_x86.cc b/compiler/optimizing/intrinsics_x86.cc
index 49d6c19..cf4a040 100644
--- a/compiler/optimizing/intrinsics_x86.cc
+++ b/compiler/optimizing/intrinsics_x86.cc
@@ -1934,10 +1934,9 @@
       Register output = output_loc.AsRegister<Register>();
       if (kEmitCompilerReadBarrier) {
         if (kUseBakerReadBarrier) {
-          Location temp = locations->GetTemp(0);
           Address src(base, offset, ScaleFactor::TIMES_1, 0);
           codegen->GenerateReferenceLoadWithBakerReadBarrier(
-              invoke, output_loc, base, src, temp, /* needs_null_check */ false);
+              invoke, output_loc, base, src, /* needs_null_check */ false);
         } else {
           __ movl(output, Address(base, offset, ScaleFactor::TIMES_1, 0));
           codegen->GenerateReadBarrierSlow(
@@ -2000,11 +1999,6 @@
     locations->SetOut(Location::RequiresRegister(),
                       can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap);
   }
-  if (type == Primitive::kPrimNot && kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
-    // We need a temporary register for the read barrier marking slow
-    // path in InstructionCodeGeneratorX86::GenerateReferenceLoadWithBakerReadBarrier.
-    locations->AddTemp(Location::RequiresRegister());
-  }
 }
 
 void IntrinsicLocationsBuilderX86::VisitUnsafeGet(HInvoke* invoke) {
@@ -2933,11 +2927,11 @@
       if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
         // /* HeapReference<Class> */ temp1 = src->klass_
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            invoke, temp1_loc, src, class_offset, temp2_loc, /* needs_null_check */ false);
+            invoke, temp1_loc, src, class_offset, /* needs_null_check */ false);
         // Bail out if the source is not a non primitive array.
         // /* HeapReference<Class> */ temp1 = temp1->component_type_
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            invoke, temp1_loc, temp1, component_offset, temp2_loc, /* needs_null_check */ false);
+            invoke, temp1_loc, temp1, component_offset, /* needs_null_check */ false);
         __ testl(temp1, temp1);
         __ j(kEqual, intrinsic_slow_path->GetEntryLabel());
         // If heap poisoning is enabled, `temp1` has been unpoisoned
@@ -2970,7 +2964,7 @@
 
       // /* HeapReference<Class> */ temp1 = dest->klass_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, temp1_loc, dest, class_offset, temp2_loc, /* needs_null_check */ false);
+          invoke, temp1_loc, dest, class_offset, /* needs_null_check */ false);
 
       if (!optimizations.GetDestinationIsNonPrimitiveArray()) {
         // Bail out if the destination is not a non primitive array.
@@ -2982,7 +2976,7 @@
         // temporaries such a `temp1`.
         // /* HeapReference<Class> */ temp2 = temp1->component_type_
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            invoke, temp2_loc, temp1, component_offset, temp3_loc, /* needs_null_check */ false);
+            invoke, temp2_loc, temp1, component_offset, /* needs_null_check */ false);
         __ testl(temp2, temp2);
         __ j(kEqual, intrinsic_slow_path->GetEntryLabel());
         // If heap poisoning is enabled, `temp2` has been unpoisoned
@@ -2995,7 +2989,7 @@
       // read barrier emitted by GenerateFieldLoadWithBakerReadBarrier below.
       // /* HeapReference<Class> */ temp2 = src->klass_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, temp2_loc, src, class_offset, temp3_loc, /* needs_null_check */ false);
+          invoke, temp2_loc, src, class_offset, /* needs_null_check */ false);
       // Note: if heap poisoning is on, we are comparing two unpoisoned references here.
       __ cmpl(temp1, temp2);
 
@@ -3004,7 +2998,7 @@
         __ j(kEqual, &do_copy);
         // /* HeapReference<Class> */ temp1 = temp1->component_type_
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            invoke, temp1_loc, temp1, component_offset, temp2_loc, /* needs_null_check */ false);
+            invoke, temp1_loc, temp1, component_offset, /* needs_null_check */ false);
         // We do not need to emit a read barrier for the following
         // heap reference load, as `temp1` is only used in a
         // comparison with null below, and this reference is not
@@ -3058,10 +3052,10 @@
     if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
       // /* HeapReference<Class> */ temp1 = src->klass_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, temp1_loc, src, class_offset, temp2_loc, /* needs_null_check */ false);
+          invoke, temp1_loc, src, class_offset, /* needs_null_check */ false);
       // /* HeapReference<Class> */ temp1 = temp1->component_type_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, temp1_loc, temp1, component_offset, temp2_loc, /* needs_null_check */ false);
+          invoke, temp1_loc, temp1, component_offset, /* needs_null_check */ false);
       __ testl(temp1, temp1);
       __ j(kEqual, intrinsic_slow_path->GetEntryLabel());
       // If heap poisoning is enabled, `temp1` has been unpoisoned
@@ -3139,11 +3133,18 @@
     __ cmpl(temp1, temp3);
     __ j(kEqual, &done);
 
-    // /* int32_t */ monitor = src->monitor_
-    __ movl(temp2, Address(src, monitor_offset));
-    // /* LockWord */ lock_word = LockWord(monitor)
-    static_assert(sizeof(LockWord) == sizeof(int32_t),
-                  "art::LockWord and int32_t have different sizes.");
+    // 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");
+    constexpr uint32_t gray_byte_position = LockWord::kReadBarrierStateShift / kBitsPerByte;
+    constexpr uint32_t gray_bit_position = LockWord::kReadBarrierStateShift % kBitsPerByte;
+    constexpr int32_t test_value = static_cast<int8_t>(1 << gray_bit_position);
+
+    // if (rb_state == ReadBarrier::gray_ptr_)
+    //   goto slow_path;
+    // At this point, just do the "if" and make sure that flags are preserved until the branch.
+    __ testb(Address(src, monitor_offset + gray_byte_position), Immediate(test_value));
 
     // Load fence to prevent load-load reordering.
     // Note that this is a no-op, thanks to the x86 memory model.
@@ -3154,13 +3155,8 @@
         new (GetAllocator()) ReadBarrierSystemArrayCopySlowPathX86(invoke);
     codegen_->AddSlowPath(read_barrier_slow_path);
 
-    // Given the numeric representation, it's enough to check the low bit of the
-    // rb_state. We do that by shifting the bit out of the lock word with SHR.
-    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");
-    __ shrl(temp2, Immediate(LockWord::kReadBarrierStateShift + 1));
-    __ j(kCarrySet, read_barrier_slow_path->GetEntryLabel());
+    // We have done the "if" of the gray bit check above, now branch based on the flags.
+    __ j(kNotZero, read_barrier_slow_path->GetEntryLabel());
 
     // Fast-path copy.
 
diff --git a/compiler/optimizing/intrinsics_x86_64.cc b/compiler/optimizing/intrinsics_x86_64.cc
index 311e1cd..a4ee546 100644
--- a/compiler/optimizing/intrinsics_x86_64.cc
+++ b/compiler/optimizing/intrinsics_x86_64.cc
@@ -1241,7 +1241,7 @@
     if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
       // /* HeapReference<Class> */ temp1 = dest->klass_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, temp1_loc, dest, class_offset, temp3_loc, /* needs_null_check */ false);
+          invoke, temp1_loc, dest, class_offset, /* needs_null_check */ false);
       // Register `temp1` is not trashed by the read barrier emitted
       // by GenerateFieldLoadWithBakerReadBarrier below, as that
       // method produces a call to a ReadBarrierMarkRegX entry point,
@@ -1249,7 +1249,7 @@
       // temporaries such a `temp1`.
       // /* HeapReference<Class> */ temp2 = src->klass_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, temp2_loc, src, class_offset, temp3_loc, /* needs_null_check */ false);
+          invoke, temp2_loc, src, class_offset, /* needs_null_check */ false);
       // If heap poisoning is enabled, `temp1` and `temp2` have been
       // unpoisoned by the the previous calls to
       // GenerateFieldLoadWithBakerReadBarrier.
@@ -1273,7 +1273,7 @@
       if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
         // /* HeapReference<Class> */ TMP = temp1->component_type_
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            invoke, TMP_loc, temp1, component_offset, temp3_loc, /* needs_null_check */ false);
+            invoke, TMP_loc, temp1, component_offset, /* needs_null_check */ false);
         __ testl(CpuRegister(TMP), CpuRegister(TMP));
         __ j(kEqual, intrinsic_slow_path->GetEntryLabel());
         // If heap poisoning is enabled, `TMP` has been unpoisoned by
@@ -1296,7 +1296,7 @@
         // read barrier emitted by GenerateFieldLoadWithBakerReadBarrier below.
         // /* HeapReference<Class> */ TMP = temp2->component_type_
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            invoke, TMP_loc, temp2, component_offset, temp3_loc, /* needs_null_check */ false);
+            invoke, TMP_loc, temp2, component_offset, /* needs_null_check */ false);
         __ testl(CpuRegister(TMP), CpuRegister(TMP));
         __ j(kEqual, intrinsic_slow_path->GetEntryLabel());
         // If heap poisoning is enabled, `TMP` has been unpoisoned by
@@ -1320,7 +1320,7 @@
       if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
         // /* HeapReference<Class> */ temp1 = temp1->component_type_
         codegen_->GenerateFieldLoadWithBakerReadBarrier(
-            invoke, temp1_loc, temp1, component_offset, temp3_loc, /* needs_null_check */ false);
+            invoke, temp1_loc, temp1, component_offset, /* needs_null_check */ false);
         // We do not need to emit a read barrier for the following
         // heap reference load, as `temp1` is only used in a
         // comparison with null below, and this reference is not
@@ -1348,10 +1348,10 @@
     if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
       // /* HeapReference<Class> */ temp1 = src->klass_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, temp1_loc, src, class_offset, temp3_loc, /* needs_null_check */ false);
+          invoke, temp1_loc, src, class_offset, /* needs_null_check */ false);
       // /* HeapReference<Class> */ TMP = temp1->component_type_
       codegen_->GenerateFieldLoadWithBakerReadBarrier(
-          invoke, TMP_loc, temp1, component_offset, temp3_loc, /* needs_null_check */ false);
+          invoke, TMP_loc, temp1, component_offset, /* needs_null_check */ false);
       __ testl(CpuRegister(TMP), CpuRegister(TMP));
       __ j(kEqual, intrinsic_slow_path->GetEntryLabel());
     } else {
@@ -1421,11 +1421,18 @@
     __ cmpl(temp1, temp3);
     __ j(kEqual, &done);
 
-    // /* int32_t */ monitor = src->monitor_
-    __ movl(CpuRegister(TMP), Address(src, monitor_offset));
-    // /* LockWord */ lock_word = LockWord(monitor)
-    static_assert(sizeof(LockWord) == sizeof(int32_t),
-                  "art::LockWord and int32_t have different sizes.");
+    // 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");
+    constexpr uint32_t gray_byte_position = LockWord::kReadBarrierStateShift / kBitsPerByte;
+    constexpr uint32_t gray_bit_position = LockWord::kReadBarrierStateShift % kBitsPerByte;
+    constexpr int32_t test_value = static_cast<int8_t>(1 << gray_bit_position);
+
+    // if (rb_state == ReadBarrier::gray_ptr_)
+    //   goto slow_path;
+    // At this point, just do the "if" and make sure that flags are preserved until the branch.
+    __ testb(Address(src, monitor_offset + gray_byte_position), Immediate(test_value));
 
     // Load fence to prevent load-load reordering.
     // Note that this is a no-op, thanks to the x86-64 memory model.
@@ -1436,13 +1443,8 @@
         new (GetAllocator()) ReadBarrierSystemArrayCopySlowPathX86_64(invoke);
     codegen_->AddSlowPath(read_barrier_slow_path);
 
-    // Given the numeric representation, it's enough to check the low bit of the
-    // rb_state. We do that by shifting the bit out of the lock word with SHR.
-    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");
-    __ shrl(CpuRegister(TMP), Immediate(LockWord::kReadBarrierStateShift + 1));
-    __ j(kCarrySet, read_barrier_slow_path->GetEntryLabel());
+    // We have done the "if" of the gray bit check above, now branch based on the flags.
+    __ j(kNotZero, read_barrier_slow_path->GetEntryLabel());
 
     // Fast-path copy.
     // Iterate over the arrays and do a raw copy of the objects. We don't need to
@@ -2087,10 +2089,9 @@
     case Primitive::kPrimNot: {
       if (kEmitCompilerReadBarrier) {
         if (kUseBakerReadBarrier) {
-          Location temp = locations->GetTemp(0);
           Address src(base, offset, ScaleFactor::TIMES_1, 0);
           codegen->GenerateReferenceLoadWithBakerReadBarrier(
-              invoke, output_loc, base, src, temp, /* needs_null_check */ false);
+              invoke, output_loc, base, src, /* needs_null_check */ false);
         } else {
           __ movl(output, Address(base, offset, ScaleFactor::TIMES_1, 0));
           codegen->GenerateReadBarrierSlow(
@@ -2113,9 +2114,7 @@
   }
 }
 
-static void CreateIntIntIntToIntLocations(ArenaAllocator* arena,
-                                          HInvoke* invoke,
-                                          Primitive::Type type) {
+static void CreateIntIntIntToIntLocations(ArenaAllocator* arena, HInvoke* invoke) {
   bool can_call = kEmitCompilerReadBarrier &&
       (invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObject ||
        invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObjectVolatile);
@@ -2129,30 +2128,25 @@
   locations->SetInAt(2, Location::RequiresRegister());
   locations->SetOut(Location::RequiresRegister(),
                     can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap);
-  if (type == Primitive::kPrimNot && kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
-    // We need a temporary register for the read barrier marking slow
-    // path in InstructionCodeGeneratorX86_64::GenerateReferenceLoadWithBakerReadBarrier.
-    locations->AddTemp(Location::RequiresRegister());
-  }
 }
 
 void IntrinsicLocationsBuilderX86_64::VisitUnsafeGet(HInvoke* invoke) {
-  CreateIntIntIntToIntLocations(arena_, invoke, Primitive::kPrimInt);
+  CreateIntIntIntToIntLocations(arena_, invoke);
 }
 void IntrinsicLocationsBuilderX86_64::VisitUnsafeGetVolatile(HInvoke* invoke) {
-  CreateIntIntIntToIntLocations(arena_, invoke, Primitive::kPrimInt);
+  CreateIntIntIntToIntLocations(arena_, invoke);
 }
 void IntrinsicLocationsBuilderX86_64::VisitUnsafeGetLong(HInvoke* invoke) {
-  CreateIntIntIntToIntLocations(arena_, invoke, Primitive::kPrimLong);
+  CreateIntIntIntToIntLocations(arena_, invoke);
 }
 void IntrinsicLocationsBuilderX86_64::VisitUnsafeGetLongVolatile(HInvoke* invoke) {
-  CreateIntIntIntToIntLocations(arena_, invoke, Primitive::kPrimLong);
+  CreateIntIntIntToIntLocations(arena_, invoke);
 }
 void IntrinsicLocationsBuilderX86_64::VisitUnsafeGetObject(HInvoke* invoke) {
-  CreateIntIntIntToIntLocations(arena_, invoke, Primitive::kPrimNot);
+  CreateIntIntIntToIntLocations(arena_, invoke);
 }
 void IntrinsicLocationsBuilderX86_64::VisitUnsafeGetObjectVolatile(HInvoke* invoke) {
-  CreateIntIntIntToIntLocations(arena_, invoke, Primitive::kPrimNot);
+  CreateIntIntIntToIntLocations(arena_, invoke);
 }
 
 
diff --git a/compiler/utils/x86/assembler_x86.cc b/compiler/utils/x86/assembler_x86.cc
index f1a9915..f2ef41f 100644
--- a/compiler/utils/x86/assembler_x86.cc
+++ b/compiler/utils/x86/assembler_x86.cc
@@ -1148,6 +1148,23 @@
 }
 
 
+void X86Assembler::testb(const Address& dst, const Immediate& imm) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitUint8(0xF6);
+  EmitOperand(EAX, dst);
+  CHECK(imm.is_int8());
+  EmitUint8(imm.value() & 0xFF);
+}
+
+
+void X86Assembler::testl(const Address& dst, const Immediate& imm) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitUint8(0xF7);
+  EmitOperand(0, dst);
+  EmitImmediate(imm);
+}
+
+
 void X86Assembler::andl(Register dst, Register src) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitUint8(0x23);
diff --git a/compiler/utils/x86/assembler_x86.h b/compiler/utils/x86/assembler_x86.h
index 63aa4a4..2ddcd76 100644
--- a/compiler/utils/x86/assembler_x86.h
+++ b/compiler/utils/x86/assembler_x86.h
@@ -496,6 +496,9 @@
   void testl(Register reg, const Immediate& imm);
   void testl(Register reg1, const Address& address);
 
+  void testb(const Address& dst, const Immediate& imm);
+  void testl(const Address& dst, const Immediate& imm);
+
   void andl(Register dst, const Immediate& imm);
   void andl(Register dst, Register src);
   void andl(Register dst, const Address& address);
diff --git a/compiler/utils/x86/assembler_x86_test.cc b/compiler/utils/x86/assembler_x86_test.cc
index 307e034..61d70d7 100644
--- a/compiler/utils/x86/assembler_x86_test.cc
+++ b/compiler/utils/x86/assembler_x86_test.cc
@@ -375,6 +375,42 @@
   DriverStr(expected, "cmovl_address");
 }
 
+TEST_F(AssemblerX86Test, TestbAddressImmediate) {
+  GetAssembler()->testb(
+      x86::Address(x86::Register(x86::EDI), x86::Register(x86::EBX), x86::TIMES_4, 12),
+      x86::Immediate(1));
+  GetAssembler()->testb(
+      x86::Address(x86::Register(x86::ESP), FrameOffset(7)),
+      x86::Immediate(-128));
+  GetAssembler()->testb(
+      x86::Address(x86::Register(x86::EBX), MemberOffset(130)),
+      x86::Immediate(127));
+  const char* expected =
+      "testb $1, 0xc(%EDI,%EBX,4)\n"
+      "testb $-128, 0x7(%ESP)\n"
+      "testb $127, 0x82(%EBX)\n";
+
+  DriverStr(expected, "TestbAddressImmediate");
+}
+
+TEST_F(AssemblerX86Test, TestlAddressImmediate) {
+  GetAssembler()->testl(
+      x86::Address(x86::Register(x86::EDI), x86::Register(x86::EBX), x86::TIMES_4, 12),
+      x86::Immediate(1));
+  GetAssembler()->testl(
+      x86::Address(x86::Register(x86::ESP), FrameOffset(7)),
+      x86::Immediate(-100000));
+  GetAssembler()->testl(
+      x86::Address(x86::Register(x86::EBX), MemberOffset(130)),
+      x86::Immediate(77777777));
+  const char* expected =
+      "testl $1, 0xc(%EDI,%EBX,4)\n"
+      "testl $-100000, 0x7(%ESP)\n"
+      "testl $77777777, 0x82(%EBX)\n";
+
+  DriverStr(expected, "TestlAddressImmediate");
+}
+
 /////////////////
 // Near labels //
 /////////////////
diff --git a/compiler/utils/x86_64/assembler_x86_64.cc b/compiler/utils/x86_64/assembler_x86_64.cc
index ddc8244..1f73aa7 100644
--- a/compiler/utils/x86_64/assembler_x86_64.cc
+++ b/compiler/utils/x86_64/assembler_x86_64.cc
@@ -1389,6 +1389,25 @@
 }
 
 
+void X86_64Assembler::testb(const Address& dst, const Immediate& imm) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitOptionalRex32(dst);
+  EmitUint8(0xF6);
+  EmitOperand(Register::RAX, dst);
+  CHECK(imm.is_int8());
+  EmitUint8(imm.value() & 0xFF);
+}
+
+
+void X86_64Assembler::testl(const Address& dst, const Immediate& imm) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitOptionalRex32(dst);
+  EmitUint8(0xF7);
+  EmitOperand(0, dst);
+  EmitImmediate(imm);
+}
+
+
 void X86_64Assembler::andl(CpuRegister dst, CpuRegister src) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitOptionalRex32(dst, src);
diff --git a/compiler/utils/x86_64/assembler_x86_64.h b/compiler/utils/x86_64/assembler_x86_64.h
index a4166f9..3a4bfca 100644
--- a/compiler/utils/x86_64/assembler_x86_64.h
+++ b/compiler/utils/x86_64/assembler_x86_64.h
@@ -528,6 +528,9 @@
   void testq(CpuRegister reg1, CpuRegister reg2);
   void testq(CpuRegister reg, const Address& address);
 
+  void testb(const Address& address, const Immediate& imm);
+  void testl(const Address& address, const Immediate& imm);
+
   void andl(CpuRegister dst, const Immediate& imm);
   void andl(CpuRegister dst, CpuRegister src);
   void andl(CpuRegister reg, const Address& address);
diff --git a/compiler/utils/x86_64/assembler_x86_64_test.cc b/compiler/utils/x86_64/assembler_x86_64_test.cc
index 36c966b..48a1876 100644
--- a/compiler/utils/x86_64/assembler_x86_64_test.cc
+++ b/compiler/utils/x86_64/assembler_x86_64_test.cc
@@ -1526,6 +1526,48 @@
   DriverStr(expected, "cmpb");
 }
 
+TEST_F(AssemblerX86_64Test, TestbAddressImmediate) {
+  GetAssembler()->testb(
+      x86_64::Address(x86_64::CpuRegister(x86_64::RDI),
+                      x86_64::CpuRegister(x86_64::RBX),
+                      x86_64::TIMES_4,
+                      12),
+      x86_64::Immediate(1));
+  GetAssembler()->testb(
+      x86_64::Address(x86_64::CpuRegister(x86_64::RSP), FrameOffset(7)),
+      x86_64::Immediate(-128));
+  GetAssembler()->testb(
+      x86_64::Address(x86_64::CpuRegister(x86_64::RBX), MemberOffset(130)),
+      x86_64::Immediate(127));
+  const char* expected =
+      "testb $1, 0xc(%RDI,%RBX,4)\n"
+      "testb $-128, 0x7(%RSP)\n"
+      "testb $127, 0x82(%RBX)\n";
+
+  DriverStr(expected, "TestbAddressImmediate");
+}
+
+TEST_F(AssemblerX86_64Test, TestlAddressImmediate) {
+  GetAssembler()->testl(
+      x86_64::Address(x86_64::CpuRegister(x86_64::RDI),
+                      x86_64::CpuRegister(x86_64::RBX),
+                      x86_64::TIMES_4,
+                      12),
+      x86_64::Immediate(1));
+  GetAssembler()->testl(
+      x86_64::Address(x86_64::CpuRegister(x86_64::RSP), FrameOffset(7)),
+      x86_64::Immediate(-100000));
+  GetAssembler()->testl(
+      x86_64::Address(x86_64::CpuRegister(x86_64::RBX), MemberOffset(130)),
+      x86_64::Immediate(77777777));
+  const char* expected =
+      "testl $1, 0xc(%RDI,%RBX,4)\n"
+      "testl $-100000, 0x7(%RSP)\n"
+      "testl $77777777, 0x82(%RBX)\n";
+
+  DriverStr(expected, "TestlAddressImmediate");
+}
+
 class JNIMacroAssemblerX86_64Test : public JNIMacroAssemblerTest<x86_64::X86_64JNIMacroAssembler> {
  public:
   using Base = JNIMacroAssemblerTest<x86_64::X86_64JNIMacroAssembler>;
diff --git a/test/537-checker-arraycopy/src/Main.java b/test/537-checker-arraycopy/src/Main.java
index 7c124ca..95a11ca 100644
--- a/test/537-checker-arraycopy/src/Main.java
+++ b/test/537-checker-arraycopy/src/Main.java
@@ -51,10 +51,10 @@
 
   /// CHECK-START-X86_64: void Main.arraycopy() disassembly (after)
   /// CHECK:          InvokeStaticOrDirect intrinsic:SystemArrayCopy
-  /// CHECK-NOT:      test
+  /// CHECK-NOT:      test {{^[^\[].*}}, {{^[^\[].*}}
   /// CHECK-NOT:      call
   /// CHECK:          ReturnVoid
-  // Checks that the call is intrinsified and that there is no test instruction
+  // Checks that the call is intrinsified and that there is no register test instruction
   // when we know the source and destination are not null.
   public static void arraycopy() {
     Object[] obj = new Object[4];