A64: Implement and use FillFields

src/a64/lithium-a64.h

Index: src/a64/lithium-a64.h
diff --git a/src/a64/lithium-a64.h b/src/a64/lithium-a64.h
index cb222bf3241e821e455964799281df1677764c8e..5308239ecd4ca796ff71e48d6b326b82611f644f 100644
--- a/src/a64/lithium-a64.h
+++ b/src/a64/lithium-a64.h
@@ -614,22 +614,25 @@ class LAddS V8_FINAL : public LTemplateInstruction<1, 2, 0> {
 };
 
 
-class LAllocate V8_FINAL : public LTemplateInstruction<1, 2, 2> {
+class LAllocate V8_FINAL : public LTemplateInstruction<1, 2, 3> {
  public:
   LAllocate(LOperand* context,
             LOperand* size,
             LOperand* temp1,
-            LOperand* temp2) {
+            LOperand* temp2,
+            LOperand* temp3) {
     inputs_[0] = context;
     inputs_[1] = size;
     temps_[0] = temp1;
     temps_[1] = temp2;
+    temps_[2] = temp3;
   }
 
   LOperand* context() { return inputs_[0]; }
   LOperand* size() { return inputs_[1]; }
   LOperand* temp1() { return temps_[0]; }
   LOperand* temp2() { return temps_[1]; }
+  LOperand* temp3() { return temps_[2]; }
 
   DECLARE_CONCRETE_INSTRUCTION(Allocate, "allocate")
   DECLARE_HYDROGEN_ACCESSOR(Allocate)