ARM64: Regenerate instead of spilling and restoring cheap lithium instructions.

src/lithium-allocator.h

Index: src/lithium-allocator.h
diff --git a/src/lithium-allocator.h b/src/lithium-allocator.h
index 83ba9afb68ca1b8cf1ffaebee13be7ab0375a7f9..0855a797ff8065c367032633020924fa7d11ad94 100644
--- a/src/lithium-allocator.h
+++ b/src/lithium-allocator.h
@@ -350,6 +350,12 @@ class LiveRange: public ZoneObject {
   // Shorten the most recently added interval by setting a new start.
   void ShortenTo(LifetimePosition start);
 
+  void set_parent_linstr(LInstruction* instr) {
+    parent_linstr_ = instr;
+    spill_operand_->set_parent_linstr(instr);
+  }
+  LInstruction* parent_linstr() const { return parent_linstr_; }
+
 #ifdef DEBUG
   // True if target overlaps an existing interval.
   bool HasOverlap(UseInterval* target) const;
@@ -378,6 +384,7 @@ class LiveRange: public ZoneObject {
   LOperand* current_hint_operand_;
   LOperand* spill_operand_;
   int spill_start_index_;
+  LInstruction* parent_linstr_;
 
   friend class LAllocator;  // Assigns to kind_.
 };