[Turbofan] Reduce register allocation work when we can.

src/compiler/register-allocator.h

Index: src/compiler/register-allocator.h
diff --git a/src/compiler/register-allocator.h b/src/compiler/register-allocator.h
index 4d94f1eac05532403898e14a654dee474c6afebc..7698a9038712c78e33baed2b23407309a0a6c241 100644
--- a/src/compiler/register-allocator.h
+++ b/src/compiler/register-allocator.h
@@ -982,6 +982,8 @@ class RegisterAllocator : public ZoneObject {
   const int* allocatable_register_codes() const {
     return allocatable_register_codes_;
   }
+  // Returns true iff. we must check float register aliasing.
+  bool check_fp_aliasing() const { return check_fp_aliasing_; }
 
   // TODO(mtrofin): explain why splitting in gap START is always OK.
   LifetimePosition GetSplitPositionForInstruction(const LiveRange* range,
@@ -1032,6 +1034,7 @@ class RegisterAllocator : public ZoneObject {
   const int num_registers_;
   int num_allocatable_registers_;
   const int* allocatable_register_codes_;
+  bool check_fp_aliasing_;
 
  private:
   bool no_combining_;