[turbofan][x64] Use the root register for comparisons with certain roots.

src/compiler/instruction-selector.h

Index: src/compiler/instruction-selector.h
diff --git a/src/compiler/instruction-selector.h b/src/compiler/instruction-selector.h
index 2981f90a1c4fcd80bf088be62ba93272b7afc5ec..e638937a67f0c5fbf915eb93fdc39d42229eb2a7 100644
--- a/src/compiler/instruction-selector.h
+++ b/src/compiler/instruction-selector.h
@@ -204,6 +204,8 @@ class InstructionSelector final {
   // to the roots register, i.e. if both a root register is available for this
   // compilation unit and the serializer is disabled.
   bool CanAddressRelativeToRootsRegister() const;
+  // Check if we can use the roots register to access GC roots.
+  bool CanUseRootsRegister() const;
 
   Isolate* isolate() const { return sequence()->isolate(); }