[turbofan] Prevent storing signalling NaNs into holey double arrays.

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 8bdbf9b2d9cde3d88477c9e6c38bf9e59d997c63..8ac8e7b2aa94d4eaccc8ad71e79c175b05e5c58a 100644
--- a/src/compiler/instruction-selector.h
+++ b/src/compiler/instruction-selector.h
@@ -273,6 +273,9 @@ class InstructionSelector final {
   void EmitPrepareArguments(ZoneVector<compiler::PushParameter>* arguments,
                             const CallDescriptor* descriptor, Node* node);
 
+  void EmitIdentity(Node* node);
+  bool CanProduceSignalingNaN(Node* node);
+
   // ===========================================================================
 
   Schedule* schedule() const { return schedule_; }