[turbofan] Validate split-edge form

src/compiler/instruction.h

Index: src/compiler/instruction.h
diff --git a/src/compiler/instruction.h b/src/compiler/instruction.h
index 8396fe30f2793bdc644e7735102a17cafbfad6dd..e719bf53aa2e1622ea2cf1f1ead16023503c07a6 100644
--- a/src/compiler/instruction.h
+++ b/src/compiler/instruction.h
@@ -1332,6 +1332,8 @@ class InstructionSequence final : public ZoneObject {
   void PrintBlock(const RegisterConfiguration* config, int block_id) const;
   void PrintBlock(int block_id) const;
 
+  void Validate();
+
  private:
   friend std::ostream& operator<<(std::ostream& os,
                                   const PrintableInstructionSequence& code);