[turbofan] Add bounds check to Node::InputAt(index) and fix tests that go out of bounds.

src/compiler/node.h

Index: src/compiler/node.h
diff --git a/src/compiler/node.h b/src/compiler/node.h
index aa0d393dbd7e9e765a0b4d7961148ac7e14a3d59..0c8f1205a70430fe35bf34d7db00aaf9f85e3f02 100644
--- a/src/compiler/node.h
+++ b/src/compiler/node.h
@@ -58,7 +58,15 @@ class Node final {
   NodeId id() const { return id_; }
 
   int InputCount() const { return input_count(); }
-  Node* InputAt(int index) const { return GetInputRecordPtr(index)->to; }
+  Node* InputAt(int index) const {
+#if DEBUG
+    if (index < 0 || index >= InputCount()) {
+      V8_Fatal(__FILE__, __LINE__, "Node #%d:%s->InputAt(%d) out of bounds",
+               id(), op()->mnemonic(), index);
+    }
+#endif
+    return GetInputRecordPtr(index)->to;
+  }
   inline void ReplaceInput(int index, Node* new_to);
   void AppendInput(Zone* zone, Node* new_to);
   void InsertInput(Zone* zone, int index, Node* new_to);