lte: return reference to prevent Dci temporary copy

saves 4.7 million allocations (26%) in the lte-cqi-generation test suite

src/lte/model/lte-control-messages.cc

@@ -69,7 +69,7 @@ DlDciLteControlMessage::SetDci(DlDciListElement_s dci)
     m_dci = dci;
 }
 
-DlDciListElement_s
+const DlDciListElement_s&
 DlDciLteControlMessage::GetDci()
 {
     return m_dci;
@@ -92,7 +92,7 @@ UlDciLteControlMessage::SetDci(UlDciListElement_s dci)
     m_dci = dci;
 }
 
-UlDciListElement_s
+const UlDciListElement_s&
 UlDciLteControlMessage::GetDci()
 {
     return m_dci;

src/lte/model/lte-control-messages.h

@@ -106,7 +106,7 @@ class DlDciLteControlMessage : public LteControlMessage
      * \brief Get dic information
      * \return dci messages
      */
-    DlDciListElement_s GetDci();
+    const DlDciListElement_s& GetDci();
 
   private:
     DlDciListElement_s m_dci; ///< DCI
@@ -135,7 +135,7 @@ class UlDciLteControlMessage : public LteControlMessage
      * \brief Get dic information
      * \return dci messages
      */
-    UlDciListElement_s GetDci();
+    const UlDciListElement_s& GetDci();
 
   private:
     UlDciListElement_s m_dci; ///< DCI

src/lte/model/lte-enb-phy.cc

@@ -706,7 +706,7 @@ LteEnbPhy::StartSubFrame()
                     mask = (mask << 1);
                 }
                 // fire trace of DL Tx PHY stats
-                for (uint8_t i = 0; i < dci->GetDci().m_mcs.size(); i++)
+                for (std::size_t i = 0; i < dci->GetDci().m_mcs.size(); i++)
                 {
                     PhyTransmissionStatParameters params;
                     params.m_cellId = m_cellId;