Refactor code for dummy sendc generation for pixel shader.

Change-Id: I98e91fa9ad5077b53cdc6c6b40d374481ebc95b0

Author: weiyu-chen

visa/BuildIR.h

@@ -1917,6 +1917,8 @@ class IR_Builder {
     G4_INST* createFenceInstruction(
         uint8_t flushParam, bool commitEnable, bool globalMemFence, bool isSendc);
 
+    G4_INST* createSLMFence();
+
     // short hand for creating a dstRegRegion
     G4_DstRegRegion* Create_Dst_Opnd_From_Dcl(G4_Declare* dcl, unsigned short hstride);
     G4_SrcRegRegion* Create_Src_Opnd_From_Dcl(G4_Declare* dcl, const RegionDesc* rd);

visa/FlowGraph.cpp

@@ -1002,7 +1002,7 @@ void FlowGraph::handleWait()
                     G4_INST* nextInst = *nextIter;
                     if (nextInst->isSend())
                     {
-                        nextInst->setOpcode(nextInst->isSplitSend() ? G4_sendsc : G4_sendc);
+                        nextInst->asSendInst()->setSendc();
                         sunk = true;
                         break;
                     }
@@ -1014,8 +1014,8 @@ void FlowGraph::handleWait()
                 }
                 if (!sunk)
                 {
-                    bool commitEnable = builder->needsFenceCommitEnable();
-                    G4_INST* fenceInst = builder->createFenceInstruction(0, commitEnable, false, true);
+                    auto fenceInst = builder->createSLMFence();
+                    fenceInst->asSendInst()->setSendc();
                     bb->insert(iter, fenceInst);
                 }
                 iter = bb->erase(iter);

visa/Gen4_IR.hpp

@@ -1357,6 +1357,18 @@ class G4_InstSend : public G4_INST
         G4_SendMsgDescriptor* md);
 
     bool isSendc() const { return op == G4_sendc || op == G4_sendsc; }
+    void setSendc()
+    {
+        // no effect if op is already G4_sendc/G4_sendsc
+        if (op == G4_send)
+        {
+            op = G4_sendc;
+        }
+        else if (op == G4_sends)
+        {
+            op = G4_sendsc;
+        }
+    }
     bool mayExceedTwoGRF() const override { return true; }
 
     G4_Operand* getMsgDescOperand() const

visa/TranslationInterface.cpp

@@ -1863,6 +1863,13 @@ int IR_Builder::translateVISAWaitInst(G4_Operand* mask)
     return VISA_SUCCESS;
 }
 
+// create a default SLM fence (no flush)
+G4_INST* IR_Builder::createSLMFence()
+{
+    bool commitEnable = needsFenceCommitEnable();
+    return createFenceInstruction(0, commitEnable, false, false);
+}
+
 void IR_Builder::generateBarrierSend()
 {