Add lifetime marker for URB writes

Change-Id: I224c5998b2a946a8dafc1d4abe2d97a0bfdf4f99

Author: wpan

IGC/Compiler/CISACodeGen/CISABuilder.cpp

@@ -4408,6 +4408,13 @@ void CEncoder::Copy(CVariable* dst, CVariable* src)
     }
 }
 
+void CEncoder::LifetimeStart(CVariable* var)
+{
+    SModifier noMod; // Default is no mod.
+    noMod.init();
+    V(vKernel->AppendVISALifetime(LIFETIME_START, GetSourceOperand(var, noMod)));
+}
+
 void CEncoder::BoolToInt(CVariable* dst, CVariable* src)
 {
     assert(src->GetType() == ISA_TYPE_BOOL);

IGC/Compiler/CISACodeGen/CISABuilder.hpp

@@ -223,6 +223,7 @@ class CEncoder
     void StackCall(CVariable *flag, llvm::Function *F, unsigned char argSize, unsigned char retSize);
     void StackRet(CVariable *flag);
     void Loc(unsigned int line);
+    void LifetimeStart(CVariable* var);
 
     inline void Jump(uint label);
     inline void Cast(CVariable* dst, CVariable* src);

IGC/Compiler/CISACodeGen/CoalescingEngine.cpp

@@ -1171,6 +1171,8 @@ CVariable* CoalescingEngine::PrepareExplicitPayload(
     {
         payload = outProgram->GetNewVariable(numOperands*numLanes(simdMode), ISA_TYPE_F, EALIGN_GRF);
 
+        encoder->LifetimeStart(payload);
+
         for(uint i=0;i < numOperands;i++)
         {
             Value* val = m_PayloadMapping.GetPayloadElementToValueMapping(inst, i);