[vISA] Add set/getInputR1() APIs in IR builder

Add set/getInputR1() APIs in IR builder

Author: fangliu2020

visa/BuildIR.h

@@ -364,6 +364,11 @@ class IR_Builder
     G4_INST* FDSpillInst = nullptr;
     G4_Declare* tmpFCRet = nullptr;
 
+
+    // input declare of R1.
+    // Used to initialize header payload of render target read message
+    G4_Declare* inputR1 = nullptr;
+
     unsigned short arg_size;
     unsigned short return_var_size;
 
@@ -667,6 +672,9 @@ class IR_Builder
     G4_Declare* getBuiltinSamplerHeader() const { return builtinSamplerHeader; }
     G4_Declare* getOldA0Dot2Temp() const { return oldA0Dot2Temp; }
 
+    G4_Declare* getInputR1() { return inputR1; }
+    void setInputR1(G4_Declare* r1) { inputR1 = r1; }
+
     bool isBindlessSampler(const G4_Operand* sampler) const {
         return sampler->isSrcRegRegion() && sampler->getTopDcl() == getBuiltinBindlessSampler();
     }

visa/VISAKernelImpl.cpp

@@ -1759,6 +1759,12 @@ int VISAKernelImpl::CreateVISAInputVar(
         }
     }
 
+    // save the G4_declare of "R1" input in builder
+    if (offset == getGRFSize() && size == getGRFSize())
+    {
+        m_builder->setInputR1(input->dcl);
+    }
+
     return status;
 }