Add register reuse + peft scheduler cost model + Useless merger

src/PIM/Compiler/PimCodeGen.hpp

@@ -9,6 +9,7 @@
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/raw_os_ostream.h"
 
+#include <array>
 #include <fstream>
 #include <limits>
 #include <optional>
@@ -170,6 +171,7 @@ class PimCodeGen {
   const llvm::DenseMap<size_t, size_t>& emittedCoreIds;
   std::optional<unsigned> batchLane;
   mutable uint32_t emittedInstructionCount = 0;
+  mutable std::array<std::optional<int32_t>, 256> scalarRegisterValues = {};
 
   size_t addressOf(mlir::Value value, const StaticValueKnowledge& knowledge) const {
     return memory.getValueAddress(value, knowledge, batchLane);
@@ -177,6 +179,7 @@ class PimCodeGen {
   size_t remapCoreId(size_t coreId) const;
 
   void emitInstruction(const pim_binary::InstructionRecord& instruction) const;
+  void updateScalarRegisterCache(const pim_binary::InstructionRecord& instruction) const;
 
   void genSetRegisterImmediateUnsigned(size_t registerNumber, size_t immediate) const;
   void setupRd(size_t rdAddress, size_t rdOffset) const;