diff --git a/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp b/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp
--- a/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp
+++ b/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp
@@ -905,8 +905,7 @@
     Scale = 2;
     break;
   default:
-    assert(0);
-    break;
+    llvm_unreachable("");
   }
 
   unsigned MaxOffs = ((1 << (Bits - 1)) - 1) * Scale;
diff --git a/llvm/lib/Target/CSKY/CSKYInstrInfo.cpp b/llvm/lib/Target/CSKY/CSKYInstrInfo.cpp
--- a/llvm/lib/Target/CSKY/CSKYInstrInfo.cpp
+++ b/llvm/lib/Target/CSKY/CSKYInstrInfo.cpp
@@ -476,9 +476,6 @@
                                 MachineBasicBlock::iterator I,
                                 const DebugLoc &DL, MCRegister DestReg,
                                 MCRegister SrcReg, bool KillSrc) const {
-
-  MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
-
   if (CSKY::GPRRegClass.contains(SrcReg) &&
       CSKY::CARRYRegClass.contains(DestReg)) {
     if (STI.hasE2()) {
diff --git a/llvm/lib/Target/CSKY/CSKYMachineFunctionInfo.h b/llvm/lib/Target/CSKY/CSKYMachineFunctionInfo.h
--- a/llvm/lib/Target/CSKY/CSKYMachineFunctionInfo.h
+++ b/llvm/lib/Target/CSKY/CSKYMachineFunctionInfo.h
@@ -18,8 +18,6 @@
 namespace llvm {
 
 class CSKYMachineFunctionInfo : public MachineFunctionInfo {
-  MachineFunction &MF;
-
   Register GlobalBaseReg = 0;
   bool SpillsCR = false;
 
@@ -33,7 +31,7 @@
   unsigned PICLabelUId = 0;
 
 public:
-  CSKYMachineFunctionInfo(MachineFunction &MF) : MF(MF) {}
+  CSKYMachineFunctionInfo(MachineFunction &) {}
 
   Register getGlobalBaseReg() const { return GlobalBaseReg; }
   void setGlobalBaseReg(Register Reg) { GlobalBaseReg = Reg; }
diff --git a/llvm/lib/Target/CSKY/Disassembler/CSKYDisassembler.cpp b/llvm/lib/Target/CSKY/Disassembler/CSKYDisassembler.cpp
--- a/llvm/lib/Target/CSKY/Disassembler/CSKYDisassembler.cpp
+++ b/llvm/lib/Target/CSKY/Disassembler/CSKYDisassembler.cpp
@@ -33,7 +33,6 @@
 namespace {
 class CSKYDisassembler : public MCDisassembler {
   std::unique_ptr<MCInstrInfo const> const MCII;
-  mutable bool inDataRegion = false;
   mutable StringRef symbolName;
 
   DecodeStatus handleCROperand(MCInst &Instr) const;
@@ -166,6 +165,8 @@
   return MCDisassembler::Success;
 }
 
+// TODO
+LLVM_ATTRIBUTE_UNUSED
 static DecodeStatus DecodesFPR128RegisterClass(MCInst &Inst, uint64_t RegNo,
                                                uint64_t Address,
                                                const MCDisassembler *Decoder) {
@@ -196,6 +197,8 @@
   return MCDisassembler::Success;
 }
 
+// TODO
+LLVM_ATTRIBUTE_UNUSED
 static DecodeStatus DecodeGPRSPRegisterClass(MCInst &Inst, uint64_t RegNo,
                                              uint64_t Address,
                                              const MCDisassembler *Decoder) {
diff --git a/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFObjectWriter.cpp b/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFObjectWriter.cpp
--- a/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFObjectWriter.cpp
+++ b/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFObjectWriter.cpp
@@ -121,6 +121,7 @@
         return ELF::R_CKCORE_ADDR32;
       }
     }
+    return ELF::R_CKCORE_NONE;
   case FK_Data_8:
     Ctx.reportError(Fixup.getLoc(), "8-byte data relocations not supported");
     return ELF::R_CKCORE_NONE;
diff --git a/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFStreamer.h b/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFStreamer.h
--- a/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFStreamer.h
+++ b/llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFStreamer.h
@@ -137,7 +137,7 @@
     EmitMappingSymbol("$d");
     MCELFStreamer::emitValueImpl(Value, Size, Loc);
   }
-  void reset() {
+  void reset() override {
     MappingSymbolCounter = 0;
     State = EMS_None;
     MCELFStreamer::reset();