diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AddressingModes.h b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AddressingModes.h
index ef5bb71..4db9dea 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AddressingModes.h
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AddressingModes.h
@@ -51,7 +51,7 @@
 /// getShiftName - Get the string encoding for the shift type.
 static inline const char *getShiftExtendName(AArch64_AM::ShiftExtendType ST) {
   switch (ST) {
-  default: assert(false && "unhandled shift type!");
+  default: llvm_unreachable("unhandled shift type!");
   case AArch64_AM::LSL: return "lsl";
   case AArch64_AM::LSR: return "lsr";
   case AArch64_AM::ASR: return "asr";
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
index 0df442f..05db044 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
@@ -132,7 +132,7 @@
   int64_t SignedValue = static_cast<int64_t>(Value);
   switch (Kind) {
   default:
-    assert(false && "Unknown fixup kind!");
+    llvm_unreachable("Unknown fixup kind!");
   case AArch64::fixup_aarch64_pcrel_adr_imm21:
     if (SignedValue > 2097151 || SignedValue < -2097152)
       report_fatal_error("fixup value out of range");
@@ -239,7 +239,7 @@
 
 void AArch64AsmBackend::relaxInstruction(const MCInst &Inst,
                                          MCInst &Res) const {
-  assert(false && "AArch64AsmBackend::relaxInstruction() unimplemented");
+  llvm_unreachable("AArch64AsmBackend::relaxInstruction() unimplemented");
 }
 
 bool AArch64AsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCCodeEmitter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCCodeEmitter.cpp
index c306b11..4756a19 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCCodeEmitter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCCodeEmitter.cpp
@@ -437,8 +437,7 @@
     return 3;
   }
 
-  assert(false && "Invalid value for vector shift amount!");
-  return 0;
+  llvm_unreachable("Invalid value for vector shift amount!");
 }
 
 uint32_t
diff --git a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
index 4fe10f4..1e2167f 100644
--- a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
@@ -891,7 +891,7 @@
         continue;
       }
       else {
-        assert(false && "Unexpected operand type");
+        llvm_unreachable("Unexpected operand type");
       }
     }
   }
diff --git a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index 5885fb1..2eb757a 100644
--- a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1412,9 +1412,7 @@
 bool MipsAsmParser::expandInstruction(MCInst &Inst, SMLoc IDLoc,
                                       SmallVectorImpl<MCInst> &Instructions) {
   switch (Inst.getOpcode()) {
-  default:
-    assert(0 && "unimplemented expansion");
-    return true;
+  default: llvm_unreachable("unimplemented expansion");
   case Mips::LoadImm32Reg:
     return expandLoadImm(Inst, IDLoc, Instructions);
   case Mips::LoadImm64Reg:
diff --git a/llvm/lib/Target/Mips/InstPrinter/MipsInstPrinter.cpp b/llvm/lib/Target/Mips/InstPrinter/MipsInstPrinter.cpp
index 80e555e..61743ff 100644
--- a/llvm/lib/Target/Mips/InstPrinter/MipsInstPrinter.cpp
+++ b/llvm/lib/Target/Mips/InstPrinter/MipsInstPrinter.cpp
@@ -134,8 +134,8 @@
   } else if (const MipsMCExpr *ME = dyn_cast<MipsMCExpr>(Expr)) {
     ME->print(OS);
     return;
-  } else if (!(SRE = dyn_cast<MCSymbolRefExpr>(Expr)))
-    assert(false && "Unexpected MCExpr type.");
+  } else
+    SRE = cast<MCSymbolRefExpr>(Expr);
 
   MCSymbolRefExpr::VariantKind Kind = SRE->getKind();
 
diff --git a/llvm/lib/Target/Mips/Mips16InstrInfo.cpp b/llvm/lib/Target/Mips/Mips16InstrInfo.cpp
index 4dd9af2..976becc 100644
--- a/llvm/lib/Target/Mips/Mips16InstrInfo.cpp
+++ b/llvm/lib/Target/Mips/Mips16InstrInfo.cpp
@@ -144,7 +144,6 @@
 /// opcode, e.g. turning BEQ to BNE.
 unsigned Mips16InstrInfo::getOppositeBranchOpc(unsigned Opc) const {
   switch (Opc) {
-  default:  llvm_unreachable("Illegal opcode!");
   case Mips::BeqzRxImmX16: return Mips::BnezRxImmX16;
   case Mips::BnezRxImmX16: return Mips::BeqzRxImmX16;
   case Mips::BeqzRxImm16: return Mips::BnezRxImm16;
@@ -166,8 +165,7 @@
   case Mips::BtnezT8SltX16: return Mips::BteqzT8SltX16;
   case Mips::BtnezT8SltiX16: return Mips::BteqzT8SltiX16;
   }
-  assert(false && "Implement this function.");
-  return 0;
+  llvm_unreachable("Illegal opcode!");
 }
 
 static void addSaveRestoreRegs(MachineInstrBuilder &MIB,
@@ -288,7 +286,7 @@
 void Mips16InstrInfo::adjustStackPtrBigUnrestricted(
     unsigned SP, int64_t Amount, MachineBasicBlock &MBB,
     MachineBasicBlock::iterator I) const {
-   assert(false && "adjust stack pointer amount exceeded");
+   llvm_unreachable("adjust stack pointer amount exceeded");
 }
 
 /// Adjust SP by Amount bytes.
diff --git a/llvm/lib/Target/Mips/MipsLongBranch.cpp b/llvm/lib/Target/Mips/MipsLongBranch.cpp
index cf267c9..9d87305 100644
--- a/llvm/lib/Target/Mips/MipsLongBranch.cpp
+++ b/llvm/lib/Target/Mips/MipsLongBranch.cpp
@@ -110,8 +110,7 @@
       return MO.getMBB();
   }
 
-  assert(false && "This instruction does not have an MBB operand.");
-  return nullptr;
+  llvm_unreachable("This instruction does not have an MBB operand.");
 }
 
 // Traverse the list of instructions backwards until a non-debug instruction is
diff --git a/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp b/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
index 78fbd45..093a2cb 100644
--- a/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
@@ -374,17 +374,15 @@
     } else if (isa<PointerType>(Ty)) {
       O << ".param .b" << TLI->getPointerTy().getSizeInBits()
         << " func_retval0";
-    } else {
-      if ((Ty->getTypeID() == Type::StructTyID) || isa<VectorType>(Ty)) {
-        unsigned totalsz = TD->getTypeAllocSize(Ty);
-        unsigned retAlignment = 0;
-        if (!llvm::getAlign(*F, 0, retAlignment))
-          retAlignment = TD->getABITypeAlignment(Ty);
-        O << ".param .align " << retAlignment << " .b8 func_retval0[" << totalsz
-          << "]";
-      } else
-        assert(false && "Unknown return type");
-    }
+    } else if ((Ty->getTypeID() == Type::StructTyID) || isa<VectorType>(Ty)) {
+       unsigned totalsz = TD->getTypeAllocSize(Ty);
+       unsigned retAlignment = 0;
+       if (!llvm::getAlign(*F, 0, retAlignment))
+         retAlignment = TD->getABITypeAlignment(Ty);
+       O << ".param .align " << retAlignment << " .b8 func_retval0[" << totalsz
+         << "]";
+    } else
+      llvm_unreachable("Unknown return type");
   } else {
     SmallVector<EVT, 16> vtparts;
     ComputeValueVTs(*TLI, Ty, vtparts);
diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
index 0b0b536..e605547 100644
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -905,16 +905,14 @@
       O << ".param .b" << size << " _";
     } else if (isa<PointerType>(retTy)) {
       O << ".param .b" << getPointerTy().getSizeInBits() << " _";
+    } else if ((retTy->getTypeID() == Type::StructTyID) ||
+               isa<VectorType>(retTy)) {
+      O << ".param .align "
+        << retAlignment
+        << " .b8 _["
+        << getDataLayout()->getTypeAllocSize(retTy) << "]";
     } else {
-      if((retTy->getTypeID() == Type::StructTyID) ||
-         isa<VectorType>(retTy)) {
-        O << ".param .align "
-          << retAlignment
-          << " .b8 _["
-          << getDataLayout()->getTypeAllocSize(retTy) << "]";
-      } else {
-        assert(false && "Unknown return type");
-      }
+      llvm_unreachable("Unknown return type");
     }
     O << ") ";
   }
diff --git a/llvm/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp b/llvm/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp
index 29c698d..447ab9d 100644
--- a/llvm/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp
+++ b/llvm/lib/Target/X86/AsmParser/X86AsmInstrumentation.cpp
@@ -666,6 +666,7 @@
                            .addImm(7));
 
   switch (AccessSize) {
+  default: llvm_unreachable("Incorrect access size");
   case 1:
     break;
   case 2: {
@@ -682,9 +683,6 @@
                              .addReg(ScratchRegI32)
                              .addImm(3));
     break;
-  default:
-    assert(false && "Incorrect access size");
-    break;
   }
 
   EmitInstruction(
@@ -715,15 +713,13 @@
   {
     MCInst Inst;
     switch (AccessSize) {
+    default: llvm_unreachable("Incorrect access size");
     case 8:
       Inst.setOpcode(X86::CMP8mi);
       break;
     case 16:
       Inst.setOpcode(X86::CMP16mi);
       break;
-    default:
-      assert(false && "Incorrect access size");
-      break;
     }
     const MCExpr *Disp = MCConstantExpr::Create(kShadowOffset, Ctx);
     std::unique_ptr<X86Operand> Op(
@@ -941,6 +937,7 @@
                            .addImm(7));
 
   switch (AccessSize) {
+  default: llvm_unreachable("Incorrect access size");
   case 1:
     break;
   case 2: {
@@ -957,9 +954,6 @@
                              .addReg(ScratchRegI32)
                              .addImm(3));
     break;
-  default:
-    assert(false && "Incorrect access size");
-    break;
   }
 
   EmitInstruction(
@@ -990,15 +984,13 @@
   {
     MCInst Inst;
     switch (AccessSize) {
+    default: llvm_unreachable("Incorrect access size");
     case 8:
       Inst.setOpcode(X86::CMP8mi);
       break;
     case 16:
       Inst.setOpcode(X86::CMP16mi);
       break;
-    default:
-      assert(false && "Incorrect access size");
-      break;
     }
     const MCExpr *Disp = MCConstantExpr::Create(kShadowOffset, Ctx);
     std::unique_ptr<X86Operand> Op(
diff --git a/llvm/lib/Target/X86/X86FixupLEAs.cpp b/llvm/lib/Target/X86/X86FixupLEAs.cpp
index 02736ac..8e033a0 100644
--- a/llvm/lib/Target/X86/X86FixupLEAs.cpp
+++ b/llvm/lib/Target/X86/X86FixupLEAs.cpp
@@ -283,6 +283,7 @@
     return;
   int addrr_opcode, addri_opcode;
   switch (opcode) {
+  default: llvm_unreachable("Unexpected LEA instruction");
   case X86::LEA16r:
     addrr_opcode = X86::ADD16rr;
     addri_opcode = X86::ADD16ri;
@@ -296,8 +297,6 @@
     addrr_opcode = X86::ADD64rr;
     addri_opcode = X86::ADD64ri32;
     break;
-  default:
-    assert(false && "Unexpected LEA instruction");
   }
   DEBUG(dbgs() << "FixLEA: Candidate to replace:"; I->dump(););
   DEBUG(dbgs() << "FixLEA: Replaced by: ";);