Subzero: Fix compiler warnings.

src/IceTargetLoweringX86BaseImpl.h:6093:13: error: unused variable 'Src1RM' [-Werror,-Wunused-variable]
      auto *Src1RM = legalize(Src1, Legal_Reg | Legal_Mem);
            ^

src/IceTargetLoweringX86BaseImpl.h:4007:3: error: default label in switch which covers all enumeration values [-Werror,-Wcovered-switch-default]
  default:
  ^

src/IceTargetLoweringMIPS32.cpp:4065:3: error: default label in switch which covers all enumeration values [-Werror,-Wcovered-switch-default]
  default:
  ^

src/IceTargetLoweringARM32.cpp:4975:3: error: default label in switch which covers all enumeration values [-Werror,-Wcovered-switch-default]
  default:
  ^

BUG= none
R=capn@chromium.org

Review URL: https://codereview.chromium.org/2434643002 .
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 47c7de8..2b65064 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -4972,9 +4972,6 @@
   Type DestTy = (Dest != nullptr) ? Dest->getType() : IceType_void;
   Intrinsics::IntrinsicID ID = Instr->getIntrinsicInfo().ID;
   switch (ID) {
-  default:
-    llvm::report_fatal_error("Unexpected intrinsic");
-    return;
   case Intrinsics::AtomicFence:
   case Intrinsics::AtomicFenceAll:
     assert(Dest == nullptr);
@@ -5290,8 +5287,8 @@
     UnimplementedLoweringError(this, Instr);
     return;
   }
-  case Intrinsics::UnknownIntrinsic:
-    Func->setError("Should not be lowering UnknownIntrinsic");
+  default: // UnknownIntrinsic
+    Func->setError("Unexpected intrinsic");
     return;
   }
   return;
diff --git a/src/IceTargetLoweringMIPS32.cpp b/src/IceTargetLoweringMIPS32.cpp
index 69080e7..99c32cc 100644
--- a/src/IceTargetLoweringMIPS32.cpp
+++ b/src/IceTargetLoweringMIPS32.cpp
@@ -4062,9 +4062,6 @@
   Variable *Dest = Instr->getDest();
   Type DestTy = (Dest == nullptr) ? IceType_void : Dest->getType();
   switch (Instr->getIntrinsicInfo().ID) {
-  default:
-    llvm::report_fatal_error("Unexpected intrinsic");
-    return;
   case Intrinsics::AtomicCmpxchg: {
     UnimplementedLoweringError(this, Instr);
     return;
@@ -4363,8 +4360,8 @@
     UnimplementedLoweringError(this, Instr); // Not required for PNaCl
     return;
   }
-  case Intrinsics::UnknownIntrinsic:
-    Func->setError("Should not be lowering UnknownIntrinsic");
+  default: // UnknownIntrinsic
+    Func->setError("Unexpected intrinsic");
     return;
   }
   return;
diff --git a/src/IceTargetLoweringX86BaseImpl.h b/src/IceTargetLoweringX86BaseImpl.h
index 87bbfde..52a5d07 100644
--- a/src/IceTargetLoweringX86BaseImpl.h
+++ b/src/IceTargetLoweringX86BaseImpl.h
@@ -4004,9 +4004,6 @@
 void TargetX86Base<TraitsType>::lowerIntrinsicCall(
     const InstIntrinsicCall *Instr) {
   switch (Intrinsics::IntrinsicID ID = Instr->getIntrinsicInfo().ID) {
-  default:
-    llvm::report_fatal_error("Unexpected intrinsic");
-    return;
   case Intrinsics::AtomicCmpxchg: {
     if (!Intrinsics::isMemoryOrderValid(
             ID, getConstantMemoryOrder(Instr->getArg(3)),
@@ -4417,8 +4414,8 @@
     }
     return;
   }
-  case Intrinsics::UnknownIntrinsic:
-    Func->setError("Should not be lowering UnknownIntrinsic");
+  default: // UnknownIntrinsic
+    Func->setError("Unexpected intrinsic");
     return;
   }
   return;
@@ -6090,7 +6087,6 @@
     if (Instr->indexesAre(0, 8, 1, 9, 2, 10, 3, 11)) {
       auto *T = makeReg(DestTy);
       auto *Src0RM = legalize(Src0, Legal_Reg | Legal_Mem);
-      auto *Src1RM = legalize(Src1, Legal_Reg | Legal_Mem);
       _movp(T, Src0RM);
       _punpckl(T, Src0RM);
       _movp(Dest, T);