Subzero: Fix build warnings/errors under g++.

src/IceAssemblerARM32.cpp

@@ -155,6 +155,9 @@ IValueT encodeShift(OperandARM32::ShiftKind Shift) {
   case OperandARM32::RRX:
     return 3; // 0b11
   }
+
+  llvm::report_fatal_error("Unknown Shift value");
+  return 0;
 }
 
 // Returns the bits in the corresponding masked value.

src/IceTargetLoweringX8632.cpp

@@ -88,12 +88,12 @@ const char *MachineTraits<TargetX8632>::TargetName = "X8632";
 
 template <>
 std::array<llvm::SmallBitVector, RCX86_NUM>
-    TargetX86Base<TargetX8632>::TypeToRegisterSet = {};
+    TargetX86Base<TargetX8632>::TypeToRegisterSet = {{}};
 
 template <>
 std::array<llvm::SmallBitVector,
            TargetX86Base<TargetX8632>::Traits::RegisterSet::Reg_NUM>
-    TargetX86Base<TargetX8632>::RegisterAliases = {};
+    TargetX86Base<TargetX8632>::RegisterAliases = {{}};
 
 template <>
 llvm::SmallBitVector

src/IceTargetLoweringX8664.cpp

@@ -88,12 +88,12 @@ const char *MachineTraits<TargetX8664>::TargetName = "X8664";
 
 template <>
 std::array<llvm::SmallBitVector, RCX86_NUM>
-    TargetX86Base<TargetX8664>::TypeToRegisterSet = {};
+    TargetX86Base<TargetX8664>::TypeToRegisterSet = {{}};
 
 template <>
 std::array<llvm::SmallBitVector,
            TargetX86Base<TargetX8664>::Traits::RegisterSet::Reg_NUM>
-    TargetX86Base<TargetX8664>::RegisterAliases = {};
+    TargetX86Base<TargetX8664>::RegisterAliases = {{}};
 
 template <>
 llvm::SmallBitVector

src/IceTargetLoweringX86BaseImpl.h

@@ -5511,7 +5511,7 @@ namespace {
 template <typename T> bool isPositiveZero(T Val) {
   static_assert(std::is_floating_point<T>::value,
                 "Input type must be floating point");
-  return Val == 0 && !signbit(Val);
+  return Val == 0 && !std::signbit(Val);
 }
 
 } // end of anonymous namespace