Make VTs and UnicodeCharSet ctors constexpr if the compiler supports it.

There are static variables of this around that we really want to go
into a read-only segment. Sadly compilers are not smart enough to figure
that out without constexpr.

llvm-svn: 230895

llvm/include/llvm/CodeGen/MachineValueType.h

@@ -161,8 +161,8 @@ namespace llvm {
 
     SimpleValueType SimpleTy;
 
-    MVT() : SimpleTy((SimpleValueType)(INVALID_SIMPLE_VALUE_TYPE)) {}
-    MVT(SimpleValueType SVT) : SimpleTy(SVT) { }
+    LLVM_CONSTEXPR MVT() : SimpleTy(INVALID_SIMPLE_VALUE_TYPE) {}
+    LLVM_CONSTEXPR MVT(SimpleValueType SVT) : SimpleTy(SVT) { }
 
     bool operator>(const MVT& S)  const { return SimpleTy >  S.SimpleTy; }
     bool operator<(const MVT& S)  const { return SimpleTy <  S.SimpleTy; }

llvm/include/llvm/CodeGen/ValueTypes.h

@@ -34,10 +34,9 @@ namespace llvm {
     Type *LLVMTy;
 
   public:
-    EVT() : V((MVT::SimpleValueType)(MVT::INVALID_SIMPLE_VALUE_TYPE)),
-            LLVMTy(nullptr) {}
-    EVT(MVT::SimpleValueType SVT) : V(SVT), LLVMTy(nullptr) { }
-    EVT(MVT S) : V(S), LLVMTy(nullptr) {}
+    LLVM_CONSTEXPR EVT() : V(MVT::INVALID_SIMPLE_VALUE_TYPE), LLVMTy(nullptr) {}
+    LLVM_CONSTEXPR EVT(MVT::SimpleValueType SVT) : V(SVT), LLVMTy(nullptr) {}
+    LLVM_CONSTEXPR EVT(MVT S) : V(S), LLVMTy(nullptr) {}
 
     bool operator==(EVT VT) const {
       return !(*this != VT);

llvm/include/llvm/Support/UnicodeCharRanges.h

@@ -50,9 +50,13 @@ public:
   /// the UnicodeCharSet instance, and should not change. Array is validated by
   /// the constructor, so it makes sense to create as few UnicodeCharSet
   /// instances per each array of ranges, as possible.
+#ifdef NDEBUG
+  LLVM_CONSTEXPR UnicodeCharSet(CharRanges Ranges) : Ranges(Ranges) {}
+#else
   UnicodeCharSet(CharRanges Ranges) : Ranges(Ranges) {
     assert(rangesAreValid());
   }
+#endif
 
   /// \brief Returns true if the character set contains the Unicode code point
   /// \p C.