diff --git a/lib/Analysis/AliasAnalysisSummary.cpp b/lib/Analysis/AliasAnalysisSummary.cpp
index 567405d0972..09a6b8217a0 100644
--- a/lib/Analysis/AliasAnalysisSummary.cpp
+++ b/lib/Analysis/AliasAnalysisSummary.cpp
@@ -7,25 +7,24 @@ namespace llvm {
 namespace cflaa {
 
 namespace {
-LLVM_CONSTEXPR unsigned AttrEscapedIndex = 0;
-LLVM_CONSTEXPR unsigned AttrUnknownIndex = 1;
-LLVM_CONSTEXPR unsigned AttrGlobalIndex = 2;
-LLVM_CONSTEXPR unsigned AttrCallerIndex = 3;
-LLVM_CONSTEXPR unsigned AttrFirstArgIndex = 4;
-LLVM_CONSTEXPR unsigned AttrLastArgIndex = NumAliasAttrs;
-LLVM_CONSTEXPR unsigned AttrMaxNumArgs = AttrLastArgIndex - AttrFirstArgIndex;
+const unsigned AttrEscapedIndex = 0;
+const unsigned AttrUnknownIndex = 1;
+const unsigned AttrGlobalIndex = 2;
+const unsigned AttrCallerIndex = 3;
+const unsigned AttrFirstArgIndex = 4;
+const unsigned AttrLastArgIndex = NumAliasAttrs;
+const unsigned AttrMaxNumArgs = AttrLastArgIndex - AttrFirstArgIndex;
 
 // NOTE: These aren't AliasAttrs because bitsets don't have a constexpr
 // ctor for some versions of MSVC that we support. We could maybe refactor,
 // but...
 using AliasAttr = unsigned;
-LLVM_CONSTEXPR AliasAttr AttrNone = 0;
-LLVM_CONSTEXPR AliasAttr AttrEscaped = 1 << AttrEscapedIndex;
-LLVM_CONSTEXPR AliasAttr AttrUnknown = 1 << AttrUnknownIndex;
-LLVM_CONSTEXPR AliasAttr AttrGlobal = 1 << AttrGlobalIndex;
-LLVM_CONSTEXPR AliasAttr AttrCaller = 1 << AttrCallerIndex;
-LLVM_CONSTEXPR AliasAttr ExternalAttrMask =
-    AttrEscaped | AttrUnknown | AttrGlobal;
+const AliasAttr AttrNone = 0;
+const AliasAttr AttrEscaped = 1 << AttrEscapedIndex;
+const AliasAttr AttrUnknown = 1 << AttrUnknownIndex;
+const AliasAttr AttrGlobal = 1 << AttrGlobalIndex;
+const AliasAttr AttrCaller = 1 << AttrCallerIndex;
+const AliasAttr ExternalAttrMask = AttrEscaped | AttrUnknown | AttrGlobal;
 }
 
 AliasAttrs getAttrNone() { return AttrNone; }
diff --git a/lib/Analysis/AliasAnalysisSummary.h b/lib/Analysis/AliasAnalysisSummary.h
index 18ca3a9feef..51a85f4e706 100644
--- a/lib/Analysis/AliasAnalysisSummary.h
+++ b/lib/Analysis/AliasAnalysisSummary.h
@@ -99,7 +99,7 @@ AliasAttrs getExternallyVisibleAttrs(AliasAttrs);
 //===----------------------------------------------------------------------===//
 
 /// The maximum number of arguments we can put into a summary.
-LLVM_CONSTEXPR static unsigned MaxSupportedArgsInSummary = 50;
+static const unsigned MaxSupportedArgsInSummary = 50;
 
 /// We use InterfaceValue to describe parameters/return value, as well as
 /// potential memory locations that are pointed to by parameters/return value,
@@ -137,7 +137,7 @@ inline bool operator>=(InterfaceValue LHS, InterfaceValue RHS) {
 // We use UnknownOffset to represent pointer offsets that cannot be determined
 // at compile time. Note that MemoryLocation::UnknownSize cannot be used here
 // because we require a signed value.
-static LLVM_CONSTEXPR int64_t UnknownOffset = INT64_MAX;
+static const int64_t UnknownOffset = INT64_MAX;
 
 inline int64_t addOffset(int64_t LHS, int64_t RHS) {
   if (LHS == UnknownOffset || RHS == UnknownOffset)
diff --git a/lib/Analysis/CFLAndersAliasAnalysis.cpp b/lib/Analysis/CFLAndersAliasAnalysis.cpp
index d85121283cc..b33938889de 100644
--- a/lib/Analysis/CFLAndersAliasAnalysis.cpp
+++ b/lib/Analysis/CFLAndersAliasAnalysis.cpp
@@ -107,12 +107,10 @@ enum class MatchState : uint8_t {
 };
 
 typedef std::bitset<7> StateSet;
-// N.B. These are unsigned instead of StateSets because some MSVC versions
-// apparently lack constexpr bitset ctors.
-LLVM_CONSTEXPR unsigned ReadOnlyStateMask =
+const unsigned ReadOnlyStateMask =
     (1U << static_cast<uint8_t>(MatchState::FlowFromReadOnly)) |
     (1U << static_cast<uint8_t>(MatchState::FlowFromMemAliasReadOnly));
-LLVM_CONSTEXPR unsigned WriteOnlyStateMask =
+const unsigned WriteOnlyStateMask =
     (1U << static_cast<uint8_t>(MatchState::FlowToWriteOnly)) |
     (1U << static_cast<uint8_t>(MatchState::FlowToMemAliasWriteOnly));
 
diff --git a/lib/Analysis/MemoryBuiltins.cpp b/lib/Analysis/MemoryBuiltins.cpp
index f23477622be..d7fcb0fccb8 100644
--- a/lib/Analysis/MemoryBuiltins.cpp
+++ b/lib/Analysis/MemoryBuiltins.cpp
@@ -114,7 +114,7 @@ static Optional<AllocFnsTy> getAllocationData(const Value *V, AllocType AllocTy,
   // MallocLike is chosen here because allocsize makes no guarantees about the
   // nullness of the result of the function, nor does it deal with strings, nor
   // does it require that the memory returned is zeroed out.
-  LLVM_CONSTEXPR auto AllocSizeAllocTy = MallocLike;
+  const AllocType AllocSizeAllocTy = MallocLike;
   if ((AllocTy & AllocSizeAllocTy) == AllocSizeAllocTy &&
       Callee->hasFnAttribute(Attribute::AllocSize)) {
     Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize);
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index d2fb6fe8e38..307782245a6 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -196,7 +196,7 @@ const DIType *DbgVariable::getType() const {
   return Ty;
 }
 
-static LLVM_CONSTEXPR DwarfAccelTable::Atom TypeAtoms[] = {
+static const DwarfAccelTable::Atom TypeAtoms[] = {
     DwarfAccelTable::Atom(dwarf::DW_ATOM_die_offset, dwarf::DW_FORM_data4),
     DwarfAccelTable::Atom(dwarf::DW_ATOM_die_tag, dwarf::DW_FORM_data2),
     DwarfAccelTable::Atom(dwarf::DW_ATOM_type_flags, dwarf::DW_FORM_data1)};
diff --git a/lib/IR/Attributes.cpp b/lib/IR/Attributes.cpp
index 93b3d2885be..95ddc3628a0 100644
--- a/lib/IR/Attributes.cpp
+++ b/lib/IR/Attributes.cpp
@@ -38,7 +38,7 @@ using namespace llvm;
 //
 // In order to do this, we need to reserve one value of the second (optional)
 // allocsize argument to signify "not present."
-LLVM_CONSTEXPR static unsigned AllocSizeNumElemsNotPresent = -1;
+static const unsigned AllocSizeNumElemsNotPresent = -1;
 
 static uint64_t packAllocSizeArgs(unsigned ElemSizeArg,
                                   const Optional<unsigned> &NumElemsArg) {
diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index 31ffffcf603..318ce10ceaf 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -1495,7 +1495,7 @@ static void KnuthDiv(unsigned *u, unsigned *v, unsigned *q, unsigned* r,
   assert(n>1 && "n must be > 1");
 
   // b denotes the base of the number system. In our case b is 2^32.
-  LLVM_CONSTEXPR uint64_t b = uint64_t(1) << 32;
+  const uint64_t b = uint64_t(1) << 32;
 
   DEBUG(dbgs() << "KnuthDiv: m=" << m << " n=" << n << '\n');
   DEBUG(dbgs() << "KnuthDiv: original:");
diff --git a/lib/Target/AArch64/AArch64InstrInfo.cpp b/lib/Target/AArch64/AArch64InstrInfo.cpp
index e3afa8924e1..3b1006fc35b 100644
--- a/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -29,7 +29,7 @@ using namespace llvm;
 #define GET_INSTRINFO_CTOR_DTOR
 #include "AArch64GenInstrInfo.inc"
 
-static LLVM_CONSTEXPR MachineMemOperand::Flags MOSuppressPair =
+static const MachineMemOperand::Flags MOSuppressPair =
     MachineMemOperand::MOTargetFlag1;
 
 static cl::opt<unsigned>