Index: libc/src/__support/integer_operations.h
===================================================================
--- libc/src/__support/integer_operations.h
+++ libc/src/__support/integer_operations.h
@@ -14,10 +14,9 @@
 namespace __llvm_libc {
 
 template <typename T>
-static inline cpp::EnableIfType<cpp::IsIntegral<T>::Value, T> integerAbs(T n) {
-  if (n < 0)
-    return -n;
-  return n;
+static constexpr cpp::EnableIfType<cpp::IsIntegral<T>::Value, T>
+integerAbs(T n) {
+  return (n < 0) ? -n : n;
 }
 
 } // namespace __llvm_libc
Index: libc/src/assert/__assert_fail.cpp
===================================================================
--- libc/src/assert/__assert_fail.cpp
+++ libc/src/assert/__assert_fail.cpp
@@ -20,7 +20,8 @@
 // will call fprintf(stderr, ...).
 static void writeToStderr(const char *s) {
   size_t length = 0;
-  for (const char *curr = s; *curr; ++curr, ++length);
+  for (const char *curr = s; *curr; ++curr)
+    ++length;
   __llvm_libc::syscall(SYS_write, 2, s, length);
 }
 
Index: libc/src/ctype/ctype_utils.h
===================================================================
--- libc/src/ctype/ctype_utils.h
+++ libc/src/ctype/ctype_utils.h
@@ -18,17 +18,17 @@
 // of a function call by inlining them.
 // ------------------------------------------------------
 
-static inline int isalpha(unsigned ch) { return (ch | 32) - 'a' < 26; }
+static constexpr int isalpha(unsigned ch) { return (ch | 32) - 'a' < 26; }
 
-static inline int isdigit(unsigned ch) { return (ch - '0') < 10; }
+static constexpr int isdigit(unsigned ch) { return (ch - '0') < 10; }
 
-static inline int isalnum(unsigned ch) { return isalpha(ch) || isdigit(ch); }
+static constexpr int isalnum(unsigned ch) { return isalpha(ch) || isdigit(ch); }
 
-static inline int isgraph(unsigned ch) { return 0x20 < ch && ch < 0x7f; }
+static constexpr int isgraph(unsigned ch) { return 0x20 < ch && ch < 0x7f; }
 
-static inline int islower(unsigned ch) { return (ch - 'a') < 26; }
+static constexpr int islower(unsigned ch) { return (ch - 'a') < 26; }
 
-static inline int isupper(unsigned ch) { return (ch - 'A') < 26; }
+static constexpr int isupper(unsigned ch) { return (ch - 'A') < 26; }
 
 } // namespace internal
 } // namespace __llvm_libc
Index: libc/src/ctype/isalnum.cpp
===================================================================
--- libc/src/ctype/isalnum.cpp
+++ libc/src/ctype/isalnum.cpp
@@ -15,6 +15,8 @@
 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isalnum, (int c)) { return internal::isalnum(c); }
+LLVM_LIBC_FUNCTION(int, isalnum, (int c)) {
+  return internal::isalnum(static_cast<unsigned>(c));
+}
 
 } // namespace __llvm_libc
Index: libc/src/ctype/isalpha.cpp
===================================================================
--- libc/src/ctype/isalpha.cpp
+++ libc/src/ctype/isalpha.cpp
@@ -15,6 +15,8 @@
 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isalpha, (int c)) { return internal::isalpha(c); }
+LLVM_LIBC_FUNCTION(int, isalpha, (int c)) {
+  return internal::isalpha(static_cast<unsigned>(c));
+}
 
 } // namespace __llvm_libc
Index: libc/src/ctype/isascii.cpp
===================================================================
--- libc/src/ctype/isascii.cpp
+++ libc/src/ctype/isascii.cpp
@@ -12,6 +12,8 @@
 
 namespace __llvm_libc {
 
-LLVM_LIBC_FUNCTION(int, isascii, (int c)) { return (c & (~0x7f)) == 0; }
+LLVM_LIBC_FUNCTION(int, isascii, (int c)) {
+  return static_cast<unsigned>(c) <= 0x7f;
+}
 
 } // namespace __llvm_libc
Index: libc/src/ctype/isblank.cpp
===================================================================
--- libc/src/ctype/isblank.cpp
+++ libc/src/ctype/isblank.cpp
@@ -15,8 +15,7 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, isblank, (int c)) {
-  const unsigned char ch = static_cast<char>(c);
-  return ch == ' ' || ch == '\t';
+  return c == ' ' || c == '\t';
 }
 
 } // namespace __llvm_libc
Index: libc/src/ctype/iscntrl.cpp
===================================================================
--- libc/src/ctype/iscntrl.cpp
+++ libc/src/ctype/iscntrl.cpp
@@ -15,7 +15,7 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, iscntrl, (int c)) {
-  const unsigned char ch = static_cast<char>(c);
+  const unsigned ch = static_cast<unsigned>(c);
   return ch < 0x20 || ch == 0x7f;
 }
 
Index: libc/src/ctype/isdigit.cpp
===================================================================
--- libc/src/ctype/isdigit.cpp
+++ libc/src/ctype/isdigit.cpp
@@ -14,6 +14,8 @@
 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isdigit, (int c)) { return internal::isdigit(c); }
+LLVM_LIBC_FUNCTION(int, isdigit, (int c)) {
+  return internal::isdigit(static_cast<unsigned>(c));
+}
 
 } // namespace __llvm_libc
Index: libc/src/ctype/isgraph.cpp
===================================================================
--- libc/src/ctype/isgraph.cpp
+++ libc/src/ctype/isgraph.cpp
@@ -15,6 +15,8 @@
 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isgraph, (int c)) { return internal::isgraph(c); }
+LLVM_LIBC_FUNCTION(int, isgraph, (int c)) {
+  return internal::isgraph(static_cast<unsigned>(c));
+}
 
 } // namespace __llvm_libc
Index: libc/src/ctype/islower.cpp
===================================================================
--- libc/src/ctype/islower.cpp
+++ libc/src/ctype/islower.cpp
@@ -15,6 +15,8 @@
 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, islower, (int c)) { return internal::islower(c); }
+LLVM_LIBC_FUNCTION(int, islower, (int c)) {
+  return internal::islower(static_cast<unsigned>(c));
+}
 
 } // namespace __llvm_libc
Index: libc/src/ctype/isprint.cpp
===================================================================
--- libc/src/ctype/isprint.cpp
+++ libc/src/ctype/isprint.cpp
@@ -15,7 +15,7 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, isprint, (int c)) {
-  const unsigned ch = c;
+  const unsigned ch = static_cast<unsigned>(c);
   return (ch - ' ') < 95;
 }
 
Index: libc/src/ctype/ispunct.cpp
===================================================================
--- libc/src/ctype/ispunct.cpp
+++ libc/src/ctype/ispunct.cpp
@@ -16,7 +16,8 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, ispunct, (int c)) {
-  return !internal::isalnum(c) && internal::isgraph(c);
+  const unsigned ch = static_cast<unsigned>(c);
+  return !internal::isalnum(ch) && internal::isgraph(ch);
 }
 
 } // namespace __llvm_libc
Index: libc/src/ctype/isspace.cpp
===================================================================
--- libc/src/ctype/isspace.cpp
+++ libc/src/ctype/isspace.cpp
@@ -15,7 +15,7 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, isspace, (int c)) {
-  const unsigned ch = c;
+  const unsigned ch = static_cast<unsigned>(c);
   return ch == ' ' || (ch - '\t') < 5;
 }
 
Index: libc/src/ctype/isupper.cpp
===================================================================
--- libc/src/ctype/isupper.cpp
+++ libc/src/ctype/isupper.cpp
@@ -15,6 +15,8 @@
 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isupper, (int c)) { return internal::isupper(c); }
+LLVM_LIBC_FUNCTION(int, isupper, (int c)) {
+  return internal::isupper(static_cast<unsigned>(c));
+}
 
 } // namespace __llvm_libc
Index: libc/src/ctype/isxdigit.cpp
===================================================================
--- libc/src/ctype/isxdigit.cpp
+++ libc/src/ctype/isxdigit.cpp
@@ -16,7 +16,7 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, isxdigit, (int c)) {
-  const unsigned ch = c;
+  const unsigned ch = static_cast<unsigned>(c);
   return internal::isdigit(ch) || (ch | 32) - 'a' < 6;
 }
 
Index: libc/src/ctype/tolower.cpp
===================================================================
--- libc/src/ctype/tolower.cpp
+++ libc/src/ctype/tolower.cpp
@@ -16,7 +16,7 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, tolower, (int c)) {
-  if (internal::isupper(c))
+  if (internal::isupper(static_cast<unsigned>(c)))
     return c + 'a' - 'A';
   return c;
 }
Index: libc/src/ctype/toupper.cpp
===================================================================
--- libc/src/ctype/toupper.cpp
+++ libc/src/ctype/toupper.cpp
@@ -16,7 +16,7 @@
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
 LLVM_LIBC_FUNCTION(int, toupper, (int c)) {
-  if (internal::islower(c))
+  if (internal::islower(static_cast<unsigned>(c)))
     return c + 'A' - 'a';
   return c;
 }
Index: libc/utils/FPUtil/x86_64/FEnvImpl.h
===================================================================
--- libc/utils/FPUtil/x86_64/FEnvImpl.h
+++ libc/utils/FPUtil/x86_64/FEnvImpl.h
@@ -61,7 +61,7 @@
 
 // Exception flags are individual bits in the corresponding registers.
 // So, we just OR the bit values to get the full set of exceptions.
-static inline uint16_t getStatusValueForExcept(int excepts) {
+static constexpr uint16_t getStatusValueForExcept(int excepts) {
   // We will make use of the fact that exception control bits are single
   // bit flags in the control registers.
   return (excepts & FE_INVALID ? ExceptionFlags::Invalid : 0) |
@@ -74,7 +74,7 @@
          (excepts & FE_INEXACT ? ExceptionFlags::Inexact : 0);
 }
 
-static inline int exceptionStatusToMacro(uint16_t status) {
+static constexpr int exceptionStatusToMacro(uint16_t status) {
   return (status & ExceptionFlags::Invalid ? FE_INVALID : 0) |
 #ifdef __FE_DENORM
          (status & ExceptionFlags::Denormal ? __FE_DENORM : 0) |
@@ -251,7 +251,7 @@
   // ensure that the writes by the exception handler are maintained
   // when raising the next exception.
 
-  auto raiseHelper = [](uint16_t  singleExceptFlag) {
+  auto raiseHelper = [](uint16_t singleExceptFlag) {
     internal::X87StateDescriptor state;
     internal::getX87StateDescriptor(state);
     state.StatusWord |= singleExceptFlag;
Index: libc/utils/HdrGen/Command.h
===================================================================
--- libc/utils/HdrGen/Command.h
+++ libc/utils/HdrGen/Command.h
@@ -36,7 +36,7 @@
   public:
     ErrorReporter(llvm::SMLoc L, llvm::SourceMgr &SM) : Loc(L), SrcMgr(SM) {}
 
-    void printFatalError(llvm::Twine Msg) const {
+    [[noreturn]] void printFatalError(llvm::Twine Msg) const {
       SrcMgr.PrintMessage(Loc, llvm::SourceMgr::DK_Error, Msg);
       std::exit(1);
     }
Index: llvm/include/llvm/Support/Compiler.h
===================================================================
--- llvm/include/llvm/Support/Compiler.h
+++ llvm/include/llvm/Support/Compiler.h
@@ -246,8 +246,10 @@
 #define LLVM_ATTRIBUTE_NORETURN __attribute__((noreturn))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_NORETURN __declspec(noreturn)
+#elif __cplusplus
+#define LLVM_ATTRIBUTE_NORETURN [[noreturn]]
 #else
-#define LLVM_ATTRIBUTE_NORETURN
+#define LLVM_ATTRIBUTE_NORETURN _Noreturn
 #endif
 
 #if __has_attribute(returns_nonnull) || LLVM_GNUC_PREREQ(4, 9, 0)
Index: llvm/lib/TableGen/Error.cpp
===================================================================
--- llvm/lib/TableGen/Error.cpp
+++ llvm/lib/TableGen/Error.cpp
@@ -11,11 +11,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/TableGen/Error.h"
 #include "llvm/ADT/Twine.h"
-#include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/WithColor.h"
-#include "llvm/TableGen/Error.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/TableGen/Record.h"
 #include <cstdlib>
 
@@ -42,9 +42,7 @@
 
 // Functions to print notes.
 
-void PrintNote(const Twine &Msg) {
-  WithColor::note() << Msg << "\n";
-}
+void PrintNote(const Twine &Msg) { WithColor::note() << Msg << "\n"; }
 
 void PrintNote(ArrayRef<SMLoc> NoteLoc, const Twine &Msg) {
   PrintMessage(NoteLoc, SourceMgr::DK_Note, Msg);
@@ -158,7 +156,7 @@
 // If not, print a nonfatal error along with the message.
 void CheckAssert(SMLoc Loc, Init *Condition, Init *Message) {
   auto *CondValue = dyn_cast_or_null<IntInit>(
-                        Condition->convertInitializerTo(IntRecTy::get()));
+      Condition->convertInitializerTo(IntRecTy::get()));
   if (!CondValue)
     PrintError(Loc, "assert condition must of type bit, bits, or int.");
   else if (!CondValue->getValue()) {