[libc][NFC] Add noreturn and constexpr qualifiers where appropriate

[gAlfonso-bit]

Summary

These functions make it clear to the compiler and user what the intended
behavior is so llvm can make them go as fast as possible.

[abrachet]

noexcept is superfluous because all LLVM is compiled with -fno-exceptions

[gAlfonso-bit]

Well that helps me out a LOT.

[lebedev.ri]

There's LLVM_ENABLE_EH cmake switch, not sure how it affects llvmlibc.

[sivachandra]

I have marked those files in which the changes are OK. Please update and I can submit this patch for you.

libc/src/__support/integer_operations.h

14

Changes in this file OK.

libc/src/ctype/ctype_utils.h

18

Changes in this file OK.

libc/utils/HdrGen/Command.h

36 ↗

(On Diff #362076)

Changes in this file OK.

llvm/include/llvm/Support/Compiler.h

27 ↗

(On Diff #362076)

You will need to move the changes in this file out to a different patch and get it reviewed by a suitable reviewer. Also, as I have suggested previously, do not mixup style cleanups with the actual intention of the patches.

[gAlfonso-bit]

Fixed according to feedback

[gAlfonso-bit]

Moved ctype function changes to its own diff. This diff now has every requested change!

[gAlfonso-bit]

@sivachandra All done!

[gAlfonso-bit]

@sivachandra Everything is ready for landing!

[gAlfonso-bit]

@ldionne May I ask if this is acceptable?

[gAlfonso-bit]

Rebased to LLVM 13's Release Branch

[sivachandra]

The frequent updates and repeated pinging of reviewers is almost like spamming us.
Please see https://llvm.org/docs/Contributing.html#how-to-submit-a-patch where it says that a good practice is to ping after a week of silence.

Again, don't get me wrong - I totally appreciate you doing this but we all have our own jobs and work which makes patches like this drop down in priority. That said, I have accepted this patch and will submit it for you some time day (US west coast time).

[gAlfonso-bit]

In D106807#2910599, @sivachandra wrote:

The frequent updates and repeated pinging of reviewers is almost like spamming us.
Please see https://llvm.org/docs/Contributing.html#how-to-submit-a-patch where it says that a good practice is to ping after a week of silence.

Again, don't get me wrong - I totally appreciate you doing this but we all have our own jobs and work which makes patches like this drop down in priority. That said, I have accepted this patch and will submit it for you some time day (US west coast time).

Ok, I read it. I apologize and should have read it earlier. I am sorry.

I was in a rush since I was hoping to get my changes in the release branch.

I definitely should have considered the people I was pinging first though. I will follow these guidelines from now on.

libc/src/__support/integer_operations.h

 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

libc/src/ctype/ctype_utils.h

 // 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

libc/src/ctype/isalnum.h

 
 namespace __llvm_libc {
 
-int isalnum(int c);
+constexpr int isalnum(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isalnum.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isalnum, (int c)) { return internal::isalnum(c); }
+constexpr LLVM_LIBC_FUNCTION(int, isalnum, (int c)) {
+  return internal::isalnum(c);
+}
 
 } // namespace __llvm_libc

libc/src/ctype/isalpha.h

 
 namespace __llvm_libc {
 
-int isalpha(int c);
+constexpr int isalpha(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isalpha.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isalpha, (int c)) { return internal::isalpha(c); }
+constexpr LLVM_LIBC_FUNCTION(int, isalpha, (int c)) {
+  return internal::isalpha(c);
+}
 
 } // namespace __llvm_libc

libc/src/ctype/isascii.h

 
 namespace __llvm_libc {
 
-int isascii(int c);
+constexpr int isascii(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isascii.cpp

 
 namespace __llvm_libc {
 
-LLVM_LIBC_FUNCTION(int, isascii, (int c)) { return (c & (~0x7f)) == 0; }
+constexpr LLVM_LIBC_FUNCTION(int, isascii, (int c)) {
+  return (c & (~0x7f)) == 0;
+}
 
 } // namespace __llvm_libc

libc/src/ctype/isblank.h

 
 namespace __llvm_libc {
 
-int isblank(int c);
+constexpr int isblank(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isblank.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isblank, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, isblank, (int c)) {
   const unsigned char ch = static_cast<char>(c);
   return ch == ' ' || ch == '\t';
 }

libc/src/ctype/iscntrl.h

 
 namespace __llvm_libc {
 
-int iscntrl(int c);
+constexpr int iscntrl(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/iscntrl.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, iscntrl, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, iscntrl, (int c)) {
   const unsigned char ch = static_cast<char>(c);
   return ch < 0x20 || ch == 0x7f;
 }

libc/src/ctype/isdigit.h

 
 namespace __llvm_libc {
 
-int isdigit(int c);
+constexpr int isdigit(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isdigit.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isdigit, (int c)) { return internal::isdigit(c); }
+constexpr LLVM_LIBC_FUNCTION(int, isdigit, (int c)) {
+  return internal::isdigit(c);
+}
 
 } // namespace __llvm_libc

libc/src/ctype/isgraph.h

 
 namespace __llvm_libc {
 
-int isgraph(int c);
+constexpr int isgraph(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isgraph.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isgraph, (int c)) { return internal::isgraph(c); }
+constexpr LLVM_LIBC_FUNCTION(int, isgraph, (int c)) {
+  return internal::isgraph(c);
+}
 
 } // namespace __llvm_libc

libc/src/ctype/islower.h

 
 namespace __llvm_libc {
 
-int islower(int c);
+constexpr int islower(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/islower.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, islower, (int c)) { return internal::islower(c); }
+constexpr LLVM_LIBC_FUNCTION(int, islower, (int c)) { return internal::islower(c); }
 
 } // namespace __llvm_libc

libc/src/ctype/isprint.h

 
 namespace __llvm_libc {
 
-int isprint(int c);
+constexpr int isprint(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isprint.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isprint, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, isprint, (int c)) {
   const unsigned ch = c;
   return (ch - ' ') < 95;
 }

libc/src/ctype/ispunct.h

 
 namespace __llvm_libc {
 
-int ispunct(int c);
+constexpr int ispunct(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/ispunct.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, ispunct, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, ispunct, (int c)) {
   return !internal::isalnum(c) && internal::isgraph(c);
 }
 

libc/src/ctype/isspace.h

 
 namespace __llvm_libc {
 
-int isspace(int c);
+constexpr int isspace(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isspace.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isspace, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, isspace, (int c)) {
   const unsigned ch = c;
   return ch == ' ' || (ch - '\t') < 5;
 }

libc/src/ctype/isupper.h

 
 namespace __llvm_libc {
 
-int isupper(int c);
+constexpr int isupper(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isupper.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isupper, (int c)) { return internal::isupper(c); }
+constexpr LLVM_LIBC_FUNCTION(int, isupper, (int c)) { return internal::isupper(c); }
 
 } // namespace __llvm_libc

libc/src/ctype/isxdigit.h

 
 namespace __llvm_libc {
 
-int isxdigit(int c);
+constexpr int isxdigit(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/isxdigit.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, isxdigit, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, isxdigit, (int c)) {
   const unsigned ch = c;
   return internal::isdigit(ch) || (ch | 32) - 'a' < 6;
 }

libc/src/ctype/toascii.h

 
 namespace __llvm_libc {
 
-int toascii(int c);
+constexpr int toascii(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/toascii.cpp

 
 namespace __llvm_libc {
 
-LLVM_LIBC_FUNCTION(int, toascii, (int c)) { return (c & 0x7f); }
+constexpr LLVM_LIBC_FUNCTION(int, toascii, (int c)) { return (c & 0x7f); }
 
 } // namespace __llvm_libc

libc/src/ctype/tolower.h

 
 namespace __llvm_libc {
 
-int tolower(int c);
+constexpr int tolower(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/tolower.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, tolower, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, tolower, (int c)) {
   if (internal::isupper(c))
-    return c + 'a' - 'A';
+    c += 'a' - 'A';
   return c;
 }
 

libc/src/ctype/toupper.h

 
 namespace __llvm_libc {
 
-int toupper(int c);
+constexpr int toupper(int c);
 
 } // namespace __llvm_libc
 

libc/src/ctype/toupper.cpp

 
 // TODO: Currently restricted to default locale.
 // These should be extended using locale information.
-LLVM_LIBC_FUNCTION(int, toupper, (int c)) {
+constexpr LLVM_LIBC_FUNCTION(int, toupper, (int c)) {
   if (internal::islower(c))
-    return c + 'A' - 'a';
+    c -= 'a' - 'A';
   return c;
 }