Compiler.h: remove old GCC checks, update docs

[jfb]

Summary

We can avoid checking for older GCC versions now that the minimum is 5.1. While I'm there, update doxygen comments for most macros.

[xbolva00]

llvm/include/llvm/Support/Compiler.h

356

Outdated?

https://github.com/llvm-mirror/clang/blob/master/test/Sema/builtin-assume-aligned.c

[jfb]

llvm/include/llvm/Support/Compiler.h

356

The comment is, but it's still true: it was added in llvm.org/r217349 from September 7th 2014 and the minimum clang supported right now is 3.5, released on September 3rd 2014. I'll update the comment, because the check _has_builtin(__builtin_assume_aligned) is sufficient.

llvm/include/llvm/Support/Compiler.h

 /// This can be used to provide lvalue/rvalue overrides of member functions.
 /// The rvalue override should be guarded by LLVM_HAS_RVALUE_REFERENCE_THIS
 #if LLVM_HAS_RVALUE_REFERENCE_THIS
 #define LLVM_LVALUE_FUNCTION &
 #else
 #define LLVM_LVALUE_FUNCTION
 #endif
 
-/// LLVM_LIBRARY_VISIBILITY - If a class marked with this attribute is linked
-/// into a shared library, then the class should be private to the library and
-/// not accessible from outside it.  Can also be used to mark variables and
-/// functions, making them private to any shared library they are linked into.
-/// On PE/COFF targets, library visibility is the default, so this isn't needed.
-#if (__has_attribute(visibility) || LLVM_GNUC_PREREQ(4, 0, 0)) &&              \
+/// \macro LLVM_LIBRARY_VISIBILITY
+/// If a class marked with this attribute is linked into a shared library, then
+/// the class should be private to the library and not accessible from outside
+/// it. Can also be used to mark variables and functions, making them private to
+/// any shared library they are linked into. On PE/COFF targets, library
+/// visibility is the default, so this isn't needed.
+#if (__has_attribute(visibility) || defined(__GNUC__)) && \
     !defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32)
 #define LLVM_LIBRARY_VISIBILITY __attribute__ ((visibility("hidden")))
 #else
 #define LLVM_LIBRARY_VISIBILITY
 #endif
 
+/// \macro LLVM_PREFETCH
 #if defined(__GNUC__)
 #define LLVM_PREFETCH(addr, rw, locality) __builtin_prefetch(addr, rw, locality)
 #else
 #define LLVM_PREFETCH(addr, rw, locality)
 #endif
 
-#if __has_attribute(used) || LLVM_GNUC_PREREQ(3, 1, 0)
+/// \macro LLVM_ATTRIBUTE_USED
+#if __has_attribute(used) || defined(__GNUC__)
 #define LLVM_ATTRIBUTE_USED __attribute__((__used__))
 #else
 #define LLVM_ATTRIBUTE_USED
 #endif
 
-/// LLVM_NODISCARD - Warn if a type or return value is discarded.
+/// \macro LLVM_NODISCARD
+/// Warn if a type or return value is discarded.
 #if __cplusplus > 201402L && __has_cpp_attribute(nodiscard)
 #define LLVM_NODISCARD [[nodiscard]]
 #elif !__cplusplus
 // Workaround for llvm.org/PR23435, since clang 3.6 and below emit a spurious
 // error when __has_cpp_attribute is given a scoped attribute in C mode.
 #define LLVM_NODISCARD
 #elif __has_cpp_attribute(clang::warn_unused_result)
 #define LLVM_NODISCARD [[clang::warn_unused_result]]
 #else
 #define LLVM_NODISCARD
 #endif
 
-// Indicate that a non-static, non-const C++ member function reinitializes
-// the entire object to a known state, independent of the previous state of
-// the object.
-//
-// The clang-tidy check bugprone-use-after-move recognizes this attribute as a
-// marker that a moved-from object has left the indeterminate state and can be
-// reused.
+/// \macro LLVM_ATTRIBUTE_REINITIALIZES
+/// Indicate that a non-static, non-const C++ member function reinitializes the
+/// entire object to a known state, independent of the previous state of the
+/// object.
+///
+/// The clang-tidy check bugprone-use-after-move recognizes this attribute as a
+/// marker that a moved-from object has left the indeterminate state and can be
+/// reused.
 #if __has_cpp_attribute(clang::reinitializes)
 #define LLVM_ATTRIBUTE_REINITIALIZES [[clang::reinitializes]]
 #else
 #define LLVM_ATTRIBUTE_REINITIALIZES
 #endif
 
-// Some compilers warn about unused functions. When a function is sometimes
-// used or not depending on build settings (e.g. a function only called from
-// within "assert"), this attribute can be used to suppress such warnings.
-//
-// However, it shouldn't be used for unused *variables*, as those have a much
-// more portable solution:
-//   (void)unused_var_name;
-// Prefer cast-to-void wherever it is sufficient.
-#if __has_attribute(unused) || LLVM_GNUC_PREREQ(3, 1, 0)
+/// \macro LLVM_ATTRIBUTE_UNUSED
+/// Some compilers warn about unused functions. When a function is sometimes
+/// used or not depending on build settings (e.g. a function only called from
+/// within "assert"), this attribute can be used to suppress such warnings.
+///
+/// However, it shouldn't be used for unused *variables*, as those have a much
+/// more portable solution:
+///   (void)unused_var_name;
+/// Prefer cast-to-void wherever it is sufficient.
+#if __has_attribute(unused) || defined(__GNUC__)
 #define LLVM_ATTRIBUTE_UNUSED __attribute__((__unused__))
 #else
 #define LLVM_ATTRIBUTE_UNUSED
 #endif
 
+/// \macro LLVM_ATTRIBUTE_WEAK
 // FIXME: Provide this for PE/COFF targets.
-#if (__has_attribute(weak) || LLVM_GNUC_PREREQ(4, 0, 0)) &&                    \
+#if (__has_attribute(weak) || defined(__GNUC__)) &&                     \
     (!defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32))
 #define LLVM_ATTRIBUTE_WEAK __attribute__((__weak__))
 #else
 #define LLVM_ATTRIBUTE_WEAK
 #endif
 
-// Prior to clang 3.2, clang did not accept any spelling of
-// __has_attribute(const), so assume it is supported.
+/// \macro LLVM_READNONE
 #if defined(__clang__) || defined(__GNUC__)
 // aka 'CONST' but following LLVM Conventions.
 #define LLVM_READNONE __attribute__((__const__))
 #else
 #define LLVM_READNONE
 #endif
 
+/// \macro LLVM_READONLY
 #if __has_attribute(pure) || defined(__GNUC__)
 // aka 'PURE' but following LLVM Conventions.
 #define LLVM_READONLY __attribute__((__pure__))
 #else
 #define LLVM_READONLY
 #endif
 
-#if __has_builtin(__builtin_expect) || LLVM_GNUC_PREREQ(4, 0, 0)
+/// \macro LLVM_LIKELY
+/// \macro LLVM_UNLIKELY
+#if __has_builtin(__builtin_expect) || defined(__GNUC__)
 #define LLVM_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
 #define LLVM_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)
 #else
 #define LLVM_LIKELY(EXPR) (EXPR)
 #define LLVM_UNLIKELY(EXPR) (EXPR)
 #endif
 
-/// LLVM_ATTRIBUTE_NOINLINE - On compilers where we have a directive to do so,
-/// mark a method "not for inlining".
-#if __has_attribute(noinline) || LLVM_GNUC_PREREQ(3, 4, 0)
+/// \macro LLVM_ATTRIBUTE_NOINLINE
+/// On compilers where we have a directive to do so, mark a method "not for
+/// inlining".
+#if __has_attribute(noinline) || defined(__GNUC__)
 #define LLVM_ATTRIBUTE_NOINLINE __attribute__((noinline))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_NOINLINE __declspec(noinline)
 #else
 #define LLVM_ATTRIBUTE_NOINLINE
 #endif
 
-/// LLVM_ATTRIBUTE_ALWAYS_INLINE - On compilers where we have a directive to do
-/// so, mark a method "always inline" because it is performance sensitive. GCC
-/// 3.4 supported this but is buggy in various cases and produces unimplemented
-/// errors, just use it in GCC 4.0 and later.
-#if __has_attribute(always_inline) || LLVM_GNUC_PREREQ(4, 0, 0)
+/// \macro LLVM_ATTRIBUTE_ALWAYS_INLINE
+/// On compilers where we have a directive to do so, mark a method "always
+/// inline" because it is performance sensitive.
+#if __has_attribute(always_inline) || defined(__GNUC__)
 #define LLVM_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_ALWAYS_INLINE __forceinline
 #else
 #define LLVM_ATTRIBUTE_ALWAYS_INLINE
 #endif
 
 #ifdef __GNUC__
 #define LLVM_ATTRIBUTE_NORETURN __attribute__((noreturn))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_NORETURN __declspec(noreturn)
 #else
 #define LLVM_ATTRIBUTE_NORETURN
 #endif
 
-#if __has_attribute(returns_nonnull) || LLVM_GNUC_PREREQ(4, 9, 0)
+/// \macro LLVM_ATTRIBUTE_RETURNS_NONNULL
+#if __has_attribute(returns_nonnull) || defined(__GNUC__)
 #define LLVM_ATTRIBUTE_RETURNS_NONNULL __attribute__((returns_nonnull))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_RETURNS_NONNULL _Ret_notnull_
 #else
 #define LLVM_ATTRIBUTE_RETURNS_NONNULL
 #endif
 
-/// \macro LLVM_ATTRIBUTE_RETURNS_NOALIAS Used to mark a function as returning a
-/// pointer that does not alias any other valid pointer.
+/// \macro LLVM_ATTRIBUTE_RETURNS_NOALIAS
+/// Used to mark a function as returning a pointer that does not alias any other
+/// valid pointer.
 #ifdef __GNUC__
 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS __attribute__((__malloc__))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS __declspec(restrict)
 #else
 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS
 #endif
 
-/// LLVM_FALLTHROUGH - Mark fallthrough cases in switch statements.
+/// \macro LLVM_FALLTHROUGH
+/// Mark fallthrough cases in switch statements.
 #if __cplusplus > 201402L && __has_cpp_attribute(fallthrough)
 #define LLVM_FALLTHROUGH [[fallthrough]]
 #elif __has_cpp_attribute(gnu::fallthrough)
 #define LLVM_FALLTHROUGH [[gnu::fallthrough]]
 #elif !__cplusplus
 // Workaround for llvm.org/PR23435, since clang 3.6 and below emit a spurious
 // error when __has_cpp_attribute is given a scoped attribute in C mode.
 #define LLVM_FALLTHROUGH
 #elif __has_cpp_attribute(clang::fallthrough)
 #define LLVM_FALLTHROUGH [[clang::fallthrough]]
 #else
 #define LLVM_FALLTHROUGH
 #endif
 
-/// LLVM_REQUIRE_CONSTANT_INITIALIZATION - Apply this to globals to ensure that
-/// they are constant initialized.
+/// \macro LLVM_REQUIRE_CONSTANT_INITIALIZATION
+/// Apply this to globals to ensure that they are constant initialized.
 #if __has_cpp_attribute(clang::require_constant_initialization)
 #define LLVM_REQUIRE_CONSTANT_INITIALIZATION                                   \
   [[clang::require_constant_initialization]]
 #else
 #define LLVM_REQUIRE_CONSTANT_INITIALIZATION
 #endif
 
-/// LLVM_EXTENSION - Support compilers where we have a keyword to suppress
-/// pedantic diagnostics.
+/// \macro LLVM_EXTENSION
+/// Support compilers where we have a keyword to suppress pedantic diagnostics.
 #ifdef __GNUC__
 #define LLVM_EXTENSION __extension__
 #else
 #define LLVM_EXTENSION
 #endif
 
-// LLVM_ATTRIBUTE_DEPRECATED(decl, "message")
+/// \macro LLVM_ATTRIBUTE_DEPRECATED
 #if __has_feature(attribute_deprecated_with_message)
 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
   decl __attribute__((deprecated(message)))
 #elif defined(__GNUC__)
 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
   decl __attribute__((deprecated))
 #elif defined(_MSC_VER)
 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
   __declspec(deprecated(message)) decl
 #else
 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
   decl
 #endif
 
-/// LLVM_BUILTIN_UNREACHABLE - On compilers which support it, expands
-/// to an expression which states that it is undefined behavior for the
-/// compiler to reach this point.  Otherwise is not defined.
-#if __has_builtin(__builtin_unreachable) || LLVM_GNUC_PREREQ(4, 5, 0)
+/// \macro LLVM_BUILTIN_UNREACHABLE
+/// On compilers which support it, expands to an expression which states that it
+/// is undefined behavior for the compiler to reach this point. Otherwise is not
+/// defined.
+#if __has_builtin(__builtin_unreachable) || defined(__GNUC__)
 # define LLVM_BUILTIN_UNREACHABLE __builtin_unreachable()
 #elif defined(_MSC_VER)
 # define LLVM_BUILTIN_UNREACHABLE __assume(false)
 #endif
 
-/// LLVM_BUILTIN_TRAP - On compilers which support it, expands to an expression
-/// which causes the program to exit abnormally.
-#if __has_builtin(__builtin_trap) || LLVM_GNUC_PREREQ(4, 3, 0)
+/// \macro LLVM_BUILTIN_TRAP
+/// On compilers which support it, expands to an expression which causes the
+/// program to exit abnormally.
+#if __has_builtin(__builtin_trap) || defined(__GNUC__)
 # define LLVM_BUILTIN_TRAP __builtin_trap()
 #elif defined(_MSC_VER)
 // The __debugbreak intrinsic is supported by MSVC, does not require forward
 // declarations involving platform-specific typedefs (unlike RaiseException),
 // results in a call to vectored exception handlers, and encodes to a short
 // instruction that still causes the trapping behavior we want.
 # define LLVM_BUILTIN_TRAP __debugbreak()
 #else
 # define LLVM_BUILTIN_TRAP *(volatile int*)0x11 = 0
 #endif
 
-/// LLVM_BUILTIN_DEBUGTRAP - On compilers which support it, expands to
-/// an expression which causes the program to break while running
-/// under a debugger.
+/// \macro LLVM_BUILTIN_DEBUGTRAP
+/// On compilers which support it, expands to an expression which causes the
+/// program to break while running under a debugger.
 #if __has_builtin(__builtin_debugtrap)
 # define LLVM_BUILTIN_DEBUGTRAP __builtin_debugtrap()
 #elif defined(_MSC_VER)
 // The __debugbreak intrinsic is supported by MSVC and breaks while
 // running under the debugger, and also supports invoking a debugger
 // when the OS is configured appropriately.
 # define LLVM_BUILTIN_DEBUGTRAP __debugbreak()
 #else
 // Just continue execution when built with compilers that have no
 // support. This is a debugging aid and not intended to force the
 // program to abort if encountered.
 # define LLVM_BUILTIN_DEBUGTRAP
 #endif
 
 /// \macro LLVM_ASSUME_ALIGNED
 /// Returns a pointer with an assumed alignment.
-#if __has_builtin(__builtin_assume_aligned) || LLVM_GNUC_PREREQ(4, 7, 0)
+#if __has_builtin(__builtin_assume_aligned) || defined(__GNUC__)
 # define LLVM_ASSUME_ALIGNED(p, a) __builtin_assume_aligned(p, a)
 #elif defined(LLVM_BUILTIN_UNREACHABLE)
 // As of today, clang does not support __builtin_assume_aligned.
 # define LLVM_ASSUME_ALIGNED(p, a) \
            (((uintptr_t(p) % (a)) == 0) ? (p) : (LLVM_BUILTIN_UNREACHABLE, (p)))
 #else
 # define LLVM_ASSUME_ALIGNED(p, a) (p)
 #endif
 
 /// \macro LLVM_PACKED
 /// Used to specify a packed structure.

 /// \macro LLVM_NO_SANITIZE
 /// Disable a particular sanitizer for a function.
 #if __has_attribute(no_sanitize)
 #define LLVM_NO_SANITIZE(KIND) __attribute__((no_sanitize(KIND)))
 #else
 #define LLVM_NO_SANITIZE(KIND)
 #endif
 
+/// \macro LLVM_DUMP_METHOD
 /// Mark debug helper function definitions like dump() that should not be
 /// stripped from debug builds.
 /// Note that you should also surround dump() functions with
 /// `#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)` so they do always
 /// get stripped in release builds.
 // FIXME: Move this to a private config.h as it's not usable in public headers.
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 #define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED