Revert "[NFC] Remove obsolete LLVM_GNUC_PREREQ"

The bots are sad, looks like GCC doesn't always have __has_builtin. I'll need to
modify the logic a bit.

llvm-svn: 367510

include/llvm/Support/Compiler.h

@@ -75,7 +75,6 @@
 #define LLVM_MSC_PREREQ(version) 0
 #endif
 
-/// \macro LLVM_HAS_RVALUE_REFERENCE_THIS
 /// Does the compiler support ref-qualifiers for *this?
 ///
 /// Sadly, this is separate from just rvalue reference support because GCC
@@ -86,7 +85,6 @@
 #define LLVM_HAS_RVALUE_REFERENCE_THIS 0
 #endif
 
-/// \macro LLVM_LVALUE_FUNCTION
 /// Expands to '&' if ref-qualifiers for *this are supported.
 ///
 /// This can be used to provide lvalue/rvalue overrides of member functions.
@@ -97,35 +95,31 @@
 #define LLVM_LVALUE_FUNCTION
 #endif
 
-/// \macro LLVM_LIBRARY_VISIBILITY
+/// LLVM_LIBRARY_VISIBILITY - If a class marked with this attribute is linked
-/// If a class marked with this attribute is linked into a shared library, then
+/// into a shared library, then the class should be private to the library and
-/// the class should be private to the library and not accessible from outside
+/// not accessible from outside it.  Can also be used to mark variables and
-/// it. Can also be used to mark variables and functions, making them private to
+/// functions, making them private to any shared library they are linked into.
-/// any shared library they are linked into. On PE/COFF targets, library
+/// On PE/COFF targets, library visibility is the default, so this isn't needed.
-/// visibility is the default, so this isn't needed.
+#if (__has_attribute(visibility) || LLVM_GNUC_PREREQ(4, 0, 0)) &&              \
-#if __has_attribute(visibility) &&                                      \
     !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
 
-/// \macro LLVM_ATTRIBUTE_USED
+#if __has_attribute(used) || LLVM_GNUC_PREREQ(3, 1, 0)
-#if __has_attribute(used)
 #define LLVM_ATTRIBUTE_USED __attribute__((__used__))
 #else
 #define LLVM_ATTRIBUTE_USED
 #endif
 
-/// \macro LLVM_NODISCARD
+/// LLVM_NODISCARD - Warn if a type or return value is discarded.
-/// Warn if a type or return value is discarded.
 #if __cplusplus > 201402L && __has_cpp_attribute(nodiscard)
 #define LLVM_NODISCARD [[nodiscard]]
 #elif !__cplusplus
@@ -138,47 +132,43 @@
 #define LLVM_NODISCARD
 #endif
 
-/// \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
-/// Indicate that a non-static, non-const C++ member function reinitializes the
+// the object.
-/// 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
-/// The clang-tidy check bugprone-use-after-move recognizes this attribute as a
+// reused.
-/// 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
 
-/// \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
-/// Some compilers warn about unused functions. When a function is sometimes
+// within "assert"), this attribute can be used to suppress such warnings.
-/// 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:
-/// However, it shouldn't be used for unused *variables*, as those have a much
+//   (void)unused_var_name;
-/// more portable solution:
+// Prefer cast-to-void wherever it is sufficient.
-///   (void)unused_var_name;
+#if __has_attribute(unused) || LLVM_GNUC_PREREQ(3, 1, 0)
-/// Prefer cast-to-void wherever it is sufficient.
-#if __has_attribute(unused)
 #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) &&                                            \
+#if (__has_attribute(weak) || LLVM_GNUC_PREREQ(4, 0, 0)) &&                    \
     (!defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32))
 #define LLVM_ATTRIBUTE_WEAK __attribute__((__weak__))
 #else
 #define LLVM_ATTRIBUTE_WEAK
 #endif
 
-/// \macro LLVM_READNONE
+// Prior to clang 3.2, clang did not accept any spelling of
+// __has_attribute(const), so assume it is supported.
 #if defined(__clang__) || defined(__GNUC__)
 // aka 'CONST' but following LLVM Conventions.
 #define LLVM_READNONE __attribute__((__const__))
@@ -186,7 +176,6 @@
 #define LLVM_READNONE
 #endif
 
-/// \macro LLVM_READONLY
 #if __has_attribute(pure) || defined(__GNUC__)
 // aka 'PURE' but following LLVM Conventions.
 #define LLVM_READONLY __attribute__((__pure__))
@@ -194,9 +183,7 @@
 #define LLVM_READONLY
 #endif
 
-/// \macro LLVM_LIKELY
+#if __has_builtin(__builtin_expect) || LLVM_GNUC_PREREQ(4, 0, 0)
-/// \macro LLVM_UNLIKELY
-#if __has_builtin(__builtin_expect)
 #define LLVM_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
 #define LLVM_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)
 #else
@@ -204,10 +191,9 @@
 #define LLVM_UNLIKELY(EXPR) (EXPR)
 #endif
 
-/// \macro LLVM_ATTRIBUTE_NOINLINE
+/// LLVM_ATTRIBUTE_NOINLINE - On compilers where we have a directive to do so,
-/// On compilers where we have a directive to do so, mark a method "not for
+/// mark a method "not for inlining".
-/// inlining".
+#if __has_attribute(noinline) || LLVM_GNUC_PREREQ(3, 4, 0)
-#if __has_attribute(noinline)
 #define LLVM_ATTRIBUTE_NOINLINE __attribute__((noinline))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_NOINLINE __declspec(noinline)
@@ -215,12 +201,11 @@
 #define LLVM_ATTRIBUTE_NOINLINE
 #endif
 
-/// \macro LLVM_ATTRIBUTE_ALWAYS_INLINE
+/// LLVM_ATTRIBUTE_ALWAYS_INLINE - On compilers where we have a directive to do
-/// On compilers where we have a directive to do so, mark a method "always
+/// so, mark a method "always inline" because it is performance sensitive. GCC
-/// inline" because it is performance sensitive. GCC 3.4 supported this but is
+/// 3.4 supported this but is buggy in various cases and produces unimplemented
-/// buggy in various cases and produces unimplemented errors, just use it in GCC
+/// errors, just use it in GCC 4.0 and later.
-/// 4.0 and later.
+#if __has_attribute(always_inline) || LLVM_GNUC_PREREQ(4, 0, 0)
-#if __has_attribute(always_inline)
 #define LLVM_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_ALWAYS_INLINE __forceinline
@@ -228,7 +213,6 @@
 #define LLVM_ATTRIBUTE_ALWAYS_INLINE
 #endif
 
-/// \macro LLVM_ATTRIBUTE_NORETURN
 #ifdef __GNUC__
 #define LLVM_ATTRIBUTE_NORETURN __attribute__((noreturn))
 #elif defined(_MSC_VER)
@@ -237,7 +221,6 @@
 #define LLVM_ATTRIBUTE_NORETURN
 #endif
 
-/// \macro LLVM_ATTRIBUTE_RETURNS_NONNULL
 #if __has_attribute(returns_nonnull) || LLVM_GNUC_PREREQ(4, 9, 0)
 #define LLVM_ATTRIBUTE_RETURNS_NONNULL __attribute__((returns_nonnull))
 #elif defined(_MSC_VER)
@@ -246,9 +229,8 @@
 #define LLVM_ATTRIBUTE_RETURNS_NONNULL
 #endif
 
-/// \macro LLVM_ATTRIBUTE_RETURNS_NOALIAS
+/// \macro LLVM_ATTRIBUTE_RETURNS_NOALIAS Used to mark a function as returning a
-/// Used to mark a function as returning a pointer that does not alias any other
+/// pointer that does not alias any other valid pointer.
-/// valid pointer.
 #ifdef __GNUC__
 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS __attribute__((__malloc__))
 #elif defined(_MSC_VER)
@@ -257,8 +239,7 @@
 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS
 #endif
 
-/// \macro LLVM_FALLTHROUGH
+/// LLVM_FALLTHROUGH - Mark fallthrough cases in switch statements.
-/// Mark fallthrough cases in switch statements.
 #if __cplusplus > 201402L && __has_cpp_attribute(fallthrough)
 #define LLVM_FALLTHROUGH [[fallthrough]]
 #elif __has_cpp_attribute(gnu::fallthrough)
@@ -273,8 +254,8 @@
 #define LLVM_FALLTHROUGH
 #endif
 
-/// \macro LLVM_REQUIRE_CONSTANT_INITIALIZATION
+/// LLVM_REQUIRE_CONSTANT_INITIALIZATION - Apply this to globals to ensure that
-/// Apply this to globals to ensure that they are constant initialized.
+/// they are constant initialized.
 #if __has_cpp_attribute(clang::require_constant_initialization)
 #define LLVM_REQUIRE_CONSTANT_INITIALIZATION                                   \
   [[clang::require_constant_initialization]]
@@ -282,8 +263,8 @@
 #define LLVM_REQUIRE_CONSTANT_INITIALIZATION
 #endif
 
-/// \macro LLVM_EXTENSION
+/// LLVM_EXTENSION - Support compilers where we have a keyword to suppress
-/// Support compilers where we have a keyword to suppress pedantic diagnostics.
+/// pedantic diagnostics.
 #ifdef __GNUC__
 #define LLVM_EXTENSION __extension__
 #else
@@ -305,18 +286,18 @@
   decl
 #endif
 
-/// On compilers which support it, expands to an expression which states that it
+/// LLVM_BUILTIN_UNREACHABLE - On compilers which support it, expands
-/// is undefined behavior for the compiler to reach this point. Otherwise is not
+/// to an expression which states that it is undefined behavior for the
-/// defined.
+/// compiler to reach this point.  Otherwise is not defined.
-#if __has_builtin(__builtin_unreachable)
+#if __has_builtin(__builtin_unreachable) || LLVM_GNUC_PREREQ(4, 5, 0)
 # define LLVM_BUILTIN_UNREACHABLE __builtin_unreachable()
 #elif defined(_MSC_VER)
 # define LLVM_BUILTIN_UNREACHABLE __assume(false)
 #endif
 
-/// On compilers which support it, expands to an expression which causes the
+/// LLVM_BUILTIN_TRAP - On compilers which support it, expands to an expression
-/// program to exit abnormally.
+/// which causes the program to exit abnormally.
-#if __has_builtin(__builtin_trap)
+#if __has_builtin(__builtin_trap) || LLVM_GNUC_PREREQ(4, 3, 0)
 # define LLVM_BUILTIN_TRAP __builtin_trap()
 #elif defined(_MSC_VER)
 // The __debugbreak intrinsic is supported by MSVC, does not require forward
@@ -328,9 +309,9 @@
 # define LLVM_BUILTIN_TRAP *(volatile int*)0x11 = 0
 #endif
 
-/// \macro LLVM_BUILTIN_DEBUGTRAP
+/// LLVM_BUILTIN_DEBUGTRAP - On compilers which support it, expands to
-/// On compilers which support it, expands to an expression which causes the
+/// an expression which causes the program to break while running
-/// program to break while running under a debugger.
+/// under a debugger.
 #if __has_builtin(__builtin_debugtrap)
 # define LLVM_BUILTIN_DEBUGTRAP __builtin_debugtrap()
 #elif defined(_MSC_VER)
@@ -347,7 +328,7 @@
 
 /// \macro LLVM_ASSUME_ALIGNED
 /// Returns a pointer with an assumed alignment.
-#if __has_builtin(__builtin_assume_aligned)
+#if __has_builtin(__builtin_assume_aligned) || LLVM_GNUC_PREREQ(4, 7, 0)
 # 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.
@@ -474,7 +455,6 @@ void AnnotateIgnoreWritesEnd(const char *file, int line);
 #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

include/llvm/Support/MathExtras.h

@@ -79,7 +79,7 @@ template <typename T> struct TrailingZerosCounter<T, 4> {
     if (ZB != ZB_Undefined && Val == 0)
       return 32;
 
-#if __has_builtin(__builtin_ctz)
+#if __has_builtin(__builtin_ctz) || LLVM_GNUC_PREREQ(4, 0, 0)
     return __builtin_ctz(Val);
 #elif defined(_MSC_VER)
     unsigned long Index;
@@ -95,7 +95,7 @@ template <typename T> struct TrailingZerosCounter<T, 8> {
     if (ZB != ZB_Undefined && Val == 0)
       return 64;
 
-#if __has_builtin(__builtin_ctzll)
+#if __has_builtin(__builtin_ctzll) || LLVM_GNUC_PREREQ(4, 0, 0)
     return __builtin_ctzll(Val);
 #elif defined(_MSC_VER)
     unsigned long Index;
@@ -148,7 +148,7 @@ template <typename T> struct LeadingZerosCounter<T, 4> {
     if (ZB != ZB_Undefined && Val == 0)
       return 32;
 
-#if __has_builtin(__builtin_clz)
+#if __has_builtin(__builtin_clz) || LLVM_GNUC_PREREQ(4, 0, 0)
     return __builtin_clz(Val);
 #elif defined(_MSC_VER)
     unsigned long Index;
@@ -164,7 +164,7 @@ template <typename T> struct LeadingZerosCounter<T, 8> {
     if (ZB != ZB_Undefined && Val == 0)
       return 64;
 
-#if __has_builtin(__builtin_clzll)
+#if __has_builtin(__builtin_clzll) || LLVM_GNUC_PREREQ(4, 0, 0)
     return __builtin_clzll(Val);
 #elif defined(_MSC_VER)
     unsigned long Index;

include/llvm/Support/SwapByteOrder.h

@@ -42,7 +42,7 @@ inline uint16_t SwapByteOrder_16(uint16_t value) {
 /// SwapByteOrder_32 - This function returns a byte-swapped representation of
 /// the 32-bit argument.
 inline uint32_t SwapByteOrder_32(uint32_t value) {
-#if defined(__llvm__) || !defined(__ICC)
+#if defined(__llvm__) || (LLVM_GNUC_PREREQ(4, 3, 0) && !defined(__ICC))
   return __builtin_bswap32(value);
 #elif defined(_MSC_VER) && !defined(_DEBUG)
   return _byteswap_ulong(value);
@@ -58,7 +58,7 @@ inline uint32_t SwapByteOrder_32(uint32_t value) {
 /// SwapByteOrder_64 - This function returns a byte-swapped representation of
 /// the 64-bit argument.
 inline uint64_t SwapByteOrder_64(uint64_t value) {
-#if defined(__llvm__) || !defined(__ICC)
+#if defined(__llvm__) || (LLVM_GNUC_PREREQ(4, 3, 0) && !defined(__ICC))
   return __builtin_bswap64(value);
 #elif defined(_MSC_VER) && !defined(_DEBUG)
   return _byteswap_uint64(value);

include/llvm/Support/type_traits.h

@@ -199,7 +199,7 @@ class is_trivially_copyable<T*> : public std::true_type {
 // macro will be left undefined.
 #if __cplusplus >= 201402L || defined(_MSC_VER)
 #define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
-#elif __has_feature(is_final)
+#elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
 #define LLVM_IS_FINAL(Ty) __is_final(Ty)
 #endif