include/llvm/Support/Compiler.h

   1 //===-- llvm/Support/Compiler.h - Compiler abstraction support --*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file defines several macros, based on the current compiler.  This allows
  10 // use of compiler-specific features in a way that remains portable.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_SUPPORT_COMPILER_H
  15 #define LLVM_SUPPORT_COMPILER_H
  16
  17 #include "llvm/Config/llvm-config.h"
  18
  19 #include <new>
  20 #include <stddef.h>
  21
  22 #if defined(_MSC_VER)
  23 #include <sal.h>
  24 #endif
  25
  26 #ifndef __has_feature
  27 # define __has_feature(x) 0
  28 #endif
  29
  30 #ifndef __has_extension
  31 # define __has_extension(x) 0
  32 #endif
  33
  34 #ifndef __has_attribute
  35 # define __has_attribute(x) 0
  36 #endif
  37
  38 #ifndef __has_cpp_attribute
  39 # define __has_cpp_attribute(x) 0
  40 #endif
  41
  42 #ifndef __has_builtin
  43 # define __has_builtin(x) 0
  44 #endif
  45
  46 /// \macro LLVM_GNUC_PREREQ
  47 /// Extend the default __GNUC_PREREQ even if glibc's features.h isn't
  48 /// available.
  49 #ifndef LLVM_GNUC_PREREQ
  50 # if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__)
  51 #  define LLVM_GNUC_PREREQ(maj, min, patch) \
  52     ((__GNUC__ << 20) + (__GNUC_MINOR__ << 10) + __GNUC_PATCHLEVEL__ >= \
  53      ((maj) << 20) + ((min) << 10) + (patch))
  54 # elif defined(__GNUC__) && defined(__GNUC_MINOR__)
  55 #  define LLVM_GNUC_PREREQ(maj, min, patch) \
  56     ((__GNUC__ << 20) + (__GNUC_MINOR__ << 10) >= ((maj) << 20) + ((min) << 10))
  57 # else
  58 #  define LLVM_GNUC_PREREQ(maj, min, patch) 0
  59 # endif
  60 #endif
  61
  62 /// \macro LLVM_MSC_PREREQ
  63 /// Is the compiler MSVC of at least the specified version?
  64 /// The common \param version values to check for are:
  65 ///  * 1900: Microsoft Visual Studio 2015 / 14.0
  66 #ifdef _MSC_VER
  67 #define LLVM_MSC_PREREQ(version) (_MSC_VER >= (version))
  68
  69 // We require at least MSVC 2015.
  70 #if !LLVM_MSC_PREREQ(1900)
  71 #error LLVM requires at least MSVC 2015.
  72 #endif
  73
  74 #else
  75 #define LLVM_MSC_PREREQ(version) 0
  76 #endif
  77
  78 /// Does the compiler support ref-qualifiers for *this?
  79 ///
  80 /// Sadly, this is separate from just rvalue reference support because GCC
  81 /// and MSVC implemented this later than everything else.
  82 #if __has_feature(cxx_rvalue_references) || LLVM_GNUC_PREREQ(4, 8, 1)
  83 #define LLVM_HAS_RVALUE_REFERENCE_THIS 1
  84 #else
  85 #define LLVM_HAS_RVALUE_REFERENCE_THIS 0
  86 #endif
  87
  88 /// Expands to '&' if ref-qualifiers for *this are supported.
  89 ///
  90 /// This can be used to provide lvalue/rvalue overrides of member functions.
  91 /// The rvalue override should be guarded by LLVM_HAS_RVALUE_REFERENCE_THIS
  92 #if LLVM_HAS_RVALUE_REFERENCE_THIS
  93 #define LLVM_LVALUE_FUNCTION &
  94 #else
  95 #define LLVM_LVALUE_FUNCTION
  96 #endif
  97
  98 /// LLVM_LIBRARY_VISIBILITY - If a class marked with this attribute is linked
  99 /// into a shared library, then the class should be private to the library and
 100 /// not accessible from outside it.  Can also be used to mark variables and
 101 /// functions, making them private to any shared library they are linked into.
 102 /// On PE/COFF targets, library visibility is the default, so this isn't needed.
 103 #if (__has_attribute(visibility) || LLVM_GNUC_PREREQ(4, 0, 0)) &&              \
 104     !defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32)
 105 #define LLVM_LIBRARY_VISIBILITY __attribute__ ((visibility("hidden")))
 106 #else
 107 #define LLVM_LIBRARY_VISIBILITY
 108 #endif
 109
 110 #if defined(__GNUC__)
 111 #define LLVM_PREFETCH(addr, rw, locality) __builtin_prefetch(addr, rw, locality)
 112 #else
 113 #define LLVM_PREFETCH(addr, rw, locality)
 114 #endif
 115
 116 #if __has_attribute(used) || LLVM_GNUC_PREREQ(3, 1, 0)
 117 #define LLVM_ATTRIBUTE_USED __attribute__((__used__))
 118 #else
 119 #define LLVM_ATTRIBUTE_USED
 120 #endif
 121
 122 /// LLVM_NODISCARD - Warn if a type or return value is discarded.
 123 #if __cplusplus > 201402L && __has_cpp_attribute(nodiscard)
 124 #define LLVM_NODISCARD [[nodiscard]]
 125 #elif !__cplusplus
 126 // Workaround for llvm.org/PR23435, since clang 3.6 and below emit a spurious
 127 // error when __has_cpp_attribute is given a scoped attribute in C mode.
 128 #define LLVM_NODISCARD
 129 #elif __has_cpp_attribute(clang::warn_unused_result)
 130 #define LLVM_NODISCARD [[clang::warn_unused_result]]
 131 #else
 132 #define LLVM_NODISCARD
 133 #endif
 134
 135 // Indicate that a non-static, non-const C++ member function reinitializes
 136 // the entire object to a known state, independent of the previous state of
 137 // the object.
 138 //
 139 // The clang-tidy check bugprone-use-after-move recognizes this attribute as a
 140 // marker that a moved-from object has left the indeterminate state and can be
 141 // reused.
 142 #if __has_cpp_attribute(clang::reinitializes)
 143 #define LLVM_ATTRIBUTE_REINITIALIZES [[clang::reinitializes]]
 144 #else
 145 #define LLVM_ATTRIBUTE_REINITIALIZES
 146 #endif
 147
 148 // Some compilers warn about unused functions. When a function is sometimes
 149 // used or not depending on build settings (e.g. a function only called from
 150 // within "assert"), this attribute can be used to suppress such warnings.
 151 //
 152 // However, it shouldn't be used for unused *variables*, as those have a much
 153 // more portable solution:
 154 //   (void)unused_var_name;
 155 // Prefer cast-to-void wherever it is sufficient.
 156 #if __has_attribute(unused) || LLVM_GNUC_PREREQ(3, 1, 0)
 157 #define LLVM_ATTRIBUTE_UNUSED __attribute__((__unused__))
 158 #else
 159 #define LLVM_ATTRIBUTE_UNUSED
 160 #endif
 161
 162 // FIXME: Provide this for PE/COFF targets.
 163 #if (__has_attribute(weak) || LLVM_GNUC_PREREQ(4, 0, 0)) &&                    \
 164     (!defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32))
 165 #define LLVM_ATTRIBUTE_WEAK __attribute__((__weak__))
 166 #else
 167 #define LLVM_ATTRIBUTE_WEAK
 168 #endif
 169
 170 // Prior to clang 3.2, clang did not accept any spelling of
 171 // __has_attribute(const), so assume it is supported.
 172 #if defined(__clang__) || defined(__GNUC__)
 173 // aka 'CONST' but following LLVM Conventions.
 174 #define LLVM_READNONE __attribute__((__const__))
 175 #else
 176 #define LLVM_READNONE
 177 #endif
 178
 179 #if __has_attribute(pure) || defined(__GNUC__)
 180 // aka 'PURE' but following LLVM Conventions.
 181 #define LLVM_READONLY __attribute__((__pure__))
 182 #else
 183 #define LLVM_READONLY
 184 #endif
 185
 186 #if __has_builtin(__builtin_expect) || LLVM_GNUC_PREREQ(4, 0, 0)
 187 #define LLVM_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
 188 #define LLVM_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)
 189 #else
 190 #define LLVM_LIKELY(EXPR) (EXPR)
 191 #define LLVM_UNLIKELY(EXPR) (EXPR)
 192 #endif
 193
 194 /// LLVM_ATTRIBUTE_NOINLINE - On compilers where we have a directive to do so,
 195 /// mark a method "not for inlining".
 196 #if __has_attribute(noinline) || LLVM_GNUC_PREREQ(3, 4, 0)
 197 #define LLVM_ATTRIBUTE_NOINLINE __attribute__((noinline))
 198 #elif defined(_MSC_VER)
 199 #define LLVM_ATTRIBUTE_NOINLINE __declspec(noinline)
 200 #else
 201 #define LLVM_ATTRIBUTE_NOINLINE
 202 #endif
 203
 204 /// LLVM_ATTRIBUTE_ALWAYS_INLINE - On compilers where we have a directive to do
 205 /// so, mark a method "always inline" because it is performance sensitive. GCC
 206 /// 3.4 supported this but is buggy in various cases and produces unimplemented
 207 /// errors, just use it in GCC 4.0 and later.
 208 #if __has_attribute(always_inline) || LLVM_GNUC_PREREQ(4, 0, 0)
 209 #define LLVM_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
 210 #elif defined(_MSC_VER)
 211 #define LLVM_ATTRIBUTE_ALWAYS_INLINE __forceinline
 212 #else
 213 #define LLVM_ATTRIBUTE_ALWAYS_INLINE
 214 #endif
 215
 216 #ifdef __GNUC__
 217 #define LLVM_ATTRIBUTE_NORETURN __attribute__((noreturn))
 218 #elif defined(_MSC_VER)
 219 #define LLVM_ATTRIBUTE_NORETURN __declspec(noreturn)
 220 #else
 221 #define LLVM_ATTRIBUTE_NORETURN
 222 #endif
 223
 224 #if __has_attribute(returns_nonnull) || LLVM_GNUC_PREREQ(4, 9, 0)
 225 #define LLVM_ATTRIBUTE_RETURNS_NONNULL __attribute__((returns_nonnull))
 226 #elif defined(_MSC_VER)
 227 #define LLVM_ATTRIBUTE_RETURNS_NONNULL _Ret_notnull_
 228 #else
 229 #define LLVM_ATTRIBUTE_RETURNS_NONNULL
 230 #endif
 231
 232 /// \macro LLVM_ATTRIBUTE_RETURNS_NOALIAS Used to mark a function as returning a
 233 /// pointer that does not alias any other valid pointer.
 234 #ifdef __GNUC__
 235 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS __attribute__((__malloc__))
 236 #elif defined(_MSC_VER)
 237 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS __declspec(restrict)
 238 #else
 239 #define LLVM_ATTRIBUTE_RETURNS_NOALIAS
 240 #endif
 241
 242 /// LLVM_FALLTHROUGH - Mark fallthrough cases in switch statements.
 243 #if __cplusplus > 201402L && __has_cpp_attribute(fallthrough)
 244 #define LLVM_FALLTHROUGH [[fallthrough]]
 245 #elif __has_cpp_attribute(gnu::fallthrough)
 246 #define LLVM_FALLTHROUGH [[gnu::fallthrough]]
 247 #elif !__cplusplus
 248 // Workaround for llvm.org/PR23435, since clang 3.6 and below emit a spurious
 249 // error when __has_cpp_attribute is given a scoped attribute in C mode.
 250 #define LLVM_FALLTHROUGH
 251 #elif __has_cpp_attribute(clang::fallthrough)
 252 #define LLVM_FALLTHROUGH [[clang::fallthrough]]
 253 #else
 254 #define LLVM_FALLTHROUGH
 255 #endif
 256
 257 /// LLVM_EXTENSION - Support compilers where we have a keyword to suppress
 258 /// pedantic diagnostics.
 259 #ifdef __GNUC__
 260 #define LLVM_EXTENSION __extension__
 261 #else
 262 #define LLVM_EXTENSION
 263 #endif
 264
 265 // LLVM_ATTRIBUTE_DEPRECATED(decl, "message")
 266 #if __has_feature(attribute_deprecated_with_message)
 267 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 268   decl __attribute__((deprecated(message)))
 269 #elif defined(__GNUC__)
 270 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 271   decl __attribute__((deprecated))
 272 #elif defined(_MSC_VER)
 273 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 274   __declspec(deprecated(message)) decl
 275 #else
 276 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 277   decl
 278 #endif
 279
 280 /// LLVM_BUILTIN_UNREACHABLE - On compilers which support it, expands
 281 /// to an expression which states that it is undefined behavior for the
 282 /// compiler to reach this point.  Otherwise is not defined.
 283 #if __has_builtin(__builtin_unreachable) || LLVM_GNUC_PREREQ(4, 5, 0)
 284 # define LLVM_BUILTIN_UNREACHABLE __builtin_unreachable()
 285 #elif defined(_MSC_VER)
 286 # define LLVM_BUILTIN_UNREACHABLE __assume(false)
 287 #endif
 288
 289 /// LLVM_BUILTIN_TRAP - On compilers which support it, expands to an expression
 290 /// which causes the program to exit abnormally.
 291 #if __has_builtin(__builtin_trap) || LLVM_GNUC_PREREQ(4, 3, 0)
 292 # define LLVM_BUILTIN_TRAP __builtin_trap()
 293 #elif defined(_MSC_VER)
 294 // The __debugbreak intrinsic is supported by MSVC, does not require forward
 295 // declarations involving platform-specific typedefs (unlike RaiseException),
 296 // results in a call to vectored exception handlers, and encodes to a short
 297 // instruction that still causes the trapping behavior we want.
 298 # define LLVM_BUILTIN_TRAP __debugbreak()
 299 #else
 300 # define LLVM_BUILTIN_TRAP *(volatile int*)0x11 = 0
 301 #endif
 302
 303 /// LLVM_BUILTIN_DEBUGTRAP - On compilers which support it, expands to
 304 /// an expression which causes the program to break while running
 305 /// under a debugger.
 306 #if __has_builtin(__builtin_debugtrap)
 307 # define LLVM_BUILTIN_DEBUGTRAP __builtin_debugtrap()
 308 #elif defined(_MSC_VER)
 309 // The __debugbreak intrinsic is supported by MSVC and breaks while
 310 // running under the debugger, and also supports invoking a debugger
 311 // when the OS is configured appropriately.
 312 # define LLVM_BUILTIN_DEBUGTRAP __debugbreak()
 313 #else
 314 // Just continue execution when built with compilers that have no
 315 // support. This is a debugging aid and not intended to force the
 316 // program to abort if encountered.
 317 # define LLVM_BUILTIN_DEBUGTRAP
 318 #endif
 319
 320 /// \macro LLVM_ASSUME_ALIGNED
 321 /// Returns a pointer with an assumed alignment.
 322 #if __has_builtin(__builtin_assume_aligned) || LLVM_GNUC_PREREQ(4, 7, 0)
 323 # define LLVM_ASSUME_ALIGNED(p, a) __builtin_assume_aligned(p, a)
 324 #elif defined(LLVM_BUILTIN_UNREACHABLE)
 325 // As of today, clang does not support __builtin_assume_aligned.
 326 # define LLVM_ASSUME_ALIGNED(p, a) \
 327            (((uintptr_t(p) % (a)) == 0) ? (p) : (LLVM_BUILTIN_UNREACHABLE, (p)))
 328 #else
 329 # define LLVM_ASSUME_ALIGNED(p, a) (p)
 330 #endif
 331
 332 /// \macro LLVM_ALIGNAS
 333 /// Used to specify a minimum alignment for a structure or variable.
 334 #if __GNUC__ && !__has_feature(cxx_alignas) && !LLVM_GNUC_PREREQ(4, 8, 1)
 335 # define LLVM_ALIGNAS(x) __attribute__((aligned(x)))
 336 #else
 337 # define LLVM_ALIGNAS(x) alignas(x)
 338 #endif
 339
 340 /// \macro LLVM_PACKED
 341 /// Used to specify a packed structure.
 342 /// LLVM_PACKED(
 343 ///    struct A {
 344 ///      int i;
 345 ///      int j;
 346 ///      int k;
 347 ///      long long l;
 348 ///   });
 349 ///
 350 /// LLVM_PACKED_START
 351 /// struct B {
 352 ///   int i;
 353 ///   int j;
 354 ///   int k;
 355 ///   long long l;
 356 /// };
 357 /// LLVM_PACKED_END
 358 #ifdef _MSC_VER
 359 # define LLVM_PACKED(d) __pragma(pack(push, 1)) d __pragma(pack(pop))
 360 # define LLVM_PACKED_START __pragma(pack(push, 1))
 361 # define LLVM_PACKED_END   __pragma(pack(pop))
 362 #else
 363 # define LLVM_PACKED(d) d __attribute__((packed))
 364 # define LLVM_PACKED_START _Pragma("pack(push, 1)")
 365 # define LLVM_PACKED_END   _Pragma("pack(pop)")
 366 #endif
 367
 368 /// \macro LLVM_PTR_SIZE
 369 /// A constant integer equivalent to the value of sizeof(void*).
 370 /// Generally used in combination with LLVM_ALIGNAS or when doing computation in
 371 /// the preprocessor.
 372 #ifdef __SIZEOF_POINTER__
 373 # define LLVM_PTR_SIZE __SIZEOF_POINTER__
 374 #elif defined(_WIN64)
 375 # define LLVM_PTR_SIZE 8
 376 #elif defined(_WIN32)
 377 # define LLVM_PTR_SIZE 4
 378 #elif defined(_MSC_VER)
 379 # error "could not determine LLVM_PTR_SIZE as a constant int for MSVC"
 380 #else
 381 # define LLVM_PTR_SIZE sizeof(void *)
 382 #endif
 383
 384 /// \macro LLVM_MEMORY_SANITIZER_BUILD
 385 /// Whether LLVM itself is built with MemorySanitizer instrumentation.
 386 #if __has_feature(memory_sanitizer)
 387 # define LLVM_MEMORY_SANITIZER_BUILD 1
 388 # include <sanitizer/msan_interface.h>
 389 #else
 390 # define LLVM_MEMORY_SANITIZER_BUILD 0
 391 # define __msan_allocated_memory(p, size)
 392 # define __msan_unpoison(p, size)
 393 #endif
 394
 395 /// \macro LLVM_ADDRESS_SANITIZER_BUILD
 396 /// Whether LLVM itself is built with AddressSanitizer instrumentation.
 397 #if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
 398 # define LLVM_ADDRESS_SANITIZER_BUILD 1
 399 # include <sanitizer/asan_interface.h>
 400 #else
 401 # define LLVM_ADDRESS_SANITIZER_BUILD 0
 402 # define __asan_poison_memory_region(p, size)
 403 # define __asan_unpoison_memory_region(p, size)
 404 #endif
 405
 406 /// \macro LLVM_THREAD_SANITIZER_BUILD
 407 /// Whether LLVM itself is built with ThreadSanitizer instrumentation.
 408 #if __has_feature(thread_sanitizer) || defined(__SANITIZE_THREAD__)
 409 # define LLVM_THREAD_SANITIZER_BUILD 1
 410 #else
 411 # define LLVM_THREAD_SANITIZER_BUILD 0
 412 #endif
 413
 414 #if LLVM_THREAD_SANITIZER_BUILD
 415 // Thread Sanitizer is a tool that finds races in code.
 416 // See http://code.google.com/p/data-race-test/wiki/DynamicAnnotations .
 417 // tsan detects these exact functions by name.
 418 #ifdef __cplusplus
 419 extern "C" {
 420 #endif
 421 void AnnotateHappensAfter(const char *file, int line, const volatile void *cv);
 422 void AnnotateHappensBefore(const char *file, int line, const volatile void *cv);
 423 void AnnotateIgnoreWritesBegin(const char *file, int line);
 424 void AnnotateIgnoreWritesEnd(const char *file, int line);
 425 #ifdef __cplusplus
 426 }
 427 #endif
 428
 429 // This marker is used to define a happens-before arc. The race detector will
 430 // infer an arc from the begin to the end when they share the same pointer
 431 // argument.
 432 # define TsanHappensBefore(cv) AnnotateHappensBefore(__FILE__, __LINE__, cv)
 433
 434 // This marker defines the destination of a happens-before arc.
 435 # define TsanHappensAfter(cv) AnnotateHappensAfter(__FILE__, __LINE__, cv)
 436
 437 // Ignore any races on writes between here and the next TsanIgnoreWritesEnd.
 438 # define TsanIgnoreWritesBegin() AnnotateIgnoreWritesBegin(__FILE__, __LINE__)
 439
 440 // Resume checking for racy writes.
 441 # define TsanIgnoreWritesEnd() AnnotateIgnoreWritesEnd(__FILE__, __LINE__)
 442 #else
 443 # define TsanHappensBefore(cv)
 444 # define TsanHappensAfter(cv)
 445 # define TsanIgnoreWritesBegin()
 446 # define TsanIgnoreWritesEnd()
 447 #endif
 448
 449 /// \macro LLVM_NO_SANITIZE
 450 /// Disable a particular sanitizer for a function.
 451 #if __has_attribute(no_sanitize)
 452 #define LLVM_NO_SANITIZE(KIND) __attribute__((no_sanitize(KIND)))
 453 #else
 454 #define LLVM_NO_SANITIZE(KIND)
 455 #endif
 456
 457 /// Mark debug helper function definitions like dump() that should not be
 458 /// stripped from debug builds.
 459 /// Note that you should also surround dump() functions with
 460 /// `#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)` so they do always
 461 /// get stripped in release builds.
 462 // FIXME: Move this to a private config.h as it's not usable in public headers.
 463 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 464 #define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED
 465 #else
 466 #define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE
 467 #endif
 468
 469 /// \macro LLVM_PRETTY_FUNCTION
 470 /// Gets a user-friendly looking function signature for the current scope
 471 /// using the best available method on each platform.  The exact format of the
 472 /// resulting string is implementation specific and non-portable, so this should
 473 /// only be used, for example, for logging or diagnostics.
 474 #if defined(_MSC_VER)
 475 #define LLVM_PRETTY_FUNCTION __FUNCSIG__
 476 #elif defined(__GNUC__) || defined(__clang__)
 477 #define LLVM_PRETTY_FUNCTION __PRETTY_FUNCTION__
 478 #else
 479 #define LLVM_PRETTY_FUNCTION __func__
 480 #endif
 481
 482 /// \macro LLVM_THREAD_LOCAL
 483 /// A thread-local storage specifier which can be used with globals,
 484 /// extern globals, and static globals.
 485 ///
 486 /// This is essentially an extremely restricted analog to C++11's thread_local
 487 /// support, and uses that when available. However, it falls back on
 488 /// platform-specific or vendor-provided extensions when necessary. These
 489 /// extensions don't support many of the C++11 thread_local's features. You
 490 /// should only use this for PODs that you can statically initialize to
 491 /// some constant value. In almost all circumstances this is most appropriate
 492 /// for use with a pointer, integer, or small aggregation of pointers and
 493 /// integers.
 494 #if LLVM_ENABLE_THREADS
 495 #if __has_feature(cxx_thread_local)
 496 #define LLVM_THREAD_LOCAL thread_local
 497 #elif defined(_MSC_VER)
 498 // MSVC supports this with a __declspec.
 499 #define LLVM_THREAD_LOCAL __declspec(thread)
 500 #else
 501 // Clang, GCC, and other compatible compilers used __thread prior to C++11 and
 502 // we only need the restricted functionality that provides.
 503 #define LLVM_THREAD_LOCAL __thread
 504 #endif
 505 #else // !LLVM_ENABLE_THREADS
 506 // If threading is disabled entirely, this compiles to nothing and you get
 507 // a normal global variable.
 508 #define LLVM_THREAD_LOCAL
 509 #endif
 510
 511 /// \macro LLVM_ENABLE_EXCEPTIONS
 512 /// Whether LLVM is built with exception support.
 513 #if __has_feature(cxx_exceptions)
 514 #define LLVM_ENABLE_EXCEPTIONS 1
 515 #elif defined(__GNUC__) && defined(__EXCEPTIONS)
 516 #define LLVM_ENABLE_EXCEPTIONS 1
 517 #elif defined(_MSC_VER) && defined(_CPPUNWIND)
 518 #define LLVM_ENABLE_EXCEPTIONS 1
 519 #endif
 520
 521 namespace llvm {
 522
 523 /// Allocate a buffer of memory with the given size and alignment.
 524 ///
 525 /// When the compiler supports aligned operator new, this will use it to to
 526 /// handle even over-aligned allocations.
 527 ///
 528 /// However, this doesn't make any attempt to leverage the fancier techniques
 529 /// like posix_memalign due to portability. It is mostly intended to allow
 530 /// compatibility with platforms that, after aligned allocation was added, use
 531 /// reduced default alignment.
 532 inline void *allocate_buffer(size_t Size, size_t Alignment) {
 533   return ::operator new(Size
 534 #ifdef __cpp_aligned_new
 535                         ,
 536                         std::align_val_t(Alignment)
 537 #endif
 538   );
 539 }
 540
 541 /// Deallocate a buffer of memory with the given size and alignment.
 542 ///
 543 /// If supported, this will used the sized delete operator. Also if supported,
 544 /// this will pass the alignment to the delete operator.
 545 ///
 546 /// The pointer must have been allocated with the corresponding new operator,
 547 /// most likely using the above helper.
 548 inline void deallocate_buffer(void *Ptr, size_t Size, size_t Alignment) {
 549   ::operator delete(Ptr
 550 #ifdef __cpp_sized_deallocation
 551                     ,
 552                     Size
 553 #endif
 554 #ifdef __cpp_aligned_new
 555                     ,
 556                     std::align_val_t(Alignment)
 557 #endif
 558   );
 559 }
 560
 561 } // End namespace llvm
 562
 563 #endif