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_REQUIRE_CONSTANT_INITIALIZATION - Apply this to globals to ensure that
 258 /// they are constant initialized.
 259 #if __has_cpp_attribute(clang::require_constant_initialization)
 260 #define LLVM_REQUIRE_CONSTANT_INITIALIZATION                                   \
 261   [[clang::require_constant_initialization]]
 262 #else
 263 #define LLVM_REQUIRE_CONSTANT_INITIALIZATION
 264 #endif
 265
 266 /// LLVM_EXTENSION - Support compilers where we have a keyword to suppress
 267 /// pedantic diagnostics.
 268 #ifdef __GNUC__
 269 #define LLVM_EXTENSION __extension__
 270 #else
 271 #define LLVM_EXTENSION
 272 #endif
 273
 274 // LLVM_ATTRIBUTE_DEPRECATED(decl, "message")
 275 #if __has_feature(attribute_deprecated_with_message)
 276 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 277   decl __attribute__((deprecated(message)))
 278 #elif defined(__GNUC__)
 279 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 280   decl __attribute__((deprecated))
 281 #elif defined(_MSC_VER)
 282 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 283   __declspec(deprecated(message)) decl
 284 #else
 285 # define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
 286   decl
 287 #endif
 288
 289 /// LLVM_BUILTIN_UNREACHABLE - On compilers which support it, expands
 290 /// to an expression which states that it is undefined behavior for the
 291 /// compiler to reach this point.  Otherwise is not defined.
 292 #if __has_builtin(__builtin_unreachable) || LLVM_GNUC_PREREQ(4, 5, 0)
 293 # define LLVM_BUILTIN_UNREACHABLE __builtin_unreachable()
 294 #elif defined(_MSC_VER)
 295 # define LLVM_BUILTIN_UNREACHABLE __assume(false)
 296 #endif
 297
 298 /// LLVM_BUILTIN_TRAP - On compilers which support it, expands to an expression
 299 /// which causes the program to exit abnormally.
 300 #if __has_builtin(__builtin_trap) || LLVM_GNUC_PREREQ(4, 3, 0)
 301 # define LLVM_BUILTIN_TRAP __builtin_trap()
 302 #elif defined(_MSC_VER)
 303 // The __debugbreak intrinsic is supported by MSVC, does not require forward
 304 // declarations involving platform-specific typedefs (unlike RaiseException),
 305 // results in a call to vectored exception handlers, and encodes to a short
 306 // instruction that still causes the trapping behavior we want.
 307 # define LLVM_BUILTIN_TRAP __debugbreak()
 308 #else
 309 # define LLVM_BUILTIN_TRAP *(volatile int*)0x11 = 0
 310 #endif
 311
 312 /// LLVM_BUILTIN_DEBUGTRAP - On compilers which support it, expands to
 313 /// an expression which causes the program to break while running
 314 /// under a debugger.
 315 #if __has_builtin(__builtin_debugtrap)
 316 # define LLVM_BUILTIN_DEBUGTRAP __builtin_debugtrap()
 317 #elif defined(_MSC_VER)
 318 // The __debugbreak intrinsic is supported by MSVC and breaks while
 319 // running under the debugger, and also supports invoking a debugger
 320 // when the OS is configured appropriately.
 321 # define LLVM_BUILTIN_DEBUGTRAP __debugbreak()
 322 #else
 323 // Just continue execution when built with compilers that have no
 324 // support. This is a debugging aid and not intended to force the
 325 // program to abort if encountered.
 326 # define LLVM_BUILTIN_DEBUGTRAP
 327 #endif
 328
 329 /// \macro LLVM_ASSUME_ALIGNED
 330 /// Returns a pointer with an assumed alignment.
 331 #if __has_builtin(__builtin_assume_aligned) || LLVM_GNUC_PREREQ(4, 7, 0)
 332 # define LLVM_ASSUME_ALIGNED(p, a) __builtin_assume_aligned(p, a)
 333 #elif defined(LLVM_BUILTIN_UNREACHABLE)
 334 // As of today, clang does not support __builtin_assume_aligned.
 335 # define LLVM_ASSUME_ALIGNED(p, a) \
 336            (((uintptr_t(p) % (a)) == 0) ? (p) : (LLVM_BUILTIN_UNREACHABLE, (p)))
 337 #else
 338 # define LLVM_ASSUME_ALIGNED(p, a) (p)
 339 #endif
 340
 341 /// \macro LLVM_ALIGNAS
 342 /// Used to specify a minimum alignment for a structure or variable.
 343 #if __GNUC__ && !__has_feature(cxx_alignas) && !LLVM_GNUC_PREREQ(4, 8, 1)
 344 # define LLVM_ALIGNAS(x) __attribute__((aligned(x)))
 345 #else
 346 # define LLVM_ALIGNAS(x) alignas(x)
 347 #endif
 348
 349 /// \macro LLVM_PACKED
 350 /// Used to specify a packed structure.
 351 /// LLVM_PACKED(
 352 ///    struct A {
 353 ///      int i;
 354 ///      int j;
 355 ///      int k;
 356 ///      long long l;
 357 ///   });
 358 ///
 359 /// LLVM_PACKED_START
 360 /// struct B {
 361 ///   int i;
 362 ///   int j;
 363 ///   int k;
 364 ///   long long l;
 365 /// };
 366 /// LLVM_PACKED_END
 367 #ifdef _MSC_VER
 368 # define LLVM_PACKED(d) __pragma(pack(push, 1)) d __pragma(pack(pop))
 369 # define LLVM_PACKED_START __pragma(pack(push, 1))
 370 # define LLVM_PACKED_END   __pragma(pack(pop))
 371 #else
 372 # define LLVM_PACKED(d) d __attribute__((packed))
 373 # define LLVM_PACKED_START _Pragma("pack(push, 1)")
 374 # define LLVM_PACKED_END   _Pragma("pack(pop)")
 375 #endif
 376
 377 /// \macro LLVM_PTR_SIZE
 378 /// A constant integer equivalent to the value of sizeof(void*).
 379 /// Generally used in combination with LLVM_ALIGNAS or when doing computation in
 380 /// the preprocessor.
 381 #ifdef __SIZEOF_POINTER__
 382 # define LLVM_PTR_SIZE __SIZEOF_POINTER__
 383 #elif defined(_WIN64)
 384 # define LLVM_PTR_SIZE 8
 385 #elif defined(_WIN32)
 386 # define LLVM_PTR_SIZE 4
 387 #elif defined(_MSC_VER)
 388 # error "could not determine LLVM_PTR_SIZE as a constant int for MSVC"
 389 #else
 390 # define LLVM_PTR_SIZE sizeof(void *)
 391 #endif
 392
 393 /// \macro LLVM_MEMORY_SANITIZER_BUILD
 394 /// Whether LLVM itself is built with MemorySanitizer instrumentation.
 395 #if __has_feature(memory_sanitizer)
 396 # define LLVM_MEMORY_SANITIZER_BUILD 1
 397 # include <sanitizer/msan_interface.h>
 398 #else
 399 # define LLVM_MEMORY_SANITIZER_BUILD 0
 400 # define __msan_allocated_memory(p, size)
 401 # define __msan_unpoison(p, size)
 402 #endif
 403
 404 /// \macro LLVM_ADDRESS_SANITIZER_BUILD
 405 /// Whether LLVM itself is built with AddressSanitizer instrumentation.
 406 #if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
 407 # define LLVM_ADDRESS_SANITIZER_BUILD 1
 408 # include <sanitizer/asan_interface.h>
 409 #else
 410 # define LLVM_ADDRESS_SANITIZER_BUILD 0
 411 # define __asan_poison_memory_region(p, size)
 412 # define __asan_unpoison_memory_region(p, size)
 413 #endif
 414
 415 /// \macro LLVM_THREAD_SANITIZER_BUILD
 416 /// Whether LLVM itself is built with ThreadSanitizer instrumentation.
 417 #if __has_feature(thread_sanitizer) || defined(__SANITIZE_THREAD__)
 418 # define LLVM_THREAD_SANITIZER_BUILD 1
 419 #else
 420 # define LLVM_THREAD_SANITIZER_BUILD 0
 421 #endif
 422
 423 #if LLVM_THREAD_SANITIZER_BUILD
 424 // Thread Sanitizer is a tool that finds races in code.
 425 // See http://code.google.com/p/data-race-test/wiki/DynamicAnnotations .
 426 // tsan detects these exact functions by name.
 427 #ifdef __cplusplus
 428 extern "C" {
 429 #endif
 430 void AnnotateHappensAfter(const char *file, int line, const volatile void *cv);
 431 void AnnotateHappensBefore(const char *file, int line, const volatile void *cv);
 432 void AnnotateIgnoreWritesBegin(const char *file, int line);
 433 void AnnotateIgnoreWritesEnd(const char *file, int line);
 434 #ifdef __cplusplus
 435 }
 436 #endif
 437
 438 // This marker is used to define a happens-before arc. The race detector will
 439 // infer an arc from the begin to the end when they share the same pointer
 440 // argument.
 441 # define TsanHappensBefore(cv) AnnotateHappensBefore(__FILE__, __LINE__, cv)
 442
 443 // This marker defines the destination of a happens-before arc.
 444 # define TsanHappensAfter(cv) AnnotateHappensAfter(__FILE__, __LINE__, cv)
 445
 446 // Ignore any races on writes between here and the next TsanIgnoreWritesEnd.
 447 # define TsanIgnoreWritesBegin() AnnotateIgnoreWritesBegin(__FILE__, __LINE__)
 448
 449 // Resume checking for racy writes.
 450 # define TsanIgnoreWritesEnd() AnnotateIgnoreWritesEnd(__FILE__, __LINE__)
 451 #else
 452 # define TsanHappensBefore(cv)
 453 # define TsanHappensAfter(cv)
 454 # define TsanIgnoreWritesBegin()
 455 # define TsanIgnoreWritesEnd()
 456 #endif
 457
 458 /// \macro LLVM_NO_SANITIZE
 459 /// Disable a particular sanitizer for a function.
 460 #if __has_attribute(no_sanitize)
 461 #define LLVM_NO_SANITIZE(KIND) __attribute__((no_sanitize(KIND)))
 462 #else
 463 #define LLVM_NO_SANITIZE(KIND)
 464 #endif
 465
 466 /// Mark debug helper function definitions like dump() that should not be
 467 /// stripped from debug builds.
 468 /// Note that you should also surround dump() functions with
 469 /// `#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)` so they do always
 470 /// get stripped in release builds.
 471 // FIXME: Move this to a private config.h as it's not usable in public headers.
 472 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 473 #define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED
 474 #else
 475 #define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE
 476 #endif
 477
 478 /// \macro LLVM_PRETTY_FUNCTION
 479 /// Gets a user-friendly looking function signature for the current scope
 480 /// using the best available method on each platform.  The exact format of the
 481 /// resulting string is implementation specific and non-portable, so this should
 482 /// only be used, for example, for logging or diagnostics.
 483 #if defined(_MSC_VER)
 484 #define LLVM_PRETTY_FUNCTION __FUNCSIG__
 485 #elif defined(__GNUC__) || defined(__clang__)
 486 #define LLVM_PRETTY_FUNCTION __PRETTY_FUNCTION__
 487 #else
 488 #define LLVM_PRETTY_FUNCTION __func__
 489 #endif
 490
 491 /// \macro LLVM_THREAD_LOCAL
 492 /// A thread-local storage specifier which can be used with globals,
 493 /// extern globals, and static globals.
 494 ///
 495 /// This is essentially an extremely restricted analog to C++11's thread_local
 496 /// support, and uses that when available. However, it falls back on
 497 /// platform-specific or vendor-provided extensions when necessary. These
 498 /// extensions don't support many of the C++11 thread_local's features. You
 499 /// should only use this for PODs that you can statically initialize to
 500 /// some constant value. In almost all circumstances this is most appropriate
 501 /// for use with a pointer, integer, or small aggregation of pointers and
 502 /// integers.
 503 #if LLVM_ENABLE_THREADS
 504 #if __has_feature(cxx_thread_local)
 505 #define LLVM_THREAD_LOCAL thread_local
 506 #elif defined(_MSC_VER)
 507 // MSVC supports this with a __declspec.
 508 #define LLVM_THREAD_LOCAL __declspec(thread)
 509 #else
 510 // Clang, GCC, and other compatible compilers used __thread prior to C++11 and
 511 // we only need the restricted functionality that provides.
 512 #define LLVM_THREAD_LOCAL __thread
 513 #endif
 514 #else // !LLVM_ENABLE_THREADS
 515 // If threading is disabled entirely, this compiles to nothing and you get
 516 // a normal global variable.
 517 #define LLVM_THREAD_LOCAL
 518 #endif
 519
 520 /// \macro LLVM_ENABLE_EXCEPTIONS
 521 /// Whether LLVM is built with exception support.
 522 #if __has_feature(cxx_exceptions)
 523 #define LLVM_ENABLE_EXCEPTIONS 1
 524 #elif defined(__GNUC__) && defined(__EXCEPTIONS)
 525 #define LLVM_ENABLE_EXCEPTIONS 1
 526 #elif defined(_MSC_VER) && defined(_CPPUNWIND)
 527 #define LLVM_ENABLE_EXCEPTIONS 1
 528 #endif
 529
 530 namespace llvm {
 531
 532 /// Allocate a buffer of memory with the given size and alignment.
 533 ///
 534 /// When the compiler supports aligned operator new, this will use it to to
 535 /// handle even over-aligned allocations.
 536 ///
 537 /// However, this doesn't make any attempt to leverage the fancier techniques
 538 /// like posix_memalign due to portability. It is mostly intended to allow
 539 /// compatibility with platforms that, after aligned allocation was added, use
 540 /// reduced default alignment.
 541 inline void *allocate_buffer(size_t Size, size_t Alignment) {
 542   return ::operator new(Size
 543 #ifdef __cpp_aligned_new
 544                         ,
 545                         std::align_val_t(Alignment)
 546 #endif
 547   );
 548 }
 549
 550 /// Deallocate a buffer of memory with the given size and alignment.
 551 ///
 552 /// If supported, this will used the sized delete operator. Also if supported,
 553 /// this will pass the alignment to the delete operator.
 554 ///
 555 /// The pointer must have been allocated with the corresponding new operator,
 556 /// most likely using the above helper.
 557 inline void deallocate_buffer(void *Ptr, size_t Size, size_t Alignment) {
 558   ::operator delete(Ptr
 559 #ifdef __cpp_sized_deallocation
 560                     ,
 561                     Size
 562 #endif
 563 #ifdef __cpp_aligned_new
 564                     ,
 565                     std::align_val_t(Alignment)
 566 #endif
 567   );
 568 }
 569
 570 } // End namespace llvm
 571
 572 #endif