Compiler.h revision 204792 
1//===-- llvm/Support/Compiler.h - Compiler abstraction support --*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines several macros, based on the current compiler.  This allows
11// use of compiler-specific features in a way that remains portable.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_SUPPORT_COMPILER_H
16#define LLVM_SUPPORT_COMPILER_H
17
18// The VISIBILITY_HIDDEN macro, used for marking classes with the GCC-specific
19// visibility("hidden") attribute.
20#if (__GNUC__ >= 4) && !defined(__MINGW32__) && !defined(__CYGWIN__)
21#define VISIBILITY_HIDDEN __attribute__ ((visibility("hidden")))
22#else
23#define VISIBILITY_HIDDEN
24#endif
25
26#if (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
27#define ATTRIBUTE_USED __attribute__((__used__))
28#else
29#define ATTRIBUTE_USED
30#endif
31
32#if (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
33#define ATTRIBUTE_UNUSED __attribute__((__unused__))
34#else
35#define ATTRIBUTE_UNUSED
36#endif
37
38#ifdef __GNUC__ // aka 'ATTRIBUTE_CONST' but following LLVM Conventions.
39#define ATTRIBUTE_READNONE __attribute__((__const__))
40#else
41#define ATTRIBUTE_READNONE
42#endif
43
44#ifdef __GNUC__  // aka 'ATTRIBUTE_PURE' but following LLVM Conventions.
45#define ATTRIBUTE_READONLY __attribute__((__pure__))
46#else
47#define ATTRIBUTE_READONLY
48#endif
49
50#if (__GNUC__ >= 4)
51#define BUILTIN_EXPECT(EXPR, VALUE) __builtin_expect((EXPR), (VALUE))
52#else
53#define BUILTIN_EXPECT(EXPR, VALUE) (EXPR)
54#endif
55
56// C++ doesn't support 'extern template' of template specializations.  GCC does,
57// but requires __extension__ before it.  In the header, use this:
58//   EXTERN_TEMPLATE_INSTANTIATION(class foo<bar>);
59// in the .cpp file, use this:
60//   TEMPLATE_INSTANTIATION(class foo<bar>);
61#ifdef __GNUC__
62#define EXTERN_TEMPLATE_INSTANTIATION(X) __extension__ extern template X
63#define TEMPLATE_INSTANTIATION(X) template X
64#else
65#define EXTERN_TEMPLATE_INSTANTIATION(X)
66#define TEMPLATE_INSTANTIATION(X)
67#endif
68
69// DISABLE_INLINE - On compilers where we have a directive to do so, mark a
70// method "not for inlining".
71#if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
72#define DISABLE_INLINE __attribute__((noinline))
73#elif defined(_MSC_VER)
74#define DISABLE_INLINE __declspec(noinline)
75#else
76#define DISABLE_INLINE
77#endif
78
79// ALWAYS_INLINE - On compilers where we have a directive to do so, mark a
80// method "always inline" because it is performance sensitive.
81// GCC 3.4 supported this but is buggy in various cases and produces
82// unimplemented errors, just use it in GCC 4.0 and later.
83#if __GNUC__ > 3
84#define ALWAYS_INLINE __attribute__((always_inline))
85#else
86// TODO: No idea how to do this with MSVC.
87#define ALWAYS_INLINE
88#endif
89
90
91#ifdef __GNUC__
92#define NORETURN __attribute__((noreturn))
93#elif defined(_MSC_VER)
94#define NORETURN __declspec(noreturn)
95#else
96#define NORETURN
97#endif
98
99#endif
100