Compiler.h revision 199481 
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#ifdef __GNUC__ // aka 'ATTRIBUTE_CONST' but following LLVM Conventions.
33#define ATTRIBUTE_READNONE __attribute__((__const__))
34#else
35#define ATTRIBUTE_READNONE
36#endif
37
38#ifdef __GNUC__  // aka 'ATTRIBUTE_PURE' but following LLVM Conventions.
39#define ATTRIBUTE_READONLY __attribute__((__pure__))
40#else
41#define ATTRIBUTE_READONLY
42#endif
43
44#if (__GNUC__ >= 4)
45#define BUILTIN_EXPECT(EXPR, VALUE) __builtin_expect((EXPR), (VALUE))
46#else
47#define BUILTIN_EXPECT(EXPR, VALUE) (EXPR)
48#endif
49
50// C++ doesn't support 'extern template' of template specializations.  GCC does,
51// but requires __extension__ before it.  In the header, use this:
52//   EXTERN_TEMPLATE_INSTANTIATION(class foo<bar>);
53// in the .cpp file, use this:
54//   TEMPLATE_INSTANTIATION(class foo<bar>);
55#ifdef __GNUC__
56#define EXTERN_TEMPLATE_INSTANTIATION(X) __extension__ extern template X
57#define TEMPLATE_INSTANTIATION(X) template X
58#else
59#define EXTERN_TEMPLATE_INSTANTIATION(X)
60#define TEMPLATE_INSTANTIATION(X)
61#endif
62
63// DISABLE_INLINE - On compilers where we have a directive to do so, mark a
64// method "not for inlining".
65#if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
66#define DISABLE_INLINE __attribute__((noinline))
67#elif defined(_MSC_VER)
68#define DISABLE_INLINE __declspec(noinline)
69#else
70#define DISABLE_INLINE
71#endif
72
73#ifdef __GNUC__
74#define NORETURN __attribute__((noreturn))
75#elif defined(_MSC_VER)
76#define NORETURN __declspec(noreturn)
77#else
78#define NORETURN
79#endif
80
81#endif
82