1 /*
2  * Copyright (c) Yann Collet, Facebook, Inc.
3  * All rights reserved.
4  *
5  * This source code is licensed under both the BSD-style license (found in the
6  * LICENSE file in the root directory of this source tree) and the GPLv2 (found
7  * in the COPYING file in the root directory of this source tree).
8  * You may select, at your option, one of the above-listed licenses.
9  */
10 
11 #ifndef ZSTD_COMPILER_H
12 #define ZSTD_COMPILER_H
13 
14 #include "portability_macros.h"
15 
16 /*-*******************************************************
17 *  Compiler specifics
18 *********************************************************/
19 /* force inlining */
20 
21 #if !defined(ZSTD_NO_INLINE)
22 #if (defined(__GNUC__) && !defined(__STRICT_ANSI__)) || defined(__cplusplus) || defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   /* C99 */
23 #  define INLINE_KEYWORD inline
24 #else
25 #  define INLINE_KEYWORD
26 #endif
27 
28 #define FORCE_INLINE_ATTR __attribute__((always_inline))
29 
30 #else
31 
32 #define INLINE_KEYWORD
33 #define FORCE_INLINE_ATTR
34 
35 #endif
36 
37 /*
38   On MSVC qsort requires that functions passed into it use the __cdecl calling conversion(CC).
39   This explicitly marks such functions as __cdecl so that the code will still compile
40   if a CC other than __cdecl has been made the default.
41 */
42 #define WIN_CDECL
43 
44 /*
45  * FORCE_INLINE_TEMPLATE is used to define C "templates", which take constant
46  * parameters. They must be inlined for the compiler to eliminate the constant
47  * branches.
48  */
49 #define FORCE_INLINE_TEMPLATE static INLINE_KEYWORD FORCE_INLINE_ATTR
50 /*
51  * HINT_INLINE is used to help the compiler generate better code. It is *not*
52  * used for "templates", so it can be tweaked based on the compilers
53  * performance.
54  *
55  * gcc-4.8 and gcc-4.9 have been shown to benefit from leaving off the
56  * always_inline attribute.
57  *
58  * clang up to 5.0.0 (trunk) benefit tremendously from the always_inline
59  * attribute.
60  */
61 #if !defined(__clang__) && defined(__GNUC__) && __GNUC__ >= 4 && __GNUC_MINOR__ >= 8 && __GNUC__ < 5
62 #  define HINT_INLINE static INLINE_KEYWORD
63 #else
64 #  define HINT_INLINE static INLINE_KEYWORD FORCE_INLINE_ATTR
65 #endif
66 
67 /* UNUSED_ATTR tells the compiler it is okay if the function is unused. */
68 #define UNUSED_ATTR __attribute__((unused))
69 
70 /* force no inlining */
71 #define FORCE_NOINLINE static __attribute__((__noinline__))
72 
73 
74 /* target attribute */
75 #define TARGET_ATTRIBUTE(target) __attribute__((__target__(target)))
76 
77 /* Target attribute for BMI2 dynamic dispatch.
78  * Enable lzcnt, bmi, and bmi2.
79  * We test for bmi1 & bmi2. lzcnt is included in bmi1.
80  */
81 #define BMI2_TARGET_ATTRIBUTE TARGET_ATTRIBUTE("lzcnt,bmi,bmi2")
82 
83 /* prefetch
84  * can be disabled, by declaring NO_PREFETCH build macro */
85 #if ( (__GNUC__ >= 4) || ( (__GNUC__ == 3) && (__GNUC_MINOR__ >= 1) ) )
86 #  define PREFETCH_L1(ptr)  __builtin_prefetch((ptr), 0 /* rw==read */, 3 /* locality */)
87 #  define PREFETCH_L2(ptr)  __builtin_prefetch((ptr), 0 /* rw==read */, 2 /* locality */)
88 #elif defined(__aarch64__)
89 #  define PREFETCH_L1(ptr)  __asm__ __volatile__("prfm pldl1keep, %0" ::"Q"(*(ptr)))
90 #  define PREFETCH_L2(ptr)  __asm__ __volatile__("prfm pldl2keep, %0" ::"Q"(*(ptr)))
91 #else
92 #  define PREFETCH_L1(ptr) (void)(ptr)  /* disabled */
93 #  define PREFETCH_L2(ptr) (void)(ptr)  /* disabled */
94 #endif  /* NO_PREFETCH */
95 
96 #define CACHELINE_SIZE 64
97 
98 #define PREFETCH_AREA(p, s)  {            \
99     const char* const _ptr = (const char*)(p);  \
100     size_t const _size = (size_t)(s);     \
101     size_t _pos;                          \
102     for (_pos=0; _pos<_size; _pos+=CACHELINE_SIZE) {  \
103         PREFETCH_L2(_ptr + _pos);         \
104     }                                     \
105 }
106 
107 /* vectorization
108  * older GCC (pre gcc-4.3 picked as the cutoff) uses a different syntax,
109  * and some compilers, like Intel ICC and MCST LCC, do not support it at all. */
110 #if !defined(__INTEL_COMPILER) && !defined(__clang__) && defined(__GNUC__) && !defined(__LCC__)
111 #  if (__GNUC__ == 4 && __GNUC_MINOR__ > 3) || (__GNUC__ >= 5)
112 #    define DONT_VECTORIZE __attribute__((optimize("no-tree-vectorize")))
113 #  else
114 #    define DONT_VECTORIZE _Pragma("GCC optimize(\"no-tree-vectorize\")")
115 #  endif
116 #else
117 #  define DONT_VECTORIZE
118 #endif
119 
120 /* Tell the compiler that a branch is likely or unlikely.
121  * Only use these macros if it causes the compiler to generate better code.
122  * If you can remove a LIKELY/UNLIKELY annotation without speed changes in gcc
123  * and clang, please do.
124  */
125 #define LIKELY(x) (__builtin_expect((x), 1))
126 #define UNLIKELY(x) (__builtin_expect((x), 0))
127 
128 #if __has_builtin(__builtin_unreachable) || (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)))
129 #  define ZSTD_UNREACHABLE { assert(0), __builtin_unreachable(); }
130 #else
131 #  define ZSTD_UNREACHABLE { assert(0); }
132 #endif
133 
134 /* disable warnings */
135 
136 /*Like DYNAMIC_BMI2 but for compile time determination of BMI2 support*/
137 
138 
139 /* compile time determination of SIMD support */
140 
141 /* C-language Attributes are added in C23. */
142 #if defined(__STDC_VERSION__) && (__STDC_VERSION__ > 201710L) && defined(__has_c_attribute)
143 # define ZSTD_HAS_C_ATTRIBUTE(x) __has_c_attribute(x)
144 #else
145 # define ZSTD_HAS_C_ATTRIBUTE(x) 0
146 #endif
147 
148 /* Only use C++ attributes in C++. Some compilers report support for C++
149  * attributes when compiling with C.
150  */
151 #define ZSTD_HAS_CPP_ATTRIBUTE(x) 0
152 
153 /* Define ZSTD_FALLTHROUGH macro for annotating switch case with the 'fallthrough' attribute.
154  * - C23: https://en.cppreference.com/w/c/language/attributes/fallthrough
155  * - CPP17: https://en.cppreference.com/w/cpp/language/attributes/fallthrough
156  * - Else: __attribute__((__fallthrough__))
157  */
158 #define ZSTD_FALLTHROUGH fallthrough
159 
160 /*-**************************************************************
161 *  Alignment check
162 *****************************************************************/
163 
164 /* this test was initially positioned in mem.h,
165  * but this file is removed (or replaced) for linux kernel
166  * so it's now hosted in compiler.h,
167  * which remains valid for both user & kernel spaces.
168  */
169 
170 #ifndef ZSTD_ALIGNOF
171 /* covers gcc, clang & MSVC */
172 /* note : this section must come first, before C11,
173  * due to a limitation in the kernel source generator */
174 #  define ZSTD_ALIGNOF(T) __alignof(T)
175 
176 #endif /* ZSTD_ALIGNOF */
177 
178 /*-**************************************************************
179 *  Sanitizer
180 *****************************************************************/
181 
182 
183 
184 #endif /* ZSTD_COMPILER_H */
185