1 /* SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause */
2 /*
3 * Copyright (c) Meta Platforms, Inc. and affiliates.
4 * All rights reserved.
5 *
6 * This source code is licensed under both the BSD-style license (found in the
7 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
8 * in the COPYING file in the root directory of this source tree).
9 * You may select, at your option, one of the above-listed licenses.
10 */
11
12 #ifndef ZSTD_COMPILER_H
13 #define ZSTD_COMPILER_H
14
15 #include <linux/types.h>
16
17 #include "portability_macros.h"
18
19 /*-*******************************************************
20 * Compiler specifics
21 *********************************************************/
22 /* force inlining */
23
24 #if !defined(ZSTD_NO_INLINE)
25 #if (defined(__GNUC__) && !defined(__STRICT_ANSI__)) || defined(__cplusplus) || defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L /* C99 */
26 # define INLINE_KEYWORD inline
27 #else
28 # define INLINE_KEYWORD
29 #endif
30
31 #define FORCE_INLINE_ATTR __attribute__((always_inline))
32
33 #else
34
35 #define INLINE_KEYWORD
36 #define FORCE_INLINE_ATTR
37
38 #endif
39
40 /*
41 On MSVC qsort requires that functions passed into it use the __cdecl calling conversion(CC).
42 This explicitly marks such functions as __cdecl so that the code will still compile
43 if a CC other than __cdecl has been made the default.
44 */
45 #define WIN_CDECL
46
47 /* UNUSED_ATTR tells the compiler it is okay if the function is unused. */
48 #define UNUSED_ATTR __attribute__((unused))
49
50 /*
51 * FORCE_INLINE_TEMPLATE is used to define C "templates", which take constant
52 * parameters. They must be inlined for the compiler to eliminate the constant
53 * branches.
54 */
55 #define FORCE_INLINE_TEMPLATE static INLINE_KEYWORD FORCE_INLINE_ATTR UNUSED_ATTR
56 /*
57 * HINT_INLINE is used to help the compiler generate better code. It is *not*
58 * used for "templates", so it can be tweaked based on the compilers
59 * performance.
60 *
61 * gcc-4.8 and gcc-4.9 have been shown to benefit from leaving off the
62 * always_inline attribute.
63 *
64 * clang up to 5.0.0 (trunk) benefit tremendously from the always_inline
65 * attribute.
66 */
67 #if !defined(__clang__) && defined(__GNUC__) && __GNUC__ >= 4 && __GNUC_MINOR__ >= 8 && __GNUC__ < 5
68 # define HINT_INLINE static INLINE_KEYWORD
69 #else
70 # define HINT_INLINE FORCE_INLINE_TEMPLATE
71 #endif
72
73 /* "soft" inline :
74 * The compiler is free to select if it's a good idea to inline or not.
75 * The main objective is to silence compiler warnings
76 * when a defined function in included but not used.
77 *
78 * Note : this macro is prefixed `MEM_` because it used to be provided by `mem.h` unit.
79 * Updating the prefix is probably preferable, but requires a fairly large codemod,
80 * since this name is used everywhere.
81 */
82 #ifndef MEM_STATIC /* already defined in Linux Kernel mem.h */
83 #define MEM_STATIC static __inline UNUSED_ATTR
84 #endif
85
86 /* force no inlining */
87 #define FORCE_NOINLINE static __attribute__((__noinline__))
88
89
90 /* target attribute */
91 #define TARGET_ATTRIBUTE(target) __attribute__((__target__(target)))
92
93 /* Target attribute for BMI2 dynamic dispatch.
94 * Enable lzcnt, bmi, and bmi2.
95 * We test for bmi1 & bmi2. lzcnt is included in bmi1.
96 */
97 #define BMI2_TARGET_ATTRIBUTE TARGET_ATTRIBUTE("lzcnt,bmi,bmi2")
98
99 /* prefetch
100 * can be disabled, by declaring NO_PREFETCH build macro */
101 #if ( (__GNUC__ >= 4) || ( (__GNUC__ == 3) && (__GNUC_MINOR__ >= 1) ) )
102 # define PREFETCH_L1(ptr) __builtin_prefetch((ptr), 0 /* rw==read */, 3 /* locality */)
103 # define PREFETCH_L2(ptr) __builtin_prefetch((ptr), 0 /* rw==read */, 2 /* locality */)
104 #elif defined(__aarch64__)
105 # define PREFETCH_L1(ptr) do { __asm__ __volatile__("prfm pldl1keep, %0" ::"Q"(*(ptr))); } while (0)
106 # define PREFETCH_L2(ptr) do { __asm__ __volatile__("prfm pldl2keep, %0" ::"Q"(*(ptr))); } while (0)
107 #else
108 # define PREFETCH_L1(ptr) do { (void)(ptr); } while (0) /* disabled */
109 # define PREFETCH_L2(ptr) do { (void)(ptr); } while (0) /* disabled */
110 #endif /* NO_PREFETCH */
111
112 #define CACHELINE_SIZE 64
113
114 #define PREFETCH_AREA(p, s) \
115 do { \
116 const char* const _ptr = (const char*)(p); \
117 size_t const _size = (size_t)(s); \
118 size_t _pos; \
119 for (_pos=0; _pos<_size; _pos+=CACHELINE_SIZE) { \
120 PREFETCH_L2(_ptr + _pos); \
121 } \
122 } while (0)
123
124 /* vectorization
125 * older GCC (pre gcc-4.3 picked as the cutoff) uses a different syntax,
126 * and some compilers, like Intel ICC and MCST LCC, do not support it at all. */
127 #if !defined(__INTEL_COMPILER) && !defined(__clang__) && defined(__GNUC__) && !defined(__LCC__)
128 # if (__GNUC__ == 4 && __GNUC_MINOR__ > 3) || (__GNUC__ >= 5)
129 # define DONT_VECTORIZE __attribute__((optimize("no-tree-vectorize")))
130 # else
131 # define DONT_VECTORIZE _Pragma("GCC optimize(\"no-tree-vectorize\")")
132 # endif
133 #else
134 # define DONT_VECTORIZE
135 #endif
136
137 /* Tell the compiler that a branch is likely or unlikely.
138 * Only use these macros if it causes the compiler to generate better code.
139 * If you can remove a LIKELY/UNLIKELY annotation without speed changes in gcc
140 * and clang, please do.
141 */
142 #define LIKELY(x) (__builtin_expect((x), 1))
143 #define UNLIKELY(x) (__builtin_expect((x), 0))
144
145 #if __has_builtin(__builtin_unreachable) || (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)))
146 # define ZSTD_UNREACHABLE do { assert(0), __builtin_unreachable(); } while (0)
147 #else
148 # define ZSTD_UNREACHABLE do { assert(0); } while (0)
149 #endif
150
151 /* disable warnings */
152
153 /* compile time determination of SIMD support */
154
155 /* C-language Attributes are added in C23. */
156 #if defined(__STDC_VERSION__) && (__STDC_VERSION__ > 201710L) && defined(__has_c_attribute)
157 # define ZSTD_HAS_C_ATTRIBUTE(x) __has_c_attribute(x)
158 #else
159 # define ZSTD_HAS_C_ATTRIBUTE(x) 0
160 #endif
161
162 /* Only use C++ attributes in C++. Some compilers report support for C++
163 * attributes when compiling with C.
164 */
165 #define ZSTD_HAS_CPP_ATTRIBUTE(x) 0
166
167 /* Define ZSTD_FALLTHROUGH macro for annotating switch case with the 'fallthrough' attribute.
168 * - C23: https://en.cppreference.com/w/c/language/attributes/fallthrough
169 * - CPP17: https://en.cppreference.com/w/cpp/language/attributes/fallthrough
170 * - Else: __attribute__((__fallthrough__))
171 */
172 #define ZSTD_FALLTHROUGH fallthrough
173
174 /*-**************************************************************
175 * Alignment
176 *****************************************************************/
177
178 /* @return 1 if @u is a 2^n value, 0 otherwise
179 * useful to check a value is valid for alignment restrictions */
ZSTD_isPower2(size_t u)180 MEM_STATIC int ZSTD_isPower2(size_t u) {
181 return (u & (u-1)) == 0;
182 }
183
184 /* this test was initially positioned in mem.h,
185 * but this file is removed (or replaced) for linux kernel
186 * so it's now hosted in compiler.h,
187 * which remains valid for both user & kernel spaces.
188 */
189
190 #ifndef ZSTD_ALIGNOF
191 /* covers gcc, clang & MSVC */
192 /* note : this section must come first, before C11,
193 * due to a limitation in the kernel source generator */
194 # define ZSTD_ALIGNOF(T) __alignof(T)
195
196 #endif /* ZSTD_ALIGNOF */
197
198 #ifndef ZSTD_ALIGNED
199 /* C90-compatible alignment macro (GCC/Clang). Adjust for other compilers if needed. */
200 #define ZSTD_ALIGNED(a) __attribute__((aligned(a)))
201 #endif /* ZSTD_ALIGNED */
202
203
204 /*-**************************************************************
205 * Sanitizer
206 *****************************************************************/
207
208 /*
209 * Zstd relies on pointer overflow in its decompressor.
210 * We add this attribute to functions that rely on pointer overflow.
211 */
212 #ifndef ZSTD_ALLOW_POINTER_OVERFLOW_ATTR
213 # if __has_attribute(no_sanitize)
214 # if !defined(__clang__) && defined(__GNUC__) && __GNUC__ < 8
215 /* gcc < 8 only has signed-integer-overlow which triggers on pointer overflow */
216 # define ZSTD_ALLOW_POINTER_OVERFLOW_ATTR __attribute__((no_sanitize("signed-integer-overflow")))
217 # else
218 /* older versions of clang [3.7, 5.0) will warn that pointer-overflow is ignored. */
219 # define ZSTD_ALLOW_POINTER_OVERFLOW_ATTR __attribute__((no_sanitize("pointer-overflow")))
220 # endif
221 # else
222 # define ZSTD_ALLOW_POINTER_OVERFLOW_ATTR
223 # endif
224 #endif
225
226 /*
227 * Helper function to perform a wrapped pointer difference without triggering
228 * UBSAN.
229 *
230 * @returns lhs - rhs with wrapping
231 */
232 MEM_STATIC
233 ZSTD_ALLOW_POINTER_OVERFLOW_ATTR
ZSTD_wrappedPtrDiff(unsigned char const * lhs,unsigned char const * rhs)234 ptrdiff_t ZSTD_wrappedPtrDiff(unsigned char const* lhs, unsigned char const* rhs)
235 {
236 return lhs - rhs;
237 }
238
239 /*
240 * Helper function to perform a wrapped pointer add without triggering UBSAN.
241 *
242 * @return ptr + add with wrapping
243 */
244 MEM_STATIC
245 ZSTD_ALLOW_POINTER_OVERFLOW_ATTR
ZSTD_wrappedPtrAdd(unsigned char const * ptr,ptrdiff_t add)246 unsigned char const* ZSTD_wrappedPtrAdd(unsigned char const* ptr, ptrdiff_t add)
247 {
248 return ptr + add;
249 }
250
251 /*
252 * Helper function to perform a wrapped pointer subtraction without triggering
253 * UBSAN.
254 *
255 * @return ptr - sub with wrapping
256 */
257 MEM_STATIC
258 ZSTD_ALLOW_POINTER_OVERFLOW_ATTR
ZSTD_wrappedPtrSub(unsigned char const * ptr,ptrdiff_t sub)259 unsigned char const* ZSTD_wrappedPtrSub(unsigned char const* ptr, ptrdiff_t sub)
260 {
261 return ptr - sub;
262 }
263
264 /*
265 * Helper function to add to a pointer that works around C's undefined behavior
266 * of adding 0 to NULL.
267 *
268 * @returns `ptr + add` except it defines `NULL + 0 == NULL`.
269 */
270 MEM_STATIC
ZSTD_maybeNullPtrAdd(unsigned char * ptr,ptrdiff_t add)271 unsigned char* ZSTD_maybeNullPtrAdd(unsigned char* ptr, ptrdiff_t add)
272 {
273 return add > 0 ? ptr + add : ptr;
274 }
275
276 /* Issue #3240 reports an ASAN failure on an llvm-mingw build. Out of an
277 * abundance of caution, disable our custom poisoning on mingw. */
278 #ifdef __MINGW32__
279 #ifndef ZSTD_ASAN_DONT_POISON_WORKSPACE
280 #define ZSTD_ASAN_DONT_POISON_WORKSPACE 1
281 #endif
282 #ifndef ZSTD_MSAN_DONT_POISON_WORKSPACE
283 #define ZSTD_MSAN_DONT_POISON_WORKSPACE 1
284 #endif
285 #endif
286
287
288
289 #endif /* ZSTD_COMPILER_H */
290