1 //===-- sanitizer_atomic_clang_other.h --------------------------*- 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 is a part of ThreadSanitizer/AddressSanitizer runtime.
10 // Not intended for direct inclusion. Include sanitizer_atomic.h.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef SANITIZER_ATOMIC_CLANG_OTHER_H
15 #define SANITIZER_ATOMIC_CLANG_OTHER_H
16 
17 namespace __sanitizer {
18 
19 
20 INLINE void proc_yield(int cnt) {
21   __asm__ __volatile__("" ::: "memory");
22 }
23 
24 template<typename T>
25 INLINE typename T::Type atomic_load(
26     const volatile T *a, memory_order mo) {
27   DCHECK(mo & (memory_order_relaxed | memory_order_consume
28       | memory_order_acquire | memory_order_seq_cst));
29   DCHECK(!((uptr)a % sizeof(*a)));
30   typename T::Type v;
31 
32   if (sizeof(*a) < 8 || sizeof(void*) == 8) {
33     // Assume that aligned loads are atomic.
34     if (mo == memory_order_relaxed) {
35       v = a->val_dont_use;
36     } else if (mo == memory_order_consume) {
37       // Assume that processor respects data dependencies
38       // (and that compiler won't break them).
39       __asm__ __volatile__("" ::: "memory");
40       v = a->val_dont_use;
41       __asm__ __volatile__("" ::: "memory");
42     } else if (mo == memory_order_acquire) {
43       __asm__ __volatile__("" ::: "memory");
44       v = a->val_dont_use;
45       __sync_synchronize();
46     } else {  // seq_cst
47       // E.g. on POWER we need a hw fence even before the store.
48       __sync_synchronize();
49       v = a->val_dont_use;
50       __sync_synchronize();
51     }
52   } else {
53     // 64-bit load on 32-bit platform.
54     // Gross, but simple and reliable.
55     // Assume that it is not in read-only memory.
56     v = __sync_fetch_and_add(
57         const_cast<typename T::Type volatile *>(&a->val_dont_use), 0);
58   }
59   return v;
60 }
61 
62 template<typename T>
63 INLINE void atomic_store(volatile T *a, typename T::Type v, memory_order mo) {
64   DCHECK(mo & (memory_order_relaxed | memory_order_release
65       | memory_order_seq_cst));
66   DCHECK(!((uptr)a % sizeof(*a)));
67 
68   if (sizeof(*a) < 8 || sizeof(void*) == 8) {
69     // Assume that aligned loads are atomic.
70     if (mo == memory_order_relaxed) {
71       a->val_dont_use = v;
72     } else if (mo == memory_order_release) {
73       __sync_synchronize();
74       a->val_dont_use = v;
75       __asm__ __volatile__("" ::: "memory");
76     } else {  // seq_cst
77       __sync_synchronize();
78       a->val_dont_use = v;
79       __sync_synchronize();
80     }
81   } else {
82     // 64-bit store on 32-bit platform.
83     // Gross, but simple and reliable.
84     typename T::Type cmp = a->val_dont_use;
85     typename T::Type cur;
86     for (;;) {
87       cur = __sync_val_compare_and_swap(&a->val_dont_use, cmp, v);
88       if (cur == cmp || cur == v)
89         break;
90       cmp = cur;
91     }
92   }
93 }
94 
95 }  // namespace __sanitizer
96 
97 #endif  // #ifndef SANITIZER_ATOMIC_CLANG_OTHER_H
98