1 /*
2 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
3 *
4 * SPDX-License-Identifier: BSD-3-Clause
5 */
6
7 #include <stdatomic.h>
8 #include "pico/sync.h"
9
10 // We use __builtin_mem* to avoid libc dependency.
11 #define memcpy __builtin_memcpy
12 #define memcmp __builtin_memcmp
13
atomic_lock(__unused const volatile void * ptr)14 static inline uint32_t atomic_lock(__unused const volatile void *ptr) {
15 return spin_lock_blocking(spin_lock_instance(PICO_SPINLOCK_ID_ATOMIC));
16 }
17
atomic_unlock(__unused const volatile void * ptr,uint32_t save)18 static inline void atomic_unlock(__unused const volatile void *ptr, uint32_t save) {
19 spin_unlock(spin_lock_instance(PICO_SPINLOCK_ID_ATOMIC), save);
20 }
21
22 #if PICO_C_COMPILER_IS_GNU
23
__atomic_test_and_set_c(volatile void * mem,__unused int model)24 _Bool __atomic_test_and_set_c(volatile void *mem, __unused int model) {
25 uint32_t save = atomic_lock(mem);
26 bool result = *(volatile bool *) mem;
27 *(volatile bool *) mem = true;
28 atomic_unlock(mem, save);
29 return result;
30 }
31
32 #define __atomic_load_c __atomic_load
33 #define __atomic_store_c __atomic_store
34 #define __atomic_exchange_c __atomic_exchange
35 #define __atomic_compare_exchange_c __atomic_compare_exchange
36 #define __atomic_is_lock_free_c __atomic_is_lock_free
37 #else
38 // Clang objects if you redefine a builtin.
39 #pragma redefine_extname __atomic_load_c __atomic_load
40 #pragma redefine_extname __atomic_store_c __atomic_store
41 #pragma redefine_extname __atomic_exchange_c __atomic_exchange
42 #pragma redefine_extname __atomic_compare_exchange_c __atomic_compare_exchange
43 #pragma redefine_extname __atomic_is_lock_free_c __atomic_is_lock_free
44 #endif
45
46 // Whether atomic operations for the given size (and alignment) are lock-free.
__atomic_is_lock_free_c(__unused size_t size,__unused const volatile void * ptr)47 bool __atomic_is_lock_free_c(__unused size_t size, __unused const volatile void *ptr) {
48 #if !__ARM_ARCH_6M__
49 if (size == 1 || size == 2 || size == 4) {
50 size_t align = size - 1;
51 return (((uintptr_t)ptr) & align) == 0;
52 }
53 #endif
54 return false;
55 }
56
57
58
59 // An atomic load operation. This is atomic with respect to the source pointer only.
__atomic_load_c(uint size,const volatile void * src,void * dest,__unused int model)60 void __atomic_load_c(uint size, const volatile void *src, void *dest, __unused int model) {
61 uint32_t save = atomic_lock(src);
62 memcpy(dest, remove_volatile_cast_no_barrier(const void *, src), size);
63 atomic_unlock(src, save);
64 }
65
66 // An atomic store operation. This is atomic with respect to the destination
67 // pointer only.
__atomic_store_c(uint size,volatile void * dest,void * src,__unused int model)68 void __atomic_store_c(uint size, volatile void *dest, void *src, __unused int model) {
69 uint32_t save = atomic_lock(src);
70 memcpy(remove_volatile_cast_no_barrier(void *, dest), src, size);
71 atomic_unlock(src, save);
72 }
73
74 // Atomic compare and exchange operation. If the value at *ptr is identical
75 // to the value at *expected, then this copies value at *desired to *ptr. If
76 // they are not, then this stores the current value from *ptr in *expected.
77 //
78 // This function returns 1 if the exchange takes place or 0 if it fails.
__atomic_compare_exchange_c(uint size,volatile void * ptr,void * expected,void * desired,__unused int success,__unused int failure)79 _Bool __atomic_compare_exchange_c(uint size, volatile void *ptr, void *expected,
80 void *desired, __unused int success, __unused int failure) {
81 uint32_t save = atomic_lock(ptr);
82 if (memcmp(remove_volatile_cast_no_barrier(void *, ptr), expected, size) == 0) {
83 memcpy(remove_volatile_cast_no_barrier(void *, ptr), desired, size);
84 atomic_unlock(ptr, save);
85 return 1;
86 }
87 memcpy(expected, remove_volatile_cast_no_barrier(void *, ptr), size);
88 atomic_unlock(ptr, save);
89 return 0;
90 }
91
92 // Performs an atomic exchange operation between two pointers. This is atomic
93 // with respect to the target address.
__atomic_exchange_c(uint size,volatile void * ptr,void * val,void * old,__unused int model)94 void __atomic_exchange_c(uint size, volatile void *ptr, void *val, void *old, __unused int model) {
95
96 uint32_t save = atomic_lock(ptr);
97 memcpy(old, remove_volatile_cast_no_barrier(void *, ptr), size);
98 memcpy(remove_volatile_cast_no_barrier(void *, ptr), val, size);
99 atomic_unlock(ptr, save);
100 }
101
102 #if __ARM_ARCH_6M__
103 #define ATOMIC_OPTIMIZED_CASES \
104 ATOMIC_OPTIMIZED_CASE(1, uint8_t) \
105 ATOMIC_OPTIMIZED_CASE(2, uint16_t) \
106 ATOMIC_OPTIMIZED_CASE(4, uint) \
107 ATOMIC_OPTIMIZED_CASE(8, uint64_t)
108 #else
109 #define ATOMIC_OPTIMIZED_CASES \
110 ATOMIC_OPTIMIZED_CASE(8, uint64_t)
111 #endif
112
113 #define ATOMIC_OPTIMIZED_CASE(n, type) \
114 type __atomic_load_##n(const volatile void *src, __unused int memorder) { \
115 uint32_t save = atomic_lock(src); \
116 type val = *(const volatile type *)src; \
117 atomic_unlock(src, save); \
118 return val; \
119 }
120
121 ATOMIC_OPTIMIZED_CASES
122
123 #undef ATOMIC_OPTIMIZED_CASE
124
125 #define ATOMIC_OPTIMIZED_CASE(n, type) \
126 void __atomic_store_##n(volatile void *dest, type val, __unused int model) { \
127 uint32_t save = atomic_lock(dest); \
128 *(volatile type *)dest = val; \
129 atomic_unlock(dest, save); \
130 }
131
132 ATOMIC_OPTIMIZED_CASES
133
134 #undef ATOMIC_OPTIMIZED_CASE
135
136 #define ATOMIC_OPTIMIZED_CASE(n, type) \
137 bool __atomic_compare_exchange_##n(volatile void *ptr, void *expected, type desired, \
138 __unused bool weak, __unused int success, __unused int failure) { \
139 uint32_t save = atomic_lock(ptr); \
140 if (*(volatile type *)ptr == *(type *)expected) { \
141 *(volatile type *)ptr = desired; \
142 atomic_unlock(ptr, save); \
143 return true; \
144 } \
145 *(type *)expected = *(volatile type *)ptr; \
146 atomic_unlock(ptr, save); \
147 return false; \
148 }
149
150 ATOMIC_OPTIMIZED_CASES
151
152 #undef ATOMIC_OPTIMIZED_CASE
153
154 #define ATOMIC_OPTIMIZED_CASE(n, type) \
155 type __atomic_exchange_##n(volatile void *dest, type val, __unused int model) { \
156 uint32_t save = atomic_lock(dest); \
157 type tmp = *(volatile type *)dest; \
158 *(volatile type *)dest = val; \
159 atomic_unlock(dest, save); \
160 return tmp; \
161 }
162
163 ATOMIC_OPTIMIZED_CASES
164
165 #undef ATOMIC_OPTIMIZED_CASE
166
167 // Atomic read-modify-write operations for integers of various sizes.
168
169 #define ATOMIC_RMW(n, type, opname, op) \
170 type __atomic_fetch_##opname##_##n(volatile void *ptr, type val, __unused int model) { \
171 uint32_t save = atomic_lock(ptr); \
172 type tmp = *(volatile type *)ptr; \
173 *(volatile type *)ptr = tmp op val; \
174 atomic_unlock(ptr, save); \
175 return tmp; \
176 }
177
178 #define ATOMIC_RMW_NAND(n, type) \
179 type __atomic_fetch_nand_##n(type *ptr, type val, __unused int model) { \
180 uint32_t save = atomic_lock(ptr); \
181 type tmp = *ptr; \
182 *ptr = ~(tmp & val); \
183 atomic_unlock(ptr, save); \
184 return tmp; \
185 }
186
187 #define ATOMIC_OPTIMIZED_CASE(n, type) ATOMIC_RMW(n, type, add, +)
188
189 ATOMIC_OPTIMIZED_CASES
190
191 #undef ATOMIC_OPTIMIZED_CASE
192 #define ATOMIC_OPTIMIZED_CASE(n, type) ATOMIC_RMW(n, type, sub, -)
193
194 ATOMIC_OPTIMIZED_CASES
195
196 #undef ATOMIC_OPTIMIZED_CASE
197 #define ATOMIC_OPTIMIZED_CASE(n, type) ATOMIC_RMW(n, type, and, &)
198
199 ATOMIC_OPTIMIZED_CASES
200
201 #undef ATOMIC_OPTIMIZED_CASE
202 #define ATOMIC_OPTIMIZED_CASE(n, type) ATOMIC_RMW(n, type, or, |)
203
204 ATOMIC_OPTIMIZED_CASES
205
206 #undef ATOMIC_OPTIMIZED_CASE
207 #define ATOMIC_OPTIMIZED_CASE(n, type) ATOMIC_RMW(n, type, xor, ^)
208
209 ATOMIC_OPTIMIZED_CASES
210
211 #undef ATOMIC_OPTIMIZED_CASE
212
213 #if __has_builtin(__c11_atomic_fetch_nand)
214 #define ATOMIC_OPTIMIZED_CASE(n, type) ATOMIC_RMW_NAND(n, type)
215 ATOMIC_OPTIMIZED_CASES
216 #undef ATOMIC_OPTIMIZED_CASE
217 #endif
218
