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1 | /* Atomic operations. ARM/Linux version. |
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2 | Copyright (C) 2002-2022 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library. If not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <stdint.h> |
20 | |
21 | /* If the compiler doesn't provide a primitive, we'll use this macro |
22 | to get assistance from the kernel. */ |
23 | #ifdef __thumb2__ |
24 | # define __arm_assisted_full_barrier() \ |
25 | __asm__ __volatile__ \ |
26 | ("movw\tip, #0x0fa0\n\t" \ |
27 | "movt\tip, #0xffff\n\t" \ |
28 | "blx\tip" \ |
29 | : : : "ip", "lr", "cc", "memory"); |
30 | #else |
31 | # define __arm_assisted_full_barrier() \ |
32 | __asm__ __volatile__ \ |
33 | ("mov\tip, #0xffff0fff\n\t" \ |
34 | "mov\tlr, pc\n\t" \ |
35 | "add\tpc, ip, #(0xffff0fa0 - 0xffff0fff)" \ |
36 | : : : "ip", "lr", "cc", "memory"); |
37 | #endif |
38 | |
39 | /* Atomic compare and exchange. This sequence relies on the kernel to |
40 | provide a compare and exchange operation which is atomic on the |
41 | current architecture, either via cleverness on pre-ARMv6 or via |
42 | ldrex / strex on ARMv6. |
43 | |
44 | It doesn't matter what register is used for a_oldval2, but we must |
45 | specify one to work around GCC PR rtl-optimization/21223. Otherwise |
46 | it may cause a_oldval or a_tmp to be moved to a different register. |
47 | |
48 | We use the union trick rather than simply using __typeof (...) in the |
49 | declarations of A_OLDVAL et al because when NEWVAL or OLDVAL is of the |
50 | form *PTR and PTR has a 'volatile ... *' type, then __typeof (*PTR) has |
51 | a 'volatile ...' type and this triggers -Wvolatile-register-var to |
52 | complain about 'register volatile ... asm ("reg")'. |
53 | |
54 | We use the same union trick in the declaration of A_PTR because when |
55 | MEM is of the from *PTR and PTR has a 'const ... *' type, then __typeof |
56 | (*PTR) has a 'const ...' type and this enables the compiler to substitute |
57 | the variable with its initializer in asm statements, which may cause the |
58 | corresponding operand to appear in a different register. */ |
59 | #ifdef __thumb2__ |
60 | /* Thumb-2 has ldrex/strex. However it does not have barrier instructions, |
61 | so we still need to use the kernel helper. */ |
62 | # define __arm_assisted_compare_and_exchange_val_32_acq(mem, newval, oldval) \ |
63 | ({ union { __typeof (mem) a; uint32_t v; } mem_arg = { .a = (mem) }; \ |
64 | union { __typeof (oldval) a; uint32_t v; } oldval_arg = { .a = (oldval) };\ |
65 | union { __typeof (newval) a; uint32_t v; } newval_arg = { .a = (newval) };\ |
66 | register uint32_t a_oldval asm ("r0"); \ |
67 | register uint32_t a_newval asm ("r1") = newval_arg.v; \ |
68 | register uint32_t a_ptr asm ("r2") = mem_arg.v; \ |
69 | register uint32_t a_tmp asm ("r3"); \ |
70 | register uint32_t a_oldval2 asm ("r4") = oldval_arg.v; \ |
71 | __asm__ __volatile__ \ |
72 | ("0:\tldr\t%[tmp],[%[ptr]]\n\t" \ |
73 | "cmp\t%[tmp], %[old2]\n\t" \ |
74 | "bne\t1f\n\t" \ |
75 | "mov\t%[old], %[old2]\n\t" \ |
76 | "movw\t%[tmp], #0x0fc0\n\t" \ |
77 | "movt\t%[tmp], #0xffff\n\t" \ |
78 | "blx\t%[tmp]\n\t" \ |
79 | "bcc\t0b\n\t" \ |
80 | "mov\t%[tmp], %[old2]\n\t" \ |
81 | "1:" \ |
82 | : [old] "=&r" (a_oldval), [tmp] "=&r" (a_tmp) \ |
83 | : [new] "r" (a_newval), [ptr] "r" (a_ptr), \ |
84 | [old2] "r" (a_oldval2) \ |
85 | : "ip", "lr", "cc", "memory"); \ |
86 | (__typeof (oldval)) a_tmp; }) |
87 | #else |
88 | # define __arm_assisted_compare_and_exchange_val_32_acq(mem, newval, oldval) \ |
89 | ({ union { __typeof (mem) a; uint32_t v; } mem_arg = { .a = (mem) }; \ |
90 | union { __typeof (oldval) a; uint32_t v; } oldval_arg = { .a = (oldval) };\ |
91 | union { __typeof (newval) a; uint32_t v; } newval_arg = { .a = (newval) };\ |
92 | register uint32_t a_oldval asm ("r0"); \ |
93 | register uint32_t a_newval asm ("r1") = newval_arg.v; \ |
94 | register uint32_t a_ptr asm ("r2") = mem_arg.v; \ |
95 | register uint32_t a_tmp asm ("r3"); \ |
96 | register uint32_t a_oldval2 asm ("r4") = oldval_arg.v; \ |
97 | __asm__ __volatile__ \ |
98 | ("0:\tldr\t%[tmp],[%[ptr]]\n\t" \ |
99 | "cmp\t%[tmp], %[old2]\n\t" \ |
100 | "bne\t1f\n\t" \ |
101 | "mov\t%[old], %[old2]\n\t" \ |
102 | "mov\t%[tmp], #0xffff0fff\n\t" \ |
103 | "mov\tlr, pc\n\t" \ |
104 | "add\tpc, %[tmp], #(0xffff0fc0 - 0xffff0fff)\n\t" \ |
105 | "bcc\t0b\n\t" \ |
106 | "mov\t%[tmp], %[old2]\n\t" \ |
107 | "1:" \ |
108 | : [old] "=&r" (a_oldval), [tmp] "=&r" (a_tmp) \ |
109 | : [new] "r" (a_newval), [ptr] "r" (a_ptr), \ |
110 | [old2] "r" (a_oldval2) \ |
111 | : "ip", "lr", "cc", "memory"); \ |
112 | (__typeof (oldval)) a_tmp; }) |
113 | #endif |
114 | |
115 | #include <sysdeps/arm/atomic-machine.h> |
116 |
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