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1 : // Protocol Buffers - Google's data interchange format
2 : // Copyright 2012 Google Inc. All rights reserved.
3 : // https://developers.google.com/protocol-buffers/
4 : //
5 : // Redistribution and use in source and binary forms, with or without
6 : // modification, are permitted provided that the following conditions are
7 : // met:
8 : //
9 : // * Redistributions of source code must retain the above copyright
10 : // notice, this list of conditions and the following disclaimer.
11 : // * Redistributions in binary form must reproduce the above
12 : // copyright notice, this list of conditions and the following disclaimer
13 : // in the documentation and/or other materials provided with the
14 : // distribution.
15 : // * Neither the name of Google Inc. nor the names of its
16 : // contributors may be used to endorse or promote products derived from
17 : // this software without specific prior written permission.
18 : //
19 : // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 : // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 : // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 : // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 : // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 : // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 : // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 : // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 : // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 : // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29 : // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 :
31 : // This module gets enough CPU information to optimize the
32 : // atomicops module on x86.
33 :
34 : #include <cstring>
35 :
36 : #include <google/protobuf/stubs/atomicops.h>
37 :
38 : // This file only makes sense with atomicops_internals_x86_gcc.h -- it
39 : // depends on structs that are defined in that file. If atomicops.h
40 : // doesn't sub-include that file, then we aren't needed, and shouldn't
41 : // try to do anything.
42 : #ifdef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_X86_GCC_H_
43 :
44 : // Inline cpuid instruction. In PIC compilations, %ebx contains the address
45 : // of the global offset table. To avoid breaking such executables, this code
46 : // must preserve that register's value across cpuid instructions.
47 : #if defined(__i386__)
48 : #define cpuid(a, b, c, d, inp) \
49 : asm("mov %%ebx, %%edi\n" \
50 : "cpuid\n" \
51 : "xchg %%edi, %%ebx\n" \
52 : : "=a" (a), "=D" (b), "=c" (c), "=d" (d) : "a" (inp))
53 : #elif defined(__x86_64__)
54 : #define cpuid(a, b, c, d, inp) \
55 : asm("mov %%rbx, %%rdi\n" \
56 : "cpuid\n" \
57 : "xchg %%rdi, %%rbx\n" \
58 : : "=a" (a), "=D" (b), "=c" (c), "=d" (d) : "a" (inp))
59 : #endif
60 :
61 : #if defined(cpuid) // initialize the struct only on x86
62 :
63 : namespace google {
64 : namespace protobuf {
65 : namespace internal {
66 :
67 : // Set the flags so that code will run correctly and conservatively, so even
68 : // if we haven't been initialized yet, we're probably single threaded, and our
69 : // default values should hopefully be pretty safe.
70 : struct AtomicOps_x86CPUFeatureStruct AtomicOps_Internalx86CPUFeatures = {
71 : false, // bug can't exist before process spawns multiple threads
72 : false, // no SSE2
73 : };
74 :
75 : namespace {
76 :
77 : // Initialize the AtomicOps_Internalx86CPUFeatures struct.
78 3 : void AtomicOps_Internalx86CPUFeaturesInit() {
79 : uint32_t eax;
80 : uint32_t ebx;
81 : uint32_t ecx;
82 : uint32_t edx;
83 :
84 : // Get vendor string (issue CPUID with eax = 0)
85 3 : cpuid(eax, ebx, ecx, edx, 0);
86 : char vendor[13];
87 3 : memcpy(vendor, &ebx, 4);
88 3 : memcpy(vendor + 4, &edx, 4);
89 3 : memcpy(vendor + 8, &ecx, 4);
90 3 : vendor[12] = 0;
91 :
92 : // get feature flags in ecx/edx, and family/model in eax
93 3 : cpuid(eax, ebx, ecx, edx, 1);
94 :
95 3 : int family = (eax >> 8) & 0xf; // family and model fields
96 3 : int model = (eax >> 4) & 0xf;
97 3 : if (family == 0xf) { // use extended family and model fields
98 0 : family += (eax >> 20) & 0xff;
99 0 : model += ((eax >> 16) & 0xf) << 4;
100 : }
101 :
102 : // Opteron Rev E has a bug in which on very rare occasions a locked
103 : // instruction doesn't act as a read-acquire barrier if followed by a
104 : // non-locked read-modify-write instruction. Rev F has this bug in
105 : // pre-release versions, but not in versions released to customers,
106 : // so we test only for Rev E, which is family 15, model 32..63 inclusive.
107 3 : if (strcmp(vendor, "AuthenticAMD") == 0 && // AMD
108 0 : family == 15 &&
109 0 : 32 <= model && model <= 63) {
110 0 : AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug = true;
111 : } else {
112 3 : AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug = false;
113 : }
114 :
115 : // edx bit 26 is SSE2 which we use to tell use whether we can use mfence
116 3 : AtomicOps_Internalx86CPUFeatures.has_sse2 = ((edx >> 26) & 1);
117 3 : }
118 :
119 : class AtomicOpsx86Initializer {
120 : public:
121 3 : AtomicOpsx86Initializer() {
122 3 : AtomicOps_Internalx86CPUFeaturesInit();
123 3 : }
124 : };
125 :
126 : // A global to get use initialized on startup via static initialization :/
127 3 : AtomicOpsx86Initializer g_initer;
128 :
129 : } // namespace
130 :
131 : } // namespace internal
132 : } // namespace protobuf
133 : } // namespace google
134 :
135 : #endif // __i386__
136 :
137 : #endif // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_X86_GCC_H_
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