| // Protocol Buffers - Google's data interchange format |
| // Copyright 2012 Google Inc. All rights reserved. |
| // https://developers.google.com/protocol-buffers/ |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
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| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following disclaimer |
| // in the documentation and/or other materials provided with the |
| // distribution. |
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| // this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| |
| // This module gets enough CPU information to optimize the |
| // atomicops module on x86. |
| |
| #include <cstring> |
| |
| #include <google/protobuf/stubs/atomicops.h> |
| |
| // This file only makes sense with atomicops_internals_x86_gcc.h -- it |
| // depends on structs that are defined in that file. If atomicops.h |
| // doesn't sub-include that file, then we aren't needed, and shouldn't |
| // try to do anything. |
| #ifdef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_X86_GCC_H_ |
| |
| // Inline cpuid instruction. In PIC compilations, %ebx contains the address |
| // of the global offset table. To avoid breaking such executables, this code |
| // must preserve that register's value across cpuid instructions. |
| #if defined(__i386__) |
| #define cpuid(a, b, c, d, inp) \ |
| asm("mov %%ebx, %%edi\n" \ |
| "cpuid\n" \ |
| "xchg %%edi, %%ebx\n" \ |
| : "=a" (a), "=D" (b), "=c" (c), "=d" (d) : "a" (inp)) |
| #elif defined(__x86_64__) |
| #define cpuid(a, b, c, d, inp) \ |
| asm("mov %%rbx, %%rdi\n" \ |
| "cpuid\n" \ |
| "xchg %%rdi, %%rbx\n" \ |
| : "=a" (a), "=D" (b), "=c" (c), "=d" (d) : "a" (inp)) |
| #endif |
| |
| #if defined(cpuid) // initialize the struct only on x86 |
| |
| namespace google { |
| namespace protobuf { |
| namespace internal { |
| |
| // Set the flags so that code will run correctly and conservatively, so even |
| // if we haven't been initialized yet, we're probably single threaded, and our |
| // default values should hopefully be pretty safe. |
| struct AtomicOps_x86CPUFeatureStruct AtomicOps_Internalx86CPUFeatures = { |
| false, // bug can't exist before process spawns multiple threads |
| false, // no SSE2 |
| }; |
| |
| namespace { |
| |
| // Initialize the AtomicOps_Internalx86CPUFeatures struct. |
| void AtomicOps_Internalx86CPUFeaturesInit() { |
| uint32_t eax; |
| uint32_t ebx; |
| uint32_t ecx; |
| uint32_t edx; |
| |
| // Get vendor string (issue CPUID with eax = 0) |
| cpuid(eax, ebx, ecx, edx, 0); |
| char vendor[13]; |
| memcpy(vendor, &ebx, 4); |
| memcpy(vendor + 4, &edx, 4); |
| memcpy(vendor + 8, &ecx, 4); |
| vendor[12] = 0; |
| |
| // get feature flags in ecx/edx, and family/model in eax |
| cpuid(eax, ebx, ecx, edx, 1); |
| |
| int family = (eax >> 8) & 0xf; // family and model fields |
| int model = (eax >> 4) & 0xf; |
| if (family == 0xf) { // use extended family and model fields |
| family += (eax >> 20) & 0xff; |
| model += ((eax >> 16) & 0xf) << 4; |
| } |
| |
| // Opteron Rev E has a bug in which on very rare occasions a locked |
| // instruction doesn't act as a read-acquire barrier if followed by a |
| // non-locked read-modify-write instruction. Rev F has this bug in |
| // pre-release versions, but not in versions released to customers, |
| // so we test only for Rev E, which is family 15, model 32..63 inclusive. |
| if (strcmp(vendor, "AuthenticAMD") == 0 && // AMD |
| family == 15 && |
| 32 <= model && model <= 63) { |
| AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug = true; |
| } else { |
| AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug = false; |
| } |
| |
| // edx bit 26 is SSE2 which we use to tell use whether we can use mfence |
| AtomicOps_Internalx86CPUFeatures.has_sse2 = ((edx >> 26) & 1); |
| } |
| |
| class AtomicOpsx86Initializer { |
| public: |
| AtomicOpsx86Initializer() { |
| AtomicOps_Internalx86CPUFeaturesInit(); |
| } |
| }; |
| |
| // A global to get use initialized on startup via static initialization :/ |
| AtomicOpsx86Initializer g_initer; |
| |
| } // namespace |
| |
| } // namespace internal |
| } // namespace protobuf |
| } // namespace google |
| |
| #endif // __i386__ |
| |
| #endif // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_X86_GCC_H_ |