tcmalloc: Use C++11 atomics where appropriate.

third_party/tcmalloc/chromium/src/base/atomicops-internals-x86.cc

-/* Copyright (c) 2007, Google Inc.
- * All rights reserved.
- * 
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- * 
- *     * Redistributions of source code must retain the above copyright
- * 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.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * 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
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * ---
- * This module gets enough CPU information to optimize the
- * atomicops module on x86.
- */
-
-#include "base/atomicops.h"
-#include "base/basictypes.h"
-#include "base/googleinit.h"
-#include "base/logging.h"
-#include <string.h>
-
-// This file only makes sense with atomicops-internals-x86.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 BASE_ATOMICOPS_INTERNALS_X86_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
-
-// Set the flags so that code will run correctly and conservatively
-// until InitGoogle() is called.
-struct AtomicOps_x86CPUFeatureStruct AtomicOps_Internalx86CPUFeatures = {
-  false,          // bug can't exist before process spawns multiple threads
-  false,          // no SSE2
-  false,          // no cmpxchg16b
-};
-
-// Initialize the AtomicOps_Internalx86CPUFeatures struct.
-static void AtomicOps_Internalx86CPUFeaturesInit() {
-  uint32 eax;
-  uint32 ebx;
-  uint32 ecx;
-  uint32 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);
-
-  // ecx bit 13 indicates whether the cmpxchg16b instruction is supported
-  AtomicOps_Internalx86CPUFeatures.has_cmpxchg16b = ((ecx >> 13) & 1);
-}
-
-REGISTER_MODULE_INITIALIZER(atomicops_x86, {
-  AtomicOps_Internalx86CPUFeaturesInit();
-});
-
-#endif
-
-#endif  /* ifdef BASE_ATOMICOPS_INTERNALS_X86_H_ */