diff --git a/src/base/atomicops-internals-x86.cc b/src/base/atomicops-internals-x86.cc
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+++ b/src/base/atomicops-internals-x86.cc
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+// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
+/* 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,          // 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;
+  }
+
+  // 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_ */