intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 59 insertions, 0 deletions

diff --git a/contrib/libs/crcutil/rdtsc.h b/contrib/libs/crcutil/rdtsc.h
new file mode 100644
index 00000000000..57aea1f1fbb
--- /dev/null
+++ b/contrib/libs/crcutil/rdtsc.h
@@ -0,0 +1,59 @@
+// Copyright 2010 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Reads CPU cycle counter on AMD64 and I386 (for performance measurements).
+// Thanks to __rdtsc() intrinsic, it's easy with Microsoft and Intel
+// compilers, but real pain with GCC.
+
+#ifndef CRCUTIL_RDTSC_H_
+#define CRCUTIL_RDTSC_H_
+
+#include "platform.h"
+
+namespace crcutil {
+
+struct Rdtsc {
+  static inline uint64 Get() {
+#if defined(_MSC_VER) && (HAVE_AMD64 || HAVE_I386)
+    return __rdtsc();
+#elif defined(__GNUC__) && HAVE_AMD64
+    int64 result;
+    __asm__ volatile(
+        "rdtsc\n"
+        : "=a" (result));
+    return result;
+#elif defined(__GNUC__) && HAVE_I386
+    // If "low" and "high" are defined as "uint64" to
+    // avoid explicit cast to uint64, GCC 4.5.0 in "-m32" mode
+    // fails with "impossible register constraint" error
+    // (no, it is not because one cannot use 64-bit value as argument
+    // for 32-bit register, but because its register allocator
+    // could not resolve a conflict under high register pressure).
+    uint32 low;
+    uint32 high;
+    __asm__ volatile(
+        "rdtsc\n"
+        : "=a" (low), "=d" (high));
+    return ((static_cast<uint64>(high) << 32) | low);
+#else
+    // It is hard to find low overhead timer with
+    // sub-millisecond resolution and granularity.
+    return 0;
+#endif
+  }
+};
+
+}  // namespace crcutil
+
+#endif  // CRCUTIL_RDTSC_H_