// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
// Copyright (c) 2004, Google Inc.
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// ----------------------------------------------------------------------
// CycleClock
//    A CycleClock tells you the current time in Cycles.  The "time"
//    is actually time since power-on.  This is like time() but doesn't
//    involve a system call and is much more precise.
//
// NOTE: Not all cpu/platform/kernel combinations guarantee that this
// clock increments at a constant rate or is synchronized across all logical
// cpus in a system.
//
// Also, in some out of order CPU implementations, the CycleClock is not 
// serializing. So if you're trying to count at cycles granularity, your
// data might be inaccurate due to out of order instruction execution.
// ----------------------------------------------------------------------

#ifndef GOOGLE_BASE_CYCLECLOCK_H_
#define GOOGLE_BASE_CYCLECLOCK_H_

#include "base/basictypes.h"   // make sure we get the def for int64
#include "base/arm_instruction_set_select.h"
// base/sysinfo.h is really big and we don't want to include it unless
// it is necessary.
#if defined(__arm__) || defined(__mips__) || defined(__aarch64__)
# include "base/sysinfo.h"
#endif
#if defined(__MACH__) && defined(__APPLE__)
# include <mach/mach_time.h>
#endif
// For MSVC, we want to use '_asm rdtsc' when possible (since it works
// with even ancient MSVC compilers), and when not possible the
// __rdtsc intrinsic, declared in <intrin.h>.  Unfortunately, in some
// environments, <windows.h> and <intrin.h> have conflicting
// declarations of some other intrinsics, breaking compilation.
// Therefore, we simply declare __rdtsc ourselves. See also
// http://connect.microsoft.com/VisualStudio/feedback/details/262047
#if defined(_MSC_VER) && !defined(_M_IX86)
extern "C" uint64 __rdtsc();
#pragma intrinsic(__rdtsc)
#endif
#if defined(ARMV3) || defined(__mips__) || defined(__aarch64__)
#include <sys/time.h>
#endif

// NOTE: only i386 and x86_64 have been well tested.
// PPC, sparc, alpha, and ia64 are based on
//    http://peter.kuscsik.com/wordpress/?p=14
// with modifications by m3b.  See also
//    https://setisvn.ssl.berkeley.edu/svn/lib/fftw-3.0.1/kernel/cycle.h
struct CycleClock {
  // This should return the number of cycles since power-on.  Thread-safe.
  static inline int64 Now() {
#if defined(__MACH__) && defined(__APPLE__)
    // this goes at the top because we need ALL Macs, regardless of
    // architecture, to return the number of "mach time units" that
    // have passed since startup.  See sysinfo.cc where
    // InitializeSystemInfo() sets the supposed cpu clock frequency of
    // macs to the number of mach time units per second, not actual
    // CPU clock frequency (which can change in the face of CPU
    // frequency scaling).  Also note that when the Mac sleeps, this
    // counter pauses; it does not continue counting, nor does it
    // reset to zero.
    return mach_absolute_time();
#elif defined(__i386__)
    int64 ret;
    __asm__ volatile ("rdtsc" : "=A" (ret) );
    return ret;
#elif defined(__x86_64__) || defined(__amd64__)
    uint64 low, high;
    __asm__ volatile ("rdtsc" : "=a" (low), "=d" (high));
    return (high << 32) | low;
#elif defined(__powerpc64__) || defined(__ppc64__)
    uint64 tb;
    __asm__ volatile (\
      "mfspr %0, 268"
      : "=r" (tb));
    return tb;
#elif defined(__powerpc__) || defined(__ppc__)
    // This returns a time-base, which is not always precisely a cycle-count.
    uint32 tbu, tbl, tmp;
    __asm__ volatile (\
      "0:\n"
      "mftbu %0\n"
      "mftbl %1\n"
      "mftbu %2\n"
      "cmpw %0, %2\n"
      "bne- 0b"
      : "=r" (tbu), "=r" (tbl), "=r" (tmp));
    return (((uint64) tbu << 32) | tbl);
#elif defined(__sparc__)
    int64 tick;
    asm(".byte 0x83, 0x41, 0x00, 0x00");
    asm("mov   %%g1, %0" : "=r" (tick));
    return tick;
#elif defined(__ia64__)
    int64 itc;
    asm("mov %0 = ar.itc" : "=r" (itc));
    return itc;
#elif defined(_MSC_VER) && defined(_M_IX86)
    // Older MSVC compilers (like 7.x) don't seem to support the
    // __rdtsc intrinsic properly, so I prefer to use _asm instead
    // when I know it will work.  Otherwise, I'll use __rdtsc and hope
    // the code is being compiled with a non-ancient compiler.
    _asm rdtsc
#elif defined(_MSC_VER)
    return __rdtsc();
#elif defined(ARMV3) || defined(__aarch64__)
#if defined(ARMV7)  // V7 is the earliest arch that has a standard cyclecount
    uint32 pmccntr;
    uint32 pmuseren;
    uint32 pmcntenset;
    // Read the user mode perf monitor counter access permissions.
    asm volatile ("mrc p15, 0, %0, c9, c14, 0" : "=r" (pmuseren));
    if (pmuseren & 1) {  // Allows reading perfmon counters for user mode code.
      asm volatile ("mrc p15, 0, %0, c9, c12, 1" : "=r" (pmcntenset));
      if (pmcntenset & 0x80000000ul) {  // Is it counting?
        asm volatile ("mrc p15, 0, %0, c9, c13, 0" : "=r" (pmccntr));
        // The counter is set up to count every 64th cycle
        return static_cast<int64>(pmccntr) * 64;  // Should optimize to << 6
      }
    }
#endif
    struct timeval tv;
    gettimeofday(&tv, NULL);
    return static_cast<int64>((tv.tv_sec + tv.tv_usec * 0.000001)
                              * CyclesPerSecond());
#elif defined(__mips__)
    // mips apparently only allows rdtsc for superusers, so we fall
    // back to gettimeofday.  It's possible clock_gettime would be better.
    struct timeval tv;
    gettimeofday(&tv, NULL);
    return static_cast<int64>((tv.tv_sec + tv.tv_usec * 0.000001)
                              * CyclesPerSecond());
#else
// The soft failover to a generic implementation is automatic only for ARM.
// For other platforms the developer is expected to make an attempt to create
// a fast implementation and use generic version if nothing better is available.
#error You need to define CycleTimer for your O/S and CPU
#endif
  }
};


#endif  // GOOGLE_BASE_CYCLECLOCK_H_