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      1 // Copyright (c) 2004, Google Inc.
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions are
      6 // met:
      7 //
      8 //     * Redistributions of source code must retain the above copyright
      9 // notice, this list of conditions and the following disclaimer.
     10 //     * Redistributions in binary form must reproduce the above
     11 // copyright notice, this list of conditions and the following disclaimer
     12 // in the documentation and/or other materials provided with the
     13 // distribution.
     14 //     * Neither the name of Google Inc. nor the names of its
     15 // contributors may be used to endorse or promote products derived from
     16 // this software without specific prior written permission.
     17 //
     18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29 
     30 // ----------------------------------------------------------------------
     31 // CycleClock
     32 //    A CycleClock tells you the current time in Cycles.  The "time"
     33 //    is actually time since power-on.  This is like time() but doesn't
     34 //    involve a system call and is much more precise.
     35 //
     36 // NOTE: Not all cpu/platform/kernel combinations guarantee that this
     37 // clock increments at a constant rate or is synchronized across all logical
     38 // cpus in a system.
     39 //
     40 // Also, in some out of order CPU implementations, the CycleClock is not
     41 // serializing. So if you're trying to count at cycles granularity, your
     42 // data might be inaccurate due to out of order instruction execution.
     43 // ----------------------------------------------------------------------
     44 
     45 #ifndef GOOGLE_BASE_CYCLECLOCK_H_
     46 #define GOOGLE_BASE_CYCLECLOCK_H_
     47 
     48 #include "base/basictypes.h"   // make sure we get the def for int64
     49 #include "base/arm_instruction_set_select.h"
     50 // base/sysinfo.h is really big and we don't want to include it unless
     51 // it is necessary.
     52 #if defined(__arm__) || defined(__mips__)
     53 # include "base/sysinfo.h"
     54 #endif
     55 #if defined(__MACH__) && defined(__APPLE__)
     56 # include <mach/mach_time.h>
     57 #endif
     58 // For MSVC, we want to use '_asm rdtsc' when possible (since it works
     59 // with even ancient MSVC compilers), and when not possible the
     60 // __rdtsc intrinsic, declared in <intrin.h>.  Unfortunately, in some
     61 // environments, <windows.h> and <intrin.h> have conflicting
     62 // declarations of some other intrinsics, breaking compilation.
     63 // Therefore, we simply declare __rdtsc ourselves. See also
     64 // http://connect.microsoft.com/VisualStudio/feedback/details/262047
     65 #if defined(_MSC_VER) && !defined(_M_IX86)
     66 extern "C" uint64 __rdtsc();
     67 #pragma intrinsic(__rdtsc)
     68 #endif
     69 #if defined(ARMV3) || defined(__mips__)
     70 #ifdef HAVE_SYS_TIME_H
     71 #include <sys/time.h>
     72 #endif
     73 #endif
     74 
     75 // NOTE: only i386 and x86_64 have been well tested.
     76 // PPC, sparc, alpha, and ia64 are based on
     77 //    http://peter.kuscsik.com/wordpress/?p=14
     78 // with modifications by m3b.  See also
     79 //    https://setisvn.ssl.berkeley.edu/svn/lib/fftw-3.0.1/kernel/cycle.h
     80 struct CycleClock {
     81   // This should return the number of cycles since power-on.  Thread-safe.
     82   static inline int64 Now() {
     83 #if defined(__MACH__) && defined(__APPLE__)
     84     // this goes at the top because we need ALL Macs, regardless of
     85     // architecture, to return the number of "mach time units" that
     86     // have passed since startup.  See sysinfo.cc where
     87     // InitializeSystemInfo() sets the supposed cpu clock frequency of
     88     // macs to the number of mach time units per second, not actual
     89     // CPU clock frequency (which can change in the face of CPU
     90     // frequency scaling).  Also note that when the Mac sleeps, this
     91     // counter pauses; it does not continue counting, nor does it
     92     // reset to zero.
     93     return mach_absolute_time();
     94 #elif defined(__i386__)
     95     int64 ret;
     96     __asm__ volatile ("rdtsc" : "=A" (ret) );
     97     return ret;
     98 #elif defined(__x86_64__) || defined(__amd64__)
     99     uint64 low, high;
    100     __asm__ volatile ("rdtsc" : "=a" (low), "=d" (high));
    101     return (high << 32) | low;
    102 #elif defined(__powerpc__) || defined(__ppc__)
    103     // This returns a time-base, which is not always precisely a cycle-count.
    104     int64 tbl, tbu0, tbu1;
    105     asm("mftbu %0" : "=r" (tbu0));
    106     asm("mftb  %0" : "=r" (tbl));
    107     asm("mftbu %0" : "=r" (tbu1));
    108     tbl &= -static_cast<int64>(tbu0 == tbu1);
    109     // high 32 bits in tbu1; low 32 bits in tbl  (tbu0 is garbage)
    110     return (tbu1 << 32) | tbl;
    111 #elif defined(__sparc__)
    112     int64 tick;
    113     asm(".byte 0x83, 0x41, 0x00, 0x00");
    114     asm("mov   %%g1, %0" : "=r" (tick));
    115     return tick;
    116 #elif defined(__ia64__)
    117     int64 itc;
    118     asm("mov %0 = ar.itc" : "=r" (itc));
    119     return itc;
    120 #elif defined(_MSC_VER) && defined(_M_IX86)
    121     // Older MSVC compilers (like 7.x) don't seem to support the
    122     // __rdtsc intrinsic properly, so I prefer to use _asm instead
    123     // when I know it will work.  Otherwise, I'll use __rdtsc and hope
    124     // the code is being compiled with a non-ancient compiler.
    125     _asm rdtsc
    126 #elif defined(_MSC_VER)
    127     return __rdtsc();
    128 #elif defined(ARMV3)
    129 #if defined(ARMV6)  // V6 is the earliest arch that has a standard cyclecount
    130     uint32 pmccntr;
    131     uint32 pmuseren;
    132     uint32 pmcntenset;
    133     // Read the user mode perf monitor counter access permissions.
    134     asm volatile ("mrc p15, 0, %0, c9, c14, 0" : "=r" (pmuseren));
    135     if (pmuseren & 1) {  // Allows reading perfmon counters for user mode code.
    136       asm volatile ("mrc p15, 0, %0, c9, c12, 1" : "=r" (pmcntenset));
    137       if (pmcntenset & 0x80000000ul) {  // Is it counting?
    138         asm volatile ("mrc p15, 0, %0, c9, c13, 0" : "=r" (pmccntr));
    139         // The counter is set up to count every 64th cycle
    140         return static_cast<int64>(pmccntr) * 64;  // Should optimize to << 6
    141       }
    142     }
    143 #endif
    144     struct timeval tv;
    145     gettimeofday(&tv, NULL);
    146     return static_cast<int64>((tv.tv_sec + tv.tv_usec * 0.000001)
    147                               * CyclesPerSecond());
    148 #elif defined(__mips__)
    149     // mips apparently only allows rdtsc for superusers, so we fall
    150     // back to gettimeofday.  It's possible clock_gettime would be better.
    151     struct timeval tv;
    152     gettimeofday(&tv, NULL);
    153     return static_cast<int64>((tv.tv_sec + tv.tv_usec * 0.000001)
    154                               * CyclesPerSecond());
    155 #else
    156 // The soft failover to a generic implementation is automatic only for ARM.
    157 // For other platforms the developer is expected to make an attempt to create
    158 // a fast implementation and use generic version if nothing better is available.
    159 #error You need to define CycleTimer for your O/S and CPU
    160 #endif
    161   }
    162 };
    163 
    164 
    165 #endif  // GOOGLE_BASE_CYCLECLOCK_H_
    166