# uname -a
Linux dcm 2.6.10-mV01-00-13 #1 Wed Dec 20 01:43:38 CET 2006 ppc GNU/Linux

Source code:
# cat /home/test/clockcycles/clockcycles.cpp
#include <cassert>
#include <iostream>
#include <stdint.h>

uint64_t GetCPU_ClockCyclesSinceStartup(void)
{
#if defined(__i386__) || defined(__x86_64)
  uint32_t uTimerValueHigh;
  uint32_t uTimerValueLow;
  __asm__ __volatile__("rdtsc;"
                       "movl %%edx, %0;"
                       "movl %%eax, %1"
                       : "=r" (uTimerValueHigh),
                         "=r" (uTimerValueLow)
                       :
                       : "%edx", "%eax"
                       );
  return (((uint64_t)(uTimerValueHigh) << 32) | uTimerValueLow);
#elif defined(__PPC__)
  uint32_t uTimeBaseLow;
  uint32_t uTimeBaseHigh;
  uint32_t uCheck;
  __asm__ __volatile__("1:     mftbu  %0;"
                       "       mftb   %1;"
                       "       mftbu  %2;"
                       "       cmpw   %2, %0;"
                       "       bne    1b"
                       : "=r" (uTimeBaseHigh),
                         "=r" (uTimeBaseLow),
                         "=r" (uCheck));
  return (((uint64_t)(uTimeBaseHigh) << 32) | uTimeBaseLow);
#else
  assert(0);
  return 0;
#endif
}

int main(int /*argc*/, char** /*argv*/)
{
  std::cout << "Clock cycles since boot: " << GetCPU_ClockCyclesSinceStartup()
            << std::endl;
  return 0;
}

// Local variables:
// compile-command: "for c in ppc_440-g++ g++; do echo $c ...; $c -Wall -W -g
clockcycles.cpp -o ${c%g++}clockcycles; done"
// End:

Full output:
# vg -v /home/test/clockcycles/ppc_440-clockcycles 
==16359== Memcheck, a memory error detector.
==16359== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.
==16359== Using LibVEX rev 1658, a library for dynamic binary translation.
==16359== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.
==16359== Using valgrind-3.2.1, a dynamic binary instrumentation framework.
==16359== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.
==16359== 
--16359-- Command line
--16359--    /home/test/clockcycles/ppc_440-clockcycles
--16359-- Startup, with flags:
--16359--    --num-callers=32
--16359--    --error-limit=no
--16359--    --suppressions=/app/bin/dcm-suppressions.txt
--16359--    -v
--16359-- Contents of /proc/version:
--16359--   Linux version 2.6.10-mV01-00-13 (build@sabekorlnx03) (gcc version
3.4.3 (MontaVista 3.4.3-25.0.107.0601076 2006-07-21)) #1 Wed Dec 20 01:43:38 CET
2006
--16359-- Arch and hwcaps: PPC32, ppc32-int
--16359-- Valgrind library directory: /mnt/usr/lib/valgrind
--16359-- Reading syms from /lib/ld-2.3.3.so (0x4000000)
--16359-- Reading syms from /home/test/clockcycles/ppc_440-clockcycles (0x10000000)
--16359-- Reading syms from /mnt/usr/lib/valgrind/ppc32-linux/memcheck (0x38000000)
--16359--    object doesn't have a dynamic symbol table
--16359-- Reading suppressions file: /app/bin/dcm-suppressions.txt
--16359-- Reading suppressions file: /mnt/usr/lib/valgrind/default.supp
--16359-- REDIR: 0x4012A20 (strlen) redirected to 0x3802F8C0
(vgPlain_ppc32_linux_REDIR_FOR_strlen)
--16359-- REDIR: 0x4012850 (strcmp) redirected to 0x3802F8E8
(vgPlain_ppc32_linux_REDIR_FOR_strcmp)
--16359-- REDIR: 0x4012778 (index) redirected to 0x3802F95C
(vgPlain_ppc32_linux_REDIR_FOR_strchr)
--16359-- Reading syms from /mnt/usr/lib/valgrind/ppc32-linux/vgpreload_core.so
(0xFFDF000)
--16359-- Reading syms from
/mnt/usr/lib/valgrind/ppc32-linux/vgpreload_memcheck.so (0xFFB9000)
--16359-- REDIR: 0x40137A0 (memcpy) redirected to 0xFFBD6C4 (memcpy)
--16359-- Reading syms from /usr/lib/libstdc++.so.6.0.3 (0xFEB3000)
--16359--    object doesn't have a symbol table
--16359-- Reading syms from /lib/libm-2.3.3.so (0xFDE7000)
--16359--    object doesn't have a symbol table
--16359-- Reading syms from /lib/libgcc_s.so.1 (0xFDBA000)
--16359--    object doesn't have a symbol table
--16359-- Reading syms from /lib/libc-2.3.3.so (0xFC6E000)
--16359--    object doesn't have a symbol table
--16359-- REDIR: 0xFCE2B08 (rindex) redirected to 0xFFBC9E0 (rindex)
--16359-- REDIR: 0xFCE2664 (strlen) redirected to 0xFFBCF58 (strlen)
--16359-- REDIR: 0xFCE28E0 (strncmp) redirected to 0xFFBD2AC (strncmp)
--16359-- REDIR: 0xFCE2040 (strcpy) redirected to 0xFFBD00C (strcpy)
--16359-- REDIR: 0xFCE38A4 (memset) redirected to 0xFFBDD24 (memset)
--16359-- REDIR: 0xFCE33E4 (bcmp) redirected to 0xFFBD908 (bcmp)
dis_proc_ctl(ppc)(mfspr,SPR)(0x10D)
disInstr(ppc): unhandled instruction: 0x7C0D42A6
                 primary 31(0x1F), secondary 678(0x2A6)
==16359== valgrind: Unrecognised instruction at address 0x100008F4.
==16359== Your program just tried to execute an instruction that Valgrind
==16359== did not recognise.  There are two possible reasons for this.
==16359== 1. Your program has a bug and erroneously jumped to a non-code
==16359==    location.  If you are running Memcheck and you just saw a
==16359==    warning about a bad jump, it's probably your program's fault.
==16359== 2. The instruction is legitimate but Valgrind doesn't handle it,
==16359==    i.e. it's Valgrind's fault.  If you think this is the case or
==16359==    you are not sure, please let us know and we'll try to fix it.
==16359== Either way, Valgrind will now raise a SIGILL signal which will
==16359== probably kill your program.
==16359== 
==16359== Process terminating with default action of signal 4 (SIGILL)
==16359==  Illegal opcode at address 0x100008F4
==16359==    at 0x100008F4: GetCPU_ClockCyclesSinceStartup() (clockcycles.cpp:30)
==16359==    by 0x100009CC: main (clockcycles.cpp:40)
Clock cycles since boot: --16359-- REDIR: 0xFCDEB54 (free) redirected to
0xFFBB634 (free)
==16359== 
==16359== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 7 from 3)
--16359-- 
--16359-- supp:    2 Ubuntu-stripped-ld.so
--16359-- supp:    1 glibc-2.3.x-on-SuSE-10.1-(PPC)-1
--16359-- supp:    4 glibc-2.3.x-on-SuSE-10.0-(PPC)-1
==16359== malloc/free: in use at exit: 0 bytes in 0 blocks.
==16359== malloc/free: 0 allocs, 0 frees, 0 bytes allocated.
==16359== 
==16359== All heap blocks were freed -- no leaks are possible.
--16359--  memcheck: sanity checks: 4 cheap, 1 expensive
--16359--  memcheck: auxmaps: 0 auxmap entries (0k, 0M) in use
--16359--  memcheck: auxmaps: 0 searches, 0 comparisons
--16359--  memcheck: SMs: n_issued      = 17 (272k, 0M)
--16359--  memcheck: SMs: n_deissued    = 0 (0k, 0M)
--16359--  memcheck: SMs: max_noaccess  = 65535 (1048560k, 1023M)
--16359--  memcheck: SMs: max_undefined = 0 (0k, 0M)
--16359--  memcheck: SMs: max_defined   = 47 (752k, 0M)
--16359--  memcheck: SMs: max_non_DSM   = 17 (272k, 0M)
--16359--  memcheck: max sec V bit nodes:    0 (0k, 0M)
--16359--  memcheck: set_sec_vbits8 calls: 0 (new: 0, updates: 0)
--16359--  memcheck: max shadow mem size:   576k, 0M
--16359-- translate:            fast SP updates identified: 466 ( 72.1%)
--16359-- translate:   generic_known SP updates identified: 141 ( 21.8%)
--16359-- translate: generic_unknown SP updates identified: 39 (  6.0%)
--16359--     tt/tc: 9,242 tt lookups requiring 9,311 probes
--16359--     tt/tc: 9,242 fast-cache updates, 63 flushes
--16359--  transtab: new        2,078 (65,564 -> 1,023,084; ratio 156:10) [0 scs]
--16359--  transtab: dumped     0 (0 -> ??)
--16359--  transtab: discarded  82 (3,884 -> ??)
--16359-- scheduler: 494,548 jumps (bb entries).
--16359-- scheduler: 4/7,504 major/minor sched events.
--16359--    sanity: 5 cheap, 1 expensive checks.
--16359--    exectx: 30,011 lists, 5 contexts (avg 0 per list)
--16359--    exectx: 7 searches, 2 full compares (285 per 1000)
--16359--    exectx: 0 cmp2, 14 cmp4, 0 cmpAll
/usr/sbin/vg: line 20: 16359 Illegal instruction     GLIBCPP_FORCE_NEW=1
GLIBCXX_FORCE_NEW=1 DISABLE_PLAYOUT=1 $EXE --num-callers=32 --error-limit=no
$SUPPRESS "${@:-/app/bin/$APP}"