Jiri points out that we don't need any time checking and time string
parsing if the --time option is not set. That makes sense.

This patch refactors the time range parsing code, move the duplicated
code from perf report and perf script to time_utils and check if --time
option is set before parsing the time string. This patch is no logic
change expected. So the usage of --time is same as before.

For example:

Select the first and second 10% time slices:
  perf report --time 10%/1,10%/2
  perf script --time 10%/1,10%/2

Select the slices from 0% to 10% and from 30% to 40%:
  perf report --time 0%-10%,30%-40%
  perf script --time 0%-10%,30%-40%

Select the time slices from timestamp 3971 to 3973
  perf report --time 3971,3973
  perf script --time 3971,3973

Committer testing:

Using the above examples, check before and after to see if it remains
the same:

  $ perf record -F 10000 -- find . -name "*.[ch]" -exec cat {} + > /dev/null
  [ perf record: Woken up 3 times to write data ]
  [ perf record: Captured and wrote 1.626 MB perf.data (42392 samples) ]
  $
  $ perf report --time 10%/1,10%/2 > /tmp/report.before.1
  $ perf script --time 10%/1,10%/2 > /tmp/script.before.1
  $ perf report --time 0%-10%,30%-40% > /tmp/report.before.2
  $ perf script --time 0%-10%,30%-40% > /tmp/script.before.2
  $ perf report --time 180457.375844,180457.377717 > /tmp/report.before.3
  $ perf script --time 180457.375844,180457.377717 > /tmp/script.before.3

For example, the 3rd test produces this slice:

  $ cat /tmp/script.before.3
        cat  3147 180457.375844:   2143 cycles:uppp:      7f79362590d9 cfree@GLIBC_2.2.5+0x9 (/usr/lib64/libc-2.28.so)
        cat  3147 180457.375986:   2245 cycles:uppp:      558b70f3d86e [unknown] (/usr/bin/cat)
        cat  3147 180457.376012:   2164 cycles:uppp:      7f7936257430 _int_malloc+0x8c0 (/usr/lib64/libc-2.28.so)
        cat  3147 180457.376140:   2921 cycles:uppp:      558b70f3a554 [unknown] (/usr/bin/cat)
        cat  3147 180457.376296:   2844 cycles:uppp:      7f7936258abe malloc+0x4e (/usr/lib64/libc-2.28.so)
        cat  3147 180457.376431:   2717 cycles:uppp:      558b70f3b0ca [unknown] (/usr/bin/cat)
        cat  3147 180457.376667:   2630 cycles:uppp:      558b70f3d86e [unknown] (/usr/bin/cat)
        cat  3147 180457.376795:   2442 cycles:uppp:      7f79362bff55 read+0x15 (/usr/lib64/libc-2.28.so)
        cat  3147 180457.376927:   2376 cycles:uppp:  ffffffff9aa00163 [unknown] ([unknown])
        cat  3147 180457.376954:   2307 cycles:uppp:      7f7936257438 _int_malloc+0x8c8 (/usr/lib64/libc-2.28.so)
        cat  3147 180457.377116:   3091 cycles:uppp:      7f7936258a70 malloc+0x0 (/usr/lib64/libc-2.28.so)
        cat  3147 180457.377362:   2945 cycles:uppp:      558b70f3a3b0 [unknown] (/usr/bin/cat)
        cat  3147 180457.377517:   2727 cycles:uppp:      558b70f3a9aa [unknown] (/usr/bin/cat)
  $

Install 'coreutils-debuginfo' to see cat's guts (symbols), but then, the
above chunk translates into this 'perf report' output:

  $ cat /tmp/report.before.3
  # To display the perf.data header info, please use --header/--header-only options.
  #
  #
  # Total Lost Samples: 0
  #
  # Samples: 13  of event 'cycles:uppp' (time slices: 180457.375844,180457.377717)
  # Event count (approx.): 33552
  #
  # Overhead  Command  Shared Object     Symbol
  # ........  .......  ................  ......................
  #
      17.69%  cat      libc-2.28.so      [.] malloc
      14.53%  cat      cat               [.] 0x000000000000586e
      13.33%  cat      libc-2.28.so      [.] _int_malloc
       8.78%  cat      cat               [.] 0x00000000000023b0
       8.71%  cat      cat               [.] 0x0000000000002554
       8.13%  cat      cat               [.] 0x00000000000029aa
       8.10%  cat      cat               [.] 0x00000000000030ca
       7.28%  cat      libc-2.28.so      [.] read
       7.08%  cat      [unknown]         [k] 0xffffffff9aa00163
       6.39%  cat      libc-2.28.so      [.] cfree@GLIBC_2.2.5

  #
  # (Tip: Order by the overhead of source file name and line number: perf report -s srcline)
  #
  $

Now lets see after applying this patch, nothing should change:

  $ perf report --time 10%/1,10%/2 > /tmp/report.after.1
  $ perf script --time 10%/1,10%/2 > /tmp/script.after.1
  $ perf report --time 0%-10%,30%-40% > /tmp/report.after.2
  $ perf script --time 0%-10%,30%-40% > /tmp/script.after.2
  $ perf report --time 180457.375844,180457.377717 > /tmp/report.after.3
  $ perf script --time 180457.375844,180457.377717 > /tmp/script.after.3
  $ diff -u /tmp/report.before.1 /tmp/report.after.1
  $ diff -u /tmp/script.before.1 /tmp/script.after.1
  $ diff -u /tmp/report.before.2 /tmp/report.after.2
  --- /tmp/report.before.2	2019-03-01 11:01:53.526094883 -0300
  +++ /tmp/report.after.2	2019-03-01 11:09:18.231770467 -0300
  @@ -352,5 +352,5 @@

   #
  -# (Tip: Generate a script for your data: perf script -g <lang>)
  +# (Tip: Treat branches as callchains: perf report --branch-history)
   #
  $ diff -u /tmp/script.before.2 /tmp/script.after.2
  $ diff -u /tmp/report.before.3 /tmp/report.after.3
  --- /tmp/report.before.3	2019-03-01 11:03:08.890045588 -0300
  +++ /tmp/report.after.3	2019-03-01 11:09:40.660224002 -0300
  @@ -22,5 +22,5 @@

   #
  -# (Tip: Order by the overhead of source file name and line number: perf report -s srcline)
  +# (Tip: List events using substring match: perf list <keyword>)
   #
  $ diff -u /tmp/script.before.3 /tmp/script.after.3
  $

Cool, just the 'perf report' tips changed, QED.
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1551435186-6008-1-git-send-email-yao.jin@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>