The fake symbols we create for inlined frames will represent different
functions but can use the symbol start address. This leads to issues
when different inline branches all lead to the same function.

Before:
~~~~~
$ perf report -s sym -i perf.inlining.data --inline --stdio -g function
...
             --38.86%--_start
                       __libc_start_main
                       main
                       |
                        --37.57%--std::norm<double> (inlined)
                                  std::_Norm_helper<true>::_S_do_it<double> (inlined)
                                  |
                                   --36.36%--std::abs<double> (inlined)
                                             std::__complex_abs (inlined)
                                             |
                                              --12.24%--std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul>::operator() (inlined)
                                                        std::__detail::__mod<unsigned long, 2147483647ul, 16807ul, 0ul> (inlined)
                                                        std::__detail::_Mod<unsigned long, 2147483647ul, 16807ul, 0ul, true, true>::__calc (inlined)
~~~~~

Note that this backtrace representation is completely bogus.
Complex abs does not call the linear congruential engine! It
is just a side-effect of a longer inlined stack being appended
to a shorter, different inlined stack, both of which originate
in the same function (main).

This patch fixes the issue:

~~~~~
$ perf report -s sym -i perf.inlining.data --inline --stdio -g function
...
             --38.86%--_start
                       __libc_start_main
                       main
                       |
                       |--35.59%--std::uniform_real_distribution<double>::operator()<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > (inlined)
                       |          std::uniform_real_distribution<double>::operator()<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > (inlined)
                       |          |
                       |           --34.37%--std::__detail::_Adaptor<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul>, double>::operator() (inlined)
                       |                     std::generate_canonical<double, 53ul, std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > (inlined)
                       |                     |
                       |                      --12.24%--std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul>::operator() (inlined)
                       |                                std::__detail::__mod<unsigned long, 2147483647ul, 16807ul, 0ul> (inlined)
                       |                                std::__detail::_Mod<unsigned long, 2147483647ul, 16807ul, 0ul, true, true>::__calc (inlined)
                       |
                        --1.99%--std::norm<double> (inlined)
                                  std::_Norm_helper<true>::_S_do_it<double> (inlined)
                                  std::abs<double> (inlined)
                                  std::__complex_abs (inlined)
~~~~~
Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: Yao Jin <yao.jin@linux.intel.com>
Link: http://lkml.kernel.org/r/20171009203310.17362-10-milian.wolff@kdab.com
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
[ Fix up conflict with c1fbc0cf ("perf callchain: Compare dsos (as well) for CCKEY_FUNCTION"), remove unneeded hunk ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>