[Bug gprofng/29015] New: On Intel Skylake the call tree is incorrect

[ruud.vanderpas at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29015

            Bug ID: 29015
           Summary: On Intel Skylake the call tree is incorrect
           Product: binutils
           Version: 2.39 (HEAD)
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gprofng
          Assignee: vladimir.mezentsev at oracle dot com
          Reporter: ruud.vanderpas at oracle dot com
  Target Milestone: ---

Created attachment 14046
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14046&action=edit
This directory contains everything needed to reproduce the problem.

The call tree output is not correct for this example I ran on an Intel Skylake
based system. The code has been parallelized using Pthreads and we should see
function "start_thread" in the call tree. It is not there though and this looks
like an issue related to stack unwind.

This is the output I get:

Functions Call Tree. Metric: Attributed Total CPU Time

Attr.      Name
Total
CPU sec.
4.827      +-<Total>
4.712        +-collector_root
4.712        |  +-driver_mxv
4.712        |    +-mxv_core
0.116        +-__libc_start_main
0.116          +-main
0.106            +-init_data
0.050            |  +-drand48
0.039            |    +-erand48_r
0.014            |      +-__drand48_iterate
0.010            +-allocate_data
0.010              +-malloc
0.010                +-_int_malloc
0.003                  +-sysmalloc
0.002                    +-__default_morecore
0.002                      +-sbrk
0.002                        +-brk

I used gcc 10 and did not enable any optimizations, but I also see this problem
if I use -O for example.

On an older Intel Haswell based system, I do see start_thread in the call tree.

The attachment has everything needed to reproduce the problem. The code is in
directory "src" and can be built with "make". On purpose I left my objects and
the binary in, as well as the experiment directory. There is a run.sh script
that was used to show the problem. Sample output of this script is in run.res.

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