[Bug tree-optimization/118442] New: -fprofile-generate wrongly adds instrumentation after musttail call

[kenjin4096 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118442

            Bug ID: 118442
           Summary: -fprofile-generate wrongly adds instrumentation after
                    musttail call
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kenjin4096 at gmail dot com
  Target Milestone: ---

Please see:

https://godbolt.org/z/5sfcxqhdb

Removing `-fprofile-generate` causes GCC 15 to compile successfully. With
`-fprofile-generate` compilation fails.


If my understanding is correct (and thanks to Andrew), instrumentation is being
added after the tail call, which triggers the tail call compilation error
message.

  <bb 6> [local count: 1073741824]:
  # DEBUG BEGIN_STMT
  buffer_2(D)->test[0] = 4;
  # DEBUG BEGIN_STMT
  resolveToBufferSlow (buffer_2(D)); [must tail call]
  PROF_edge_counter_7 = __gcov0._Z15resolveToBufferP4Span[1];
  PROF_edge_counter_8 = PROF_edge_counter_7 + 1;
  __gcov0._Z15resolveToBufferP4Span[1] = PROF_edge_counter_8;


Thank you.