[PATCH] Fix profile corruption with -O1 (PR gcov-profile/79259)

[Martin Liška]

Hello.

During investigation of another issue, I accidentally came a profile inconsistency
mentioned in the PR. Problem is that flag_ipa_bit_cp is enabled in use stage of PGO
and not in instrumentation stage. That causes ccp1 to find nonzero bits and that leads
to a CFG changes as a condition can be folded away.

Solution is to enable the same flag in generate phase. However I've got one more question:
In -fprofile-generate we have 2 more functions available in symtab:

_GLOBAL__sub_I_00100_0_c ()
{
  <bb 2> [0.00%]:
  __gcov_init (&*.LPBX0);
  return;

}

_GLOBAL__sub_D_00100_1_c ()
{
  <bb 2> [0.00%]:
  __gcov_exit ();
  return;

}

I'm wondering whether it can potentially influence early inlining decision?

Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.

Ready to be installed?
Martin
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