https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61776
--- Comment #7 from davidxl <xinliangli at gmail dot com> ---
(In reply to wmi from comment #6)
> (In reply to davidxl from comment #5)
> > (In reply to wmi from comment #4)
> > > Can we move the pure/const resetting loop to an earlier place: inside
> > > branch_prob , after instrument_edges and before gsi_commit_edge_inserts
> > > (where stmt_ends_bb_p is checked), so that gsi_commit_edge_inserts()
> > > which
> > > changes cfg could take reset const/pure flags into consideration?
> >
> > Sounds plausible. Have you tried it?
> >
> > David
>
> I just tried but found it was not very easy.
>
> FOR_EACH_DEFINED_FUNCTION (node) {
> execute_fixup_cfg() and cleanup_tree_cfg()
> branch_prob()
> }
>
> For the above loop, branch_prob is called one by one for each defined func.
> Because a func could possibly call any other funcs on the cgraph, we need to
> reset the const/pure flags for every defined func before any branch_prob()
> is called, so we cannot put the const/pure reset code inside branch_prob().
>
As you noted below, resetting the flag before branch_prob will lead to cfg
mismatch between instr and profile-use build.
David
> We also cannot move the const/pure reset loop before the branch_prob() loop,
> because execute_fixup_cfg will use const/pure flags to generate different
> cfg. If we put the const/pure reset code before the branch_prob() loop, the
> const/pure reset code should only be executed in intrumentation phase, not
> in annotation phase, so that we may get different cfg between intrumentation
> and annotation.
>
> Wei.
