https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112657
--- Comment #8 from Jan Hubicka <hubicka at gcc dot gnu.org> --- The negative return value branch predictor is set to have 98% hitrate (measured on SPEC2k17 some time ago). There is --param predictable-branch-outcome that is also set to 2% so indeed we consider the branch as well predictable by this heuristics. Reducing --param should make cmov to happen. With profile_probability data type we could try something smarter on guessing if given branch is predictable (such as ignoring guessed values and let predictor to optionally mark branches as (un)predictable). But it is not quite clear to me what desired behavior would be... Guessing predictability of data branches is generally quite hard problem. Predictablity of loop branches is easier, but we hardly apply BRANCH_COST on branch closing loop since those are not if-conversion candidates.
