We currently use the core_hint_black_box feature from subtle, which uses a particular optimization barrier.
However, the standard library documentation cautions against the use of std::hint::black_box for cryptographic use. This has led subtle to remove it in an upcoming release, at which point the feature will do nothing.
This PR takes the proactive step of removing the feature. There is still an optimization barrier in place, which will become the default after the feature is deprecated.
We currently use the
core_hint_black_boxfeature fromsubtle, which uses a particular optimization barrier.However, the standard library documentation cautions against the use of
std::hint::black_boxfor cryptographic use. This has ledsubtleto remove it in an upcoming release, at which point the feature will do nothing.This PR takes the proactive step of removing the feature. There is still an optimization barrier in place, which will become the default after the feature is deprecated.