They were not necessary, as the CPU would run the both sides of the branch in parallel and scrap the irrelevant side when it was known to be false.
Essentially making a hint pointless, as it was not utilized at all.
Now the execution of both sides of a branch is basis for the 'Specter' side-channel attack. Access restricted data in the false branch, data access still happen even though it was restricted.
That is essentially impossible to prevent and disabling it killed a lot of cpu performance, branch hints might be the next best thing.
Now the execution of both sides of a branch is basis for the 'Specter' side-channel attack. Access restricted data in the false branch, data access still happen even though it was restricted.
That is essentially impossible to prevent and disabling it killed a lot of cpu performance, branch hints might be the next best thing.