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> I've always wondered if any CPUs have tried to reduce the branch penalty by speculatively executing both ways at once in parallel They already do it (edit: t
by anileated 1y ago
> I've always wondered if any CPUs have tried to reduce the branch penalty by speculatively executing both ways at once in parallel
They already do it (edit: they don’t). It is difficult to get security right, however (see https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)#Mechanism https://en.wikipedia.org/wiki/Spectre_(security_vulnerabilit...).
- School-Cotton 1y agoThat is not true, and several people have already make the same mistake in this thread. What is done now is speculatively executing one path, not two or more paths in parallel.
- anileated 1y agoTrue, it was incorrect for me to say they already do parallel execution. However, when parallel execution is a special case of speculative execution, the security concern I meant to highlight still applies, doesn’t it?