3 ms·

I'm not sure how close this is to the retpoline mitigation but ... https://blogs.msdn.microsoft.com/vcblog/2018/01/15/spectre-mitigations-in-msvc/ https://blogs

I'm not sure how close this is to the retpoline mitigation but ... https://blogs.msdn.microsoft.com/vcblog/2018/01/15/spectre-mitigations-in-msvc/ https://blogs.msdn.microsoft.com/vcblog/2018/01/15/spectre-m... Our tests show the performance impact of /Qspectre to be negligible. We have built all of Windows with /Qspectre enabled and did not notice any performance regressions of concern. Performance gains from speculative execution are lost where the mitigation is applied but the mitigation was needed in a relatively small number of instances across the large codebases that we recompiled.

shakna 9y ago
Thanks! I think that and the inner-linked post tell us what we need to know. From Terry's post: > For context, on newer CPUs such as on Skylake and beyond, Intel has refined the instructions used to disable branch speculation to be more specific to indirect branches, reducing the overall performance penalty of the Spectre mitigation. And your link: > /d2guardspecload, that is currently equivalent to /Qspectre. It seems equivalent to reptoline, at least from a high level perspective. So MSVC is probably protected, but only optionally. They're leaving it up to developers to use the /Qspectre flag, it isn't something automatically enabled when you use an /O(x) optimise flag. Edit: I should add that /Qspectre is currently being added to a lot of Windows, but they're assessing where before doing so, because not everywhere should need it.
- cesarb 9y ago
  From what I understood from that link, /Qspectre is for variant 1, while retpoline is for variant 2, so it's not equivalent.