Just a quick note to make you aware that the version of Visual Studio 2017 that includes support for the /Qspectre switch, and the “__declspec(spectre(nomitigation))” decoration that can be used to exempt performance critical code segments from fence insertion, is now available for download.
The version is VS 2017 V15.5.5… Check it out here: https://www.visualstudio.com/en-us/news/releasenotes/vs2017-relnotes