After fixes were introduced for several variants of the Spectre speculative execution exploit, performance took a nose dive. Microsoft and many other industry giants have been working to patch security flaws for over a year now, but most fixes have degraded performance. Borrowing ideas from Google, Microsoft has now pushed out “retpoline for Windows” to improve CPU performance.
Retpoline is a portmanteau of return and trampoline. Instead of guessing where a program will jump to next during its execution, an indirect method of determining where to go is implemented.