As the latest on the Spectre/Meltdown front for the Linux kernel, the in-development Linux 5.1 kernel is bringing an optimization for Retpolines “return trampolines” so GCC will generate more efficient code on x86/x86_64 in its mitigations against Spectre Variant Two…

Source: Phoronix – Linux 5.1 Getting A Minor Spectre V2 Retpolines Optimization For Select Instances