GCC and LLVM appear to have agreed on x86_64 levels of instruction set extension bundles. The levels are defined in x86-64-ABI/low-level-sys-info.tex · master · x86 psABIs / x86-64 psABI · GitLab .
What's the current thinking on making rustc recognize these and distributing pre-built standard library as Linux and Windows targets? (That is,
x86_64_v2-unknown-linux-gnu and so on.)
(On Mac, Rust currently aligns to the features of the oldest CPU capable of running Lion. It would probably make sense to provide another target that covers the CPU with the fewest extensions that a newer still-supported macOS release runs on.)