Ask HN: Do any of these GCC/LLVM features exist?

This is a list of 3 things I would love to see in an optimizing C/C++ compiler. I know how to do none of them, but maybe somebody knows an alternative work-around....

1. Useful pragmas for defining optimization regions. 95% of my code can be relatively portable and acceptably performant with -mtune=generic.

Pragmas would simply classify optimization regions which cross compile multiple targets. Then drops in the correct one at runtime.

(I know this is possible to do, but wouldn't a builtin be better?)

2. Pragmas for linker hints. I have noticed -flto just doesn't do great on larger more complicated projects (perhaps it's the partial templates?). But, usually I have a good idea which ones need to go together.

    Like (for a function used in two different tight loops):
       ```
       [[:linker_group="LinearOptimizer"]]
       [[:linker_group="Descent"]]
       void
       Function(...) {}
       ```

3. And this one is a long long shot. Wouldn't it be cool if every major hardware vendor could support some consistent RISC instructions? So that the compiler could have a universal initializer language capable of extracting the relevant target program. Not sure how it works around ELF/DWARF/...