What attributes help runtime .Net performance?

Question

I am looking for attributes I can use to ensure the best runtime performance for my .Net application by giving hints to the loader, JIT compiler or ngen.

For example we

Answer 1

Ecma-335 specifies some more CompilationRelaxations for relaxed exception handling (so-called e-relaxed calls) in Annex F "Imprecise faults", but they have not been exposed by Microsoft.

Specifically CompilationRelaxations.RelaxedArrayExceptions and CompilationRelaxations.RelaxedNullReferenceException are mentioned there.

It'd be intersting what happens when you just try some integers in the CompilationRelaxationsAttribute's ctor ;)