I'm doing a presentation in few months about .Net performance and optimization, I wanted to provide some samples of unnecessary optimization, things that will be done by the compiler anyways.
where can I find some explanation on what optimizations the compiler is actually capable of maybe some before and after code?
check out these links
Also checkout this book on MSIL
1. Microsoft Intermediate Language: Comparison Between C# and VB.NET / Niranjan Kumar
What I think would be even better than examples of "things that will be done by the compiler anyways" would be examples of scenarios where the compiler doesn't perform "optimizations" that the developer assumes will yield a performance improvement but which, in fact, won't.
For example sometimes a developer will assume that caching a value locally will improve performance, when actually the savings of having one less value on the stack outweighs the miniscule cost of a field access that can be inlined.
Or the developer might assume that "force-inlining" a method call (essentially by stripping out the call itself and replacing with copied/pasted code) will be worthwhile, when in reality keeping the method call as-is would result in its getting inlined by the compiler only when it makes sense (when the benefit of inlining outweighs the growth in code size).
This is only a general idea, of course. I don't have concrete code samples that I can point to; but maybe you can scrounge some up if you look for them.
来源：https://stackoverflow.com/questions/3720140/examples-of-clr-compiler-optimizations