It will make the code slower.

Writing maintainable assembly is at odds with writing fast assembly in most circumstances.

A key optimization that's hard to pull off is inlining.

An optimizing compiler can see that a method is small enough that it can be pulled into the caller, it can then further eliminate from that smaller method branches that can't be executed due to the nature of the caller (Imagine calling a function with a `bool` parameter and you send in `true` at the call site).

To make the code faster in hand written assembly, you have to do the inlining, but that makes writing more structured code a lot harder. You are duplicating logic paths in the name of performance.

Not to mention the fact that the compiler gets updated and knows about more instructions and architectures then you do or then you could have. Hard to write the FMA instruction if it didn't exist when you were writing the assembly in the first place.