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Why does JIT have to do everything?

DrGUI · 2004-06-08T09:27:06

Why, why, why? Firstly, I would like to know where some of you find out about all the optimization the JIT makes. Why does the JIT have to do things like dead code removal, loop invariant hoisting and constant copy propagation? The compiler should do this from the IL (though if you''re a neat coder, you should not really have declared unused variables in the scope of the loop). What are the patterns for the JIT to recognize vector and matrix ops so 3DNow and SSE/SSE2 can be used? There should be a force inline keyword so that IL is actually inlined rather than JIT doing all the work. I could understand loops with uninitialized variables being slower than with the variables being declared outside the loop because of the automatic setting of 0 to them, however initialized variables are still set to 0 before initialization (though I hear this is likely to change). I am soon going to gradually move to C# from VB .NET BUT... DirectCast in VB unboxes value types 10x faster than CType. C#''s cast (casttype) is most likely identical to CType in IL. Is there a way in C# to unbox variables 10x faster? I could not find anything. Any help on this?