Suppress JIT optimization on module load (managed only)

9
votes

If I run a release build in VS but WITH debugger attached. So I can set breakpoints and investigate the optimized code disassembly. Usually, in order to see all optimizations I need to run WITHOUT a debugger attached and detach to the running proccess.

Does unselecting the "Suppress JIT optimization on module load (managed only)" switch in Visual Studio is sufficient to bring the same result? By 'same result' I mean: same (optimized) machine instructions as by starting without debugger attached?

I heard the JIT compiler would only utilize ALL optimization options, if the assembly was a release build and NO debugger was attached. Now I wonder if this switch could make my debugging / inspecting live easier?

1
c#.netvisual-studiojitcompiler-optimization
Because it would not make any rule clear. – JGrand
I did try and it seems to do the same. but I dont know if this is defined behaviour though. – Paul Wendler

1 Answers

4
votes

There is small differences in IL between DEBUG and RELEASE builds, so you do want to use RELEASE build in this case (i.e. all Debug.XXX calls are compiled out in Release case).

Un-checking "Suppress JIT optimization on module load (managed only)" should allow JIT do do optimizations as if no debugger attached. I'm not aware of any differences between these 2 cases.