[LLVMdev] PassManager vs. FunctionPassManager

[David Greene]

The opt tool uses two helpers to run passes:
createStandardFunctionPasses and createStandardModulePasses.  How were
the passes to be instantiated by each function chosen?  There are some
FunctionPasses instantiated by createStandardModulePasses which is a
bit counterintuitive.

I see that all passes added by the user on the command line are added
to "Passes" in opt, meaning they're added to the same pass manager
as the passes in createStandardModulePasses.

What's the point of having two pass managers here?  Why not just use
"Passes" for everything?

Thanks for the insight.

                         -Dave