[IRSim][IROutliner] Adding a cost model, and debug option to turn the model off.

[AndrewLitteken]

Summary

This adds a cost model that takes into account the total number of machine instructions to be removed from each region, the number of instructions added by adding a new function with a set of instructions, and the instructions added by handling arguments.

Tests not adding flags:

• llvm/test/Transforms/IROutliner/outlining-cost-model.ll

[jroelofs]

llvm/lib/Transforms/IPO/IROutliner.cpp

1588

What's the benefit from having this member variable as opposed to just reading the option directly where needed?

[AndrewLitteken]

llvm/lib/Transforms/IPO/IROutliner.cpp

1588

It seems like something that might need to be referenced in either the interface file at some point, or somewhere that is not the main file. Since the command line option is static, it can't be accessed if it's not in the class.

[jroelofs]

LGTM

llvm/lib/Transforms/IPO/IROutliner.cpp

1588

sounds reasonable then.

[AndrewLitteken]

Fixing an extra addition that fell out of refactoring causing overestimates in the number of instructions outlined.