LLVM? More likely LoLVM

LLVM has some ENTERPRISE QUALITY.

It has function createMCSubtargetInfo in Target class that creates subtarget for processor and its features. Unless you pass "help" string to it instead of CPU model.

In this case this function prints everything to stderr and calls exit(1), shutting down your whole application.

You write GUI program that has no stderr? Well, sucks to be you.
You can't get list of processors or features otherwise. Only by passing "help" and quiting application.
Thanks goodness LLVM has a nice license.

Formally, assuming the axiom of choice, the cardinality of a set X is the least ordinal α such that there is a bijection between X and α. This definition is known as the von Neumann cardinal assignment. If the axiom of choice is not assumed we need to do something different. The oldest definition of the cardinality of a set X (implicit in Cantor and explicit in Frege and Principia Mathematica) is as the class [X] of all sets that are equinumerous with X. This does not work in ZFC or other related systems of axiomatic set theory because if X is non-empty, this collection is too large to be a set. In fact, for X ≠ ∅ there is an injection from the universe into [X] by mapping a set m to {m} × X and so by limitation of size, [X] is a proper class. The definition does work however in type theory and in New Foundations and related systems. However, if we restrict from this class to those equinumerous with X that have the least rank, then it will work (this is a trick due to Dana Scott: it works because the collection of objects with any given rank is a set).