Add OwnershipLiveness.swift. Core OSSA APIs.

This is what you need to correctly analyze OSSA.

- computeLinearLiveness

- computeInteriorLiveness

- InteriorUseVisitor

- OwnershipUseVisitor

- LivenessBoundary

Along with BorrowUtils.swift, all of our OSSA transformations are
built on top of these fundamentals. With these APIs, we can build
anything OSSA-related in SwiftCompilerSources. These utilities are
immediately needed for borrowed arguments and lifetime dependence. In
the near future, we can also use them to complete OSSA lifetimes and
*correctly* fixup OSSA after transformation without introducing lots
of copies and creating lots of incorrect corner cases.

Author: atrick

SwiftCompilerSources/Sources/Optimizer/Utilities/CMakeLists.txt

@@ -11,8 +11,9 @@ swift_compiler_sources(Optimizer
   DiagnosticEngine.swift
   Devirtualization.swift
   EscapeUtils.swift
-  OptUtils.swift
   ForwardingUtils.swift
+  OptUtils.swift
+  OwnershipLiveness.swift
   SSAUpdater.swift
   StaticInitCloner.swift
   Test.swift