Add DfgUserMap as a handle around the one pointer worth of algorithm
specific 'user' storage in each DfgVertex. This reduces verbosity,
improves type safety and correctness. Also enables us to remove one
pointer from DfgVertex to reduce memory use. No functional change.
Large scale refactoring to simplify some of the more obtuse internals of
DFG. Remove multiple redundant internal APIs, simplify representation of
variables, fix potential unsoundness in circular decomposition. No
functional change intended.
Both V3DfgBreakCycles.cpp and V3DfgDecomposition.cpp used to contain an
implementation of the same algorithm to color strongly connected
components. Now there is only one, and it lives in V3DfgColorSCCs.cpp.
Geza Lore