When MemoryDependenceAnalysis hits a CFG with many transparent blocks, the algorithm easily degrades into quadratic memory and time complexity. The easiest example is a long chain of BBs that don't otherwise use a location. The patch introduces a limit similar to the existing instructions-per-block limit, counting the total number of blocks checked. If the limit it reached, entries are considered unknown.
I'm not entirely sure how to best test this. The test cases for the original bug are huge, when they should trigger on a moderately large machine.