[clang][FlowSensitive] Do a quick check and bail early for massive CFGs - #186808
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Bail out early if the visiting each reachable basic block once would have exceeded the MaxBlockVisits limit. If that is the case, then actually visiting and doing the dataflow analysis would hit the limit, but we would have wasted a lot of time.
Another possibility is that we run out of memory (OOM) and the process crashes. We've seen example of CFGs with # of blocks that are 2-8x the visit limit. Those examples also have lots of
Locs, which we track in MapVectors for each BB. Since the maps do not share memory across BBs, this leads to non-linear memory usage and OOMing before hitting the max visit limit. With this, we can avoid OOMing, and at least get some results for the other CFGs in the TU, instead of losing all results from the process crashing.