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It's reasonably common. At one time I had mostly convinced myself that fixing PRE was the way to go as many of the complex threading cases would be much simpler if PRE was more effective at removing partial redundancies.the redundancy elimination performed by DOM can be better handled elsewhere. The interesting question is there redundancy elimination left in DOM that is unique and if not, can we get the same overall effect if we remove the redundancy elimination from DOM and instead using existing passes for redundancy elimination. Same overall effect doesn't mean identical code, but
... though I am not sure (I didn't investigate) how much of the redundancy elimination code feeds the jump threading parts. I was thinking of moving the jump threading parts over to SCCVN instead, given that VRP lacks capabilities regarding to symbolical conditions.
One of the indicators to watch is whether or not the RTL jump threading code starts to become more important -- if it does, then we're ripping too much out of DOM.
Thanks. It seems the last DOM pass doesn't do very much as well, so I'll be playing with removing that as a last step of cleaning up the pipeline. Even if that might need another run of FRE instead of DOM.
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