[PATCH] D58444: Make MergeBlockIntoPredecessor conformant to the precondition of calling DTU.applyUpdates

Wed Feb 20 10:07:41 PST 2019

NutshellySima added a comment.

In D58444#1404242 <https://reviews.llvm.org/D58444#1404242>, @brzycki wrote:

> Thank you for looking into this. I was working on applying `MergeBLockIntoPredecessor` replacement in `JumpThreading.cpp` (via D48202 <https://reviews.llvm.org/D48202>) and ran into check failures that I haven't had time to properly debug. I suspect at least one of these is related to the change you made above.

Thanks for your comment! I am worried about the difficulty in discovering and debugging bugs involving incremental DT updating. I think it is indeed easy to violet the preconditions of `applyUpdates()` and I believe if it is a concern, a strict validation should be added to check if preconditions are fulfilled in DEBUG mode later.

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