swift

705373c2 - [pred-deadalloc-elim] Fix memory safety issue and handle promoting paths where there is dynamically no value by inserting compensating destroys.

[pred-deadalloc-elim] Fix memory safety issue and handle promoting paths where there is dynamically no value by inserting compensating destroys. This commit is fixing two things: 1. In certain cases, we are seeing cases where either SILGen or the optimizer are eliminating destroy_addr along paths where we know that an enum is dynamically trivial. This can not be expressed in OSSA, so I added code to pred-deadalloc-elim so that I check if any of our available values after we finish promoting away an allocation now need to have their consuming use set completed. 2. That led me to discover that in certain cases load [take] that we were promoting were available values of other load [take]. This means that we have a memory safety issue if we promote one load before the other. Consider the following SIL: ``` %mem = alloc_stack store %arg to [init] %mem %0 = load [take] %mem store %0 to [init] %mem %1 = load [take] %mem destroy_value %1 dealloc_stack %mem ``` In this case, if we eliminate %0 before we eliminate %1, we will have a stale pointer to %0. I also took this as an opportunity to turn off predictable mem access opt on SIL that was deserialized canonicalized and non-OSSA SIL. We evidently need to still do this for pred mem opts for perf reasons (not sure why). But I am pretty sure this isn't needed and allows me to avoid some nasty code.