If a function has lifetime dependencies, disable FSO's dead param optimization. Dead params maybe dependency sources and we should not delete them. It is also problematic to dead code params that are not dependency sources, since lifetime dependent sources are stored as indices and deleting dead parameters will require recomputation of these indices.
Computes the side effects for a function, which consists of argument- and global effects.
This is similar to the ComputeEscapeEffects pass, just for side-effects.
The existential -> generic transformation in FSO didn't preserve the argument declaration.
This caused an assert to hit in a later FSO transformation.
rdar://problem/61206439
https://bugs.swift.org/browse/SR-12487
