The main changes are:
*) Rewrite everything in swift. So far, parts of memory-behavior analysis were already implemented in swift. Now everything is done in swift and lives in `AliasAnalysis.swift`. This is a big code simplification.
*) Support many more instructions in the memory-behavior analysis - especially OSSA instructions, like `begin_borrow`, `end_borrow`, `store_borrow`, `load_borrow`. The computation of end_borrow effects is now much more precise. Also, partial_apply is now handled more precisely.
*) Simplify and reduce type-based alias analysis (TBAA). The complexity of the old TBAA comes from old days where the language and SIL didn't have strict aliasing and exclusivity rules (e.g. for inout arguments). Now TBAA is only needed for code using unsafe pointers. The new TBAA handles this - and not more. Note that TBAA for classes is already done in `AccessBase.isDistinct`.
*) Handle aliasing in `begin_access [modify]` scopes. We already supported truly immutable scopes like `begin_access [read]` or `ref_element_addr [immutable]`. For `begin_access [modify]` we know that there are no other reads or writes to the access-address within the scope.
*) Don't cache memory-behavior results. It turned out that the hit-miss rate was pretty bad (~ 1:7). The overhead of the cache lookup took as long as recomputing the memory behavior.
Replace the generic `List` with the (non-generic) `InstructionList` and `BasicBlockList`.
The `InstructionList` is now a bit different than the `BasicBlockList` because it supports that instructions are deleted while iterating over the list.
Also add a test pass which tests instruction modification while iteration.
Dead-end blocks are blocks from which there is no path to the function exit (`return`, `throw` or unwind).
These are blocks which end with an unreachable instruction and blocks from which all paths end in "unreachable" blocks.
Provides a list of instructions, which reference a function.
A function "use" is an instruction in another (or the same) function which references the function.
In most cases those are `function_ref` instructions, but can also be e.g. `keypath` instructions.
'FunctionUses' performs an analysis of all functions in the module and collects instructions which reference other functions.
This utility can be used to do inter-procedural caller-analysis.
