This is a safer API than using
```
let argIdx = applySite.calleeArgumentIndex(of: op)
let arg = callee.arguments[argIdx]
```
because there is no potential misuse of the index.
Layers:
- FunctionConvention: AST FunctionType: results, parameters
- ArgumentConventions: SIL function arguments
- ApplyOperandConventions: applied operands
The meaning of an integer index is determined by the collection
type. All the mapping between the various indices (results,
parameters, SIL argument, applied arguments) is restricted to the
collection type that owns that mapping. Remove the concept of a
"caller argument index".
* Disallow stores in the return -> argument path. When walking up in the EscapeUtils, it's allowed to follow stores. Therefore stores wouldn't be handled correctly.
* Also make sure that there is a return -> argument path at all
Fixes a wrong address-escaping effect in case the called function copies an indirect argument to a newly created object.
rdar://105133434
* split the `PassContext` into multiple protocols and structs: `Context`, `MutatingContext`, `FunctionPassContext` and `SimplifyContext`
* change how instruction passes work: implement the `simplify` function in conformance to `SILCombineSimplifyable`
* add a mechanism to add a callback for inserted instructions
This is consistent with `Type.isTrivial`.
Also, introduce corresponding properties in `Value`: `hasTrivialType` and `hasTrivialNonPointerType`, because
1. It's less to type than `Type.isTrivial(in: function)` because `Value` knows in which function it is.
2. It fixes the corner case where value is an `Undef`, which has not parent function.
Erik Eckstein
Meghana Gupta
Andrew Trick