Introduce a new pass MandatoryTempRValueElimination, which works as the original TempRValueElimination, except that it does not remove any alloc_stack instruction which are associated with source variables.
Running this pass at Onone helps to reduce copies of large structs, e.g. InlineArrays or structs containing InlineArrays.
Copying large structs can be a performance problem, even at Onone.
rdar://151629149
Type annotations for instruction operands are omitted, e.g.
```
%3 = struct $S(%1, %2)
```
Operand types are redundant anyway and were only used for sanity checking in the SIL parser.
But: operand types _are_ printed if the definition of the operand value was not printed yet.
This happens:
* if the block with the definition appears after the block where the operand's instruction is located
* if a block or instruction is printed in isolation, e.g. in a debugger
The old behavior can be restored with `-Xllvm -sil-print-types`.
This option is added to many existing test files which check for operand types in their check-lines.
Optional's `init_enum_data_addr` and `inject_enum_addr` instructions are generated in presence of non-loadable Optional values. The compiler used to treat these instructions as inactive, and this resulted in silent run-time
issues described in #64223.
The patch marks `init_enum_data_addr` as "active" if its Optional operand is also active, and in PullbackCloner we differentiate through it and the related `inject_enum_addr`.
However, we only determine this relation in simple cases when both instructions are in the same block. There is no def-use relation between them (both take the same Optional operand), so if there is more than one set of instructions
operating on the same Optional, or there is some control flow, we currently bail out.
In PullbackCloner, we walk over instructions in reverse order and start from `inject_enum_addr` and its `Optional<Wrapped>.TangentVector` operand. Assuming that is is already initialized, we emit an `unchecked_take_enum_data_addr` and set it as the adjoint buffer of `init_enum_data_addr`. The Optional value is
invalidated, and we have to destroy the enum data address later when we reach `init_enum_data_addr`.
