Use the new builtins for COW representation in Array, ContiguousArray and ArraySlice.
The basic idea is to strictly separate code which mutates an array buffer from code which reads from an array.
The concept is explained in more detail in docs/SIL.rst, section "Copy-on-Write Representation".
The main change is to use beginCOWMutation() instead of isUniquelyReferenced() and insert endCOWMutation() at the end of all mutating functions. Also, reading from the array buffer must be done differently, depending on if the buffer is in a mutable or immutable state.
All the required invariants are enforced by runtime checks - but only in an assert-build of the library: a bit in the buffer object side-table indicates if the buffer is mutable or not.
Along with the library changes, also two optimizations needed to be updated: COWArrayOpt and ObjectOutliner.
All unoptimized tests should now pass when Swift is built with
'build-script -- --swift-stdlib-enable-resilience=1'.
There are still some issues when the tests themselves are built
with optimizations via 'check-swift-validation-optimize'.
Fixes <rdar://problem/28409189>.
This reduces the amount of SIL generated for array operations significantly.
The generated code should be mostly the same (modulo different inlining decisions).
This reduces the amount of SIL generated for array operations significantly.
The generated code should be mostly the same (modulo different inlining decisions).
