Codegen is the same, but `begin_dealloc_ref` consumes the operand and produces a new SSA value.
This cleanly splits the liferange to the region before and within the destructor of a class.
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.
We run GlobalOpt multiple times in the pass pipeline but in some cases object outlining shouldn't be done too early.
Having it done in a separate pass enables to run it independently from GlobalOpt.
We run GlobalOpt multiple times in the pass pipeline but in some cases object outlining shouldn't be done too early.
Having it done in a separate pass enables to run it independently from GlobalOpt.
eraseFromParent() might invalidate the iterator, so when we're
walking the pointer to the next instruction in the SILBB we end up
crashing. In order to avoid this issue, collect a SmallVector of
instructions to remove, and defer the actualy removal after we
iterated the whole SILBasicBlock, as we know it's safe.
Fixes SR-6215.
