Specifically, improved debug info retention in:
* tryReplaceRedundantInstructionPair,
* splitAggregateLoad,
* TempLValueElimination,
* Mem2Reg,
* ConstantFolding.
The changes to Mem2Reg allow debug info to be retained in the case tested by
self-nostorage.swift in -O builds, so we have just enabled -O in that file
instead of writing a new test for it.
We attempted to add a case to salvageDebugInfo for unchecked_enum_data, but it
caused crashes in Linux CI that we were not able to reproduce.
If exclusivity is checked for the alloc_stack we must not replace it with the copy-destination.
If the copy-destination is also in an access-scope this would result in an exclusivity violation which was not there before.
Fixes a miscompile which results in a wrong exclusivity violation error at runtime.
https://github.com/swiftlang/swift/issues/83924
rdar://159220436
This peephole optimization also combined the instructions if the `destroy_addr` appears before the `copy_addr` in the same basic block.
https://github.com/swiftlang/swift/issues/82466
rdar://154236276
* re-implement the pass in swift
* support alloc_stack liveranges which span over multiple basic blocks
* support `load`-`store` pairs, copying from the alloc_stack (in addition to `copy_addr`)
Those improvements help to reduce temporary stack allocations, especially for InlineArrays.
rdar://151606382
