[6.2] IRGen: Fix out-of-order task_dealloc with parameter pack metadata #81523
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
slavapestov
changed the title
slavapestov
force-pushed
the
fix-pack-task-dealloc-6.2
branch
3 times, most recently
from
ce40ded to
7fb678c
Compare
|
@swift-ci Please test |
adrian-prantl
approved these changes
May 15, 2025
slavapestov
force-pushed
the
fix-pack-task-dealloc-6.2
branch
from
7fb678c to
9b26ab1
Compare
We deallocate an instruction's packs at points where no further control flow path uses the value. In the case of an alloc_stack, this will be right after the dealloc_stack. Thus, if alloc_stack allocates some packs to build type metadata for a tuple type that contains a pack, and then proceeds to allocate a value large enough to hold the tuple, we will free the second allocation first, before we free the pack, as expected. However, after stack allocating the value, alloc_stack does some further work to emit debug info. This could result in emission of additional metadata packs. Split up the debug info emission into two parts; the first we do before we perform the stack allocation, the rest we do after. - Fixes swiftlang#67702. - Fixes rdar://problem/141363236.
slavapestov
force-pushed
the
fix-pack-task-dealloc-6.2
branch
from
9b26ab1 to
bf8d836
Compare
|
@swift-ci Please test |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
6.2 cherry-pick of #81516
Description: Fixes a miscompile resulting in a runtime crash when parameter packs are used together with async functions. On-stack packs were sometimes deallocated in the wrong order because of a bad interaction with debug info. While not specific to async functions, in a non-async function this was not actually a problem because of how LLVM lowers the instructions in question.
Origination: This problem has been there since parameter packs shipped in Swift 5.9.
Risk: Low.
Reviewed by: @adrian-prantl