JIT: Add missing lvTracked check in optLocalHasNonLoopUses#109505
Merged
jakobbotsch merged 1 commit intodotnet:mainfrom Nov 5, 2024
Merged
JIT: Add missing lvTracked check in optLocalHasNonLoopUses#109505jakobbotsch merged 1 commit intodotnet:mainfrom
lvTracked check in optLocalHasNonLoopUses#109505jakobbotsch merged 1 commit intodotnet:mainfrom
Conversation
`optLocalHasNonLoopUses` checks if a local might be used after a loop by making use of its liveness information, but it does not check `lvTracked` before doing so. This is generally not a problem as there are other checks that the local is in SSA, and normally SSA implies lvTracked, but that's not the case for locals put into SSA by CSE. Since it is possible to have CSE defs in a loop with uses outside the loop, this check is necessary for correctness. It is expected to regress a bunch of IV opts cases, but in the future we can get those back by computing the necessary liveness when we insert into SSA.
Contributor
|
Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
Member
Author
|
I added this check in #106637 and identified it as the cause of regressions like #106637 (comment). |
Member
Author
|
cc @dotnet/jit-contrib PTAL @AndyAyersMS I plan to add the necessary liveness computations as part of #106637, or maybe as a follow-up. |
AndyAyersMS
approved these changes
Nov 4, 2024
Open
3 tasks
Member
Author
|
/ba-g MacOS 12 brownout and infra timeouts |
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
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
2 participants
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
optLocalHasNonLoopUseschecks if a local might be used after a loop by making use of its liveness information, but it does not checklvTrackedbefore doing so. This is generally not a problem as there are other checks that the local is in SSA, and normally SSA implieslvTracked, but that's not the case for locals put into SSA by CSE.Since it is possible to have CSE defs in a loop with uses outside the loop, this check is necessary for correctness. It is expected to regress a bunch of IV opts cases, but in the future we can get those back by computing the necessary liveness when we insert into SSA.