Wasmtime GitHub notifications bot (Oct 07 2022 at 00:17): Wasmtime GitHub notifications bot (Oct 07 2022 at 00:17):cfallin requested elliottt for a review on PR #5029.
Wasmtime GitHub notifications bot (Oct 07 2022 at 00:17):cfallin opened PR #5029 from cherrypick-2.0.0-pr5023 to release-2.0.0:
- Fix StructReturn handling: properly mark the clobber, and offset actual rets.
The legalization of
StructReturnwas causing issues in the new call-handling code: theStructReturnret was included in theSigDataas if it were an actual CLIF-level return value, but it is not.Prior to using regalloc constraints for return values, we unconditionally included rax (or the architecture's usual return register) as a def, so it would be properly handled as "clobbered" by the regalloc. With the new scheme, we include defs on the call only for CLIF-level outputs. Callees with
StructReturnargs were thus not known to clobber the return-value register, and values might be corrupted.This PR updates the code to include a
StructReturnret as a clobber rather than a returned value in the relevant spots. I observed it causing saves/restores of rax in some CLIF that @bjorn3 provided me, but I was having difficulty minimizing this into a test-case that I would be comfortable including as a precise-output case (including the whole thing verbatim would lock down a bunch of other irrelevant details and cause test-update noise later). If we can find a more minimized example I'm happy to include it as a filetest.<!--
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Wasmtime GitHub notifications bot (Oct 07 2022 at 00:18):cfallin edited PR #5029 from cherrypick-2.0.0-pr5023 to release-2.0.0:
The legalization of
StructReturnwas causing issues in the new call-handling code: theStructReturnret was included in theSigDataas if it were an actual CLIF-level return value, but it is not.Prior to using regalloc constraints for return values, we unconditionally included rax (or the architecture's usual return register) as a def, so it would be properly handled as "clobbered" by the regalloc. With the new scheme, we include defs on the call only for CLIF-level outputs. Callees with
StructReturnargs were thus not known to clobber the return-value register, and values might be corrupted.This PR updates the code to include a
StructReturnret as a clobber rather than a returned value in the relevant spots. I observed it causing saves/restores of rax in some CLIF that @bjorn3 provided me, but I was having difficulty minimizing this into a test-case that I would be comfortable including as a precise-output case (including the whole thing verbatim would lock down a bunch of other irrelevant details and cause test-update noise later). If we can find a more minimized example I'm happy to include it as a filetest.<!--
Please ensure that the following steps are all taken care of before submitting
the PR.
[ ] This has been discussed in issue #..., or if not, please tell us why
here.[ ] A short description of what this does, why it is needed; if the
description becomes long, the matter should probably be discussed in an issue
first.[ ] This PR contains test cases, if meaningful.
- [ ] A reviewer from the core maintainer team has been assigned for this PR.
If you don't know who could review this, please indicate so. The list of
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Wasmtime GitHub notifications bot (Oct 07 2022 at 00:21):elliottt submitted PR review.
Wasmtime GitHub notifications bot (Oct 07 2022 at 02:41):cfallin updated PR #5029 from cherrypick-2.0.0-pr5023 to release-2.0.0.
Wasmtime GitHub notifications bot (Oct 07 2022 at 04:37):cfallin merged PR #5029.
Last updated: Dec 23 2024 at 12:05 UTC