Fix a fuzz issue with #6984 #6988
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Actually the test update here reverts almost all the test updates from #6984 - those changes were on blocks with unreachable children. The change was safe on them, but in general removing a block value in the presence of unreachable code is tricky, so it's best to avoid it. |
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| ;; GUFA manages to generate IR that makes merge-blocks leave a stale type, if we | ||
| ;; are not careful. simplify-locals-notee then errors if that stale type is | ||
| ;; present, so all the passes are needed to hit this bizarre corner case. |
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Not sure what this means... Why do all the passes need to hit this corner case wheh simplify-lcoals-notee errors out?
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It isn't that the passes each need to do that, but that the testcase must include all those passes, for it to hit the error. I improved the text now.
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Hmm, the testcase now errors on CI for some reason I can't figure out. As it was a very low-value testcase anyhow (with that weird sequence of passes, it is hard to actually understand what's going wrong), I removed it. |
… too (#6994) In #6984 we optimized dropped blocks even if they had unreachable code. In #6988 that part was reverted, and blocks with unreachable code were ignored once more. However, I realized that the check was not actually for unreachable code, but for having an unreachable child, so it would miss things like this: (block (block .. (br $somewhere) ;; unreachable type, but no unreachable code ) ) But it is useful to merge such blocks: we don't need the inner block here. To fix this, just run ReFinalize if we change anything, which will propagate unreachability as needed. I think MergeBlocks was written before we had that utility, so it didn't use it... This is not only useful for itself but will unblock an EH optimization in a later PR, that has code in this form. It also simplifies the code by removing the hasUnreachableChild checks.
When I refactored the optimizeDroppedBlock logic in #6982, I didn't move the
unreachability check with that code, which was wrong. When that function
was called from another place in #6984, the fuzzer found an issue.
Diff without whitespace is smaller.
The testcase is a little bizarre, but it's the one the fuzzer found and I can't
find a way to generate a better one (other than to reduce it, which I did).