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When TupleOptimization splits a tuple local.set into several local.sets, if a set's value contained a get of a prior tuple element, that value would previously have incorrectly been the updated rather than original element. Avoid reading trampled values by copying the original values to scratch locals before starting to emit the sequence of local sets. Fixes #9210.
kripken
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Oct 5, 2026
| ;; CHECK-NEXT: ) | ||
| ;; CHECK-NEXT: (local.set $2 | ||
| ;; CHECK-NEXT: (local.get $4) | ||
| ;; CHECK-NEXT: ) |
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This is adding extra vars even in trivial cases like this one. How about doing something like ChildLocalizer, conceptually, that is, check for interferences?
Seems like it could be a simple scan of the tuple.make inputs to see that copied fields (from the same tuple) are read in order.
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I experimented with emitting scratch locals only as necessary, but I didn't like how complicated it was. Let me see if I can better encapsulate the complexity.
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@kripken, see the last commit, which adds a utility for determining precisely when scratch locals are necessary. It seems like a good deal of extra complexity, but maybe it's worth it. |
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When TupleOptimization splits a tuple local.set into several local.sets,
if a set's value contained a get of a prior tuple element, that value
would previously have incorrectly been the updated rather than original
element. Avoid reading trampled values by copying the original values to
scratch locals before starting to emit the sequence of local sets.
Fixes #9210.