Expand the GC hole fix for explicitly initialized structs #69501
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Liveness code already recognizes that it cannot delete certain local stores with the implicit side effect of "explicit initialization". However, it was only doing that for indirect "InitBlk" forms, while the store can have more or less arbitrary shape (the only requirement is that is must be "entire"). Fix this by not constraining the check to "InitBlk"s.
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AndyAyersMS
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May 18, 2022
If we had separate read counts vs write counts, we could improve here -- we use ref count > 1 as a proxy for "there might be a read" but if there are only writes then we simply keep all the writes around. I have been tempted to separate out read/write counts for other reasons... perhaps it is something to put on the admittedly lengthy todo list. |
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The problem fixed in #67825 applies to arbitrary "entire" struct stores.
Should fix issues seen in stress runs over at #68986.
A small number of regressions in the diffs. Seem to be cases where we now fail to dead-code a store to a local that would end up having a ref count of zero.