[5.3] CSE: disable CSE of lazy property getters of struct #33741
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We cannot prove that the whole struct is overwritten between two lazy property getters. We would need AliasAnalysis for this, but currently this is not used in CSE. rdar://problem/67734844
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airspeedswift
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Sep 1, 2020
AnthonyLatsis
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swift 5.3
🍒 release cherry pick
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We cannot prove that the whole struct is overwritten between two lazy property getters.
We would need AliasAnalysis for this, but currently this is not used in CSE.
Original: #33713
Radar: rdar://problem/67734844
Explanation: This fixes a miscompile with lazy struct properties.
Scope: This is a bug which was introduced by a new optimization in 5.3. It shows up if a value type (e.g. a struct) with a lazy property is overwritten between two accesses of the property.
Risk: Low. The only change is to add an additional bail-out condition,.
Reviewer: @atrick