PredMemOpt Extract at Store site instead of load site #12817
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This rename makes since since: 1. This is SILGen specific functionality. 2. In the next commit I am going to be adding a SIL SavedInsertionPoint class. I want to make sure the two can not be confused.
… typealias to std::pair. For pred-memopt to work with ownership, we need to insert instructions in two different places: 1. When loading not-available values, we must insert the load at the site of the load we are trying to promote. 2. When propagating an available value, we must destructure and or copy before each one of the stores that provide our value. By changing AvailableValue to be a struct, I am providing a cleaner API, but more importantly the ability to start tracking that information. rdar://31521023
… at the store site. Previously in PredMemOpts, we would insert any extracts at the load site, i.e.: store %foo to %0 ... %1 = struct_element_addr %0, $Type, $Type.field %2 = load %1 ... apply %use(%2) would transform to: store %foo to %0 ... %2 = struct_extract %foo apply %use(%2) This framework will not work with Ownership enabled since the value stored is considered consumed by the store. This change fixes the issue by moving such non-destructive extracts to occur while %foo is considered live, i.e. before the store: %2 = struct_extract %foo store %foo to %0 ... apply %use(%2) This means that we have to store insertion points for each store that provides us with available values and insert the extracts at those points. This creates some complications in the case where we have multiple stores since we need to deal with phi nodes. Rather than dealing with it by hand, we just insert the extracts at each point and then use the SSA updater to insert the relevant phi nodes. rdar://31521023
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@swift-ci test |
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@swift-ci test source compatibility |
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This is the last missing piece that will allow me to land my patch updating pred mem opt for ownership.
rdar://31521023