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sample loader pass. In https://reviews.llvm.org/rG5fb65c02ca5e91e7e1a00e0efdb8edc899f3e4b9, to prevent repeated indirect call promotion for the same indirect call and the same target, we used zero-count value profile to indicate an indirect call has been promoted for a certain target. We removed PromotedInsns cache in the same patch. However, there was a problem in that patch described below, and that problem led me to add PromotedInsns back as a mitigation in https://reviews.llvm.org/rG4ffad1fb489f691825d6c7d78e1626de142f26cf. When we get value profile from metadata by calling getValueProfDataFromInst, we need to specify the maximum possible number of values we expect to read. We uses MaxNumPromotions in the last patch so the maximum number of value information extracted from metadata is MaxNumPromotions. If we have many values including zero-count values when we write the metadata, some of them will be dropped when we read them because we only read MaxNumPromotions values. It will allow repeated indirect call promotion again. We need to make sure if there are values indicating promoted targets, those values need to be saved in metadata with higher priority than other values. The patch fixed that problem. We change to use -1 to represent the count of a promoted target instead of 0 so it is easier to sort the values. When we prepare to update the metadata in updateIDTMetaData, we will sort the values in the descending count order and extract only MaxNumPromotions values to write into metadata. Since -1 is the max uint64_t number, if we have equal to or less than MaxNumPromotions of -1 count values, they will all be kept in metadata. If we have more than MaxNumPromotions of -1 count values, we will only save MaxNumPromotions such values maximally. In such case, we have logic in place in doesHistoryAllowICP to guarantee no more promotion in sample loader pass will happen for the indirect call, because it has been promoted enough. With this change, now we can remove PromotedInsns without problem. Differential Revision: https://reviews.llvm.org/D97350
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