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99a5482014
I'm not sure what the effect of this change will be on all of the affected tests or a larger benchmark, but it fixes the horizontal add/sub problems noted here: https://reviews.llvm.org/D59710?vs=227972&id=228095&whitespace=ignore-most#toc The costs are based on reciprocal throughput numbers in Agner's tables for PEXTR*; these appear to be very slow ops on Silvermont. This is a small step towards the larger motivation discussed in PR43605: https://bugs.llvm.org/show_bug.cgi?id=43605 Also, it seems likely that insert/extract is the source of perf regressions on other CPUs (up to 30%) that were cited as part of the reason to revert D59710, so maybe we'll extend the table-based approach to other subtargets. Differential Revision: https://reviews.llvm.org/D70607