Michael Kruse 67da1c2e76 [ADT] Add zip_longest iterators. ... Like the already existing zip_shortest/zip_first iterators, zip_longest iterates over multiple iterators at once, but has as many iterations as the longest sequence. This means some iterators may reach the end before others do. zip_longest uses llvm::Optional's None value to mark a past-the-end value. zip_longest is not reverse-iteratable because the tuples iterated over would be different for different length sequences (IMHO for the same reason neither zip_shortest nor zip_first should be reverse-iteratable; one can still reverse the ranges individually if that's the expected behavior). In contrast to zip_shortest/zip_first, zip_longest tuples contain rvalues instead of references. This is because llvm::Optional cannot contain reference types and the value-initialized default does not have a memory location a reference could point to. The motivation for these iterators is to use C++ foreach to compare two lists of ordered attributes in D48100 (SemaOverload.cpp and ASTReaderDecl.cpp). Idea by @hfinkel. This re-commits r348301 which was reverted by r348303. The compilation error by gcc 5.4 was resolved using make_tuple in the in the initializer_list. The compileration error by msvc14 was resolved by splitting ZipLongestValueType (which already was a workaround for msvc15) into ZipLongestItemType and ZipLongestTupleType. Differential Revision: https://reviews.llvm.org/D48348 llvm-svn: 348323		2018-12-05 00:31:54 +00:00
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llvm	[ADT] Add zip_longest iterators.	2018-12-05 00:31:54 +00:00
llvm-c	[IR] Add a dedicated FNeg IR Instruction	2018-11-13 18:15:47 +00:00