[PATCH] D106721: [AArch64] Implemnt MSVC __mulh and __umulh builtins and corresponding IR level intrinsics

[Eli Friedman via Phabricator via cfe-commits]

efriedma added a comment.

We won't call compiler-rt for i128 multiply on aarch64.  It's not worthwhile under any circumstances.

Pattern-matching 64/64->128 multiply in SelectionDAG legalization has been reliable in practice, as far as I know.  And even it misses due to weird behavior in instcombine or something like that, we only end up with one or two extra mla instructions, so not a big deal.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D106721/new/

https://reviews.llvm.org/D106721