[PATCH] D118979: [AArch64] Set maximum VF with shouldMaximizeVectorBandwidth

Dave Green via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Thu Feb 10 01:18:56 PST 2022


dmgreen added a comment.

Yeah. I had https://godbolt.org/z/3qWoY769v as an example, where is can make better use of the umull2 instructions, because of the wider vector loads as a single operation. That's what makes it beneficial for AArch64.

It sounds like D96522 <https://reviews.llvm.org/D96522> might be a more limited way of getting the same result we want from this? That might be a good way forward. There were a number of regressions we would have to work through with this patch in the benchmarks I have access to, cases where either the codegen or the costmodelling need to be tweaked. (The only one I have so far is from some bad smull generation: https://godbolt.org/z/enox4ojhf. I still need to look through the rest).


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