[PATCH] D67614: [ARM] SBFX from rsb patterns

Dave Green via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Sep 24 04:14:50 PDT 2019


dmgreen added a comment.

Hello

That wouldn't help the MVE predicate case, which is what i was really after here. It is coming from a insert_vector_elt(extract_vector_elt(..)), where we generate a sign_extend_inreg, which is legalised to the rsb and the and. D67956 <https://reviews.llvm.org/D67956> contains an alternative where we lower that using a LSL, SRA pair instead, which will then transform to the SBFX as desired.

I didn't see any other cases of this coming up in the tests I ran, so that alternative might be the simpler approach.


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