[PATCH] D151736: [RISCV] Lower inserts into identity shuffles as v{,f}slide1ups

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

Description wise, calling an slideup-by-one mask an identity mask feels very odd to me.  It took me a bit reading the code to figure out what you meant by that, and I'd suggest rewording.  I'd suggest something along the lines of "would be identity mask if shifted down by one position" or something along those lines.

Did you look at the alternative of adding a DAG combine to reverse the shuffle+insert form into the insert+shuffle form?  That'd been what I'd been tentatively thinking about, but I hadn't explored it past idea phase.



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Comment at: llvm/test/CodeGen/RISCV/rvv/fixed-vector-shuffle-vslide1up.ll:318
 
+define <2 x double> @vslide1up_v2f64_inverted_swapped(<2 x double> %v, double %b) {
+; CHECK-LABEL: vslide1up_v2f64_inverted_swapped:
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You can go ahead and precommit these tests without further review.  


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  https://reviews.llvm.org/D151736/new/

https://reviews.llvm.org/D151736