[PATCH] D155041: [RISCV] Remove unnecessary move of undefined with subregister liveness enabled

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

A random thought on optimization here.

In the common case where only one sub-register is defined, inserting the defined element into an undefined pseudo - i.e. doing the inverse of the current code - might be better.  We could maybe generalize this when multiple sub-regs are defined, but that starts looking like somekind of subreg_select like construct, and I don't know of any support for that.


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https://reviews.llvm.org/D155041