[PATCH] D156164: [HACK] X86: Disable isCopyInstrImpl for undef subregister defs

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

I think the real fix is to make SUBREG_TO_REG use a tied operand with a subregister but that will be a much larger patch


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  https://reviews.llvm.org/D156164/new/

https://reviews.llvm.org/D156164