The comment shows that at the time we were worried about producing the
alias in assembly that might be ingested by a binutils version that
doesn't yet support it. binutils gained support over 4 years ago
<https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=c2137f55ad04e451d834048d4bfec1de2daea20e>.
With all the changes in areas such as ELF attributes, if you tried to
use LLVM's RISC-V assembler output with a binutils that old then zext.b
would be the least of your worries.
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