[Bug target/110751] RISC-V: Suport undefined value that allows VSETVL PASS use TA/MA

[juzhe.zhong at rivai dot ai via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110751

--- Comment #15 from JuzheZhong <juzhe.zhong at rivai dot ai> ---
I am wondering: do we have have other situations need "undef" value to do
optimizations? If yes, I am aggree with Richard that we need to support "undef"
value.  But "undef" value in Gimple IR support would be a long term work since
it
is not an easy job. For example, in llvm, undef + a -> undef, but undef & a ->
0.