[Bug target/70119] AArch64 should take advantage of implicit truncation of variable shift amount without defining SHIFT_COUNT_TRUNCATED

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70119

--- Comment #3 from ktkachov at gcc dot gnu.org ---
Right, I see we have the same issue on aarch64 as on x86.
So what would be the accepted solution here?
I've been playing with a patch to simplify-rtx to move the subreg inside the
AND and transform the AND into a QImode operation, but there were concerns on
it pessimising other code