[clang] [llvm] [X86] Use vXi1 for `k` constraint in inline asm (PR #77733)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> Should we add test coverage for the gpr <-> mask transfers?

Is the concern about existing BC files using gpr? It's covered by existing test case, e.g., function `@a` in pr41678.ll
We don't remove the iN type support in X86ISelLowering.cpp, but add extra vXi1 support.

https://github.com/llvm/llvm-project/pull/77733