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

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> > > Why not return `i32` for 64-bit mask in 32-bit mode?
> > 
> > 
> > You mean in two `i32` registers? The problem is the inline asm constraint has 1:1 map with physical register except corner cases. And represent a `k` constraint into two GPR registers is inefficient.
> 
> Is it represented by i64 x 1 in 32-bit mode after this patch?

Yes.

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