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

[Shengchen Kan via llvm-commits]

KanRobert 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?

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