[clang] [CIR][AArch64] Lower NEON Saturating substract intrinsics (PR #207189)

[Jiahao Guo via cfe-commits]

E00N777 wrote:

@banach-space @iamvickynguyen  Hi, I noticed that the lowering logic for the SISD intrinsics in this PR is very similar to that in PR https://github.com/llvm/llvm-project/pull/209389. I’ve therefore narrowed the scope of this PR to cover only the SIMD intrinsics. Once PR #207189 is merged, I’ll open a separate follow-up PR for the SISD intrinsics to avoid unnecessary complications.

https://github.com/llvm/llvm-project/pull/207189