[clang] [CIR][AArch64] Upstream for vector vector shl (PR #191655)

[Andrzej Warzyński via cfe-commits]

================
@@ -2439,6 +2439,260 @@ uint64x1_t test_vshl_n_u64(uint64x1_t a) {
  return vshl_n_u64(a, 1);
 }
 
----------------
banach-space wrote:

Please add a block comment here (similar that what we have for other intrinsic groups)

https://github.com/llvm/llvm-project/pull/191655