Fastest way to test a 128 bit NEON register for a value of 0 using intrinsics?

Question

I\'m looking for the fastest way to test if a 128 NEON register contains all zeros, using NEON intrinsics. I\'m currently using 3 OR operations, and 2 MOVs:

Answer 1

You seem to be looking for intrinsics and this is the way:

inline bool is_zero(int32x4_t v) noexcept
{
  v = v == int32x4{};

  return !int32x2_t(
    vtbl2_s8(
      int8x8x2_t{
        int8x8_t(vget_low_s32(v)),
        int8x8_t(vget_high_s32(v))
      },
      int8x8_t{0, 4, 8, 12}
    )
  )[0];
}

Nils Pipenbrinck's answer has a flaw in that he assumes the QC, cumulative saturation flag to be clear.