+.macro vzero vz=v31
+ // Set VZ (default v31) to zero.
+ dup \vz\().4s, wzr
+.endm
+
+.macro vshl128 vd, vn, nbit, vz=v31
+ // Set VD to VN shifted left by NBIT. Assume VZ (default v31) is
+ // all-bits-zero. NBIT must be a multiple of 8.
+ .if \nbit&3 != 0
+ .error "shift quantity must be whole number of bytes"
+ .endif
+ ext \vd\().16b, \vz\().16b, \vn\().16b, #16 - (\nbit >> 3)
+.endm
+
+.macro vshr128 vd, vn, nbit, vz=v31
+ // Set VD to VN shifted right by NBIT. Assume VZ (default v31) is
+ // all-bits-zero. NBIT must be a multiple of 8.
+ .if \nbit&3 != 0
+ .error "shift quantity must be whole number of bytes"
+ .endif
+ ext \vd\().16b, \vn\().16b, \vz\().16b, #\nbit >> 3
+.endm
+