USUBW, USUBW2 Unsigned subtract wide This instruction subtracts each vector element of the second source SIMD&FP register from the corresponding vector element in the lower or upper half of the first source SIMD&FP register, places the result in a vector, and writes the vector to the SIMD&FP destination register. All the values in this instruction are unsigned integer values. The vector elements of the destination register and the first source register are twice as long as the vector elements of the second source register. The USUBW instruction extracts vector elements from the lower half of the first source register. The USUBW2 instruction extracts vector elements from the upper half of the first source register. Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped. If PSTATE.DIT is 1: The execution time of this instruction is independent of: The values of the data supplied in any of its registers. The values of the NZCV flags. The response of this instruction to asynchronous exceptions does not vary based on: The values of the data supplied in any of its registers. The values of the NZCV flags. 0 1 0 1 1 1 0 1 0 0 1 1 0 0 USUBW{2} <Vd>.<Ta>, <Vn>.<Ta>, <Vm>.<Tb> if size == '11' then UNDEFINED; constant integer d = UInt(Rd); constant integer n = UInt(Rn); constant integer m = UInt(Rm); constant integer esize = 8 << UInt(size); constant integer datasize = 64; constant integer part = UInt(Q); constant integer elements = datasize DIV esize; 2 Is the second and upper half specifier. If present it causes the operation to be performed on the upper 64 bits of the registers holding the narrower elements, and is Q 2 0 [absent] 1 [present] <Vd> Is the name of the SIMD&FP destination register, encoded in the "Rd" field. <Ta> Is an arrangement specifier, size <Ta> 00 8H 01 4S 10 2D 11 RESERVED <Vn> Is the name of the first SIMD&FP source register, encoded in the "Rn" field. <Vm> Is the name of the second SIMD&FP source register, encoded in the "Rm" field. <Tb> Is an arrangement specifier, size Q <Tb> 00 0 8B 00 1 16B 01 0 4H 01 1 8H 10 0 2S 10 1 4S 11 x RESERVED CheckFPAdvSIMDEnabled64(); constant bits(2*datasize) operand1 = V[n, 2*datasize]; constant bits(datasize) operand2 = Vpart[m, part, datasize]; bits(2*datasize) result; integer element1; integer element2; integer sum; for e = 0 to elements-1 element1 = UInt(Elem[operand1, e, 2*esize]); element2 = UInt(Elem[operand2, e, esize]); sum = element1 - element2; Elem[result, e, 2*esize] = sum<2*esize-1:0>; V[d, 2*datasize] = result;