SUBS (immediate) Subtract (immediate), setting flags This instruction subtracts an optionally-shifted immediate value from a register value, and writes the result to the destination register. It updates the condition flags based on the result. 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. This instruction is used by the alias CMP (immediate) Rd == '11111' See below for details of when the alias is preferred. 1 1 1 0 0 0 1 0 0 SUBS <Wd>, <Wn|WSP>, #<imm>{, <shift>} 1 SUBS <Xd>, <Xn|SP>, #<imm>{, <shift>} constant integer d = UInt(Rd); constant integer n = UInt(Rn); constant integer datasize = 32 << UInt(sf); constant bits(24) imm = if sh == '0' then Zeros(12):imm12 else imm12:Zeros(12); <Wd> Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field. <Wn|WSP> Is the 32-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field. <imm> Is an unsigned immediate, in the range 0 to 4095, encoded in the "imm12" field. <shift> Is the optional left shift to apply to the immediate, defaulting to LSL #0 and sh <shift> 0 LSL #0 1 LSL #12 <Xd> Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field. <Xn|SP> Is the 64-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field. Alias Conditions constant bits(datasize) operand1 = if n == 31 then SP[]<datasize-1:0> else X[n, datasize]; constant bits(datasize) operand2 = ZeroExtend(imm, datasize); bits(datasize) result; bits(4) nzcv; (result, nzcv) = AddWithCarry(operand1, NOT(operand2), '1'); X[d, datasize] = result; PSTATE.<N,Z,C,V> = nzcv;