SUB (immediate)

Subtract (immediate) subtracts an optionally-shifted immediate value from a register value, and writes the result to the destination register.

313029282726252423222120191817161514131211109876543210
sf1010001shiftimm12RnRd
opS

32-bit (sf == 0)

SUB <Wd|WSP>, <Wn|WSP>, #<imm>{, <shift>}

64-bit (sf == 1)

SUB <Xd|SP>, <Xn|SP>, #<imm>{, <shift>}

integer d = UInt(Rd); integer n = UInt(Rn); integer datasize = if sf == '1' then 64 else 32; bits(datasize) imm; case shift of when '00' imm = ZeroExtend(imm12, datasize); when '01' imm = ZeroExtend(imm12:Zeros(12), datasize); when '1x' ReservedValue();

Assembler Symbols

<Wd|WSP>

Is the 32-bit name of the destination general-purpose register or stack pointer, 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.

<Xd|SP>

Is the 64-bit name of the destination general-purpose register or stack pointer, 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.

<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 encoded in shift:
shift <shift>
00 LSL #0
01 LSL #12
1x RESERVED

Operation

bits(datasize) result; bits(datasize) operand1 = if n == 31 then SP[] else X[n]; bits(datasize) operand2; operand2 = NOT(imm); (result, -) = AddWithCarry(operand1, operand2, '1'); if d == 31 then SP[] = result; else X[d] = result;


Internal version only: isa v25.07, AdvSIMD v23.0, pseudocode v31.3

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