SUB (immediate)

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

313029282726252423222120191817161514131211109876543210
sf10100010shimm12RnRd
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); constant integer datasize = 32 << UInt(sf); bits(datasize) imm; case sh of when '0' imm = ZeroExtend(imm12, datasize); when '1' imm = ZeroExtend(imm12:Zeros(12), datasize);

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.

<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 sh:

sh <shift>
0 LSL #0
1 LSL #12
<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.

Operation

bits(datasize) result; bits(datasize) operand1 = if n == 31 then SP[]<datasize-1:0> else X[n, datasize]; bits(datasize) operand2; operand2 = NOT(imm); (result, -) = AddWithCarry(operand1, operand2, '1'); if d == 31 then SP[] = ZeroExtend(result, 64); else X[d, datasize] = result;

Operational information

If PSTATE.DIT is 1:


Internal version only: aarchmrs v2023-12_rel, pseudocode v2023-12_rel, sve v2023-12_rel ; Build timestamp: 2023-12-15T16:46

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