Index

SUBS (immediate)

Subtract (immediate), setting flags, 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.

This instruction is used by the alias CMP (immediate).

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
sf 1 1 1 0 0 0 1 0 sh imm12 Rn Rd
op S

32-bit (sf == 0)

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

64-bit (sf == 1)

SUBS <Xd>, <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>

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.
<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.
<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

Alias Conditions

Alias Is preferred when
CMP (immediate) Rd == '11111'

Operation

bits(datasize) result;
bits(datasize) operand1 = if n == 31 then SP[]<datasize-1:0> else X[n, datasize];
bits(datasize) operand2;
bits(4) nzcv;

operand2 = NOT(imm);
(result, nzcv) = AddWithCarry(operand1, operand2, '1');

PSTATE.<N,Z,C,V> = nzcv;

X[d, datasize] = result;

Operational information

If PSTATE.DIT is 1: