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SBCS

Subtract with Carry, setting flags, subtracts a register value and the value of NOT (Carry flag) 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 NGCS.

313029282726252423222120191817161514131211109876543210
sf1111010000Rm000000RnRd
opS

32-bit (sf == 0)

SBCS <Wd>, <Wn>, <Wm>

64-bit (sf == 1)

SBCS <Xd>, <Xn>, <Xm>

integer d = UInt(Rd);
integer n = UInt(Rn);
integer m = UInt(Rm);
integer datasize = if sf == '1' then 64 else 32;

Assembler Symbols

<Wd>

Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field.

<Wn>

Is the 32-bit name of the first general-purpose source register, encoded in the "Rn" field.

<Wm>

Is the 32-bit name of the second general-purpose source register, encoded in the "Rm" field.

<Xd>

Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field.

<Xn>

Is the 64-bit name of the first general-purpose source register, encoded in the "Rn" field.

<Xm>

Is the 64-bit name of the second general-purpose source register, encoded in the "Rm" field.

Alias Conditions

AliasIs preferred when
NGCSRn == '11111'

Operation

bits(datasize) result;
bits(datasize) operand1 = X[n];
bits(datasize) operand2 = X[m];
bits(4) nzcv;

operand2 = NOT(operand2);

(result, nzcv) = AddWithCarry(operand1, operand2, PSTATE.C);

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

X[d] = result;

Operational information

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.
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