sbc

Subtract with Carry

SBC <Wd>, <Wn>, <Wm>

Subtracts with borrow (Carry - 1).

Pseudocode Operation

borrow ← NOT(C)
result ← Wn - (Wm + borrow)
Wd ← result
N ← result[31]
Z ← (result == 0)
C ← NOT(BorrowFrom(Wn - (Wm + borrow)))
V ← OverflowFrom(Wn - (Wm + borrow))

Example

SBC w0, w1, w2

Encoding

Binary Layout

11010000

28:21

20:16

000000

15:10

9:5

4:0

Format Data Processing

Opcode 0x5A000000

Extension Base

Operands

Wd
Destination 32-bit integer register
Wn
First source / base 32-bit integer register
Wm
Second source / offset 32-bit integer register

Other forms of sbc

sbc Subtract with Carry (A32)

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x5A000000	SBC <Wd>, <Wn>, <Wm>		A64		0 \| 1 \| 0 \| 11010000 \| Rm \| 000000 \| Rn \| Rd
0xDA000000	SBC <Xd>, <Xn>, <Xm>		A64		1 \| 1 \| 0 \| 11010000 \| Rm \| 000000 \| Rn \| Rd

Description

Subtract with Carry subtracts a register value and the value of NOT (Carry flag) from a register value, and writes the result to the destination register.

Operation

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

operand2 = NOT(operand2);

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

X[d, datasize] = result;

sbc