subps

Subtract Pointers, Setting Flags

SUBPS <Xd>, <Xn|SP>, <Xm|SP>

Subtracts pointers (ignoring tags) and sets condition flags.

Pseudocode Operation

Xd ← Xn - Xm
// Flags affected: N, Z, C, V

Example

SUBPS x0, x1, x2

Encoding

Binary Layout

11010110

28:21

20:16

000000

15:10

9:5

4:0

Format Data Processing

Opcode 0xBAC00000

Extension MTE (Memory Tagging)

Operands

Xd
Destination 64-bit integer register
Xn
Addr 1
Xm
Addr 2

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xBAC00000	SUBPS <Xd>, <Xn\|SP>, <Xm\|SP>		A64		1 \| 0 \| 1 \| 11010110 \| Xm \| 000000 \| Xn \| Xd

Description

Subtract Pointer, setting Flags subtracts the 56-bit address held in the second source register from the 56-bit address held in the first source register, sign-extends the result to 64-bits, and writes the result to the destination register. It updates the condition flags based on the result of the subtraction.

Operation

bits(64) operand1 = if n == 31 then SP[] else X[n, 64];
bits(64) operand2 = if m == 31 then SP[] else X[m, 64];
operand1 = SignExtend(operand1<55:0>, 64);
operand2 = SignExtend(operand2<55:0>, 64);

bits(64) result;
bits(4) nzcv;

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

PSTATE.<N,Z,C,V> = nzcv;
X[d, 64] = result;