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QSUB

Signed saturating Subtract.

Syntax

QSUB{cond} {Rd}, Rm, Rn

where:

cond

is an optional condition code.

Rd

is the destination register.

Rm, Rn

are the registers holding the operands.

Operation

The QSUB instruction subtracts the value in Rn from the value in Rm. It saturates the result to the signed range –231x ≤ 231–1.

Note

All values are treated as two’s complement signed integers by this instruction.

Register restrictions

You cannot use PC for any operand.

You can use SP in A32 instructions but this is deprecated. You cannot use SP in T32 instructions.

Q flag

If saturation occurs, this instruction sets the Q flag. To read the state of the Q flag, use an MRS instruction.

Availability

The 32-bit instruction is available in A32 and T32.

There is no 16-bit version of this instruction in T32.

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