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Signed saturating parallel subtract and add halfwords with exchange.


QSAX{cond} {Rd}, Rn, Rm



is an optional condition code.


is the destination register.

Rm, Rn

are the ARM registers holding the operands.


This instruction exchanges the two halfwords of the second operand, then performs a subtraction on the two top halfwords of the operands and an addition on the bottom two halfwords. It writes the results into the corresponding halfwords of the destination. It saturates the results to the signed range -215x ≤ 215 -1. The Q flag is not affected even if this operation saturates.

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.

Condition flags

This instruction does not affect the N, Z, C, V, Q, or GE flags.


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

For the ARMv7-M architecture, the 32-bit T32 instruction is only available in an ARMv7E-M implementation.

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