13.85 QASX

Signed saturating parallel add and subtract halfwords with exchange.

Syntax

QASX{cond} {Rd}, Rn, Rm

where:

cond

is an optional condition code.

Rd

is the destination register.

Rm, Rn

are the general-purpose registers holding the operands.

Operation

This instruction exchanges the two halfwords of the second operand, then performs an addition on the two top halfwords of the operands and a subtraction 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.

Availability

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 Arm®v7E-M implementation.

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

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