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13.85 QSAX

Signed saturating parallel subtract and add halfwords with exchange.

Syntax

QSAX{cond} {Rd}, Rn, Rm

where:

cond

is an optional condition code.

Rd

is the destination register.

Rm, Rn

are the ARM registers holding the operands.

Operation

This instruction exchanges the two halfwords of the secondoperand, then performs a subtraction on the two top halfwords ofthe operands and an addition on the bottom two halfwords. It writesthe 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 evenif 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 GEflags.

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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