Signed halving parallel subtract and add halfwords with exchange.
is an optional condition code.
is the destination register.
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 halves the results and writes them into the corresponding halfwords of the destination. This cannot cause overflow.
You cannot use PC for any register.
You can use SP in ARM instructions but this is deprecated in ARMv6T2 and above. You cannot use SP in Thumb instructions.
This instruction does not affect the N, Z, C, V, Q, or GE flags.
This ARM instruction is available in ARMv6 and above.
This 32-bit Thumb instruction is available in ARMv6T2 and above. For the ARMv7-M architecture, it is only available in an ARMv7E-M implementation.
There is no 16-bit version of this instruction in Thumb.