You copied the Doc URL to your clipboard.


Signed Long Multiply, with 32-bit operands and 64-bit result.


SMULL{S}{cond} RdLo, RdHi, Rn, Rm



is an optional suffix available in A32 state only. If S is specified, the condition flags are updated on the result of the operation.


is an optional condition code.

RdLo, RdHi

are the destination registers. RdLo and RdHi must be different registers

Rn, Rm

are ARM registers holding the operands.


The SMULL instruction interprets the values from Rn and Rm as two's complement signed integers. It multiplies these integers and places the least significant 32 bits of the result in RdLo, and the most significant 32 bits of the result in RdHi.

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

If S is specified, this instruction:

  • Updates the N and Z flags according to the result.
  • Does not affect the C or V flags.


This instruction is available in A32 and T32.

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