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Signed Multiply Wide, with one 32-bit and one 16-bit operand, providing the top 32 bits of the result.


SMULW<y>{cond} {Rd}, Rn, Rm



is either B or T. B means use the bottom half (bits [15:0]) of Rm, T means use the top half (bits [31:16]) of Rm.


is an optional condition code.


is the destination register.

Rn, Rm

are the registers holding the values to be multiplied.


SMULWy multiplies the signed integer from the selected half of Rm by the signed integer from Rn, and places the upper 32-bits of the 48-bit result in Rd.

Register restrictions

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.

Condition flags

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


This ARM instruction is available in ARMv6 and above, and E variants of ARMv5T.

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.