SMULH Signed multiply high This instruction multiplies two 64-bit register values, and writes bits[127:64] of the 128-bit result to the 64-bit destination register. This instruction is a data-independent-time instruction as described in About PSTATE.DIT. 1 0 0 1 1 0 1 1 0 1 0 0 (1) (1) (1) (1) (1) SMULH <Xd>, <Xn>, <Xm> let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn); let m : integer{} = UInt(Rm); <Xd> Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field. <Xn> Is the 64-bit name of the first general-purpose source register holding the multiplicand, encoded in the "Rn" field. <Xm> Is the 64-bit name of the second general-purpose source register holding the multiplier, encoded in the "Rm" field. let operand1 : bits(64) = X{}(n); let operand2 : bits(64) = X{}(m); let result : integer = SInt(operand1) * SInt(operand2); X{64}(d) = result[127:64]; 2026-03-26 20:27:25 2026-03_rel