SMLAL, SMLALS Signed Multiply Accumulate Long Signed Multiply Accumulate Long multiplies two signed 32-bit values to produce a 64-bit value, and accumulates this with a 64-bit value. In A32 instructions, the condition flags can optionally be updated based on the result. Use of this option adversely affects performance on many implementations. For more information about the CONSTRAINED UNPREDICTABLE behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors. This instruction is a data-independent-time instruction as described in About the DIT bit. It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) . != 1111 0 0 0 0 1 1 1 1 0 0 1 1 SMLALS{<c>}{<q>} <RdLo>, <RdHi>, <Rn>, <Rm> 0 SMLAL{<c>}{<q>} <RdLo>, <RdHi>, <Rn>, <Rm> let dLo : integer = UInt(RdLo); let dHi : integer = UInt(RdHi); let n : integer = UInt(Rn); let m : integer = UInt(Rm); let setflags : boolean = (S == '1'); if dLo == 15 || dHi == 15 || n == 15 || m == 15 then UnpredictableProcedure(); end; if dHi == dLo then UnpredictableProcedure(); end; dHi == dLo 1 1 1 1 1 0 1 1 1 1 0 0 0 0 0 0 SMLAL{<c>}{<q>} <RdLo>, <RdHi>, <Rn>, <Rm> let dLo : integer = UInt(RdLo); let dHi : integer = UInt(RdHi); let n : integer = UInt(Rn); let m : integer = UInt(Rm); let setflags : boolean = FALSE; if dLo == 15 || dHi == 15 || n == 15 || m == 15 then UnpredictableProcedure(); end; // Armv8-A removes UNPREDICTABLE for R13 if dHi == dLo then UnpredictableProcedure(); end; dHi == dLo <c> See Standard assembler syntax fields. <q> See Standard assembler syntax fields. <RdLo> Is the general-purpose source register holding the lower 32 bits of the addend, and the destination register for the lower 32 bits of the result, encoded in the "RdLo" field. <RdHi> Is the general-purpose source register holding the upper 32 bits of the addend, and the destination register for the upper 32 bits of the result, encoded in the "RdHi" field. <Rn> Is the first general-purpose source register holding the multiplicand, encoded in the "Rn" field. <Rm> Is the second general-purpose source register holding the multiplier, encoded in the "Rm" field. if ConditionPassed() then EncodingSpecificOperations(); let result : integer = SInt(R(n)) * SInt(R(m)) + SInt(R(dHi)::R(dLo)); R(dHi) = result[63:32]; R(dLo) = result[31:0]; if setflags then PSTATE.N = result[63]; PSTATE.Z = IsZeroBit{64}(result[63:0]); // PSTATE.C, PSTATE.V unchanged end; end; 2026-03-26 20:27:25 2026-03_rel