SMMLS, SMMLSR
Signed Most Significant Word Multiply Subtract
Signed
Most Significant Word Multiply Subtract multiplies two signed 32-bit
values, subtracts the result from a 32-bit accumulate value that
is shifted left by 32 bits, and extracts the most significant 32
bits of the result of that subtraction.
Optionally, the instruction can specify that the result of
the instruction is rounded instead of being truncated. In this case,
the constant 0x80000000 is added to the result
of the subtraction before the high word is extracted.
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
1
1
1
0
1
0
1
1
1
1
0
SMMLS{<c>}{<q>} <Rd>, <Rn>, <Rm>, <Ra>
1
SMMLSR{<c>}{<q>} <Rd>, <Rn>, <Rm>, <Ra>
let d : integer = UInt(Rd);
let n : integer = UInt(Rn);
let m : integer = UInt(Rm);
let a : integer = UInt(Ra);
let round : boolean = (R == '1');
if d == 15 || n == 15 || m == 15 || a == 15 then UnpredictableProcedure(); end;
1
1
1
1
1
0
1
1
0
1
1
0
0
0
0
0
SMMLS{<c>}{<q>} <Rd>, <Rn>, <Rm>, <Ra>
1
SMMLSR{<c>}{<q>} <Rd>, <Rn>, <Rm>, <Ra>
let d : integer = UInt(Rd);
let n : integer = UInt(Rn);
let m : integer = UInt(Rm);
let a : integer = UInt(Ra);
let round : boolean = (R == '1');
// Armv8-A removes UNPREDICTABLE for R13
if d == 15 || n == 15 || m == 15 || a == 15 then UnpredictableProcedure(); end;
<c>
See Standard assembler syntax fields.
<q>
See Standard assembler syntax fields.
<Rd>
Is the general-purpose destination register, encoded in the "Rd" 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.
<Ra>
Is the third general-purpose source register holding the addend, encoded in the "Ra" field.
if ConditionPassed() then
EncodingSpecificOperations();
var result : integer = (SInt(R(a)) << 32) - SInt(R(n)) * SInt(R(m));
if round then result = result + 0x80000000; end;
R(d) = result[63:32];
end;
2026-03-12 12:23:09
2025-09_rel_asl1