MUL, MULS
Multiply
Multiply multiplies two register values. The least significant 32
bits of the result are written to the destination register. These 32
bits do not depend on whether the source register values are
considered to be signed values or unsigned values.
Optionally, it can update the condition flags based on the
result. In the T32 instruction set, this option is limited to only a
few forms of the instruction. 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
and
T2
)
.
!= 1111
0
0
0
0
0
0
0
(0)
(0)
(0)
(0)
1
0
0
1
1
MULS{<c>}{<q>} <Rd>, <Rn>{, <Rm>}
0
MUL{<c>}{<q>} <Rd>, <Rn>{, <Rm>}
let d : integer = UInt(Rd);
let n : integer = UInt(Rn);
let m : integer = UInt(Rm);
let setflags : boolean = (S == '1');
if d == 15 || n == 15 || m == 15 then UnpredictableProcedure(); end;
0
1
0
0
0
0
1
1
0
1
MUL<c>{<q>} <Rdm>, <Rn>{, <Rdm>}
MULS{<q>} <Rdm>, <Rn>{, <Rdm>}
let d : integer = UInt(Rdm);
let n : integer = UInt(Rn);
let m : integer = UInt(Rdm);
let setflags : boolean = !InITBlock();
1
1
1
1
1
0
1
1
0
0
0
0
1
1
1
1
0
0
0
0
MUL{<c>}{<q>} <Rd>, <Rn>{, <Rm>}
MUL<c>.W <Rd>, <Rn>{, <Rm>}
let d : integer = UInt(Rd);
let n : integer = UInt(Rn);
let m : integer = UInt(Rm);
let setflags : boolean = FALSE;
// Armv8-A removes UNPREDICTABLE for R13
if d == 15 || n == 15 || m == 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. If omitted, <Rd> is used.
<Rdm>
Is the second general-purpose source register holding the multiplier and the destination register, encoded in the "Rdm" field.
if ConditionPassed() then
EncodingSpecificOperations();
let operand1 : integer = SInt(R(n)); // operand1 = UInt(R[n]) produces the same final results
let operand2 : integer = SInt(R(m)); // operand2 = UInt(R[m]) produces the same final results
let result : integer = operand1 * operand2;
R(d) = result[31:0];
if setflags then
PSTATE.N = result[31];
PSTATE.Z = IsZeroBit{32}(result[31:0]);
// PSTATE.C, PSTATE.V unchanged
end;
end;
2026-03-12 12:23:09
2025-09_rel_asl1