MLA (vector)

Multiply-add to accumulator (vector)

This instruction multiplies corresponding elements in the vectors of the two source SIMD&FP registers, and accumulates the results with the vector elements of the destination SIMD&FP register.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

Encoding: Three registers of the same type

Variants: FEAT_AdvSIMD (ARMv8.0)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0		0	0	1	1	1	0			1						1	0	0	1	0	1
	Q	U						size			Rm					opcode						Rn					Rd

MLA <Vd>.<T>, <Vn>.<T>, <Vm>.<T>

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer m = UInt(Rm);
if size == '11' then EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer datasize = 64 << UInt(Q);
constant integer elements = datasize DIV esize;

Operation

CheckFPAdvSIMDEnabled64();
constant bits(datasize) operand1 = V[n, datasize];
constant bits(datasize) operand2 = V[m, datasize];
constant bits(datasize) operand3 = V[d, datasize];
bits(datasize) result;
bits(esize) element1;
bits(esize) element2;
bits(esize) product;

for e = 0 to elements-1
    element1 = Elem[operand1, e, esize];
    element2 = Elem[operand2, e, esize];
    product = (UInt(element1) * UInt(element2));
    Elem[result, e, esize] = Elem[operand3, e, esize] + product;

V[d, datasize] = result;

Explanations

<Vd>: Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
<T>: <Vn>: Is the name of the first SIMD&FP source register, encoded in the "Rn" field.
<Vm>: Is the name of the second SIMD&FP source register, encoded in the "Rm" field.

Operational Notes

If PSTATE.DIT is 1:

• The execution time of this instruction is independent of:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.
• The response of this instruction to asynchronous exceptions does not vary based on:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.