ADDP (scalar)

Add pair of elements (scalar)

This instruction adds two vector elements in the source SIMD&FP register and writes the scalar result into 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: Advanced SIMD

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	1	0	1	1	1	1	0	1	1	1	1	0	0	0	1	1	0	1	1	1	0
		U						size							opcode							Rn					Rd

ADDP D<d>, <Vn>.2D

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer esize = 64;
constant integer datasize = 128;

Operation

CheckFPAdvSIMDEnabled64();
constant bits(datasize) operand = V[n, datasize];
V[d, esize] = IntReduce(ReduceOp_ADD, operand, esize);

Explanations

<d>: Is the number of the SIMD&FP destination register, encoded in the "Rd" field.
<Vn>: Is the name of the SIMD&FP source register, encoded in the "Rn" 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.