SADDV

Signed add reduction to scalar

Signed add horizontally across all lanes of a vector, and place the result in the SIMD&FP scalar destination register. Narrow elements are first sign-extended to 64 bits. Inactive elements in the source vector are treated as zero.

Encoding: SVE

Variants: FEAT_SVE || FEAT_SME (FEAT_SVE || FEAT_SME)

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	0	0	1	0	0			0	0	0	0	0	0	0	0	1
								size						op	U				Pg			Zn					Vd

SADDV <Dd>, <Pg>, <Zn>.<T>

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
if size == '11' then EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer g = UInt(Pg);
constant integer n = UInt(Zn);
constant integer d = UInt(Vd);

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
constant bits(PL) mask = P[g, PL];
constant bits(VL) operand = Z[n, VL];
integer sum = 0;

for e = 0 to elements-1
    if ActivePredicateElement(mask, e, esize) then
        constant integer element = SInt(Elem[operand, e, esize]);
        sum = sum + element;

V[d, 64] = sum<63:0>;

Explanations

<Dd>: Is the 64-bit name of the destination SIMD&FP register, encoded in the "Vd" field.
<Pg>: Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.
<Zn>: Is the name of the source scalable vector register, encoded in the "Zn" field.
<T>:

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 operand registers when its governing predicate register contains the same value for each execution.
  • 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 operand registers when its governing predicate register contains the same value for each execution.
  • The values of the NZCV flags.