SPLICE

Splice two vectors under predicate control

Select a region from the first source vector and copy it to the lowest-numbered elements of the result. Then set any remaining elements of the result to a copy of the lowest-numbered elements from the second source vector. The region is selected using the first and last true elements in the vector select predicate register. The result is placed destructively in the destination and first source vector, or constructively in the destination vector.

Encoding: Constructive

Variants: FEAT_SVE2 || FEAT_SME (FEAT_SVE2 || 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	1			1	0	1	1	0	1	1	0	0
								size											Pv			Zn					Zd

SPLICE <Zd>.<T>, <Pv>, { <Zn1>.<T>, <Zn2>.<T> }

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer v = UInt(Pv);
constant integer dst = UInt(Zd);
constant integer s1 = UInt(Zn);
constant integer s2 = (s1 + 1) MOD 32;

Encoding: Destructive

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	1			1	0	1	1	0	0	1	0	0
								size											Pv			Zm					Zdn

SPLICE <Zdn>.<T>, <Pv>, <Zdn>.<T>, <Zm>.<T>

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer v = UInt(Pv);
constant integer dst = UInt(Zdn);
constant integer s1 = dst;
constant integer s2 = UInt(Zm);

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
constant bits(PL) mask = P[v, PL];
constant bits(VL) operand1 = if AnyActiveElement(mask, esize) then Z[s1, VL] else Zeros(VL);
constant bits(VL) operand2 = Z[s2, VL];
bits(VL) result;
integer x = 0;
boolean active = FALSE;
constant integer lastnum = LastActiveElement(mask, esize);

if lastnum >= 0 then
    for e = 0 to lastnum
        active = active || ActivePredicateElement(mask, e, esize);
        if active then
            Elem[result, x, esize] = Elem[operand1, e, esize];
            x = x + 1;

constant integer nelements = (elements - x) - 1;
for e = 0 to nelements
    Elem[result, x, esize] = Elem[operand2, e, esize];
    x = x + 1;

Z[dst, VL] = result;

Explanations

<Zd>: Is the name of the destination scalable vector register, encoded in the "Zd" field.
<T>: <Pv>: Is the name of the vector select predicate register P0-P7, encoded in the "Pv" field.
<Zn1>: Is the name of the first scalable vector register of the source multi-vector group, encoded in the "Zn" field.
<Zn2>: Is the name of the second scalable vector register of the source multi-vector group, encoded in the "Zn" field.
<Zdn>: Is the name of the first source and destination scalable vector register, encoded in the "Zdn" field.
<Zm>: Is the name of the second source scalable vector register, encoded in the "Zm" field.

Operational Notes

The destructive variant of this instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and the destructive variant of this instruction is CONSTRAINED UNPREDICTABLE:

• The MOVPRFX must be unpredicated.
• The MOVPRFX must specify the same destination register as this instruction.
• The destination register must not refer to architectural register state referenced by any other source operand register of this instruction.