ST1B (scalar plus vector)

Scatter store bytes from a vector (vector index)

Scatter store of bytes from the active elements of a vector register to the memory addresses generated by a 64-bit scalar base plus vector index. The index values are optionally sign or zero-extended from 32 to 64 bits. Inactive elements are not written to memory.

This instruction is illegal when executed in Streaming SVE mode, unless FEAT_SME_FA64 is implemented and enabled.

Encoding: 32-bit unpacked unscaled offset

Variants: FEAT_SVE (PROFILE_A)

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
1	1	1	0	0	1	0	0	0	0	0						1		0
							msz				Zm						xs		Pg			Rn					Zt

ST1B { <Zt>.D }, <Pg>, [<Xn|SP>, <Zm>.D, <mod>]

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) then EndOfDecode(Decode_UNDEF);
constant integer t = UInt(Zt);
constant integer n = UInt(Rn);
constant integer m = UInt(Zm);
constant integer g = UInt(Pg);
constant integer esize = 64;
constant integer msize = 8;
constant integer offs_size = 32;
constant boolean offs_unsigned = xs == '0';
constant integer scale = 0;

Encoding: 32-bit unscaled offset

Variants: FEAT_SVE (PROFILE_A)

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
1	1	1	0	0	1	0	0	0	1	0						1		0
							msz				Zm						xs		Pg			Rn					Zt

ST1B { <Zt>.S }, <Pg>, [<Xn|SP>, <Zm>.S, <mod>]

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) then EndOfDecode(Decode_UNDEF);
constant integer t = UInt(Zt);
constant integer n = UInt(Rn);
constant integer m = UInt(Zm);
constant integer g = UInt(Pg);
constant integer esize = 32;
constant integer msize = 8;
constant integer offs_size = 32;
constant boolean offs_unsigned = xs == '0';
constant integer scale = 0;

Encoding: 64-bit unscaled offset

Variants: FEAT_SVE (PROFILE_A)

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
1	1	1	0	0	1	0	0	0	0	0						1	0	1
							msz				Zm								Pg			Rn					Zt

ST1B { <Zt>.D }, <Pg>, [<Xn|SP>, <Zm>.D]

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) then EndOfDecode(Decode_UNDEF);
constant integer t = UInt(Zt);
constant integer n = UInt(Rn);
constant integer m = UInt(Zm);
constant integer g = UInt(Pg);
constant integer esize = 64;
constant integer msize = 8;
constant integer offs_size = 64;
constant boolean offs_unsigned = TRUE;
constant integer scale = 0;

Operation

CheckNonStreamingSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
bits(64) base;
constant bits(PL) mask = P[g, PL];
bits(VL) offset;
bits(VL) src;
constant integer mbytes = msize DIV 8;
constant boolean contiguous = FALSE;
constant boolean nontemporal = FALSE;
constant boolean tagchecked = TRUE;
constant AccessDescriptor accdesc = CreateAccDescSVE(MemOp_STORE, nontemporal, contiguous,
                                                     tagchecked);

if !AnyActiveElement(mask, esize) then
    if n == 31 && ConstrainUnpredictableBool(Unpredictable_CHECKSPNONEACTIVE) then
        CheckSPAlignment();
else
    if n == 31 then CheckSPAlignment();
    base = if n == 31 then SP[64] else X[n, 64];
    offset = Z[m, VL];
    src = Z[t, VL];

for e = 0 to elements-1
    if ActivePredicateElement(mask, e, esize) then
        constant integer off = Int(Elem[offset, e, esize], offs_unsigned);
        constant bits(64) addr = AddressAdd(base, off << scale, accdesc);
        Mem[addr, mbytes, accdesc] = Elem[src, e, esize];

Explanations

<Zt>: Is the name of the scalable vector register to be transferred, encoded in the "Zt" field.
<Pg>: Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.
<Xn|SP>: Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.
<Zm>: Is the name of the offset scalable vector register, encoded in the "Zm" field.
<mod>:

Operational Notes

If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored when its governing predicate register contains the same value for each execution.