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ST1W (scalar plus scalar, single register)

Contiguous store words from vector (scalar index)

This instruction performs a contiguous store of words from elements of a vector register to the memory address generated by a 64-bit scalar base and scalar index that is multiplied by 4 and added to the base address. After each element access the index value is incremented, but the index register is not updated. Inactive elements are not written to memory.

The 128-bit element variant is illegal when executed in Streaming SVE mode, unless FEAT_SME_FA64 is implemented and enabled.

It has encodings from 2 classes: 32-bit and 64-bit elements and 128-bit element

32-bit and 64-bit elements class

(FEAT_SVE || FEAT_SME)

313029282726252423222120191817161514131211109876543210
1110010101sz!= 11111010PgRnZt
opcRm

Encoding

ST1W { <Zt>.<T> }, <Pg>, [<Xn|SP>, <Xm>, LSL #2]

Decode

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); if Rm == '11111' then EndOfDecode(Decode_UNDEF); constant integer t = UInt(Zt); constant integer n = UInt(Rn); constant integer m = UInt(Rm); constant integer g = UInt(Pg); constant integer esize = 32 << UInt(sz); constant integer msize = 32;

128-bit element class

(FEAT_SVE2p1)

313029282726252423222120191817161514131211109876543210
11100101000!= 11111010PgRnZt
opco2Rm

Encoding

ST1W { <Zt>.Q }, <Pg>, [<Xn|SP>, <Xm>, LSL #2]

Decode

if !IsFeatureImplemented(FEAT_SVE2p1) then EndOfDecode(Decode_UNDEF); if Rm == '11111' then EndOfDecode(Decode_UNDEF); constant integer t = UInt(Zt); constant integer n = UInt(Rn); constant integer m = UInt(Rm); constant integer g = UInt(Pg); constant integer esize = 128; constant integer msize = 32;

Assembler Symbols

<Zt>

Is the name of the scalable vector register to be transferred, encoded in the "Zt" field.

<T>

Is the size specifier, encoded in sz:

sz <T>
0 S
1 D
<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.

<Xm>

Is the 64-bit name of the general-purpose offset register, encoded in the "Rm" field.

Operation

if esize < 128 then CheckSVEEnabled(); else 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(64) offset; bits(64) addr; bits(VL) src; constant integer mbytes = msize DIV 8; constant boolean contiguous = TRUE; constant boolean nontemporal = FALSE; constant boolean predicated = TRUE; constant boolean tagchecked = TRUE; constant AccessDescriptor accdesc = CreateAccDescSVE(MemOp_STORE, nontemporal, contiguous, predicated, tagchecked); if !AnyActiveElement(mask, esize) then if n == 31 && ConstrainUnpredictableBool(Unpredictable_CHECKSPNONEACTIVE) then CheckSPAlignment(); else if n == 31 then CheckSPAlignment(); src = Z[t, VL]; base = if n == 31 then SP[64] else X[n, 64]; offset = X[m, 64]; addr = AddressAdd(base, UInt(offset) * mbytes, accdesc); for e = 0 to elements-1 if ActivePredicateElement(mask, e, esize) then Mem[addr, mbytes, accdesc] = Elem[src, e, esize]<msize-1:0>; addr = AddressIncrement(addr, mbytes, accdesc);

Operational information

This instruction is a data-independent-time instruction as described in About PSTATE.DIT.


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