ST4 (multiple structures)

Store multiple 4-element structures from four registers. This instruction stores multiple 4-element structures to memory from four SIMD&FP registers, with interleaving. Every element of each register is stored.

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.

It has encodings from 2 classes: No offset and Post-index

No offset

313029282726252423222120191817161514131211109876543210
0Q001100000000000000sizeRnRt
Lopcode

ST4 { <Vt>.<T>, <Vt2>.<T>, <Vt3>.<T>, <Vt4>.<T> }, [<Xn|SP>]

integer t = UInt(Rt); integer n = UInt(Rn); integer m = integer UNKNOWN; boolean wback = FALSE; boolean nontemporal = FALSE; boolean tagchecked = wback || n != 31;

Post-index

313029282726252423222120191817161514131211109876543210
0Q001100100Rm0000sizeRnRt
Lopcode

Immediate offset (Rm == 11111)

ST4 { <Vt>.<T>, <Vt2>.<T>, <Vt3>.<T>, <Vt4>.<T> }, [<Xn|SP>], <imm>

Register offset (Rm != 11111)

ST4 { <Vt>.<T>, <Vt2>.<T>, <Vt3>.<T>, <Vt4>.<T> }, [<Xn|SP>], <Xm>

integer t = UInt(Rt); integer n = UInt(Rn); integer m = UInt(Rm); boolean wback = TRUE; boolean nontemporal = FALSE; boolean tagchecked = wback || n != 31;

Assembler Symbols

<Vt>

Is the name of the first or only SIMD&FP register to be transferred, encoded in the "Rt" field.

<T>

Is an arrangement specifier, encoded in size:Q:

size Q <T>
00 0 8B
00 1 16B
01 0 4H
01 1 8H
10 0 2S
10 1 4S
11 0 RESERVED
11 1 2D
<Vt2>

Is the name of the second SIMD&FP register to be transferred, encoded as "Rt" plus 1 modulo 32.

<Vt3>

Is the name of the third SIMD&FP register to be transferred, encoded as "Rt" plus 2 modulo 32.

<Vt4>

Is the name of the fourth SIMD&FP register to be transferred, encoded as "Rt" plus 3 modulo 32.

<Xn|SP>

Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.

<imm>

Is the post-index immediate offset, encoded in Q:

Q <imm>
0 #32
1 #64
<Xm>

Is the 64-bit name of the general-purpose post-index register, excluding XZR, encoded in the "Rm" field.

Shared Decode

constant integer datasize = 64 << UInt(Q); constant integer esize = 8 << UInt(size); integer elements = datasize DIV esize; integer rpt = 1; integer selem = 4; // .1D format only permitted with LD1 & ST1 if size:Q == '110' && selem != 1 then UNDEFINED;

Operation

CheckFPAdvSIMDEnabled64(); bits(64) address; bits(64) eaddr; bits(64) offs; bits(datasize) rval; integer tt; constant integer ebytes = esize DIV 8; AccessDescriptor accdesc = CreateAccDescASIMD(MemOp_STORE, nontemporal, tagchecked); if n == 31 then CheckSPAlignment(); address = SP[]; else address = X[n, 64]; offs = Zeros(64); for r = 0 to rpt-1 for e = 0 to elements-1 tt = (t + r) MOD 32; for s = 0 to selem-1 rval = V[tt, datasize]; eaddr = AddressIncrement(address, offs, accdesc); Mem[eaddr, ebytes, accdesc] = Elem[rval, e, esize]; offs = offs + ebytes; tt = (tt + 1) MOD 32; if wback then if m != 31 then offs = X[m, 64]; address = AddressAdd(address, offs, accdesc); if n == 31 then SP[] = address; else X[n, 64] = address;

Operational information

If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.


Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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