ST2B (scalar plus immediate)

Contiguous store two-byte structures from two vectors (immediate index)

Contiguous store two-byte structures, each from the same element number in two vector registers to the memory address generated by a 64-bit scalar base and an immediate index which is a multiple of 2 in the range -16 to 14 that is multiplied by the vector's in-memory size, irrespective of predication,

Each predicate element applies to the same element number in each of the two vector registers, or equivalently to the two consecutive bytes in memory which make up each structure. Inactive structures are not written to memory.

313029282726252423222120191817161514131211109876543210
111001000011imm4111PgRnZt
msz<1>msz<0>

ST2B { <Zt1>.B, <Zt2>.B }, <Pg>, [<Xn|SP>{, #<imm>, MUL VL}]

if !HaveSVE() && !HaveSME() then UNDEFINED; integer t = UInt(Zt); integer n = UInt(Rn); integer g = UInt(Pg); integer esize = 8; integer offset = SInt(imm4); integer nreg = 2;

Assembler Symbols

<Zt1>

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

<Zt2>

Is the name of the second scalable vector register to be transferred, encoded as "Zt" plus 1 modulo 32.

<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.

<imm>

Is the optional signed immediate vector offset, a multiple of 2 in the range -16 to 14, defaulting to 0, encoded in the "imm4" field.

Operation

CheckSVEEnabled(); integer elements = VL DIV esize; bits(64) base; bits(PL) mask = P[g]; constant integer mbytes = esize DIV 8; array [0..1] of bits(VL) values; if HaveMTEExt() then SetTagCheckedInstruction(n != 31); 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[] else X[n]; for r = 0 to nreg-1 values[r] = Z[(t+r) MOD 32]; for e = 0 to elements-1 for r = 0 to nreg-1 if ElemP[mask, e, esize] == '1' then integer eoff = (offset * elements * nreg) + (e * nreg) + r; bits(64) addr = base + eoff * mbytes; Mem[addr, mbytes, AccType_NORMAL] = Elem[values[r], e, esize];


Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41

Copyright © 2010-2021 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.