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ZERO (quad-vector)

Zero ZA quad-vector groups

This instruction zeroes one, two, or four ZA quad-vector groups.

The quad-vector group within all of, each half of, or each quarter of the ZA array is selected by the sum of the vector select register and offset range, modulo all, half, or quarter the number of ZA array vectors.

The vector group symbol, VGx2 or VGx4, indicates that the ZA operand consists of two or four ZA quad-vector groups respectively.

It has encodings from 3 classes: One ZA quad-vector , Two ZA quad-vectors and Four ZA quad-vectors

One ZA quad-vector class

(FEAT_SME2p1)

313029282726252423222120191817161514131211109876543210
11000000000011101Rv00000000000off2
opc

Encoding

ZERO ZA.D[<Wv>, <offs1>:<offs4>]

Decode

if !IsFeatureImplemented(FEAT_SME2p1) then EndOfDecode(Decode_UNDEF); constant integer v = UInt('010':Rv); constant integer offset = UInt(off2:'00'); constant integer ngrp = 1; constant integer nvec = 4;

Two ZA quad-vectors class

(FEAT_SME2p1)

313029282726252423222120191817161514131211109876543210
11000000000011110Rv000000000000o1
opc

Encoding

ZERO ZA.D[<Wv>, <offs1>:<offs4>, VGx2]

Decode

if !IsFeatureImplemented(FEAT_SME2p1) then EndOfDecode(Decode_UNDEF); constant integer v = UInt('010':Rv); constant integer offset = UInt(o1:'00'); constant integer ngrp = 2; constant integer nvec = 4;

Four ZA quad-vectors class

(FEAT_SME2p1)

313029282726252423222120191817161514131211109876543210
11000000000011111Rv000000000000o1
opc

Encoding

ZERO ZA.D[<Wv>, <offs1>:<offs4>, VGx4]

Decode

if !IsFeatureImplemented(FEAT_SME2p1) then EndOfDecode(Decode_UNDEF); constant integer v = UInt('010':Rv); constant integer offset = UInt(o1:'00'); constant integer ngrp = 4; constant integer nvec = 4;

Assembler Symbols

<Wv>

Is the 32-bit name of the vector select register W8-W11, encoded in the "Rv" field.

<offs1>

For the "One ZA quad-vector" variant: is the first vector select offset, encoded as "off2" field times 4.

For the "Four ZA quad-vectors" and "Two ZA quad-vectors" variants: is the first vector select offset, encoded as "o1" field times 4.

<offs4>

For the "One ZA quad-vector" variant: is the fourth vector select offset, encoded as "off2" field times 4 plus 3.

For the "Four ZA quad-vectors" and "Two ZA quad-vectors" variants: is the fourth vector select offset, encoded as "o1" field times 4 plus 3.

Operation

CheckStreamingSVEAndZAEnabled(); constant integer VL = CurrentVL; constant integer vectors = VL DIV 8; constant integer vstride = vectors DIV ngrp; constant bits(32) vbase = X[v, 32]; integer vec = (UInt(vbase) + offset) MOD vstride; vec = vec - (vec MOD nvec); for r = 0 to ngrp-1 for i = 0 to nvec-1 ZAvector[vec + i, VL] = Zeros(VL); vec = vec + vstride;

Operational information

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

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