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REVB, REVH, REVW

Reverse bytes / halfwords / words within elements (predicated).

Reverse the order of 8-bit bytes, 16-bit halfwords or 32-bit words within each active element of the source vector, and place the results in the corresponding elements of the destination vector. Inactive elements in the destination vector register remain unmodified.

It has encodings from 3 classes: Byte , Halfword and Word

Byte

313029282726252423222120191817161514131211109876543210
00000101size100100100PgZnZd

Byte

REVB <Zd>.<T>, <Pg>/M, <Zn>.<T>

if !HaveSVE() then UNDEFINED; if size == '00' then UNDEFINED; integer esize = 8 << UInt(size); integer g = UInt(Pg); integer n = UInt(Zn); integer d = UInt(Zd); integer swsize = 8;

Halfword

313029282726252423222120191817161514131211109876543210
00000101size100101100PgZnZd

Halfword

REVH <Zd>.<T>, <Pg>/M, <Zn>.<T>

if !HaveSVE() then UNDEFINED; if size != '1x' then UNDEFINED; integer esize = 8 << UInt(size); integer g = UInt(Pg); integer n = UInt(Zn); integer d = UInt(Zd); integer swsize = 16;

Word

313029282726252423222120191817161514131211109876543210
00000101size100110100PgZnZd

Word

REVW <Zd>.D, <Pg>/M, <Zn>.D

if !HaveSVE() then UNDEFINED; if size != '11' then UNDEFINED; integer esize = 8 << UInt(size); integer g = UInt(Pg); integer n = UInt(Zn); integer d = UInt(Zd); integer swsize = 32;

Assembler Symbols

<Zd>

Is the name of the destination scalable vector register, encoded in the "Zd" field.

<T> For the byte variant: is the size specifier, encoded in size:
size<T>
00RESERVED
01H
10S
11D
For the halfword variant: is the size specifier, encoded in size<0>:
size<0><T>
0S
1D
<Pg>

Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Zn>

Is the name of the source scalable vector register, encoded in the "Zn" field.

Operation

CheckSVEEnabled(); integer elements = VL DIV esize; bits(PL) mask = P[g]; bits(VL) operand = Z[n]; bits(VL) result = Z[d]; for e = 0 to elements-1 if ElemP[mask, e, esize] == '1' then bits(esize) element = Elem[operand, e, esize]; Elem[result, e, esize] = Reverse(element, swsize); Z[d] = result;

Operational information

If PSTATE.DIT is 1:

This instruction might be immediately preceded in program order by a MOVPRFX instruction that conforms to all of the following requirements, otherwise the behavior of either or both instructions is unpredictable:

The MOVPRFX instructions that can be used with this instruction are as follows:


Internal version only: isa v30.44v30.42, AdvSIMD v27.08, pseudocode v8.5-2019-06_rc2-5-g22901f2future-20190403, sve v2019-06_rc4v8.5-00bet10_rc5 ; Build timestamp: 2019-06-26T222019-04-17T09:0458

Copyright © 2010-2019 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.

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