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LASTB (scalar)

Extract last element to general-purpose registerregister.

If there is an active element then extract the last active element from the final source vector register. If there are no active elements, extract the highest-numbered element. Then zero-extend and place the extracted element in the destination general-purpose register.

.

If there is an active element then extract the last active element from the final source vector register. If there are no active elements, extract the highest-numbered element. Then zero-extend and place the extracted element in the destination general-purpose register.

313029282726252423222120191817161514131211109876543210
00000101size100001101PgZnRd
B

LASTB <R><d>, <Pg>, <Zn>.<T>

if !HaveSVE() then UNDEFINED; integer esize = 8 << UInt(size); integer rsize = if esize < 64 then 32 else 64; integer g = UInt(Pg); integer n = UInt(Zn); integer d = UInt(Rd); boolean isBefore = TRUE;

Assembler Symbols

<R>

Is a width specifier, encoded in size:

size<R>
01W
x0W
11X
<R> Is a width specifier, encoded in size:
size<R>
01W
x0W
11X
<d>

Is the number [0-30] of the destination general-purpose register or the name ZR (31), encoded in the "Rd" field.

<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.

<T>

Is the size specifier, encoded in size:

size<T>
00B
01H
10S
11D
<T> Is the size specifier, encoded in size:
size<T>
00B
01H
10S
11D

Operation

CheckSVEEnabled(); integer elements = VL DIV esize; bits(PL) mask = P[g]; bits(VL) operand = Z[n]; bits(rsize) result; integer last = LastActiveElement(mask, esize); if isBefore then if last < 0 then last = elements - 1; else last = last + 1; if last >= elements then last = 0; result = ZeroExtend(Elem[operand, last, esize]); X[d] = result;


Internal version only: isa v32.12v32.06, AdvSIMD v29.04, pseudocode v2020-09_xmlv2020-06_rel, sve v2020-09_rc3v2020-06_rel0 ; Build timestamp: 2020-11-18T172020-07-03T12:2342

Copyright © 2010-2020 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.

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