SEL (predicates)

Conditionally select elements from two predicates

Read active elements from the first source predicate and inactive elements from the second source predicate and place in the corresponding elements of the destination predicate. Does not set the condition flags.

This instruction is used by the alias MOV (predicate, predicated, merging).

313029282726252423222120191817161514131211109876543210
001001010000Pm01Pg1Pn1Pd
S

SEL <Pd>.B, <Pg>, <Pn>.B, <Pm>.B

if !HaveSVE() && !HaveSME() then UNDEFINED; constant integer esize = 8; integer g = UInt(Pg); integer n = UInt(Pn); integer m = UInt(Pm); integer d = UInt(Pd);

Assembler Symbols

<Pd>

Is the name of the destination scalable predicate register, encoded in the "Pd" field.

<Pg>

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

<Pn>

Is the name of the first source scalable predicate register, encoded in the "Pn" field.

<Pm>

Is the name of the second source scalable predicate register, encoded in the "Pm" field.

Alias Conditions

AliasIs preferred when
MOV (predicate, predicated, merging)Pd == Pm

Operation

CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; bits(PL) mask = P[g, PL]; bits(PL) operand1 = P[n, PL]; bits(PL) operand2 = P[m, PL]; bits(PL) result; constant integer psize = esize DIV 8; for e = 0 to elements-1 bit element1 = PredicateElement(operand1, e, esize); bit element2 = PredicateElement(operand2, e, esize); if ActivePredicateElement(mask, e, esize) then Elem[result, e, psize] = ZeroExtend(element1, psize); else Elem[result, e, psize] = ZeroExtend(element2, psize); P[d, PL] = result;

Operational information

If FEAT_SVE2 is implemented or FEAT_SME is implemented, then if PSTATE.DIT is 1:


Internal version only: aarchmrs v2023-12_rel, pseudocode v2023-12_rel, sve v2023-12_rel ; Build timestamp: 2023-12-15T16:46

Copyright © 2010-2023 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.