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SEL (predicates)

Conditionally select elements from two predicates

This instruction reads Active elements from the first source predicate and Inactive elements from the second source predicate and places them in the corresponding elements of the destination predicate. This instruction does not set the condition flags.

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

SVE class

(FEAT_SVE || FEAT_SME)

313029282726252423222120191817161514131211109876543210
001001010000Pm01Pg1Pn1Pd
opSo2o3

Encoding

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

Decode

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8; let g : integer = UInt(Pg); let n : integer = UInt(Pn); let m : integer = UInt(Pm); let d : integer = 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, merging)Pd == Pm

Operation

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

Operational information

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

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