PFIRST

Set the first active predicate element to true

Sets the first active element in the destination predicate to true, otherwise elements from the source predicate are passed through unchanged. Sets the First (N), None (Z), !Last (C) condition flags based on the predicate result, and the V flag to zero.

313029282726252423222120191817161514131211109876543210
00100101010110001100000Pg0Pdn
S

PFIRST <Pdn>.B, <Pg>, <Pdn>.B

if !HaveSVE() then UNDEFINED; integer esize = 8; integer g = UInt(Pg); integer dn = UInt(Pdn);

Assembler Symbols

<Pdn>

Is the name of the source and destination scalable predicate register, encoded in the "Pdn" field.

<Pg>

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

Operation

CheckSVEEnabled(); integer elements = VL DIV esize; bits(PL) mask = P[g]; bits(PL) result = P[dn]; integer first = -1; for e = 0 to elements-1 if ElemP[mask, e, esize] == '1' && first == -1 then first = e; if first >= 0 then ElemP[result, first, esize] = '1'; PSTATE.<N,Z,C,V> = PredTest(mask, result, esize); P[dn] = result;


Internal version only: isa v32.15, AdvSIMD v29.05, pseudocode v2021-03, sve v2021-03_rc2 ; Build timestamp: 2021-03-30T21:36

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