PTEST

Set condition flags for predicate

This instruction sets the First (N), None (Z), and !Last (C) condition flags based on the predicate source register, and sets the V flag to zero.

SVE
(FEAT_SVE || FEAT_SME)

313029282726252423222120191817161514131211109876543210
001001010101000011Pg0Pn00000
opSopc2

Encoding

PTEST <Pg>, <Pn>.B

Decode for this encoding

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);

Assembler Symbols

<Pg>

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

<Pn>

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

Operation

CheckSVEEnabled(); let VL : integer{} = CurrentVL(); let PL : integer{} = VL DIV 8; let mask : bits(PL) = P{}(g); let result : bits(PL) = P{}(n); PSTATE.[N,Z,C,V] = PredTest{PL}(mask, result, esize);

Operational information

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

If FEAT_SME is implemented and the PE is in Streaming SVE mode, then any subsequent instruction which is dependent on the predicate register written by this instruction might be significantly delayed.


2026-03_rel 2026-03-26 20:48:11

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