BRKNS

Propagate break to next partition, setting the condition flags

If the last active element of the first source predicate is false then set the destination predicate to all-false. Otherwise leaves the destination and second source predicate unchanged. Sets the First (N), None (Z), !Last (C) condition flags based on the predicate result, and the V flag to zero.

Encoding: Setting the condition flags

Variants: FEAT_SVE || FEAT_SME (FEAT_SVE || FEAT_SME)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	1	0	0	1	0	1	0	1	0	1	1	0	0	0	0	1					0					0
									S									Pg					Pn					Pdm

BRKNS <Pdm>.B, <Pg>/Z, <Pn>.B, <Pdm>.B

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant integer g = UInt(Pg);
constant integer n = UInt(Pn);
constant integer dm = UInt(Pdm);
constant boolean setflags = TRUE;

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant bits(PL) mask = P[g, PL];
constant bits(PL) operand1 = P[n, PL];
constant bits(PL) operand2 = P[dm, PL];
bits(PL) result;

if LastActive(mask, operand1, 8) == '1' then
    result = operand2;
else
    result = Zeros(PL);

if setflags then
    PSTATE. = PredTest(Ones(PL), result, 8);
P[dm, PL] = result;

Explanations

<Pdm>: Is the name of the second source and destination scalable predicate register, encoded in the "Pdm" 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.

Operational Notes

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