XAFLAG

Convert floating-point condition flags from external format to Arm format

This instruction converts the state of the PSTATE.{N,Z,C,V} flags from an alternative representation required by some software to a form representing the result of an Arm floating-point scalar compare instruction.

Encoding: System

Variants: FEAT_FlagM2 (ARMv8.5)

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
1	1	0	1	0	1	0	1	0	0	0	0	0	0	0	0	0	1	0	0	(0)	(0)	(0)	(0)	0	0	1	1	1	1	1	1
													op1							CRm				op2			Rt

XAFLAG

Decoding algorithm

if !IsFeatureImplemented(FEAT_FlagM2) then EndOfDecode(Decode_UNDEF);

Operation

constant bit n = NOT(PSTATE.C) AND NOT(PSTATE.Z);
constant bit z = PSTATE.Z AND PSTATE.C;
constant bit c = PSTATE.C OR PSTATE.Z;
constant bit v = NOT(PSTATE.C) AND PSTATE.Z;

PSTATE.N = n;
PSTATE.Z = z;
PSTATE.C = c;
PSTATE.V = v;

Explanations