Condition Flags
Allows access to the condition flags.
This register is present only when FEAT_AA64 is implemented. Otherwise, direct accesses to NZCV are UNDEFINED.
This register is a Special-purpose register.
NZCV is a 64-bit register.
| 63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 | 32 |
| 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 |
| RES0 | |||||||||||||||||||||||||||||||
| N | Z | C | V | RES0 | |||||||||||||||||||||||||||
Reserved, RES0.
Negative condition flag. Set to 1 if the result of the last flag-setting instruction was negative.
Zero condition flag. Set to 1 if the result of the last flag-setting instruction was zero, and to 0 otherwise. A result of zero often indicates an equal result from a comparison.
Carry condition flag. Set to 1 if the last flag-setting instruction resulted in a carry condition, for example an unsigned overflow on an addition.
Overflow condition flag. Set to 1 if the last flag-setting instruction resulted in an overflow condition, for example a signed overflow on an addition.
Reserved, RES0.
The MSR (register) and MRS instructions used to access NZCV are data-independent-time instructions as described in About PSTATE.DIT.
Accesses to this register use the following encodings in the System register encoding space:
MRS <Xt>, NZCV
(op0 = 0b11, op1 = 0b011, CRn = 0b0100, CRm = 0b0010, op2 = 0b000)
if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then X{64}(t) = Zeros{32} :: PSTATE.[N,Z,C,V] :: Zeros{28}; elsif PSTATE.EL == EL1 then X{64}(t) = Zeros{32} :: PSTATE.[N,Z,C,V] :: Zeros{28}; elsif PSTATE.EL == EL2 then X{64}(t) = Zeros{32} :: PSTATE.[N,Z,C,V] :: Zeros{28}; elsif PSTATE.EL == EL3 then X{64}(t) = Zeros{32} :: PSTATE.[N,Z,C,V] :: Zeros{28}; end;
MSR NZCV, <Xt>
(op0 = 0b11, op1 = 0b011, CRn = 0b0100, CRm = 0b0010, op2 = 0b000)
if !IsFeatureImplemented(FEAT_AA64) then Undefined(); elsif PSTATE.EL == EL0 then PSTATE.[N,Z,C,V] = X{64}(t)[31:28]; elsif PSTATE.EL == EL1 then PSTATE.[N,Z,C,V] = X{64}(t)[31:28]; elsif PSTATE.EL == EL2 then PSTATE.[N,Z,C,V] = X{64}(t)[31:28]; elsif PSTATE.EL == EL3 then PSTATE.[N,Z,C,V] = X{64}(t)[31:28]; end;
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