Arm® A32/T32 Instruction Set Architecture: Armv8, for Armv8-A architecture profile Documentation | MVN, MVNS (register-shifted register): Bitwise NOT (register-shifted register).

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MVN, MVNS (register-shifted register)

Bitwise NOT (register-shifted register) writes the bitwise inverse of a register-shifted register value to the destination register. It can optionally update the condition flags based on the result.

A1

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
!= 1111				0	0	0	1	1	1	1	S	(0)	(0)	(0)	(0)	Rd				Rs				0	stype		1	Rm
cond

Flag setting (S == 1)

MVNS{<c>}{<q>} <Rd>, <Rm>, <shift> <Rs>

Not flag setting (S == 0)

MVN{<c>}{<q>} <Rd>, <Rm>, <shift> <Rs>

d = UInt(Rd);  m = UInt(Rm);  s = UInt(Rs);
setflags = (S == '1');  shift_t = DecodeRegShift(stype);
if d == 15 || m == 15 || s == 15 then UNPREDICTABLE;

For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.

Assembler Symbols

<c>	See Standard assembler syntax fields.

<q>	See Standard assembler syntax fields.

<Rd>	Is the general-purpose destination register, encoded in the "Rd" field.

<Rm>	Is the general-purpose source register, encoded in the "Rm" field.

<shift>

Is the type of shift to be applied to the second source register, encoded in stype:

stype	<shift>
00	LSL
01	LSR
10	ASR
11	ROR

<Rs>	Is the general-purpose source register holding a shift amount in its bottom 8 bits, encoded in the "Rs" field.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    shift_n = UInt(R[s]<7:0>);
    (shifted, carry) = Shift_C(R[m], shift_t, shift_n, PSTATE.C);
    result = NOT(shifted);
    R[d] = result;
    if setflags then
        PSTATE.N = result<31>;
        PSTATE.Z = IsZeroBit(result);
        PSTATE.C = carry;
        // PSTATE.V unchanged

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