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MVN, MVNS (immediate)

Bitwise NOT (immediate) writes the bitwise inverse of an immediate value to the destination register.

If the destination register is not the PC, the MVNS variant of the instruction updates the condition flags based on the result.

The field descriptions for <Rd> identify the encodings where the PC is permitted as the destination register. ARM deprecates any use of these encodings. However, when the destination register is the PC:

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

313029282726252423222120191817161514131211109876543210
!= 11110011111S(0)(0)(0)(0)Rdimm12
cond

MVN (S == 0)

MVN{<c>}{<q>} <Rd>, #<const>

MVNS (S == 1)

MVNS{<c>}{<q>} <Rd>, #<const>

d = UInt(Rd);  setflags = (S == '1');
(imm32, carry) = A32ExpandImm_C(imm12, PSTATE.C);

T1

15141312111098765432101514131211109876543210
11110i00011S11110imm3Rdimm8

MVN (S == 0)

MVN{<c>}{<q>} <Rd>, #<const>

MVNS (S == 1)

MVNS{<c>}{<q>} <Rd>, #<const>

d = UInt(Rd);  setflags = (S == '1');
(imm32, carry) = T32ExpandImm_C(i:imm3:imm8, PSTATE.C);
if d == 15 then UNPREDICTABLE; // Armv8-A removes UNPREDICTABLE for R13

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>

For encoding A1: is the general-purpose destination register, encoded in the "Rd" field. Arm deprecates using the PC as the destination register, but if the PC is used:

For encoding T1: is the general-purpose destination register, encoded in the "Rd" field.

<const>

For encoding A1: an immediate value. See Modified immediate constants in A32 instructions for the range of values.

For encoding T1: an immediate value. See Modified immediate constants in T32 instructions for the range of values.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    result = NOT(imm32);
    if d == 15 then          // Can only occur for A32 encoding
        if setflags then
            ALUExceptionReturn(result);
        else
            ALUWritePC(result);
    else
        R[d] = result;
        if setflags then
            PSTATE.N = result<31>;
            PSTATE.Z = IsZeroBit(result);
            PSTATE.C = carry;
            // PSTATE.V unchanged
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