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NOP

No Operation does nothing. This instruction can be used for instruction alignment purposes.

The timing effects of including a NOP instruction in a program are not guaranteed. It can increase execution time, leave it unchanged, or even reduce it. Therefore, NOP instructions are not suitable for timing loops.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 and T2 ) .

A1

313029282726252423222120191817161514131211109876543210
!= 1111001100100000(1)(1)(1)(1)(0)(0)(0)(0)00000000
cond

A1

NOP{<c>}{<q>}

// No additional decoding required

T1

1514131211109876543210
1011111100000000

T1

NOP{<c>}{<q>}

// No additional decoding required

T2

15141312111098765432101514131211109876543210
111100111010(1)(1)(1)(1)10(0)0(0)00000000000

T2

NOP{<c>}.W

// No additional decoding required

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.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    // Do nothing

Operational information

If CPSR.DIT is 1 and this instruction passes its condition execution check:

  • The execution time of this instruction is independent of:
    • The values of the data supplied in any of its registers.
    • The values of the NZCV flags.
  • The response of this instruction to asynchronous exceptions does not vary based on:
    • The values of the data supplied in any of its registers.
    • The values of the NZCV flags.
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