You copied the Doc URL to your clipboard.

TST (immediate)

Test (immediate) performs a bitwise AND operation on a register value and an immediate value. It updates the condition flags based on the result, and discards the result.

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

A1

313029282726252423222120191817161514131211109876543210
!= 111100110001Rn(0)(0)(0)(0)imm12
cond

A1

TST{<c>}{<q>} <Rn>, #<const>

n = UInt(Rn);
(imm32, carry) = A32ExpandImm_C(imm12, PSTATE.C);

T1

15141312111098765432101514131211109876543210
11110i000001Rn0imm31111imm8

T1

TST{<c>}{<q>} <Rn>, #<const>

n = UInt(Rn);
(imm32, carry) = T32ExpandImm_C(i:imm3:imm8, PSTATE.C);
if n == 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.

<Rn>

For encoding A1: is the general-purpose source register, encoded in the "Rn" field. The PC can be used, but this is deprecated.

For encoding T1: is the general-purpose source register, encoded in the "Rn" 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 = R[n] AND imm32;
    PSTATE.N = result<31>;
    PSTATE.Z = IsZeroBit(result);
    PSTATE.C = carry;
    // PSTATE.V unchanged

Operational information

If CPSR.DIT is 1, this instruction has passed its condition execution check, and does not use R15 as either its source or destination:

  • 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.
Was this page helpful? Yes No