TST (immediate)

Test bits (immediate)

This instruction performs a bitwise AND of a register value and an immediate value, and discards the results. It updates the condition flags based on the result.

Encoding: Setting the condition flags

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
	1	1	1	0	0	1	0	0																			1	1	1	1	1
sf	opc								N	immr						imms						Rn					Rd

32-bit (sf == 0 && N == 0)

TST <Wn>, #<imm>

Equivalent to: ANDS WZR, <Wn>, #<imm>

64-bit (sf == 1)

TST <Xn>, #<imm>

Equivalent to: ANDS XZR, <Xn>, #<imm>

Explanations

<Wn>: Is the 32-bit name of the general-purpose source register, encoded in the "Rn" field.
<imm>: For the "32-bit" variant: is the bitmask immediate, encoded in "imms:immr".
<imm>: For the "64-bit" variant: is the bitmask immediate, encoded in "N:imms:immr".
<Xn>: Is the 64-bit name of the general-purpose source register, encoded in the "Rn" field.

Operational Notes

If PSTATE.DIT is 1:

• 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.