chkfeat

Check

CHK <#imm>

Check feature status (FEAT_CHK).

Details

Checks the status of a system feature identified by the immediate operand and raises a CHK exception if the feature is not available or in the expected state. The specific behavior depends on the feature ID encoded in the immediate. Requires FEAT_CHK extension; AArch64 only; may only execute at EL0 and EL1 (subject to CHKFEATURE_EL0 register control).

Pseudocode Operation

feature_id ← imm
if not CheckFeature(feature_id) then raise_exception(CHK_EXCEPTION)

Example

CHK #imm

Encoding

Binary Layout

11010101000000110010

0101

000

11111

Format System

Opcode 0xD503251F

Extension FEAT_CHK

Operands

imm
Feature ID

Reference (Arm A64 ISA)

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xD503251F	CHKFEAT X16		A64		11010101000000110010 \| 0101 \| 000 \| 11111

Description

Check feature status. This instruction indicates the status of features. If FEAT_CHK is not implemented, this instruction executes as a NOP.

Operation

X[16, 64] = AArch64.ChkFeat(X[16, 64]);