Apparatus and method for controlling a change in instruction set

A method of controlling a change in instruction set within an apparatus having processing circuitry to execute instructions of a current instruction set, the processing circuitry being arranged to operate in a bounded pointer domain comprising bounded pointers used to constrain operations performed by the processing circuitry when executing said instructions, wherein each bounded pointer includes a pointer value and range information specifying an allowable range of addresses when using the bounded pointer, the method comprising:

• storing, within program counter bounded pointer storage, a program counter bounded pointer used by the processing circuitry to determine a program counter value;
• arranging the processing circuitry to be responsive to execution of at least one type of instruction that is used to load an identified bounded pointer into the program counter bounded pointer storage, to invoke a bounded pointer based operation to control change of the current instruction set, said bounded pointer based operation comprising:
• performing a bounded pointer check operation in respect of the identified bounded pointer;
• and
• causing the instruction set to be identified by an instruction set identifier field from the identified bounded pointer provided the bounded pointer check operation is passed.

An apparatus comprising:

• processing means for executing instructions of an instruction set, the processing means for operating in a bounded pointer domain comprising bounded pointers used to constrain operations performed by the processing means when executing said instructions, wherein each bounded pointer includes a pointer value and range information specifying an allowable range of addresses when using the bounded pointer;
• and
• means for storing a program counter bounded pointer used by the processing means to determine a program counter value;
• the processing means employing a bounded pointer based operation to change the instruction set, in response to execution of at least one type of instruction that is used to load an identified bounded pointer into the program counter bounded pointer storage element, the processing means for invoking the bounded pointer based operation in order to perform a bounded pointer check operation in respect of the identified bounded pointer and to cause the instruction set to be identified by an instruction set identifier field from the identified bounded pointer provided the bounded pointer check operation is passed.

A non-transitory computer-readable storage medium storing a virtual machine computer program comprising program instructions to control a host data processing apparatus to provide an instruction execution environment corresponding to an apparatus, the apparatus comprising:

• processing circuitry to execute instructions of an instruction set, the processing circuitry being arranged to operate in a bounded pointer domain comprising bounded pointers used to constrain operations performed by the processing circuitry when executing said instructions, wherein each bounded pointer includes a pointer value and range information specifying an allowable range of addresses when using the bounded pointer;
• and
• program counter bounded pointer storage to store a program counter bounded pointer used by the processing circuitry to determine a program counter value;
• the processing circuitry being arranged to employ a bounded pointer based operation to change the instruction set, in response to execution of at least one type of instruction that is used to load an identified bounded pointer into the program counter bounded pointer storage, the processing circuitry being arranged to invoke the bounded pointer based operation in order to perform a bounded pointer check operation in respect of the identified bounded pointer and to cause the instruction set to be identified by an instruction set identifier field from the identified bounded pointer provided the bounded pointer check operation is passed.