A secure processor, comprising a logic execution unit configured to process data based on instructions; a communication interface unit, configured to transfer of the instructions and the data, and metadata tags accompanying respective instructions and data; a metadata processing unit, configured to enforce specific restrictions with respect to at least execution of instructions, access to resources, and manipulation of data, selectively dependent on the received metadata tags; and a control transfer processing unit, configured to validate a branch instruction execution and an entry point instruction of each control transfer, selectively dependent on the respective metadata tags.

An apparatus and method of operating an apparatus are disclosed. The apparatus has a program counter permitted range storage element defining a permitted range of program counter values for the sequence of instructions it executes. Branch prediction circuitry predicts target instruction addresses for branch instructions. In response to a program counter modifying event, a program counter speculative range storage element is updated corresponding to each speculatively executed instruction after a branch instruction. Program counter permitted range verification circuitry is responsive to resolution of a modification of the program counter permitted range indication resulting from the program counter modifying event to determine whether the speculatively executed program counter range satisfies the permitted range of program counter values. A branch mis-prediction mechanism may support the response of the apparatus if the permitted range of program counter values is violated.

Branch instructions are managed in an emulation environment that is executing a program. A plurality of slots in a Polymorphic Inline Cache is populated. A plurality of entries is populated in a branch target buffer residing within an emulated environment in which the program is executing. When an indirect branch instruction associated with the program is encountered, a target address associated with the instruction is identified from the indirect branch instruction. At least one address in each of the slots of the Polymorphic Inline Cache is compared to the target address associated with the indirect branch instruction. If none of the addresses in the slots of the Polymorphic Inline Cache matches the target address associated with the indirect branch instruction, the branch target buffer is searched to identify one of the entries in the branch target buffer that is associated with the target address of the indirect branch instruction.

An apparatus and method are provided for controlling instruction execution behaviour. The apparatus includes a set of data registers for storing data values, and a set of bounded pointer storage elements, where each bounded pointer storage element stores a pointer having associated range information indicative of an allowable range of addresses when using that pointer. A control storage element stores a current instruction context, and that current instruction context is used to influence the behaviour of at least one instruction executed by processing circuitry, that at least one instruction specifying a pointer reference for a required pointer, where the pointer reference is within at least a first subset of values (in one embodiment the behaviour is influenced irrespective of the value of the required pointer). In particular, when the current instruction context identifies a default state, the processing circuitry uses the pointer reference to identify one of the data registers whose stored data value forms the required pointer. However, when the current instruction context identifies a bounded pointer state, the processing circuitry instead uses the pointer reference to identify one of the bounded pointer storage elements whose stored pointer forms the required pointer. This allows an instruction set to be provided that can be used for both bounded pointer aware code and bounded pointer unaware code, without significantly increasing the pressure on instruction set encoding space.

A method updating a program in a flash memory includes executing a first image of the program while an address space of the program is imaged onto the memory blocks, which are operated in a single-level mode; copying part of the first image from a range within the address space, which is imaged onto one of the blocks, into a backup block; setting the one of the blocks to a multi-level mode; while the address range is imaged onto the backup block, programming the one of the blocks with part of the second image besides for the part of the first image; switching the address range back to the block while the block remains in the multi-level mode; as long as the second image is incomplete, repeating the copying, programming, and switching with further parts of the second image; and subsequently executing the second image instead of the first image.

As disclosed herein a method, executed by a processor, for accelerated instruction execution includes retrieving an execute instruction including a register reference and a reference to a target instruction, retrieving the target instruction, decoding the execute instruction using an instruction pipeline, decoding the target instruction using the instruction pipeline, associating the register reference to the target instruction, and executing the target instruction using the register reference as a source operand modifier. The instruction pipeline is configured such that it allows the target instruction to continue processing without waiting for the register reference to be resolved. The contents of the referenced register may be retrieved in a later stage of the instruction pipeline, and the target instruction may be modified and executed. An apparatus corresponding to the described method is also disclosed herein.

An apparatus includes a circular buffer which includes a fixed number of entries and allows data overflow to occur while maintaining the most recently stored entries in order. The circular buffer could be used as a return address stack used to push and pop return addresses for subroutine calls in a processor. Additional circuitry dynamically links entries to maintain a last-in first-out stack. A system return pointer tracks the next entry to be returned when an entry is to be read. When data is pushed to an entry in the circular buffer, that entry stores a pointer to the entry for the previous system return pointer. By tracking the previous system return pointer in the pushed entry, the dynamically linked entries may skip intervening entries that have been previously popped and, thus, track the order of most recently written non-popped entries without having to separately maintain free and used lists.

A microprocessor implemented method for performing early dependency resolution and data forwarding is disclosed. The method comprises mapping a plurality of instructions in a guest address space into a corresponding plurality of instructions in a native address space. For each current guest branch instruction in the native address space fetched during execution, performing (a) determining a youngest prior guest branch target stored in a guest branch target register, wherein the guest branch register is operable to speculatively store a plurality of prior guest branch targets corresponding to prior guest branch instructions; (b) determining a current branch target for a respective current guest branch instruction by adding an offset value for the respective current guest branch instruction to the youngest prior guest branch target; and (c) creating an entry in the guest branch target register for the current branch target.

A computer processor with an address register file is disclosed. The computer processor may include a memory. The computer processor may further include a general purpose register file comprising at least one general purpose register. The computer processor may further include an address register file comprising at least one address register. The computer processor may further include having access to the memory, the general purpose register file, and the address register file. The processing logic may execute a memory access instruction that accesses one or more memory locations in the memory at one or more corresponding addresses computed by retrieving the value of an address register of the at least one register of the address register file specified in the instruction and adding a displacement value encoded in the instruction.

An apparatus includes an instruction issuer that issues an instruction; and a cache including a cache data memory and a cache tag including cache entries, and a cache controller configured to perform cache-hit judgement, in response to a memory-access instruction issued from the instruction issuer, based on an address of the memory-access instruction and configured to issue a memory-access request to a memory in a case where the cache-hit judgement is a cache miss, wherein the cache controller registers, when issuing the memory-access request, data obtained by the memory-access request in the cache data memory, and registers provisional registration information of a provisional registration state indicating that cache registration is performed by execution of a speculative memory-access instruction in the cache tag, and judges as a speculative entry cache miss and issues the memory-access request.