A split level history buffer in a central processing unit is provided. A first instruction and a second instruction are fetched, tagged, and the first instruction is stored an entry of a register file. The first instruction is evicted from the entry and the second instruction is stored in the entry. If the first instruction is evicted, then the first instruction is stored in a first portion of a history buffer. If a result for the first instruction is generated, then the first instruction is moved to a second portion of the history buffer and the result is stored with the first instruction in the second portion of the history buffer. If it is determined that a third instruction evicts the second instruction from the entry, then the second instruction is stored in the first portion of the history buffer.

Operation of a multi-slice processor that includes a plurality of execution slices. Operation of such a multi-slice processor includes: receiving a first instruction indicating a first target register; receiving a second instruction indicating the first target register as a source operand; responsive to the second instruction indicating the first target register as a source operand, updating a dependent count corresponding to the first instruction; and issuing, in dependence upon the dependent count for the first instruction being greater than a dependent count for another instruction, the first instruction to an execution slice of the plurality of execution slices.

Methods and apparatus relating to register file virtualization techniques are described. In an embodiment, a register file includes a plurality of register file cells. Each of the register file cells includes a register file entry and a shadow buffer. Logic circuitry causes storage of input data to the shadow buffer, while data stored in the register file entry is accessible to perform one or more operations. Other embodiments are also disclosed and claimed.

A method includes asserting a field of an event flag mask register configured to inhibit an event handler. The method also includes, responsive to an event that corresponds to the field of the event flag mask register being triggered: asserting a field of an event flag register associated with the event; and based the field in the event flag register being asserted, taking an action by a task being executed by the data processor core.

Techniques are disclosed for restoring register data in a processor. In one embodiment, a method includes receiving an instruction to flush one or more general purpose registers (GPRs) in a processor. The method also includes determining history buffer entries of a history buffer to be restored to the one or more GPRs. The method includes creating a mask vector that indicates which history buffer entries will be restored to the one or more GPRs. The method further includes restoring the indicated history buffer entries to the one or more GPRs. As each indicated history buffer entry is restored, the method includes updating the mask vector to indicate which history buffer entries have been restored.

Technologies for indirect branch target security include a computing device having a processor to execute an indirect branch instruction. The processor may determine an indirect branch target of the indirect branch instruction, load a memory tag associated with the indirect branch target, and determine whether the memory tag is set. The processor may generate a security fault if the memory tag is not set. The processor may load an encrypted indirect branch target, decrypt the encrypted branch target using an activation record key stored in an activation key register, and perform a jump to the indirect branch target. The processor may generate a next activation record coordinate as a function of the activation record key and a return address of a call instruction and generate the next activation record key as a function of the next activation record coordinate. Other embodiments are described and claimed.

Various embodiments of microprocessors and methods of operating a microprocessor during runahead operation are disclosed herein. One example method of operating a microprocessor includes identifying a runahead-triggering event associated with a runahead-triggering instruction and, responsive to identification of the runahead-triggering event, entering runahead operation and inserting the runahead-triggering instruction along with one or more additional instructions in a queue. The example method also includes resuming non-runahead operation of the microprocessor in response to resolution of the runahead-triggering event and re-dispatching the runahead-triggering instruction along with the one or more additional instructions from the queue to the execution logic.

Operation of a multi-slice processor that includes a plurality of execution slices, a plurality of load/store slices, and one or more page walk caches, where operation includes: receiving, at a load/store slice, an instruction to be issued; determining, at the load/store slice, a process type indicating a source of the instruction to be a host process or a guest process; and determining, in accordance with an allocation policy and in dependence upon the process type, an allocation of an entry of the page walk cache, wherein the page walk cache comprises one or more entries for both host processes and guest processes.

A method includes receiving an execute packet that includes a first instruction and a second instruction and executing the first instruction and the second instruction using a pipeline. Executing the first and second instructions includes storing a result of the first instruction in a holding register; determining whether an event that interrupts execution of the execute packet occurs prior to completion of the executing of the second instruction; and based on the event not occurring, committing the result of the first instruction after completion of the executing of the second instruction.

A TRANSACTION BEGIN instruction begins execution of a transaction and includes a general register save mask having bits, that when set, indicate registers to be saved in the event the transaction is aborted. At the beginning of the transaction, contents of the registers are saved in memory not accessible to the program, and if the transaction is aborted, the saved contents are copied to the registers.