Abstract: In one embodiment, a method for identifying and replacing code translations that generate spurious fault events includes detecting, while executing a first native translation of target instruction set architecture (ISA) instructions, occurrence of a fault event, executing the target ISA instructions or a functionally equivalent version thereof, determining whether occurrence of the fault event is replicated while executing the target ISA instructions or the functionally equivalent version thereof, and in response to determining that the fault event is not replicated, determining whether to allow future execution of the first native translation or to prevent such future execution in favor of forming and executing one or more alternate native translations.

Abstract: 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.

Abstract: Embodiments related to methods and devices operative, in the event that execution of an instruction produces a runahead-triggering event, to cause a microprocessor to enter into and operate in a runahead without reissuing the instruction are provided. In one example, a microprocessor is provided. The example microprocessor includes fetch logic for retrieving an instruction, scheduling logic for issuing the instruction retrieved by the fetch logic for execution, and runahead control logic. The example runahead control logic is operative, in the event that execution of the instruction as scheduled by the scheduling logic produces a runahead-triggering event, to cause the microprocessor to enter into and operate in a runahead mode without reissuing the instruction, and carry out runahead policies while the microprocessor is in the runahead mode that governs operation of the microprocessor and cause the microprocessor to operate differently than when not in the runahead mode.

Abstract: Embodiments related to managing lazy runahead operations at a microprocessor are disclosed. For example, an embodiment of a method for operating a microprocessor described herein includes identifying a primary condition that triggers an unresolved state of the microprocessor. The example method also includes identifying a forcing condition that compels resolution of the unresolved state. The example method also includes, in response to identification of the forcing condition, causing the microprocessor to enter a runahead mode.

Abstract: Embodiments related to managing potentially invalid results generated/obtained by a microprocessor during runahead are provided. In one example, a method for operating a microprocessor includes causing the microprocessor to enter runahead upon detection of a runahead event. The example method also includes, during runahead, determining that an operation associated with an instruction referencing a storage location would produce a potentially invalid result based on a value of an architectural poison bit associated with the storage location and performing a different operation in response.

Abstract: A processing system comprising a microprocessor core and a translator. Within the microprocessor core is arranged a hardware decoder configured to selectively decode instructions for execution in the microprocessor core, and, a logic structure configured to track usage of the hardware decoder. The translator is operatively coupled to the logic structure and configured to selectively translate the instructions for execution in the microprocessor core, based on the usage of the hardware decoder as determined by the logic structure.

Abstract: Embodiments related to re-dispatching an instruction selected for re-execution from a buffer upon a microprocessor re-entering a particular execution location after runahead are provided. In one example, a microprocessor is provided. The example microprocessor includes fetch logic, one or more execution mechanisms for executing a retrieved instruction provided by the fetch logic, and scheduler logic for scheduling the retrieved instruction for execution. The example scheduler logic includes a buffer for storing the retrieved instruction and one or more additional instructions, the scheduler logic being configured, upon the microprocessor re-entering at a particular execution location after runahead, to re-dispatch, from the buffer, an instruction that has been previously dispatched to one of the execution mechanisms.

Abstract: In one embodiment, a microprocessor is provided. The microprocessor includes instruction memory and a branch prediction unit. The branch prediction unit is configured to use information from the instruction memory to selectively power up the branch prediction unit from a powered-down state when fetched instruction data includes a branch instruction and maintain the branch prediction unit in the powered-down state when the fetched instruction data does not include a branch instruction in order to reduce power consumption of the microprocessor during instruction fetch operations.

Abstract: In one embodiment, a microprocessor is provided. The microprocessor includes a branch prediction unit. The branch prediction unit is configured to track the presence of branches in instruction data that is fetched from an instruction memory after a redirection at a target of a predicted taken branch. The branch prediction unit is selectively powered up from a powered-down state when the fetched instruction data includes a branch instruction and is maintained in the powered-down state when the fetched instruction data does not include an instruction branch in order to reduce power consumption of the microprocessor during instruction fetch operations.

Abstract: In one embodiment, a micro-processing system includes a hardware structure disposed on a processor core. The hardware structure includes a plurality of entries, each of which are associated with portion of code and a translation of that code which can be executed to achieve substantially equivalent functionality. The hardware structure includes a redirection array that enables, when referenced, execution to be redirected from a portion of code to its counterpart translation. The entries enabling such redirection are maintained within or evicted from the hardware structure based on usage information for the entries.

Abstract: Embodiments related to fetching instructions and alternate versions achieving the same functionality as the instructions from an instruction cache included in a microprocessor are provided. In one example, a method is provided, comprising, at an example microprocessor, fetching an instruction from an instruction cache. The example method also includes hashing an address for the instruction to determine whether an alternate version of the instruction which achieves the same functionality as the instruction exists. The example method further includes, if hashing results in a determination that such an alternate version exists, aborting fetching of the instruction and retrieving and executing the alternate version.

Abstract: In one embodiment, a method for controlling an instruction cache including a least-recently-used bits array, a tag array, and a data array, includes looking up, in the least-recently-used bits array, least-recently-used bits for each of a plurality of cacheline sets in the instruction cache, determining a most-recently-used way in a designated cacheline set of the plurality of cacheline sets based on the least-recently-used bits for the designated cacheline, looking up, in the tag array, tags for one or more ways in the designated cacheline set, looking up, in the data array, data stored in the most-recently-used way in the designated cacheline set, and if there is a cache hit in the most-recently-used way, retrieving the data stored in the most-recently-used way from the data array.

Abstract: A method for executing an instruction with a semi-fast operation in a staggered ALU. The method of one embodiment comprises generating a first operation and a second operation from a micro-instruction. The first and second operations are scheduled for execution in a staggered arithmetic logic unit (ALU). The first and second operations are separated by N clock cycles. Data from the first operation is communicated to the second operation for use with execution of the second operation.

Abstract: A method for executing an instruction with a semi-fast operation in a staggered ALU. The method of one embodiment comprises generating a first operation and a second operation from a micro-instruction. The first and second operations are scheduled for execution in a staggered arithmetic logic unit (ALU). The first and second operations are separated by N clock cycles. Data from the first operation is communicated to the second operation for use with execution of the second operation.

Abstract: A method and an apparatus for decoding a variable length instruction. The method includes selecting with a first pointer one of a plurality of permutations, each permutation representing a possible location of the instruction in a portion of the datastream, calculating a possible length of the instruction for each byte in the selected permutation, and selecting the length of the instruction from one of the calculated possible lengths in the selected permutation. An example of an application includes decoding X86 instruction formats.

Abstract: A dual-cycle address generation unit is described to generate linear addresses. The dual-cycle address generation unit includes a first adder to add a product of an index and a scaling factor to an offset and a segment base during a first clock cycle and a second adder to add output of the first adder with a base during a second clock cycle.

Abstract: A method for executing an instruction with a semi-fast operation in a staggered ALU. The method of one embodiment comprises generating a first operation and a second operation from a micro-instruction. The first and second operations are scheduled for execution in a staggered arithmetic logic unit (ALU). The first and second operations are separated by N clock cycles. Data from the first operation is communicated to the second operation for use with execution of the second operation.

Abstract: A dual-cycle address generation unit is described to generate linear addresses. The dual-cycle address generation unit includes a first adder to add a product of an index and a scaling factor to an offset and a segment base during a first clock cycle and a second adder to add output of the first adder with a base during a second clock cycle.