Abstract: Apparatus and methods to filter memory record updates. A microprocessor can include a memory record update filter. The memory record update filter can include a table memory populated by a plurality of data entries. Each data entry can include a data tag field to store a data tag, a data field to store a data value, and a filter field to store a filter value. A first comparator can be in communication with the data tag field of the table memory and a data accessing information input to perform a data tag comparison. A second comparator can be in communication with the filter field of the table memory and a data value input. A control circuit can be in communication with the table memory, the first comparator, and the second comparator.

Abstract: A microprocessor having a correlated address predictor, and methods of performing correlated address prediction. A first table memory can be populated by a plurality of buffer entries. Each buffer entry can include a first buffer field to store a first tag based on an instruction pointer and a second buffer field to store an address history. A second table memory can be populated by a plurality of link entries. Each link entry can include a first link field to store a link tag based on an address history and a second link field to store a predicted address. A first comparator can be in communication with the first table memory and an instruction pointer input. A second comparator can be in communication with the first table memory and the second table memory. An output in communication with the second table memory.

Abstract: A branch predicting apparatus is disclosed that reduces branch mispredictions in a processor. The branch prediction apparatus includes a base misprediction history register. The branch prediction apparatus includes a meta predictor that receives an index value and a branch prediction to generate a misprediction value in accordance with the base misprediction history register. The branch prediction apparatus also includes a logic gate that receives the branch prediction and the misprediction value to generate a final prediction. The final prediction may be used to predict whether a branch is taken or not taken.

Abstract: A system and method for storing only one copy of a data block that is shared by two or more processes is described. In one embodiment, a global/non-global predictor predicts whether a data block, specified by a linear address, is shared or not shared by two or more processes. If the data block is predicted to be non-shared, then a portion of the linear address referencing the data block is combined with a process identifier that is unique to form a global/non-global linear address. If the data block is predicted to be shared, then the global/non-global linear address is the linear address itself. If the prediction as to whether or not the data block is shared is incorrect, then the actual value of whether or not the data block is shared is used in computing a corrected global/non-global linear address.

Abstract: A processor having a register renaming structure and method is disclosed to recover a free list. The processor includes a physical register file including physical registers. The processor also includes a decoder to decode an instruction to indicate a destination logical register. The processor also includes a register allocation table to map the destination logical register to an allocated physical register. The processor also includes an active list that includes an old field and a new field. The old field includes at least one evicted physical register from the register alias table. The new field includes the allocated physical register. The processor also includes the free list of unallocated physical registers reclaimed from the active list.

Abstract: A multi-mode predictor for a processor having a plurality of prediction modes is disclosed. The prediction modes are used to predict non-binary values. The predictor is a multi-mode predictor comprising a per-IP (“PIP”) table and a next value table. The PIP table includes a plurality of PIP information fields and the next value table includes a plurality of fields. The multi-mode predictor also includes a plurality of prediction modes. The processor includes a set of instructions that index the PIP table to provide a valid signal. The processor also includes a set of predicted values for the set of instructions. The set of predicted values is stored in the PIP table and the next value table. According to the valid signal a hit/miss condition in the next value table, a predicted value is selected from the PIP table or the next value table.

Abstract: A system and method for reducing linear address aliasing is described. In one embodiment, a portion of a linear address is combined with a process identifier, e.g., a page directory base pointer to form an adjusted-linear address. The page directory base pointer is unique to a process and combining it with a portion of the linear address produces an adjusted-linear address that provides a high probability of no aliasing. A portion of the adjusted-linear address is used to search an adjusted-linear-addressed cache memory for a data block specified by the linear address. If the data block does not reside in the adjusted-linear-addressed cache memory, then a replacement policy selects one of the cache lines in the adjusted-linear-addressed cache memory and replaces the data block of the selected cache line with a data block located at a physical address produced from translating the linear address.

Abstract: Embodiments of the present invention provide a pre-decoder in a front-end system provided between an instruction cache and a decoder. The front-end system may toggle between two modes of operation. In a first mode, called the “fast mode” the front-end system retrieves pre-decoded instructions from the instruction cache and decodes them directly. In a second mode, called the “marking mode,” the front-end system retrieves data from the instruction cache and synchronizes to them prior to decoding. Synchronization results may be stored back in the instruction cache for later use.

Abstract: Apparatus and methods to filter memory record updates. A microprocessor can include a memory record update filter. The memory record update filter can include a table memory populated by a plurality of data entries. Each data entry can include a data tag field to store a data tag, a data field to store a data value, and a filter field to store a filter value. A first comparator can be in communication with the data tag field of the table memory and a data accessing information input to perform a data tag comparison. A second comparator can be in communication with the filter field of the table memory and a data value input. A control circuit can be in communication with the table memory, the first comparator, and the second comparator.

Abstract: A filtering system for instruction segments determines whether a new instruction segment satisfies a predetermined filtering condition prior to storage. If the instruction segment fails the filtering condition, the new instruction segment is not stored. Various filtering conditions are available; but all filtering conditions test to determine whether it is more likely than not that a new instruction segment will be reused by the execution unit in the future.