Intel Corporation

Niranjan K Soundararajan

Sreenivas Subramoney

Ronak Singhal

Anant V Nori

Jared Warner Stark, Iv

Rahul Pal

Ragavendra Natarajan

Prathmesh Kallurkar

Hong Wang

Lihu Rappoport

Saurabh Gupta

Jayesh Gaur

Gilles A Pokam

Adrian C Moga

Hanna Alam

Sr Swamy Saranam Chongala

Oleg Ladin

Daniel Deng

S R Swamy Saranam Chongala

Methods and apparatus relating to de-prioritizing speculative code lines in on-chip caches are described. In an embodiment, logic circuitry determines whether a storage structure includes a reference to a code miss request prior to transmission of the code miss request to a shared cache. The logic circuitry causes de-prioritization of a code line, corresponding to the code miss request, in the shared cache in response to an absence of the reference in the storage structure. Other embodiments are also disclosed and claimed.

De-prioritizing speculative code lines in on-chip caches

Methods and apparatus relating to throttling a code fetch for speculative code paths are described. In an embodiment, a first storage structure stores a reference to a code line in response to a request to be received from a cache. A second storage structure to store a reference to the code line in response to an update to an Instruction Dispatch Queue (IDQ). Logic circuitry controls additional code line fetch operations based at least in part on a comparison of a number of ongoing speculative code fetches and a determination that the code line is speculative. Other embodiments are also disclosed and claimed.

Throttling code fetch for speculative code paths

In one embodiment, a processor includes a branch predictor to predict whether a branch instruction is to be taken and a branch target buffer (BTB) coupled to the branch predictor. The branch target buffer may be segmented into a first cache portion and a second cache portion, where, in response to an indication that the branch is to be taken, the BTB is to access an entry in one of the first cache portion and the second cache portion based at least in part on a type of the branch instruction, an occurrence frequency of the branch instruction, and spatial information regarding a distance between a target address of a target of the branch instruction and an address of the branch instruction. Other embodiments are described and claimed.

Segmented branch target buffer based on branch instruction type

An embodiment of an integrated circuit may comprise a core, a front end unit coupled to the core to decode one or more instruction wherein the front end unit includes a first decode path, a second decode path, and circuitry to: predict a taken branch of a conditional branch instruction of the one or more instructions, decode a predicted path of the taken branch on the first decode path, determine if the conditional branch instruction corresponds to a hard-to-predict conditional branch instruction and if the second decode path is available and, if so determined, decode an alternate path of a not-taken branch of the hard-to-predict conditional branch instruction on the second decode path. Other embodiments are disclosed and claimed.

Alternate path decode for hard-to-predict branch

Apparatus and method for memorizing repeat function calls are described herein. An apparatus embodiment includes: uop buffer circuitry to identify a function for memorization based on retiring micro-operations (uops) from a processing pipeline; memorization retirement circuitry to generate a signature of the function which includes input and output data of the function; a memorization data structure to store the signature; and predictor circuitry to detect an instance of the function to be executed by the processing pipeline and to responsively exclude a first subset of uops associated with the instance from execution when a confidence level associated with the function is above a threshold. One or more instructions that are data-dependent on execution of the instance is then provided with the output data of the function from the memorization data structure.

Apparatus and method for hardware-based memoization of function calls to reduce instruction execution

Methods and apparatus relating to branch prefetch mechanisms for mitigating front-end branch resteers are described. In an embodiment, predecodes an entry in a cache to generate a predecoded branch operation. The entry is associated with a cold branch operation, where the cold branch operation corresponds to an operation that is detected for a first time after storage in an instruction cache and wherein the cold branch operation remains undecoded since it is stored at a location in a cache line prior to a subsequent location of a branch operation in the cache line. The predecoded branch operation is stored in a Branch Prefetch Buffer (BPB) in response to a cache line fill operation of the cold branch operation in an instruction cache. Other embodiments are also disclosed and claimed.

Branch prefetch mechanisms for mitigating frontend branch resteers

Embodiments of apparatuses, methods, and systems for misprediction-triggered local history-based branch prediction are described. In one embodiments, an apparatus includes a current pattern table and a local pattern table. The current pattern table has a plurality of entries, each entry in which to store a plurality of pattern lengths of a current pattern of one of a plurality of branch instructions. The local pattern table is to provide a first branch prediction based on the current pattern.

Misprediction-triggered local history-based branch prediction

A processor may include a baseline branch predictor and an empirical branch bias override circuit. The baseline branch predictor may receive a branch instruction associated with a given address identifier, and generate, based on a global branch history, an initial prediction of a branch direction for the instruction. The empirical branch bias override circuit may determine, dependent on a direction of an observed branch direction bias in executed branch instruction instances associated with the address identifier, whether the initial prediction should be overridden, may determine, in response to determining that the initial prediction should be overridden, a final prediction that matches the observed branch direction bias, or may determine, in response determining that the initial prediction should not be overridden, a final prediction that matches the initial prediction. The predictor may update an entry in the global branch history reflecting the resolved branch direction for the instruction following its execution.

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Bengaluru, India

Niranjan K Soundararajan