Intel Corporation

Jared Warner Stark, Iv

Lihu Rappoport

Jason W Brandt

Joseph Nuzman

Robert S Chappell

Hong Wang

Sreenivas Subramoney

Stanislav Shwartsman

Franck Sala

Zeev Sperber

Per H Hammarlund

Christopher B Wilkerson

Perry H Wang

Saurabh Gupta

Igor Yanover

John P Shen

Sergiu D Ghetie

Deepak K Gupta

Rodrigo Branco

Stephen J Robinson

Scott P Bobholz

Pedro Marcuello

Gerolf F Hoflehner

Patrick Lu

Chris Wilkerson

Binh Q Pham

George Leifman

Steve Shih-wei Liao

Niranjan K Soundararajan

Wojciech S Powiertowski

Gadi Haber

Ragavendra Natarajan

Tor M Aamodt

Sagar V Dalvi

Ariel Sabba

Scott J Cape

Renju Thomas

Amjad Aboud

Yair Berger

Gilad Holzstein

Edward Thomas Grochowski

Michael Mishaeli

Gideon Gerzon

Ronak Singhal

Mary Douglass Brown

Antonio Gonzalez

Jayesh Gaur

Gilles A Pokam

Ido Ouziel

Rahul Pal

Hisham Shafi

Antonio González

Niranjan Soundararajan

Pavel I Kryukov

Michael Tal

Kamil Garifullin

Alexey Sivtsov

Sumeet Bandishte

Yogesh Bijlani

Oleg Ladin

Daniel Deng

Gil Shmueli

Adrian Flesler

Gal Diskin

Techniques and mechanisms for a processor to determine an execution of instructions based on a prediction of a taken branch. In an embodiment, a first prediction unit generates each of multiple branch predictions in one cycle of successive branch prediction cycles. An indication of the branch predictions is provided to an execution pipeline, which prepares to execute an instruction based on the indication. Where a first one of the branch predictions is determined to be of a low confidence type, said first branch prediction is further indicated to a second prediction unit, which performs a second branch prediction based on the same branch instruction for which the first branch prediction was made. In another embodiment, the second prediction unit signals that a state of the execution pipeline is to be cleared, based on a determination that the first and second branch predictions are inconsistent with each other.

Device, method, and system to facilitate improved bandwidth of a branch prediction unit

Methods and apparatuses relating to mitigations for speculative execution side channels are described. Speculative execution hardware and environments that utilize the mitigations are also described. For example, three indirect branch control mechanisms and their associated hardware are discussed herein: (i) indirect branch restricted speculation (IBRS) to restrict speculation of indirect branches, (ii) single thread indirect branch predictors (STIBP) to prevent indirect branch predictions from being controlled by a sibling thread, and (iii) indirect branch predictor barrier (IBPB) to prevent indirect branch predictions after the barrier from being controlled by software executed before the barrier.

Apparatuses and methods for speculative execution side channel mitigation

Systems, methods, and apparatuses relating to microarchitectural mechanisms for the prevention of side-channel attacks are disclosed herein. In one embodiment, a processor core includes an instruction fetch circuit to fetch instructions; a branch target buffer comprising a plurality of entries that each include a thread identification (TID) and a privilege level bit; and a branch predictor, coupled to the instruction fetch circuit and the branch target buffer, to predict a target instruction corresponding to a branch instruction based on at least one entry of the plurality of entries in the branch target buffer, and cause the target instruction to be fetched by the instruction fetch circuit.

Microarchitectural mechanisms for the prevention of side-channel attacks using a thread identification (TID) and a privilege level bit

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

In an embodiment, a processor includes a branch prediction circuit and a plurality of processing engines. The branch prediction circuit is to: detect a coherence operation associated with a first memory address; identify a first branch instruction associated with the first memory address; and predict a direction for the identified branch instruction based on the detected coherence operation. Other embodiments are described and claimed.

Branch prediction based on coherence operations in processors

Systems, methods, and apparatuses relating to microarchitectural mechanisms for the prevention of side-channel attacks are disclosed herein. In one embodiment, a processor includes a core having a plurality of physical contexts to execute a plurality of threads, a plurality of structures shared by the plurality of threads, a context mapping structure to map context signatures to respective physical contexts of the plurality of physical contexts, each physical context to identify and differentiate state of the plurality of structures, and a context manager circuit to, when one or more of a plurality of fields that comprise a context signature is changed, search the context mapping structure for a match to another context signature, and when the match is found, a physical context associated with the match is set as an active physical context for the core.

Microarchitectural mechanisms for the prevention of side-channel attacks

An apparatus and method for a speculative conditional move instruction. A processor comprising: a decoder to decode a first speculative conditional move instruction; a prediction storage to store prediction data related to previously executed speculative conditional move instructions; and execution circuitry to read first prediction data associated with the speculative conditional move instruction and to execute the speculative conditional move instruction either speculatively or non-speculatively based on the first prediction data.

Apparatus and method for speculative conditional move operation

A method for handling load faults in an out-of-order processor is described. The method includes detecting, by a memory ordering buffer of the out-of-order processor, a load fault corresponding to a load instruction that was executed out-of-order by the out-of-order processor; determining, by the memory ordering buffer, whether instant reclamation is available for resolving the load fault of the load instruction; and performing, in response to determining that instant reclamation is available for resolving the load fault of the load instruction, instant reclamation to re-fetch the load instruction for execution prior to attempting to retire the load instruction.

Accelerating memory fault resolution by performing fast re-fetching

Disclosed embodiments relate to the usage of a branch prediction unit in service of performance sensitive microcode flows. In one example, a processor includes a branch prediction unit (BPU) and a pipeline including a fetch stage to fetch an instruction specifying an opcode, an operand, and a loop condition based on the operand, wherein the BPU is to generate a hint reflecting a predicted result of the loop condition, a decode stage to generate either a first or a second micro-operation flow as per the hint, the pipeline to begin executing the generated micro-operation flow; a read stage to read the operand and resolve the loop condition; and execution circuitry to continue the generated micro-operation flow if the prediction was correct, and, otherwise, to flush the pipeline, update the prediction, and switch from the generated micro-operation flow to the other of the first and second micro-operation flows.

Branch prediction unit in service of short microcode flows

In one embodiment, an apparatus includes a context-based prediction circuit to receive an instruction address for a branch instruction and a plurality of predictions associated with the branch instruction from a global prediction circuit. The context-based prediction circuit may include: a table having a plurality of entries each to store a context prediction value for a corresponding branch instruction; and a control circuit to generate, for the branch instruction, an index value to index into the table, the control circuit to generate the index value based at least in part on at least some of the plurality of predictions associated with the branch instruction and the instruction address for the branch instruction. Other embodiments are described and claimed.

System, apparatus and method for context-based override of history-based branch predictions

A processor includes a processor core and a micro-op cache communicably coupled to the processor core. The micro-op cache includes a micro-op tag array, wherein tag array entries in the micro-op tag array are indexed according to set and way of set-associative cache, and a micro-op data array to store multiple micro-ops. The data array entries in the micro-op data array are indexed according to bank number of a plurality of cache banks and to a set within one cache bank of the plurality of cache banks.

Defragmented and efficient micro-operation cache

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

Growing community of inventors

Portland, OR, United States of America

Jared Warner Stark, Iv