Prophet/critic hybrid branch prediction

Falcón, Ayose; Stark, Jared; Ramírez, Alex; Lai, Konrad; Valero, Mateo

doi:10.1109/isca.2004.1310779

Cited by 10 publications

(7 citation statements)

References 29 publications

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“…Falcón et al present Prophet/Critic Hybrid Branch Prediction [7]. This technique utilizes a traditional branch predictor to generate a sequence of future branch predictions, which are then interpreted to evaluate the accuracy of the current branch prediction.…”

Section: Related Workmentioning

confidence: 99%

Control Flow Optimization Via Dynamic Reconvergence Prediction

Collins

Tullsen

Wang

2004

37th International Symposium on Microarchitecture (MICRO-37'04)

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Section: Related Workmentioning

confidence: 99%

Control Flow Optimization Via Dynamic Reconvergence Prediction

Collins

Tullsen

Wang

2004

37th International Symposium on Microarchitecture (MICRO-37'04)

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“…In previous work, 1 we fully describe our simulation methodology and benchmarks, and provide expanded simulation results.…”

Section: Simulation Methodologymentioning

confidence: 99%

“…1 We initially describe this technique and the intuition behind why it works by drawing an analogy between running a program and taking a ride in a taxicab. The taxi is the processor, the driver is the branch predictor, and the passenger is the pipeline.…”

mentioning

confidence: 99%

Better Branch Prediction Through Prophet/Critic Hybrids

et al. 2005

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“…Bias of each branch 1,67,83 Using choice predictors 18,34 Majority voting 57,71,89 Giving preference to tagged predictor with longest history, 23 to predictor having highest confidence, 13 to the critic BP in prophet-critic hybrid BP design 58 and to the larger BP in overriding BP designs Combining strategies Adding 30 or fusing 71 the predictions of the components to obtain final prediction FIGURE 26 The tagged BP proposed by Eden et al, 36 which is hybrid of gshare and bimodal BPs such occurrences in direction PHTs, they store 6-8 least significant bits of the branch address as the tags in every entry. These narrow tags almost completely remove aliasing, especially after context-switching.…”

Section: From the Predictions Of Multiple Components The Single Finamentioning

confidence: 99%

A survey of techniques for dynamic branch prediction

Mittal

2018

Concurrency and Computation

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Branch predictor (BP) is an essential component in modern processors since high BP accuracy can improve performance and reduce energy by decreasing the number of instructions executed on wrong-path. However, reducing the latency and storage overhead of BP while maintaining high accuracy presents significant challenges. In this paper, we present a survey of dynamic branch prediction techniques. We classify the works based on key features to underscore their differences and similarities. We believe this paper will spark further research in this area and will be useful for computer architects, processor designers, and researchers. KEYWORDSdynamic branch predictor, hybrid BP, neural BP, perceptron predictorside BP, pipelining, predictor accuracy, review, side BP, speculative execution, two-level BP INTRODUCTIONControl-changing instructions such as branches add uncertainty in the execution of dependent instructions and thus lead to large performance loss in pipelined processors. To offset their overhead, accurate prediction of branch outcomes is vital. Since branch misprediction incurs high latency (eg, 14 to 25 cycles 1 ) and wastes energy due to execution of instructions on wrong-path, an improvement in BP* accuracy can boost performance and energy efficiency significantly. For example, experiments on real processors showed that reducing the branch mispredictions by half improved the processor performance by 13%. 2Effective design and management of BPs, however, presents several challenges. Design of BP involves a strict tradeoff between area, energy, accuracy, and latency. An increase in BP complexity for improving accuracy may make it infeasible for implementation or offset its performance benefit. For example, a 512 KB perceptron predictor may provide lower instruction-per-cycle than its 32 KB version, 3 and a 2-cycle fully accurate BP may provide lower instruction-per-cycle than a 1-cycle partially inaccurate BP. 4 Further, due to its high access frequency, BP becomes a thermal hot-spot, 5 and hence, reducing its dynamic and leakage energy is important. Clearly, intelligent techniques are required for resolving these issues.Further, recently, researchers have demonstrated two security vulnerabilities viz., "Meltdown" and "Spectre," which exploit speculative execution feature of modern CPUs. 6-8 For example, Spectre vulnerability works on the observation that the speculative execution due to a branch misprediction may leave side effects, which can reveal sensitive data to attackers, eg, if the memory accesses performed during speculative execution depends on sensitive data, the resulting state of the cache forms a side-channel through which the sensitive data can be leaked. These vulnerabilities affect nearly every modern CPU. While avoiding speculative execution (eg, disabling branch prediction) can mitigate these vulnerabilities, it leads to significant performance loss. In light of these vulnerabilities and associated tradeoffs, a deeper study of branch predictors is definitely required. Contributions:In this ...

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Prophet/critic hybrid branch prediction

Abstract: Abstract

Cited by 10 publications

References 29 publications

Control Flow Optimization Via Dynamic Reconvergence Prediction

Control Flow Optimization Via Dynamic Reconvergence Prediction

Better Branch Prediction Through Prophet/Critic Hybrids

A survey of techniques for dynamic branch prediction

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