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Indirect branch predictor and prediction method based on global historical classification

A technology of branch prediction and predictor, which is applied in the direction of machine execution devices and concurrent instruction execution, can solve the problems of low prediction accuracy and the inability to make full use of the advantages of path history and direction history information, so as to improve prediction accuracy and overcome Waste of resources, the effect of a wide range of applications

Pending Publication Date: 2022-04-08
JIANGNAN UNIV
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  • Application Information

AI Technical Summary

Problems solved by technology

[0014] In order to solve the problem that the existing indirect branch predictors cannot make full use of the advantages of path history and direction history information, resulting in low prediction accuracy, the present invention provides an indirect branch predictor and prediction method based on global history classification

Method used

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  • Indirect branch predictor and prediction method based on global historical classification
  • Indirect branch predictor and prediction method based on global historical classification
  • Indirect branch predictor and prediction method based on global historical classification

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Experimental program
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Embodiment 1

[0067] This embodiment provides an indirect branch predictor based on global history classification. The indirect branch predictor includes: a basic predictor P0, a predictor P1 with tag matching, a predictor P2 with tag matching, and a target An address arbiter and a multiplexer; both the predictor P1 and the predictor P2 are connected to the target address arbiter, and the predictor P0 and the target address arbiter are both connected to the multiplexer.

[0068] The basic predictor P0 is used to predict the target address of a single-target indirect jump branch, which can be realized by using the existing branch target buffer BTB, and the branch prediction table inside P0 is indexed by the instruction PC address.

[0069] Both predictors P1 and P2 are used to predict the target addresses of those multi-target indirect jump branches, and have similar functions and structures, and can be implemented by using existing TTC or ITTAGE predictors; the difference is that the interna...

Embodiment 2

[0074] This embodiment provides an indirect branch predictor based on global history classification, see Figure 4, the indirect branch predictor includes: a base predictor P0, a predictor P1 with tag matching, a predictor P2 with tag matching, a target address arbiter and a multiplexer.

[0075] The basic predictor P0 is used to predict the target address of a single-target indirect jump branch, which is realized by using the existing branch target buffer BTB, and its structure is as follows Figure 5 shown.

[0076] Both predictors P1 and P2 are used to predict the target addresses of those multi-target indirect jump branches, and have similar functions and composition structures; P1 and P2 use the existing ITTAGE predictors to implement the structure as follows Figure 6 The difference is that the internal branch prediction table of P1 is indexed by the hash result of the instruction PC address and the path history PHIST, while the index address of the P2 internal branch p...

Embodiment 3

[0092] This embodiment provides an indirect branch prediction method based on global history classification. The method is implemented based on the indirect branch predictor described in Embodiment 1 or Embodiment 2, including:

[0093] S1: Using the basic predictor P0 to predict the target address of the single-target indirect jump branch, the branch prediction table inside the basic predictor P0 uses the instruction PC address to index, and outputs the basic predicted target address target0;

[0094] The target address of the multi-target indirect jump branch is predicted by using the first predictor P1 with label matching and the second predictor P2 with label match, wherein:

[0095] The branch prediction table inside the first tag-matched predictor P1 is indexed by the hash result of the instruction PC address and the path history PHIST, and outputs the first target address target1;

[0096] The branch prediction table inside the second label matching predictor P2 is inde...

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Abstract

The invention discloses an indirect branch predictor based on global historical classification and a prediction method, and belongs to the field of branch predictor design of processors. The indirect branch predictor based on global historical classification comprises a single target address prediction module, a multi-target address prediction module, a target address arbitration module and a multipath selection module. According to the method, prediction advantages of instruction path history and direction history can be respectively utilized, and more reasonable historical information is selected for prediction according to confidence, so that the prediction accuracy of the indirect branch predictor can be further improved; the predictor adopted in the method can be realized by adopting different indirect branch predictors according to actual design requirements, so that the performance and area requirements of various processors are met, hardware resources can be reasonably utilized, and the method has better applicability in design of different types of processors.

Description

technical field [0001] The invention relates to an indirect branch predictor and a prediction method based on global history classification, and belongs to the field of branch predictor design of processors. Background technique [0002] In recent years, with the development of superscalar and deep pipeline technology, branch predictors have increasingly become an indispensable part of modern high-performance processors. [0003] The branch predictor mainly completes the prediction of the direction of the branch instruction in the program flow (whether to jump) and the jump target address. It can be divided into two types according to the source of the target address of the branch instruction, namely, direct jump branch and indirect jump. branch. For a direct jump branch, since its offset is given by an immediate value, there will only be a single target address; for an indirect jump branch, since its offset comes from a general-purpose register, the general-purpose registe...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F9/38
Inventor 虞致国郭俊顾晓峰
Owner JIANGNAN UNIV
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