This branch predictor combines a perceptron predictor with a Gshare predictor. It uses 2K perceptrons with 18 weights each and a global history table of 17 bits. The Gshare predictor is of size 128K with each entry containing a 2-bit predictor. A choice table of 16K 2-bit saturating counters is used to choose between the perceptron prediction and the Gshare prediction for a particular branch. Both the Gshare and perceptron predictor are updated on each branch outcome. The choice table, perceptron table, and Gshare table are all indexed by the last 10 bits of the global history register XORed with the last 10 bits of the PC address.

This branch predictor is meant to be run with the simulator available at https://drive.google.com/open?id=0B5TPQrtyq9_kRmxmak1ESFF4cXc . To install the simulator, run the following commands:

tar -xzvf bpc6421AU15.tar.gz
cd bpc6421AU15
cd sim
make ./predictor ../traces/SHORT-INT-1.cbp4.gz

After installing the simulator, overwrite the existing predictor.cc and predictor.h files with the CC and H files in this repository. Run using either runall.pl or doit.sh in the scripts directory. You can view your results using the getdata.pl script.

This predictor achieves the following results with respect to misprediction rate:

LONG-SPEC2K6-00 6.417

LONG-SPEC2K6-01 7.382

LONG-SPEC2K6-02 8.793

LONG-SPEC2K6-03 6.689

LONG-SPEC2K6-04 11.426

LONG-SPEC2K6-05 5.992

LONG-SPEC2K6-06 5.758

LONG-SPEC2K6-07 16.262

LONG-SPEC2K6-08 3.562

LONG-SPEC2K6-09 6.549

SHORT-FP-1 4.613

SHORT-FP-2 1.157

SHORT-FP-3 0.525

SHORT-INT-1 9.531

SHORT-INT-2 9.101

SHORT-INT-3 12.738

SHORT-MM-1 9.719

SHORT-MM-2 11.077

SHORT-MM-3 5.047

SHORT-SERV-1 3.766

SHORT-SERV-2 3.643

SHORT-SERV-3 6.598

AMEAN 7.107