Using speculative functional units in high level synthesis

Alberto A. Del Barrio, Maria C. Molina, Jose M. Mendias, Roman Hermida, Seda Ogrenci Memik

Research output: Chapter in Book/Report/Conference proceedingConference contribution

7 Scopus citations


Speculative Functional Units (SFUs) enable a new execution paradigm for High Level Synthesis (HLS). SFUs are arithmetic functional units that operate using a predictor for the carry signal, which reduces the critical path delay. The performance of these units is determined by the success in the prediction of the carry value, i.e. the hit rate of the prediction. Hence SFUs reduce critical path at a low cost, but they cannot be used in HLS with the current techniques. In order to use them, it is necessary to include hardware support to recover from mispredictions of the carry signals. In this paper, we present techniques for designing a datapath controller for seamless deployment of SFUs in HLS. We have developed two techniques for this goal. The first approach stops the execution of the entire datapath for each misprediction and resumes execution once the correct value of the carry is known. The second approach decouples the functional unit suffering from the misprediction from the rest of the datapath. Hence, it allows the rest of the SFUs to carry on execution and be at different scheduling states at different times. Experiments show that it is possible to reduce execution time by as much as 38% and by 33% on average.

Original languageEnglish (US)
Title of host publicationDATE 10 - Design, Automation and Test in Europe
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages6
ISBN (Print)9783981080162
StatePublished - 2010
EventDesign, Automation and Test in Europe Conference and Exhibition, DATE 2010 - Dresden, Germany
Duration: Mar 8 2010Mar 12 2010

Publication series

NameProceedings -Design, Automation and Test in Europe, DATE
ISSN (Print)1530-1591


OtherDesign, Automation and Test in Europe Conference and Exhibition, DATE 2010


  • Dynamic scheduling
  • HLS
  • Speculation

ASJC Scopus subject areas

  • General Engineering


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