+++
title = "Speculative loop pipelining using GSA"
date = "2022-04-29"
author = "Yann Herklotz"
tags = []
categories = []
backlinks = ["1c6c"]
forwardlinks = ["2e1b", "1c6e"]
zettelid = "1c6d"
+++

This is work by Steven Derrien from Irisa Rennes \[1\].

Using GSA ([\#2e1b]), one can generate loop pipelines with speculative
execution support that can then be passed to a high-level synthesis tool
(as this is a source-to-source translation). This is done by generating
the GSA representation then using the predicates in the γ-functions to
generate an FSM controlling the selection of the values for the
γ-functions and control whether a rollback of the state is necessary, as
well as generating an entry block and a commit block at the end to
choose a correct value that is not speculated.

The main idea is to perform a source-to-source translation which can
still take advantage of static scheduling tools, therefore, this dynamic
scheduling is introduced into the source code, in addition to the FSM
that actually picks the state that should be gone into (if one has to
perform a rollback or if everything is OK). Then, the actual memory
accesses are transformed into accesses that the static scheduling tool
can understand well, as affine expressions so that the distances are
clear.

<div id="refs" class="references csl-bib-body" markdown="1">

<div id="ref-derrien20_towar_specul_loop_pipel_high_level_synth"
class="csl-entry" markdown="1">

<span class="csl-left-margin">\[1\]
</span><span class="csl-right-inline">S. Derrien, T. Marty, S. Rokicki,
and T. Yuki, “Toward speculative loop pipelining for high-level
synthesis,” *IEEE Transactions on Computer-Aided Design of Integrated
Circuits and Systems*, vol. 39, no. 11, pp. 4229–4239, Nov. 2020, doi:
[10.1109/tcad.2020.3012866].</span>

</div>

</div>

  [\#2e1b]: /zettel/2e1b
  [10.1109/tcad.2020.3012866]: https://doi.org/10.1109/tcad.2020.3012866