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E. J. Maroun, M. Schoeberl, P. Puschner:
"Compiling for time-predictability with dual-issue single-path code";
Journal of Systems Architecture, 118 (2021), 102230.

Designed for real-time systems, the Patmos instruction-set architecture´s features ensure a high degree of
predictability. One such feature is its dual-issue pipeline, which can issue and execute bundles of up to two
instructions at a time. Executing instructions in the second issue slot is a predictable way to increase the
throughput of a processor, but without dedicated support from the compiler, this benefit cannot be unlocked.
A compiler generates highly predictable programs by generating single-path code. This technique produces code
that always follows the same trace of instructions. While Patmos´ compiler can already produce single-path
code, it does not assign any instructions to the second issue-slot. This limitation is unfortunate, as single-path
code inherently possesses a high degree of instruction-level parallelism. In this paper, we present a singlepath
code generation technique with support for dual-issue pipelines. It can also support different bundling
algorithms, which allows changing algorithms without having to edit other parts of the compiler. We present
a simple bundling algorithm plugged into the single-path code generator. It looks for branches and bundles
the basic blocks on each path of the branch. While this specific bundling algorithm is too simple to provide a
real-world benefit, it highlights the potential that further work on bundling algorithms can unlock.

Real-time systems, Time-predictable computer architecture, Single-path code generation

http://dx.doi.org/10.1016/j.sysarc.2021.102230

https://publik.tuwien.ac.at/files/publik_299085.pdf