Analysis: Unifying Static and Dynamic Control in ADL Compilation with Piezo

In the field of accelerator design, compilers for accelerator design languages (ADLs) play a crucial role in translating high-level languages into application-specific hardware. These compilers rely on a hardware control interface to compose different hardware units together. Traditionally, there have been two options for this control mechanism: static control and dynamic control.

Static Control

Static control relies on cycle-level timing to coordinate the execution of different hardware units. It is efficient as it eliminates the need for explicit signaling, but it can be brittle and prone to timing issues. Any variation in the timing can lead to failures or incorrect behavior in the hardware design.

Dynamic Control

On the other hand, dynamic control avoids depending on timing details and instead uses explicit signaling to coordinate the behavior of hardware units. This approach is more flexible and less prone to timing-related issues. However, dynamic control introduces additional hardware costs to support compositional reasoning. The explicit signaling mechanisms require extra resources and overhead.

Piezo: Unifying Static and Dynamic Control

Piezo is an ADL compiler that aims to bridge the gap between static and dynamic control in a single intermediate language (IL). It offers a key insight that the static fragment of the IL is a refinement of its dynamic fragment. In other words, code written in the static control style is a subset of the run-time behaviors of its equivalent dynamic code.

This insight allows Piezo to optimize code by combining facts from both static and dynamic submodules. It can leverage information from the static code to make more informed decisions during compilation. Additionally, Piezo opportunistically converts code from dynamic to static control styles where it makes sense. This conversion further enhances the efficiency of the compiled hardware design.

Piezo Implementation

To demonstrate the capabilities of Piezo, the researchers have implemented it as an extension to an existing dynamic ADL compiler named Calyx. They have also developed an MLIR frontend, a systolic array generator, and a packet-scheduling hardware generator using Piezo. These implementations showcase the optimization techniques and highlight the static-dynamic interactions enabled by Piezo.

By unifying static and dynamic control in ADL compilation, Piezo offers a promising approach to improving the efficiency and flexibility of hardware designs. It allows developers to leverage the benefits of both control mechanisms while mitigating their respective drawbacks. The ability to optimize code based on combined static and dynamic analysis opens up new possibilities for achieving high-performance hardware designs.

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