  Traditionally, compiler researchers either conduct experiments within an
existing production compiler or develop their own prototype compiler; both
options come with trade-offs. On one hand, prototyping in a production compiler
can be cumbersome, as they are often optimized for program compilation speed at
the expense of software simplicity and development speed. On the other hand,
the transition from a prototype compiler to production requires significant
engineering work. To bridge this gap, we introduce the concept of sidekick
compiler frameworks, an approach that uses multiple frameworks that
interoperate with each other by leveraging textual interchange formats and
declarative descriptions of abstractions. Each such compiler framework is
specialized for specific use cases, such as performance or prototyping.
Abstractions are by design shared across frameworks, simplifying the transition
from prototyping to production. We demonstrate this idea with xDSL, a sidekick
for MLIR focused on prototyping and teaching. xDSL interoperates with MLIR
through a shared textual IR and the exchange of IRs through an IR Definition
Language. The benefits of sidekick compiler frameworks are evaluated by showing
on three use cases how xDSL impacts their development: teaching, DSL
compilation, and rewrite system prototyping. We also investigate the trade-offs
that xDSL offers, and demonstrate how we simplify the transition between
frameworks using the IRDL dialect. With sidekick compilation, we envision a
future in which engineers minimize the cost of development by choosing a
framework built for their immediate needs, and later transitioning to
production with minimal overhead.
