  MLIR is an emerging compiler infrastructure for modern hardware, but existing
programs cannot take advantage of MLIR's high-performance compilation if they
are described in lower-level general purpose languages. Consequently, to avoid
programs needing to be rewritten manually, this has led to efforts to
automatically raise lower-level to higher-level dialects in MLIR. However,
current methods rely on manually-defined raising rules, which limit their
applicability and make them challenging to maintain as MLIR dialects evolve.
  We present mlirSynth -- a novel approach which translates programs from
lower-level MLIR dialects to high-level ones without manually defined rules.
Instead, it uses available dialect definitions to construct a program space and
searches it effectively using type constraints and equivalences. We demonstrate
its effectiveness \revi{by raising C programs} to two distinct high-level MLIR
dialects, which enables us to use existing high-level dialect specific
compilation flows. On Polybench, we show a greater coverage than previous
approaches, resulting in geomean speedups of 2.5x (Intel) and 3.4x (AMD) over
state-of-the-art compilation flows for the C programming language. mlirSynth
also enables retargetability to domain-specific accelerators, resulting in a
geomean speedup of 21.6x on a TPU.
