[all-commits] [llvm/llvm-project] 3fb392: [mlir] Add a new "Pattern Descriptor Language" (PD...

[River Riddle via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 3fb3927bd333cded1f51025161a4ee7e7ca722c1
      https://github.com/llvm/llvm-project/commit/3fb3927bd333cded1f51025161a4ee7e7ca722c1
  Author: River Riddle <riddleriver at gmail.com>
  Date:   2020-08-19 (Wed, 19 Aug 2020)

  Changed paths:
    M mlir/include/mlir/Dialect/CMakeLists.txt
    A mlir/include/mlir/Dialect/PDL/CMakeLists.txt
    A mlir/include/mlir/Dialect/PDL/IR/CMakeLists.txt
    A mlir/include/mlir/Dialect/PDL/IR/PDL.h
    A mlir/include/mlir/Dialect/PDL/IR/PDLBase.td
    A mlir/include/mlir/Dialect/PDL/IR/PDLOps.td
    A mlir/include/mlir/Dialect/PDL/IR/PDLTypes.h
    M mlir/include/mlir/IR/OpImplementation.h
    M mlir/include/mlir/InitAllDialects.h
    M mlir/lib/Dialect/CMakeLists.txt
    A mlir/lib/Dialect/PDL/CMakeLists.txt
    A mlir/lib/Dialect/PDL/IR/CMakeLists.txt
    A mlir/lib/Dialect/PDL/IR/PDL.cpp
    M mlir/lib/Parser/Parser.cpp
    A mlir/test/Dialect/PDL/invalid.mlir
    A mlir/test/Dialect/PDL/ops.mlir
    M mlir/tools/mlir-tblgen/OpFormatGen.cpp

  Log Message:
  -----------
  [mlir] Add a new "Pattern Descriptor Language" (PDL) dialect.

PDL presents a high level abstraction for the rewrite pattern infrastructure available in MLIR. This abstraction allows for representing patterns transforming MLIR, as MLIR. This allows for applying all of the benefits that the general MLIR infrastructure provides, to the infrastructure itself. This means that pattern matching can be more easily verified for correctness, targeted by frontends, and optimized.

PDL abstracts over various different aspects of patterns and core MLIR data structures. Patterns are specified via a `pdl.pattern` operation. These operations contain a region body for the "matcher" code, and terminate with a `pdl.rewrite` that either dispatches to an external rewriter or contains a region for the rewrite specified via `pdl`. The types of values in `pdl` are handle types to MLIR C++ types, with `!pdl.attribute`, `!pdl.operation`, and `!pdl.type` directly mapping to `mlir::Attribute`, `mlir::Operation*`, and `mlir::Value` respectively.

An example pattern is shown below:

```mlir
// pdl.pattern contains metadata similarly to a `RewritePattern`.
pdl.pattern : benefit(1) {
  // External input operand values are specified via `pdl.input` operations.
  // Result types are constrainted via `pdl.type` operations.

  %resultType = pdl.type
  %inputOperand = pdl.input
  %root, %results = pdl.operation "foo.op"(%inputOperand) -> %resultType
  pdl.rewrite(%root) {
    pdl.replace %root with (%inputOperand)
  }
}
```

This is a culmination of the work originally discussed here: https://groups.google.com/a/tensorflow.org/g/mlir/c/j_bn74ByxlQ

Differential Revision: https://reviews.llvm.org/D84578