[all-commits] [llvm/llvm-project] f88f8f: [mlir] Add a generic mem2reg implementation.

[Théo Degioanni via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f88f8fd0bca34dc8e5571cb828b1a159a50fd504
      https://github.com/llvm/llvm-project/commit/f88f8fd0bca34dc8e5571cb828b1a159a50fd504
  Author: Théo Degioanni <theo.degioanni at nextsilicon.com>
  Date:   2023-04-27 (Thu, 27 Apr 2023)

  Changed paths:
    M llvm/include/llvm/ADT/DenseMap.h
    M mlir/include/mlir/Dialect/LLVMIR/LLVMDialect.h
    M mlir/include/mlir/Dialect/LLVMIR/LLVMIntrinsicOps.td
    M mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
    M mlir/include/mlir/Interfaces/CMakeLists.txt
    A mlir/include/mlir/Interfaces/Mem2RegInterfaces.h
    A mlir/include/mlir/Interfaces/Mem2RegInterfaces.td
    A mlir/include/mlir/Transforms/Mem2Reg.h
    M mlir/include/mlir/Transforms/Passes.h
    M mlir/include/mlir/Transforms/Passes.td
    M mlir/lib/Dialect/LLVMIR/CMakeLists.txt
    A mlir/lib/Dialect/LLVMIR/IR/LLVMMem2Reg.cpp
    M mlir/lib/Interfaces/CMakeLists.txt
    A mlir/lib/Interfaces/Mem2RegInterfaces.cpp
    M mlir/lib/Transforms/CMakeLists.txt
    A mlir/lib/Transforms/Mem2Reg.cpp
    A mlir/test/Transforms/mem2reg-llvmir-dbginfo.mlir
    A mlir/test/Transforms/mem2reg-llvmir.mlir

  Log Message:
  -----------
  [mlir] Add a generic mem2reg implementation.

This patch introduces a generic implementation of mem2reg on
unstructured control-flow, along with a specialization for LLVM IR. This
is achieved by defining three new interfaces, representing 1. allocating
operations, 2. operations doing memory accesses, 3. operations that can
be rewired and/or deleted to stop using a specific use.

The file containing the core implementation of the algorithm
(`Mem2Reg.cpp`) contains a detailed explanation of how the algorithm
works. The contract for this pass is that given a memory slot with a
single non-aliased pointer, the pass will either remove all the uses of
the pointer or not change anything.

To help review this patch, I recommend starting by looking at the
interfaces defined in `Mem2Reg.td`, along with their reference
implementation for LLVM IR defined in `LLVMMem2Reg.cpp`. Then, the core
algorithm is implemented in `Mem2Reg.cpp`.

If this is all good I also have an implementation of the interfaces for
0-dimensional memref promotion that I can upstream afterwards.

Reviewed By: gysit

Differential Revision: https://reviews.llvm.org/D148109