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[MLIR] [affine-loop-fusion] Fix a bug about non-result ops in affine-loop-fusion

Authored by tungld on Feb 5 2021, 11:59 PM.

Description

[MLIR] [affine-loop-fusion] Fix a bug about non-result ops in affine-loop-fusion

This patch fixes the following bug when calling --affine-loop-fusion

Input program:

mlir
func @should_not_fuse_since_top_level_non_affine_non_result_users(
    %in0 : memref<32xf32>, %in1 : memref<32xf32>) {
  %c0 = constant 0 : index
  %cst_0 = constant 0.000000e+00 : f32

  affine.for %d = 0 to 32 {
    %lhs = affine.load %in0[%d] : memref<32xf32>
    %rhs = affine.load %in1[%d] : memref<32xf32>
    %add = addf %lhs, %rhs : f32
    affine.store %add, %in0[%d] : memref<32xf32>
  }
  store %cst_0, %in0[%c0] : memref<32xf32>
  affine.for %d = 0 to 32 {
    %lhs = affine.load %in0[%d] : memref<32xf32>
    %rhs = affine.load %in1[%d] : memref<32xf32>
    %add = addf %lhs, %rhs: f32
    affine.store %add, %in0[%d] : memref<32xf32>
  }
  return
}

call --affine-loop-fusion, we got an incorrect output:

mlir
func @should_not_fuse_since_top_level_non_affine_non_result_users(%arg0: memref<32xf32>, %arg1: memref<32xf32>) {
  %c0 = constant 0 : index
  %cst = constant 0.000000e+00 : f32
  store %cst, %arg0[%c0] : memref<32xf32>
  affine.for %arg2 = 0 to 32 {
    %0 = affine.load %arg0[%arg2] : memref<32xf32>
    %1 = affine.load %arg1[%arg2] : memref<32xf32>
    %2 = addf %0, %1 : f32
    affine.store %2, %arg0[%arg2] : memref<32xf32>
    %3 = affine.load %arg0[%arg2] : memref<32xf32>
    %4 = affine.load %arg1[%arg2] : memref<32xf32>
    %5 = addf %3, %4 : f32
    affine.store %5, %arg0[%arg2] : memref<32xf32>
  }
  return
}

This happened because when analyzing the source and destination nodes,
affine loop fusion ignored non-result ops sandwitched between them. In
other words, the MemRefDependencyGraph in the affine loop fusion ignored
these non-result ops.

This patch solves the issue by adding these non-result ops to the
MemRefDependencyGraph.

Reviewed By: bondhugula

Differential Revision: https://reviews.llvm.org/D95668