| Issue |
61604
|
| Summary |
MLIR Affine Dialect Loop Fusion pass appears to not work
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
rohany
|
I’m playing around with the Affine dialect of MLIR, in particular the Loop Fusion pass. I haven’t been able to get it to work with `mlir-opt` on some simple examples, including the ones from the documentation page here: https://mlir.llvm.org/docs/Passes/#-affine-loop-fusion-fuse-affine-loop-nests.
At a high level, I’m doing the following:
* Copying some MLIR source with fusable loops into a file “testing.mlir”
* Running `bin/mlir-opt testing.mlir —affine-loop-fusion —dump-pass-pipeline`
Here is concrete input and output:
```
➜ build git:(main) ✗ cat ../testing.mlir
func.func @producer_consumer_fusion(%arg0: memref<10xf32>, %arg1: memref<10xf32>) {
%0 = memref.alloc() : memref<10xf32>
%1 = memref.alloc() : memref<10xf32>
%cst = arith.constant 0.000000e+00 : f32
affine.for %arg2 = 0 to 10 {
affine.store %cst, %0[%arg2] : memref<10xf32>
affine.store %cst, %1[%arg2] : memref<10xf32>
}
affine.for %arg2 = 0 to 10 {
%2 = affine.load %0[%arg2] : memref<10xf32>
%3 = arith.addf %2, %2 : f32
affine.store %3, %arg0[%arg2] : memref<10xf32>
}
affine.for %arg2 = 0 to 10 {
%2 = affine.load %1[%arg2] : memref<10xf32>
%3 = arith.mulf %2, %2 : f32
affine.store %3, %arg1[%arg2] : memref<10xf32>
}
return
}
func.func @sibling_fusion(%arg0: memref<10x10xf32>, %arg1: memref<10x10xf32>,
%arg2: memref<10x10xf32>, %arg3: memref<10x10xf32>,
%arg4: memref<10x10xf32>) {
affine.for %arg5 = 0 to 3 {
affine.for %arg6 = 0 to 3 {
%0 = affine.load %arg0[%arg5, %arg6] : memref<10x10xf32>
%1 = affine.load %arg1[%arg5, %arg6] : memref<10x10xf32>
%2 = arith.mulf %0, %1 : f32
affine.store %2, %arg3[%arg5, %arg6] : memref<10x10xf32>
}
}
affine.for %arg5 = 0 to 3 {
affine.for %arg6 = 0 to 3 {
%0 = affine.load %arg0[%arg5, %arg6] : memref<10x10xf32>
%1 = affine.load %arg2[%arg5, %arg6] : memref<10x10xf32>
%2 = arith.addf %0, %1 : f32
affine.store %2, %arg4[%arg5, %arg6] : memref<10x10xf32>
}
}
return
}
➜ build git:(main) ✗ bin/mlir-opt ../testing.mlir --affine-loop-fusion --dump-pass-pipeline
Pass Manager with 1 passes:
builtin.module(affine-loop-fusion{fusion-compute-tolerance=3.000000e-01 fusion-fast-mem-space=0 fusion-local-buf-threshold=0 fusion-maximal=false mode=producer})
module {
func.func @producer_consumer_fusion(%arg0: memref<10xf32>, %arg1: memref<10xf32>) {
%alloc = memref.alloc() : memref<10xf32>
%alloc_0 = memref.alloc() : memref<10xf32>
%cst = arith.constant 0.000000e+00 : f32
affine.for %arg2 = 0 to 10 {
affine.store %cst, %alloc[%arg2] : memref<10xf32>
affine.store %cst, %alloc_0[%arg2] : memref<10xf32>
}
affine.for %arg2 = 0 to 10 {
%0 = affine.load %alloc[%arg2] : memref<10xf32>
%1 = arith.addf %0, %0 : f32
affine.store %1, %arg0[%arg2] : memref<10xf32>
}
affine.for %arg2 = 0 to 10 {
%0 = affine.load %alloc_0[%arg2] : memref<10xf32>
%1 = arith.mulf %0, %0 : f32
affine.store %1, %arg1[%arg2] : memref<10xf32>
}
return
}
func.func @sibling_fusion(%arg0: memref<10x10xf32>, %arg1: memref<10x10xf32>, %arg2: memref<10x10xf32>, %arg3: memref<10x10xf32>, %arg4: memref<10x10xf32>) {
affine.for %arg5 = 0 to 3 {
affine.for %arg6 = 0 to 3 {
%0 = affine.load %arg0[%arg5, %arg6] : memref<10x10xf32>
%1 = affine.load %arg1[%arg5, %arg6] : memref<10x10xf32>
%2 = arith.mulf %0, %1 : f32
affine.store %2, %arg3[%arg5, %arg6] : memref<10x10xf32>
}
}
affine.for %arg5 = 0 to 3 {
affine.for %arg6 = 0 to 3 {
%0 = affine.load %arg0[%arg5, %arg6] : memref<10x10xf32>
%1 = affine.load %arg2[%arg5, %arg6] : memref<10x10xf32>
%2 = arith.addf %0, %1 : f32
affine.store %2, %arg4[%arg5, %arg6] : memref<10x10xf32>
}
}
return
}
}
```
A related bug is that I seem to be unable to set the value of the argument `mode` to the loop fusion pass. Even if I do `—affine-loop-fusion=“mode=greedy”`, the output from the pass manager always reports that `mode` is `producer`.
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