<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/130045>130045</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
[mlir] Inconsistent output when executing MLIR program with `--test-loop-fusion="test-loop-fusion-transformation"`
</td>
</tr>
<tr>
<th>Labels</th>
<td>
mlir
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
Emilyaxe
</td>
</tr>
</table>
<pre>
git version: 953838dceaff
system: `Ubuntu 18.04.6 LTS`
## Description:
I am experiencing an inconsistent result when executing the same MLIR program with and without `--test-loop-fusion="test-loop-fusion-transformation"`.
## Steps to Reproduce:
### 1. **MLIR Program (a.mlir)**:
a.mlir:
```
module {
func.func private @printMemrefI32(tensor<*xi32>)
func.func private @printMemrefF32(tensor<*xf32>)
func.func @entry(%arg0: index) -> tensor<1x2xi32> {
%11 = "tosa.const"() <{value = dense<0> : tensor<1x2x2xi32>}> : () -> tensor<1x2x2xi32>
%12 = tosa.while_loop (%arg1 = %11) : (tensor<1x2x2xi32>) -> tensor<1x2x2xi32> {
%51 = "tosa.const"() <{value = dense<6> : tensor<1x2x2xi32>}> : () -> tensor<1x2x2xi32>
%52 = tosa.greater %51, %arg1 : (tensor<1x2x2xi32>, tensor<1x2x2xi32>) -> tensor<1x2x2xi1>
%extracted = tensor.extract %52[%arg0, %arg0, %arg0] : tensor<1x2x2xi1>
%from_elements = tensor.from_elements %extracted : tensor<i1>
tosa.yield %from_elements : tensor<i1>
} do {
^bb0(%arg1: tensor<1x2x2xi32>):
%51 = "tosa.const"() <{value = dense<1> : tensor<1x2x2xi32>}> : () -> tensor<1x2x2xi32>
%52 = tosa.add %arg1, %51 : (tensor<1x2x2xi32>, tensor<1x2x2xi32>) -> tensor<1x2x2xi32>
tosa.yield %52 : tensor<1x2x2xi32>
}
%50 = tosa.argmax %12 {axis = 1 : i32} : (tensor<1x2x2xi32>) -> tensor<1x2xi32>
return %50 : tensor<1x2xi32>
}
func.func @main() {
%idx0 = index.constant 0
%0 = call @entry(%idx0) : (index) -> tensor<1x2xi32>
%cast = tensor.cast %0 : tensor<1x2xi32> to tensor<*xi32>
call @printMemrefI32(%cast) : (tensor<*xi32>) -> ()
return
}
}
```
### 2. **Command to Run without `--test-loop-fusion` :**
```
/data/szy/MLIR/llvm-release/llvm-project/install/mlir-opt /data/szy/workspace/mlir-inconsistent/a.mlir -tosa-to-scf \
| /data/szy/MLIR/llvm-release/llvm-project/install/mlir-opt -pass-pipeline="builtin.module(func.func(tosa-to-linalg))" \
| /data/szy/MLIR/llvm-release/llvm-project/install/mlir-opt -tosa-to-arith -convert-scf-to-cf -convert-arith-to-llvm \
-convert-linalg-to-loops -convert-linalg-to-parallel-loops -convert-linalg-to-loops -one-shot-bufferize="bufferize-function-boundaries" \
--expand-strided-metadata -convert-linalg-to-affine-loops -finalize-memref-to-llvm -lower-affine -convert-scf-to-cf \
-convert-cf-to-llvm -finalize-memref-to-llvm -convert-func-to-llvm -convert-index-to-llvm -reconcile-unrealized-casts \
| timeout 10 /data/szy/MLIR/llvm-release/llvm-project/build/bin/mlir-cpu-runner -e main -entry-point-result=void \
--shared-libs=/data/szy/MLIR/llvm-release/llvm-project/build/lib/libmlir_c_runner_utils.so \
--shared-libs=/data/szy/MLIR/llvm-release/llvm-project/build/lib/libmlir_runner_utils.so \
--shared-libs=/data/szy/MLIR/llvm-release/llvm-project/build/lib/libmlir_async_runtime.so
```
### 3. **Output without `--test-loop-fusion` :**:
```
[[0, 0]]
```
### 4. **Command to Run with `--test-loop-fusion` :**
```
/data/szy/MLIR/llvm-release/llvm-project/install/mlir-opt /data/szy/workspace/mlir-inconsistent/a.mlir -tosa-to-scf \
| /data/szy/MLIR/llvm-release/llvm-project/install/mlir-opt -pass-pipeline="builtin.module(func.func(tosa-to-linalg))" \
| /data/szy/MLIR/llvm-release/llvm-project/install/mlir-opt -tosa-to-arith -convert-scf-to-cf -convert-arith-to-llvm \
-convert-linalg-to-loops -convert-linalg-to-parallel-loops -convert-linalg-to-loops -one-shot-bufferize="bufferize-function-boundaries" \
--expand-strided-metadata -convert-linalg-to-affine-loops -finalize-memref-to-llvm --test-loop-fusion="test-loop-fusion-transformation" \ -lower-affine -convert-scf-to-cf -convert-cf-to-llvm -finalize-memref-to-llvm -convert-func-to-llvm -convert-index-to-llvm \
-reconcile-unrealized-casts | timeout 10 /data/szy/MLIR/llvm-release/llvm-project/build/bin/mlir-cpu-runner -e main -entry-point-result=void \
--shared-libs=/data/szy/MLIR/llvm-release/llvm-project/build/lib/libmlir_c_runner_utils.so \
--shared-libs=/data/szy/MLIR/llvm-release/llvm-project/build/lib/libmlir_runner_utils.so \
--shared-libs=/data/szy/MLIR/llvm-release/llvm-project/build/lib/libmlir_async_runtime.so
```
### 5. **Output with `--test-loop-fusion` :**
```
[[1, 1]]
```
### 6. **Analysis for this case :**
As some developers have discussed in issue https://github.com/llvm/llvm-project/issues/118631, the test-pass should also preserve the semantics of MLIR.
This MLIR program is expected to correctly output [0, 0] for `%50 = tosa.argmax %12`, given that all elements in` %12` are equal. However, instead of the expected result, it incorrectly outputs [1, 1], which corresponds to the last index of` %12`.
To debug this issue, I printed the IR after each pass and found that the input IR [input.txt](https://github.com/user-attachments/files/19105934/input.txt) is correct before applying the `--test-loop-fusion="test-loop-fusion-transformation"` pass. As shown in the first image, %173 is initialized before the three-level computation (lines 221–237). However, after running `--test-loop-fusion="test-loop-fusion-transformation"`, %173 is instead initialized inside the innermost loop, which causes it to overwrite the assigned value at line 253 in the second image [output.txt](https://github.com/user-attachments/files/19105936/output.txt).
Additionally, I try the `affine-loop-fusion` pass on the same input IR. As shown in the third image, %173 should be initialized in the second loop, leading to the correct result.
</pre>
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