[all-commits] [llvm/llvm-project] c84061: [mlir][vector] Fix a `target-rank=0` unrolling (#7...

[Rik Huijzer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c84061fd343cdd647dd18321aa555c5d358c2d65
      https://github.com/llvm/llvm-project/commit/c84061fd343cdd647dd18321aa555c5d358c2d65
  Author: Rik Huijzer <github at huijzer.xyz>
  Date:   2023-11-30 (Thu, 30 Nov 2023)

  Changed paths:
    M mlir/lib/Conversion/VectorToSCF/VectorToSCF.cpp
    M mlir/test/Conversion/VectorToSCF/vector-to-scf.mlir

  Log Message:
  -----------
  [mlir][vector] Fix a `target-rank=0` unrolling (#73365)

Fixes https://github.com/llvm/llvm-project/issues/64269.

With this patch, calling `mlir-opt "-convert-vector-to-scf=full-unroll
target-rank=0"` on
```mlir
func.func @main(%vec : vector<2xi32>) {
  %alloc = memref.alloc() : memref<4xi32>
  %c0 = arith.constant 0 : index
  vector.transfer_write %vec, %alloc[%c0] : vector<2xi32>, memref<4xi32>
  return
}
```
will result in
```mlir
module {
  func.func @main(%arg0: vector<2xi32>) {
    %c0 = arith.constant 0 : index
    %c1 = arith.constant 1 : index
    %alloc = memref.alloc() : memref<4xi32>
    %0 = vector.extract %arg0[0] : i32 from vector<2xi32>
    %1 = vector.broadcast %0 : i32 to vector<i32>
    vector.transfer_write %1, %alloc[%c0] : vector<i32>, memref<4xi32>
    %2 = vector.extract %arg0[1] : i32 from vector<2xi32>
    %3 = vector.broadcast %2 : i32 to vector<i32>
    vector.transfer_write %3, %alloc[%c1] : vector<i32>, memref<4xi32>
    return
  }
}
```

I've also tried to proactively find other `target-rank=0` bugs, but
couldn't find any. `options.targetRank` is only used 8 times throughout
the `mlir` folder, all inside `VectorToSCF.cpp`. None of the other uses
look like they could cause a crash. I've also tried

```mlir
func.func @main(%vec : vector<2xi32>) -> vector<2xi32> {
  %alloc = memref.alloc() : memref<4xindex>
  %c0 = arith.constant 0 : index
  %out = vector.transfer_read %alloc[%c0], %c0 : memref<4xindex>, vector<2xi32>
  return %out : vector<2xi32>
}
```
with `"--convert-vector-to-scf=full-unroll target-rank=0"` and that also
didn't crash. (Maybe obvious. I have to admit that I'm not very familiar
with these ops.)