[Mlir-commits] [mlir] [MLIR] Fix VectorEmulateNarrowType constant op mask bug (PR #116064)

[Han-Chung Wang]

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@@ -129,6 +132,45 @@ static FailureOr<Operation *> getCompressedMaskOp(OpBuilder &rewriter,
       auto denseAttr = DenseElementsAttr::get(newMaskType, newMaskValues);
       newMask = rewriter.create<arith::ConstantOp>(loc, newMaskType, denseAttr);
     }
+  } else if (constantOp) {
+    assert(shape.size() == 1 && "expected 1-D mask");
+    // Rearrange the original mask values to cover the whole potential loading
+    // region. For example, in the case of using byte-size for emulation, given
+    // the following mask:
+    //
+    //   %mask = vector.constant_mask [0, 1, 0, 1, 0, 0] : vector<6xi2>
+    //
+    // with front offset of 1, the mask will be padded zeros in the front and
+    // back so that its length is multiple of `scale` (and the total coverage
+    // size is mulitiple of bytes):
+    //   %new_mask = vector.constant_mask [0, 0, 1, 0, 1, 0, 0, 0] :
+    //   vector<8xi2>
+    //
+    // The %new_mask is now aligned with the effective loading area and can now
+    // be compressed.
+    SmallVector<bool> maskValues(intraDataOffset, false);
+    if (auto denseAttr =
+            mlir::dyn_cast<DenseIntElementsAttr>(constantOp.getValue())) {
----------------
hanhanW wrote:

nit: drop `mlir::`
style nit: prefer using early-exit to simplify the code, so it can be something like:

```cpp
auto denseAttr = dyn_cast...
if (!denseAttr)
  return failure();
// The rest code in the if branch..
``` 

https://llvm.org/docs/CodingStandards.html#use-early-exits-and-continue-to-simplify-code

https://github.com/llvm/llvm-project/pull/116064