[Mlir-commits] [mlir] [mlir] Add missing pad reshape propagation patterns (PR #168888)

[Ian Wood]

================
@@ -1921,6 +2023,52 @@ struct FoldReshapeWithGenericOpByCollapsing
   ControlFusionFn controlFoldingReshapes;
 };
 
+/// Computes the collapsed padding information for the given pad operation based
+/// on the provided collapsed shape and reassociation indices. Returns a
+/// PadDimInfo containing the low and high padding amounts and the collapsed
+/// shape for each dimension, or failure if the collapse is not possible.
+static FailureOr<PadDimInfo>
+computeCollapsedPadding(tensor::PadOp padOp,
+                        ArrayRef<ReassociationIndices> reassociations,
+                        PatternRewriter &rewriter) {
+  ArrayRef<int64_t> low = padOp.getStaticLow();
+  ArrayRef<int64_t> high = padOp.getStaticHigh();
+
+  // Collapsed dimensions cannot have padding because this can produce strided
+  // padding that isn't representable by a tensor.pad op. There are some special
+  // cases where it it possible (like collapsing unit dims), but supporting
----------------
IanWood1 wrote:

```suggestion
  // cases where it is possible (like collapsing unit dims), but supporting
```

https://github.com/llvm/llvm-project/pull/168888