[MemRef] Remove memref.dim OffsetSizeAndStrideOpInterface folding (llvm#169327)

OffsetSizeAndStrideOpInterface does not specify whether it's operating
on the input or output shape and in fact different ops implement this in
different ways, which is also why SubviewOp is special cased here.

This "marked as dynamic but not really dynamic" folding is better
handled by shape inference, so just remove the bad fold.

Author: d0k

mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp

@@ -1074,13 +1074,6 @@ OpFoldResult DimOp::fold(FoldAdaptor adaptor) {
     return subview.getDynamicSize(sourceIndex);
   }
 
-  if (auto sizeInterface =
-          dyn_cast_or_null<OffsetSizeAndStrideOpInterface>(definingOp)) {
-    assert(sizeInterface.isDynamicSize(unsignedIndex) &&
-           "Expected dynamic subview size");
-    return sizeInterface.getDynamicSize(unsignedIndex);
-  }
-
   // dim(memrefcast) -> dim
   if (succeeded(foldMemRefCast(*this)))
     return getResult();

mlir/test/Dialect/MemRef/canonicalize.mlir

@@ -208,19 +208,6 @@ func.func @subview_negative_stride2(%arg0 : memref<7xf32>) -> memref<?xf32, stri
 
 // -----
 
-// CHECK-LABEL: func @dim_of_sized_view
-//  CHECK-SAME:   %{{[a-z0-9A-Z_]+}}: memref<?xi8>
-//  CHECK-SAME:   %[[SIZE:.[a-z0-9A-Z_]+]]: index
-//       CHECK:   return %[[SIZE]] : index
-func.func @dim_of_sized_view(%arg : memref<?xi8>, %size: index) -> index {
-  %c0 = arith.constant 0 : index
-  %0 = memref.reinterpret_cast %arg to offset: [0], sizes: [%size], strides: [1] : memref<?xi8> to memref<?xi8>
-  %1 = memref.dim %0, %c0 : memref<?xi8>
-  return %1 : index
-}
-
-// -----
-
 // CHECK-LABEL: func @no_fold_subview_negative_size
 //  CHECK:        %[[SUBVIEW:.+]] = memref.subview
 //  CHECK:        return %[[SUBVIEW]]