[mlir][memref] Fix computeCollapsedLayoutMap for contiguous dynamic dim

Author: amrami

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

@@ -23,6 +23,7 @@
 #include "mlir/Interfaces/ViewLikeInterface.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallBitVector.h"
+#include <algorithm>
 
 using namespace mlir;
 using namespace mlir::memref;
@@ -2401,11 +2402,19 @@ computeCollapsedLayoutMap(MemRefType srcType,
     if (!ShapedType::isDynamic(srcShape[ref.back()]) || ref.size() == 1) {
       resultStrides.push_back(srcStrides[ref.back()]);
     } else {
-      // Dynamically-sized dims may turn out to be dims of size 1 at runtime, so
-      // the corresponding stride may have to be skipped. (See above comment.)
-      // Therefore, the result stride cannot be statically determined and must
-      // be dynamic.
-      resultStrides.push_back(ShapedType::kDynamic);
+      bool contiguousSrcDim = srcStrides[ref.back()] == 1;
+      bool dynamicSizeIsPreserved =
+          std::all_of(ref.begin(), ref.end() - 1,
+                      [srcShape](int64_t dim) { return srcShape[dim] == 1; });
+      if (contiguousSrcDim && dynamicSizeIsPreserved)
+        resultStrides.push_back(1);
+      else {
+        // Dynamically-sized dims may turn out to be dims of size 1 at runtime,
+        // so the corresponding stride may have to be skipped. (See above
+        // comment.) Therefore, the result stride cannot be statically
+        // determined and must be dynamic.
+        resultStrides.push_back(ShapedType::kDynamic);
+      }
     }
   }
 

mlir/test/Dialect/MemRef/invalid.mlir

@@ -502,6 +502,14 @@ func.func @collapse_shape_wrong_collapsed_type(%arg0: memref<?x?x?xf32>) {
 
 // -----
 
+func.func @collapse_shape_infer_stride_of_dynamic_dim(%arg0: memref<1x1x?x1xsi32, strided<[36960, 4620, 1, 330]>, 1>, %dim : index) -> (memref<?xsi32, strided<[?]>, 1>) {
+  // expected-error @+1 {{expected collapsed type to be 'memref<?xsi32, strided<[1]>, 1>' but found 'memref<?xsi32, strided<[?]>, 1>'}}
+  %collapse_shape = memref.collapse_shape %arg0 [[0, 1, 2, 3]] : memref<1x1x?x1xsi32, strided<[36960, 4620, 1, 330]>, 1> into memref<?xsi32, strided<[?]>, 1>
+  return %collapse_shape : memref<?xsi32, strided<[?]>, 1>
+}
+
+// -----
+
 func.func @expand_shape_illegal_static_memref
   (%arg0: memref<2x3x20xf32>) -> memref<2x3x2x4x5xf32> {
   // expected-error @+1 {{collapsed dim size (20) must equal reassociation group size (40)}}