[mlir][memref]: Allow collapse of strided unit dim even if strides are dynamic

Author: amrami

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

@@ -2401,6 +2401,11 @@ computeCollapsedLayoutMap(MemRefType srcType,
     auto trailingReassocs = ArrayRef<int64_t>(reassoc).drop_front();
     auto stride = SaturatedInteger::wrap(resultStrides[resultStrideIndex--]);
     for (int64_t idx : llvm::reverse(trailingReassocs)) {
+      // Dimensions of size 1 should be skipped, because their strides are
+      // meaningless and could have any arbitrary value.
+      if (srcShape[idx - 1] == 1)
+        continue;
+
       stride = stride * SaturatedInteger::wrap(srcShape[idx]);
 
       // Both source and result stride must have the same static value. In that
@@ -2415,11 +2420,6 @@ computeCollapsedLayoutMap(MemRefType srcType,
       if (strict && (stride.saturated || srcStride.saturated))
         return failure();
 
-      // Dimensions of size 1 should be skipped, because their strides are
-      // meaningless and could have any arbitrary value.
-      if (srcShape[idx - 1] == 1)
-        continue;
-
       if (!stride.saturated && !srcStride.saturated && stride != srcStride)
         return failure();
     }

mlir/test/Dialect/MemRef/ops.mlir

@@ -431,7 +431,8 @@ func.func @expand_collapse_shape_dynamic(%arg0: memref<?x?x?xf32>,
          %arg4: index,
          %arg5: index,
          %arg6: index,
-         %arg7: memref<4x?x4xf32>) {
+         %arg7: memref<4x?x4xf32>,
+         %arg8: memref<1x1x18x?xsi8, strided<[?, ?, ?, 1], offset: ?>>) {
 //       CHECK:   memref.collapse_shape {{.*}} {{\[}}[0, 1], [2]]
 //  CHECK-SAME:     memref<?x?x?xf32> into memref<?x?xf32>
   %0 = memref.collapse_shape %arg0 [[0, 1], [2]] :
@@ -480,6 +481,10 @@ func.func @expand_collapse_shape_dynamic(%arg0: memref<?x?x?xf32>,
 //       CHECK:   memref.expand_shape {{.*}} {{\[}}[0, 1], [2], [3, 4]]
   %4 = memref.expand_shape %arg7 [[0, 1], [2], [3, 4]] output_shape [2, 2, %arg4, 2, 2]
         : memref<4x?x4xf32> into memref<2x2x?x2x2xf32>
+
+//       CHECK:   memref.collapse_shape {{.*}} {{\[}}[0, 1], [2], [3]]
+//  CHECK-SAME:     memref<1x1x18x?xsi8, strided<[?, ?, ?, 1], offset: ?>> into memref<1x18x?xsi8, strided<[?, ?, 1], offset: ?>>
+  %5 = memref.collapse_shape %arg8 [[0, 1], [2], [3]] : memref<1x1x18x?xsi8, strided<[?, ?, ?, 1], offset: ?>> into memref<1x18x?xsi8, strided<[?, ?, 1], offset: ?>>
   return
 }