[mlir][linalg] Add missing check for isaCopyOpInterface

This PR fixes a missing validation in `isaCopyOpInterface` by checking that the `linalg.yield` operand is identical to the first block argument, indicating a direct copy.

Author: CoTinker

mlir/lib/Dialect/Linalg/IR/LinalgInterfaces.cpp

@@ -68,8 +68,14 @@ bool linalg::isaCopyOpInterface(LinalgOp op) {
       !mapRange.back().isIdentity()) {
     return false;
   }
-  // Region.
-  return llvm::hasSingleElement(op.getBlock()->getOperations());
+  // Check yield first block argument.
+  Block *body = op.getBlock();
+  if (body->getOperations().size() != 1)
+    return false;
+  auto yieldOp = dyn_cast<linalg::YieldOp>(body->back());
+  if (!yieldOp || yieldOp.getNumOperands() != 1)
+    return false;
+  return yieldOp->getOperand(0) == body->getArgument(0);
 }
 
 //===----------------------------------------------------------------------===//

mlir/test/Dialect/Linalg/specialize-generic-ops-fail.mlir

@@ -29,3 +29,20 @@ func.func @neither_permutation_nor_broadcast(%init : tensor<8xi32>) -> tensor<8x
   } -> tensor<8xi32>
   return %res : tensor<8xi32>
 }
+
+// -----
+
+#map = affine_map<(d0) -> (d0)>
+// CHECK-LABEL: func @not_copy
+//  CHECK-NOT:    linalg.copy
+//      CHECK:    linalg.generic
+func.func @not_copy(%input: tensor<8xi32>, %init: tensor<8xi32>) -> tensor<8xi32> {
+  %c0_i32 = arith.constant 0 : i32
+  %res = linalg.generic {
+    indexing_maps = [#map, #map], iterator_types = ["parallel"]
+  } ins(%input: tensor<8xi32>) outs(%init: tensor<8xi32>) {
+  ^bb0(%in: i32, %out: i32):
+    linalg.yield %c0_i32 : i32
+  } -> tensor<8xi32>
+  return %res : tensor<8xi32>
+}