diff --git a/mlir/include/mlir/Dialect/Shape/IR/ShapeOps.td b/mlir/include/mlir/Dialect/Shape/IR/ShapeOps.td
--- a/mlir/include/mlir/Dialect/Shape/IR/ShapeOps.td
+++ b/mlir/include/mlir/Dialect/Shape/IR/ShapeOps.td
@@ -70,28 +70,32 @@
 def Shape_BroadcastOp : Shape_Op<"broadcast", [Commutative]> {
   let summary = "Returns the broadcasted output shape of two inputs";
   let description = [{
-    Computes the broadcasted output shape following:
-    1. If any inputs are unranked, output is unranked;
-    2. Else the input array with number of dimensions smaller than the max
-       input dimension, has 1’s prepended to its shapes and the output shape is
-       calculated as follows:
-
-           output[i] = lhs[i] if lhs[i] == rhs[i] or rhs[i] is unknown/undefined
-                     = rhs[i] if lhs[i] is unknown/undefined
-                     = lhs[i] if rhs[i] == 1
-                     = rhs[i] if lhs[i] == 1
-                     = error  if lhs[i] != rhs[i]
-
-    Op has an optional string attribute for the error case where there is no
-    broadcastable output shape possible for the given inputs.
+    Returns the broadcasted shape for two input shapes or extent tensors. Both
+    operands and the result type can be of type `shape.shape` or
+    `tensor<?xindex>`. If the two operand shapes are of different rank the
+    smaller one is padded with 1's from the left. The resulting broadcasted
+    shape is then defined as
+
+        result[i] = lhs[i] if lhs[i] == rhs[i]
+                  = lhs[i] if rhs[i] == 1
+                  = rhs[i] if lhs[i] == 1.
+
+    In case the resulting shape is undefined, i.e. if corresponding extents are
+    different from each other but none is 1, the result is an error shape.
+    Likewise error values are propagated if any of the operands holds an error
+    value. If the result type is an extent tensor (and can therefore not hold
+    the error value) the behavior is undefined. The optional string attribute
+    can be used to describe the error case.
   }];
 
   let arguments = (ins Shape_ShapeOrExtentTensorType:$lhs,
                        Shape_ShapeOrExtentTensorType:$rhs,
                        OptionalAttr<StrAttr>:$error);
-  let results = (outs Shape_ShapeType:$result);
+  let results = (outs Shape_ShapeOrExtentTensorType:$result);
 
-  let assemblyFormat = "$lhs `,` $rhs attr-dict `:` type($lhs) `,` type($rhs)";
+  let assemblyFormat = [{
+    $lhs `,` $rhs attr-dict `:` type($lhs) `,` type($rhs) `->` type($result)
+  }];
 
   let hasFolder = 1;
 }
diff --git a/mlir/test/Dialect/Shape/canonicalize.mlir b/mlir/test/Dialect/Shape/canonicalize.mlir
--- a/mlir/test/Dialect/Shape/canonicalize.mlir
+++ b/mlir/test/Dialect/Shape/canonicalize.mlir
@@ -54,18 +54,30 @@
   // CHECK: shape.const_shape [7, 2] : !shape.shape
   %0 = shape.const_shape [1, 2] : !shape.shape
   %1 = shape.const_shape [7, 1] : !shape.shape
-  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape
+  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape -> !shape.shape
   return %2 : !shape.shape
 }
 
 // -----
 
+// Basic case including extent tensors.
+// CHECK-LABEL: @broadcast
+func @broadcast() -> tensor<?xindex> {
+  // CHECK: shape.const_shape [7, 2] : tensor<?xindex>
+  %0 = shape.const_shape [1, 2] : !shape.shape
+  %1 = shape.const_shape [7, 1] : tensor<?xindex>
+  %2 = shape.broadcast %0, %1 : !shape.shape, tensor<?xindex> -> tensor<?xindex>
+  return %2 : tensor<?xindex>
+}
+
+// -----
+
 // Rhs is a scalar.
 // CHECK-LABEL: func @f
 func @f(%arg0 : !shape.shape) -> !shape.shape {
   // CHECK: return %arg0
   %0 = shape.const_shape [] : !shape.shape
-  %1 = shape.broadcast %arg0, %0 : !shape.shape, !shape.shape
+  %1 = shape.broadcast %arg0, %0 : !shape.shape, !shape.shape -> !shape.shape
   return %1 : !shape.shape
 }
 
@@ -76,7 +88,7 @@
 func @f(%arg0 : !shape.shape) -> !shape.shape {
   // CHECK: return %arg0
   %0 = shape.const_shape [] : !shape.shape
-  %1 = shape.broadcast %0, %arg0 : !shape.shape, !shape.shape
+  %1 = shape.broadcast %0, %arg0 : !shape.shape, !shape.shape -> !shape.shape
   return %1 : !shape.shape
 }
 
@@ -89,7 +101,7 @@
   // CHECK: return %[[CST]]
   %0 = shape.const_shape [] : !shape.shape
   %1 = shape.const_shape [1, 2, 3] : !shape.shape
-  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape
+  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape -> !shape.shape
   return %2 : !shape.shape
 }
 
@@ -101,7 +113,7 @@
   // CHECK: shape.broadcast
   %0 = shape.const_shape [2] : !shape.shape
   %1 = shape.const_shape [7] : !shape.shape
-  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape
+  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape -> !shape.shape
   return %2 : !shape.shape
 }
 
diff --git a/mlir/test/Dialect/Shape/ops.mlir b/mlir/test/Dialect/Shape/ops.mlir
--- a/mlir/test/Dialect/Shape/ops.mlir
+++ b/mlir/test/Dialect/Shape/ops.mlir
@@ -49,7 +49,7 @@
 func @test_broadcast_fixed() {
   %0 = shape.const_shape [10, 1, 57, 92] : !shape.shape
   %1 = shape.const_shape [4, 57, 92] : !shape.shape
-  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape
+  %2 = shape.broadcast %0, %1 : !shape.shape, !shape.shape -> !shape.shape
   %3 = "shape.print"(%2) : (!shape.shape) -> !shape.shape
   return
 }