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
@@ -49,25 +49,24 @@
 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.
-
-    Op may also return an ExtentTensor, but this should only be done when this
-    is statically guaranteed to never fail, either because of a dependency on a
-    cstr_broadcastable operation or other details of the construction of the
-    program.
+    Returns the broadcasted shape for two input shapes or extent tensors. Both
+    operands can be of type `shape.shape` or `tensor<?xindex>`. The result is of
+    type `shape.shape` and, if both operands are tensors, may be of type
+    `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 may be undefined. The optional string
+    attribute can be used to describe the error case.
   }];
 
   let arguments = (ins Shape_ShapeOrExtentTensorType:$lhs,
@@ -75,8 +74,11 @@
                        OptionalAttr<StrAttr>:$error);
   let results = (outs Shape_ShapeOrExtentTensorType:$result);
 
-  let assemblyFormat = "$lhs `,` $rhs attr-dict `:` type($lhs) `,` type($rhs) `->` type($result)";
+  let assemblyFormat = [{
+    $lhs `,` $rhs attr-dict `:` type($lhs) `,` type($rhs) `->` type($result)
+  }];
 
+  let verifier = [{ return ::verifyShapeOrExtentTensorOp(*this); }];
   let hasFolder = 1;
 
   let verifier = [{ return ::verifyShapeOrExtentTensorOp(*this); }];
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
@@ -60,6 +60,31 @@
 
 // -----
 
+// 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] : tensor<?xindex>
+  %1 = shape.const_shape [7, 1] : tensor<?xindex>
+  %2 = shape.broadcast %0, %1
+      : tensor<?xindex>, tensor<?xindex> -> tensor<?xindex>
+  return %2 : tensor<?xindex>
+}
+
+// -----
+
+// Basic case including extent tensors.
+// CHECK-LABEL: @broadcast
+func @broadcast() -> !shape.shape {
+  // CHECK: shape.const_shape [7, 2] : !shape.shape
+  %0 = shape.const_shape [1, 2] : tensor<?xindex>
+  %1 = shape.const_shape [7, 1] : tensor<?xindex>
+  %2 = shape.broadcast %0, %1 : tensor<?xindex>, tensor<?xindex> -> !shape.shape
+  return %2 : !shape.shape
+}
+
+// -----
+
 // Rhs is a scalar.
 // CHECK-LABEL: func @f
 func @f(%arg0 : !shape.shape) -> !shape.shape {
diff --git a/mlir/test/Dialect/Shape/invalid.mlir b/mlir/test/Dialect/Shape/invalid.mlir
--- a/mlir/test/Dialect/Shape/invalid.mlir
+++ b/mlir/test/Dialect/Shape/invalid.mlir
@@ -138,17 +138,19 @@
 
 // -----
 
-func @broadcast_error_possible(%arg0 : !shape.shape, %arg1 : !shape.shape) -> tensor<?xindex> {
+func @broadcast(%arg0 : !shape.shape, %arg1 : !shape.shape) -> tensor<?xindex> {
   // expected-error@+1 {{if at least one of the operands can hold error values then the result must be of type `shape` to propagate them}}
-  %result = shape.broadcast %arg0, %arg1 : !shape.shape, !shape.shape -> tensor<?xindex>
+  %result = shape.broadcast %arg0, %arg1
+      : !shape.shape, !shape.shape -> tensor<?xindex>
   return %result : tensor<?xindex>
 }
 
 
 // -----
 
-func @broadcast_error_possible(%arg0 : !shape.shape, %arg1 : tensor<?xindex>) -> tensor<?xindex> {
+func @broadcast(%arg0 : !shape.shape, %arg1 : tensor<?xindex>) -> tensor<?xindex> {
   // expected-error@+1 {{if at least one of the operands can hold error values then the result must be of type `shape` to propagate them}}
-  %result = shape.broadcast %arg0, %arg1 : !shape.shape, tensor<?xindex> -> tensor<?xindex>
+  %result = shape.broadcast %arg0, %arg1
+      : !shape.shape, tensor<?xindex> -> tensor<?xindex>
   return %result : tensor<?xindex>
 }