[MLIR][Shape] Allow `num_elements` to operate on extent tensors

Re-landing with dependent change landed and error condition relaxed.
Beyond the change to error condition exactly https://reviews.llvm.org/D84445.

mlir/include/mlir/Dialect/Shape/IR/ShapeOps.td

@@ -333,19 +333,19 @@ def Shape_NumElementsOp : Shape_Op<"num_elements", [NoSideEffect]> {
   let summary = "Returns the number of elements for a given shape";
   let description = [{
     Returns the number of elements for a given shape which is the product of its
-    dimensions.
+    extents. If the argument is of type `shape` then the result will be of type
-
+    `size` and potential errors will be propagated. Otherwise, if the argument
-    ```mlir
+    is and extent tensor `tensor<?xindex>` then the result will be of type
-    %product = shape.mul %lhs, %rhs
+    `index`.
-    ```
   }];
 
-  let arguments = (ins Shape_ShapeType:$shape);
+  let arguments = (ins Shape_ShapeOrExtentTensorType:$shape);
-  let results = (outs Shape_SizeType:$result);
+  let results = (outs Shape_SizeOrIndexType:$result);
 
-  let assemblyFormat = "$shape attr-dict";
+  let assemblyFormat = "$shape `:` type($shape) `->` type($result) attr-dict";
 
   let hasFolder = 1;
+  let verifier = [{ return ::verifySizeOrIndexOp(*this); }];
 }
 
 def Shape_ReduceOp : Shape_Op<"reduce",

mlir/test/Dialect/Shape/canonicalize.mlir

@@ -217,7 +217,7 @@ func @num_elements() -> !shape.size {
   // CHECK-NOT: shape.const_shape
   %shape = shape.const_shape [4, 5, 6] : !shape.shape
   // CHECK-NOT: shape.num_elements
-  %num_elements = shape.num_elements %shape
+  %num_elements = shape.num_elements %shape : !shape.shape -> !shape.size
   // CHECK: %[[NUM:.*]] = shape.const_size 120
   // CHECK-NEXT: return %[[NUM]] : !shape.size
   return %num_elements : !shape.size
@@ -229,7 +229,7 @@ func @num_elements() -> !shape.size {
 // CHECK-LABEL: func @nonfoldable_num_elements
 func @nonfoldable_num_elements(%shape : !shape.shape) -> !shape.size {
   // CHECK-NOT: shape.const_{{.*}}
-  %num_elements = shape.num_elements %shape
+  %num_elements = shape.num_elements %shape : !shape.shape -> !shape.size
   return %num_elements : !shape.size
 }
 

mlir/test/Dialect/Shape/invalid.mlir

@@ -120,3 +120,11 @@ func @mul_error_possible(%lhs : !shape.size, %rhs : index) -> index {
   return %result : index
 }
 
+// -----
+
+func @num_elements_error_possible(%arg : !shape.shape) -> index {
+  // expected-error@+1 {{if at least one of the operands can hold error values then the result must be of type `size` to propagate them}}
+  %result = shape.num_elements %arg : !shape.shape -> index
+  return %result : index
+}
+

mlir/test/Dialect/Shape/ops.mlir

@@ -195,3 +195,14 @@ func @any() {
   return
 }
 
+func @num_elements_extent_tensor(%arg : tensor<?xindex>) -> index {
+  %result = shape.num_elements %arg : tensor<?xindex> -> index
+  return %result : index
+}
+
+func @num_elements_shape(%arg : !shape.shape) -> !shape.size {
+  %result = shape.num_elements %arg : !shape.shape -> !shape.size
+  return %result : !shape.size
+}
+
+

mlir/test/Dialect/Shape/shape-to-shape.mlir

@@ -1,9 +1,9 @@
 // RUN: mlir-opt -shape-to-shape-lowering -split-input-file %s | FileCheck %s
 
-// CHECK-LABEL: func @num_elements_to_reduce(
+// CHECK-LABEL: func @num_elements_to_reduce
-// CHECK-SAME:    [[ARG:%.*]]: !shape.shape) -> !shape.size {
+// CHECK-SAME:  ([[ARG:%.*]]: !shape.shape) -> !shape.size
 func @num_elements_to_reduce(%shape : !shape.shape) -> !shape.size {
-  %num_elements = shape.num_elements %shape
+  %num_elements = shape.num_elements %shape : !shape.shape -> !shape.size
   return %num_elements : !shape.size
 }
 // CHECK: [[C1:%.*]] = shape.const_size 1