[mlir] Add RSqrt tp ComplexOps.td.

[bkramer]

Looks good

mlir/include/mlir/Dialect/Complex/IR/ComplexOps.td

let description = [{
     ```
   }];
 
   let results = (outs AnyFloat:$real);
   let hasFolder = 1;
 }
 
 //===----------------------------------------------------------------------===//
+// RsqrtOp
+//===----------------------------------------------------------------------===//
+
+def RsqrtOp : ComplexUnaryOp<"rsqrt", [SameOperandsAndResultType]> {
+  let summary = "complex reciprocal of square root";
+  let description = [{
+    The `rsqrt` operation computes reciprocal of square root.
+
+    Example:
+
+    ```mlir
+    %a = complex.rsqrt %b : complex<f32>
+    ```
+  }];
+
+  let results = (outs Complex<AnyFloat>:$result);
+}
+
+//===----------------------------------------------------------------------===//
 // SignOp
 //===----------------------------------------------------------------------===//
 
 def SignOp : ComplexUnaryOp<"sign", [SameOperandsAndResultType]> {
   let summary = "computes sign of a complex number";
   let description = [{
     The `sign` op takes a single complex number and computes the sign of
     it, i.e. `y = sign(x) = x / |x|` if `x != 0`, otherwise `y = 0`.

mlir/test/Dialect/Complex/ops.mlir

func.func @ops(%f: f32) {
   // CHECK: complex.sign %[[C]] : complex<f32>
   %sign = complex.sign %complex : complex<f32>
 
   // CHECK: complex.sin %[[C]] : complex<f32>
   %sin = complex.sin %complex : complex<f32>
 
   // CHECK: complex.sub %[[C]], %[[C]] : complex<f32>
   %diff = complex.sub %complex, %complex : complex<f32>
+
+  // CHECK: complex.tanh %[[C]] : complex<f32>
+  %tanh = complex.tanh %complex : complex<f32>
+
+  // CHECK: complex.pow %[[C]], %[[C]] : complex<f32>
+  %pow = complex.pow %complex, %complex : complex<f32>
+
+  // CHECK: complex.sqrt %[[C]] : complex<f32>
+  %sqrt = complex.sqrt %complex : complex<f32>
+
+  // CHECK: complex.rsqrt %[[C]] : complex<f32>
+  %rsqrt = complex.rsqrt %complex : complex<f32>
+
   return
 }