[MLIR][Standard] Add `atan2` to standard dialect

[frgossen]

See https://llvm.discourse.group/t/standard-add-atan2-to-the-standard-dialect/1837

[bondhugula]

mlir/include/mlir/Dialect/StandardOps/IR/Ops.td

532

Are you missing a test case? I think a short test case should suffice.

541–544

This description is not saying what the op is doing! :-) but only how many inputs and outputs it has!

[frgossen]

Address comments

[bondhugula]

mlir/test/Dialect/Standard/ops.mlir

37–42 ↗

(On Diff #294676)

Please add CHECK-LABEL's to prevent overrun matches.

[frgossen]

Address comments

mlir/include/mlir/Dialect/StandardOps/IR/Ops.td

let description = [{
 
     // Tensor element-wise arcus tangent.
     %x = atan %y : tensor<4x?xf8>
     ```
   }];
 }
 
 //===----------------------------------------------------------------------===//
+// Atan2Op
+//===----------------------------------------------------------------------===//
+
+def Atan2Op : FloatArithmeticOp<"atan2">{
+  let summary = "2-argument arcus tangent of the given values";
+  let description = [{
+    Syntax:
+
+    ```
+    operation ::= ssa-id `=` `std.atan2` ssa-use `,` ssa-use `:` type
+    ```
+
+    The `atan2` operation takes two operands and returns one result, all of
+    which must be of the same type.  This type may be a floating point scalar
+    type, a vector whose element type is a floating point type, or a floating
+    point tensor.
+
+    Example:
+
+    ```mlir
+    // Scalar variant.
+    %a = atan2 %b, %c : f32
+
+    // SIMD vector variant.
+    %f = atan2 %g, %h : vector<4xf32>
+
+    // Tensor variant.
+    %x = atan2 %y, %z : tensor<4x?xf32>
+    ```
+  }];
+}
+
+//===----------------------------------------------------------------------===//
 // AtomicRMWOp
 //===----------------------------------------------------------------------===//
 
 def AtomicRMWOp : Std_Op<"atomic_rmw", [
       AllTypesMatch<["value", "result"]>,
       TypesMatchWith<"value type matches element type of memref",
                      "memref", "value",
                      "$_self.cast<MemRefType>().getElementType()">