[C2y] Claim conformance to WG14 N3460

This moves some Annex G requirements for complex numbers into the main
body of the standard.

Author: AaronBallman

clang/test/C/C2y/n3460.c

@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -verify -std=c2y -Wall %s
+
+/* WG14 N3460: Clang 12
+ * Complex operators
+ *
+ * This moves some Annex G requirements into the main body of the standard.
+ */
+
+// CMPLX(0.0, inf) * 2.0, the result should be CMPLX(0.0, inf), not CMPLX(nan, inf)
+static_assert(__builtin_complex(0.0, __builtin_inf()) * 2.0 ==
+              __builtin_complex(0.0, __builtin_inf()));
+
+// CMPLX(0.0, 1.0) * -0.0 is CMPLX(-0.0, -0.0), not CMPLX(-0.0, +0.0)
+static_assert(__builtin_complex(0.0, 1.0) * -0.0 ==
+              __builtin_complex(-0.0, -0.0));
+
+// Testing for -0.0 is a pain because -0.0 == +0.0, so forcefully generate a
+// diagnostic and check the note.
+static_assert(__builtin_complex(0.0, 1.0) * -0.0 == 1); /* expected-error {{static assertion failed due to requirement '__builtin_complex(0., 1.) * -0. == 1'}} \
+                                                           expected-note {{expression evaluates to '(-0 + -0i) == 1'}}
+                                                         */
+
+// CMPLX(0.0, inf) / 2.0, the result should be CMPLX(0.0, inf),
+// not CMPLX(nan, inf)
+static_assert(__builtin_complex(0.0, __builtin_inf()) / 2.0 ==
+              __builtin_complex(0.0, __builtin_inf()));
+
+// CMPLX(2.0, 3.0) * 2.0, the result should be CMPLX(4.0, 6.0)
+static_assert(__builtin_complex(2.0, 3.0) * 2.0 ==
+              __builtin_complex(4.0, 6.0));
+
+// CMPLX(2.0, 4.0) / 2.0, the result should be CMPLX(1.0, 2.0)
+static_assert(__builtin_complex(2.0, 4.0) / 2.0 ==
+              __builtin_complex(1.0, 2.0));
+
+// CMPLX(2.0, 3.0) * CMPLX(4.0, 5.0), the result should be
+// CMPLX(8.0 - 15.0, 12.0 + 10.0)
+static_assert(__builtin_complex(2.0, 3.0) * __builtin_complex(4.0, 5.0) ==
+              __builtin_complex(-7.0, 22.0));
+
+// CMPLX(2.0, 3.0) / CMPLX(4.0, 5.0), the result should be
+// CMPLX((8.0 + 15.0)/(4.0^2 + 5.0^2), (12.0 - 10.0)/(4.0^2 + 5.0^2))
+static_assert(__builtin_complex(2.0, 3.0) / __builtin_complex(4.0, 5.0) ==
+              __builtin_complex(23.0 / 41.0, 2.0 / 41.0));
+
+
+// 2.0 / CMPLX(2.0, 4.0), the result should be
+// CMPLX(4.0 /(2.0^2 + 4.0^2), -8.0/(2.0^2 + 4.0^2))
+static_assert(2.0 / __builtin_complex(2.0, 4.0) ==
+              __builtin_complex(4.0 / 20.0, -8.0 / 20.0));
+

clang/www/c_status.html

@@ -318,7 +318,7 @@ <h2 id="c2y">C2y implementation status</h2>
     <tr>
       <td>Complex operators</td>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3460.pdf">N3460</a></td>
-      <td class="unknown" align="center">Unknown</td>
+      <td class="full" align="center">Clang 12</td>
 	</tr>
 </table>
 </details>