[clang] [CLANG] Full support of complex multiplication and division. (PR #81514)

[Zahira Ammarguellat via cfe-commits]

================
@@ -1847,19 +1847,33 @@ floating point semantic models: precise (the default), strict, and fast.
    * ``16`` - Forces ``_Float16`` operations to be emitted without using excess
      precision arithmetic.
 
-.. option:: -fcx-limited-range:
-
-   This option enables the naive mathematical formulas for complex division and
-   multiplication with no NaN checking of results. The default is
-   ``-fno-cx-limited-range``, but this option is enabled by the ``-ffast-math``
-   option.
-
-.. option:: -fcx-fortran-rules:
-
-   This option enables the naive mathematical formulas for complex
-   multiplication and enables application of Smith's algorithm for complex
-   division. See SMITH, R. L. Algorithm 116: Complex division. Commun.
-   ACM 5, 8 (1962). The default is ``-fno-cx-fortran-rules``.
+.. option:: -fcomplex-arithmetic=<value>:
+
+   This option specifies the implementation for complex multiplication and division.
+
+   Valid values are: ``basic``, ``improved``, ``full`` and ``promoted``.
+
+   * ``basic`` Implementation of complex division and multiplication using
+     algebraic formulas at source precision. No special handling to avoid
+     overflow. NaN and infinite and  values are not handled.
+   * ``improved`` Implementation of complex division using the Smith algorithm at
+     source precision. Smith's algorithm for complex division.
+     See SMITH, R. L. Algorithm 116: Complex division. Commun. ACM 5, 8 (1962).
+     This value offers improved handling for overflow in intermediate calculations,
+     but overflow may occur. NaN and infinite and  values are not handled in some
----------------
zahiraam wrote:

If I don't mention the Smith's algorithm here then I wouldn't have to add that. But this is what the Smith's algorithm comment indicates:
"The method used her tends to avoid arithmetic overflow or underflow. Such spills could otherwise occur when squaring the component parts of the denominator if the usual method were used.”

https://github.com/llvm/llvm-project/pull/81514