[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
+     cases.
+   * ``full``  Implementation of complex division and multiplication using a
----------------
zahiraam wrote:

-ffast-math implies "basic".
 -ffast-math -fcomplex-arithmetic=full generates this warning:
" overriding '-fcomplex-arithmetic=basic' option with '-fcomplex-arithmetic=full'
-fcomplex-arithmetic=full -ffast-math doesn't generate any warning. I can add one mentioning the presence of nnan/ninf and "full" option.

>>
In the case of complex multiplication, if the 'nnan' and 'ninf' flags are set on the generated instructions, the "full" implementation will be optimized to the "basic" implementation.
>>
This is not the case currently. I will add that.


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