patch to C++ ABI doc for decimal float classes

[Janis Johnson]

On Tue, 2009-10-13 at 15:51 -0700, Janis Johnson wrote:
> This patch to the C++ ABI document provides exceptions to the usual
> function calling convention and mangling rules to treat the decimal
> classes defined in TR 24733 the same as the corresponding native
> scalar types.  Please consider it and, if it's acceptable, apply it.
> 
> Janis Johnson

No one has commented on this patch, although discussion about
other aspects of decimal float continued in another thread.

Janis

> --- abi.html.orig	2009-10-13 15:36:16.000000000 -0700
> +++ abi.html	2009-10-13 15:46:08.000000000 -0700
> @@ -2577,7 +2577,12 @@
>  <p>
>  In general, C++ value parameters are handled just like C parameters.
>  This includes class type parameters passed wholly or partially in registers.
> -However, in the special case where the parameter type has a non-trivial
> +There are, however, some special cases.
> +</p><ol type="1">
> +<p>
> +</p><li>
> +<p>
> +In the special case where the parameter type has a non-trivial
>  copy constructor or destructor,
>  the caller must allocate space for a temporary copy,
>  and pass the resulting copy by reference (below).
> @@ -2622,7 +2627,16 @@
>  If necessary (e.g. if the parameter was allocated on the heap),
>  the caller deallocates space after return and destruction.
>  
> +<p></p> </li></ul>
> +<li>
> +In the case where the parameter type is class
> +<code>std::decimal::decimal32</code>, <code>std::decimal::decimal64</code>,
> +or <code>std::decimal::decimal128</code> as defined in TR 24733, the
> +parameter is passed the same as the corresponding native decimal
> +floating-point scalar type.
> +<p></p>
>  </li></ul>
> +</ol>
>  
> 
>  <p>
> @@ -2663,6 +2677,12 @@
>  The callee constructs the return value into this temporary.
>  
>  </p><p>
> +Another exception is that a return value type of class
> +<code>std::decimal::decimal32</code>, <code>std::decimal::decimal64</code>,
> +or <code>std::decimal::decimal128</code> as defined in TR 24733 is returned
> +the same as the corresponding native decimal floating-point scalar type.
> +
> +</p><p>
>  A result of an empty class type will be returned as though it were
>  a struct containing a single char,
>  i.e. <code>struct S { char c; };</code>.
> @@ -4343,6 +4363,13 @@
>    <class-enum-type> ::= <name>
>  </font></code></pre>
>  
> +<p>
> +An exception, however, is that class <code>std::decimal::decimal32</code>,
> +<code>std::decimal::decimal64</code>, or <code>std::decimal::decimal128</code>
> +as defined in TR 24733 uses the same encoding as the corresponding native
> +decimal-floating point scalar type.
> +
> +</p><p>
>  Unnamed class, union, and enum types that aren't closure types, that
>  haven't acquired a "name for linkage purposes" (through a typedef), and
>  that aren't anonymous union types, follow
>