From: Jakub Jelinek <jakub@redhat.com>
To: Gerald Pfeifer <gerald@pfeifer.com>
Cc: "Martin Liška" <mliska@suse.cz>, gcc-patches@gcc.gnu.org
Subject: Re: [wwwdocs] gcc-13/porting_to.html: Document C++ -fexcess-precision=standard
Date: Thu, 9 Mar 2023 09:05:37 +0100 [thread overview]
Message-ID: <ZAmTUfGaA0VeEyDW@tucnak> (raw)
In-Reply-To: <1a4e7d15-0bb8-d083-e168-0a9cc6b38584@pfeifer.com>
On Thu, Mar 09, 2023 at 08:09:02AM +0100, Gerald Pfeifer wrote:
> I struggled a bit understanding this and so have come up with what I
> hope is simpler (without changing the meaning).
>
> What do you think of the change below?
LGTM, thanks.
>
> diff --git a/htdocs/gcc-13/porting_to.html b/htdocs/gcc-13/porting_to.html
> index 170da096..8a2822ff 100644
> --- a/htdocs/gcc-13/porting_to.html
> +++ b/htdocs/gcc-13/porting_to.html
> @@ -122,12 +122,14 @@ the operand as an lvalue.<br>
>
> <h3 id="excess-precision">Excess precision changes</h3>
>
> -<p>GCC 13 implements in C++ <a href="changes.html#cxx">excess precision support</a>
> -which has been before implemented just in the C front end. The new behavior is
> -enabled by default in <code>-std=c++</code><em>NN</em> modes and e.g. when
> -<code>FLT_EVAL_METHOD</code> is 1 or 2 affects behavior of floating point
> -constants and expressions. E.g. for <code>FLT_EVAL_METHOD</code> equal
> -to 2 on ia32:
> +<p>GCC 13 implements <a href="changes.html#cxx">excess precision
> +support</a>, which was implemented just in the C front end
> +before, in C++. The new behavior is enabled by default in
> +<code>-std=c++</code><em>NN</em> modes and when
> +<code>FLT_EVAL_METHOD</code> is 1 or 2 and affects the behavior of
> +floating point constants and expressions.</p>
> +
> +<p>E.g. for <code>FLT_EVAL_METHOD</code> equal to 2 on ia32
>
> <pre><code>
> #include <stdlib.h>
> @@ -139,11 +141,11 @@ will not abort with standard excess precision, because constants and expressions
> in <code>float</code> or <code>double</code> are evaluated in precision of
> <code>long double</code> and demoted only on casts or assignments, but will
> abort with fast excess precision, where whether something is evaluated in
> -precision of <code>long double</code> or not depends on what evaluations are
> -done in the i387 floating point stack or are spilled from it.
> +<code>long double</code> precision depends on what evaluations are
> +done in the i387 floating point stack or are spilled from it.</p>
>
> -The <code>-fexcess-precision=fast</code> option can be used to request the
> -previous behavior.
> +</p>The <code>-fexcess-precision=fast</code> option can be used to
> +request the previous behavior.</p>
>
> <h3 id="alloc-rebind">allocator_traits<A>::rebind_alloc<A::value_type> must be A</h3>
>
Jakub
prev parent reply other threads:[~2023-03-09 8:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-09 16:20 [wwwdocs] gcc-13/changes.html: " Jakub Jelinek
2023-02-10 9:06 ` Gerald Pfeifer
2023-03-02 10:32 ` [wwwdocs] gcc-13/porting_to.html: " Jakub Jelinek
2023-03-02 12:40 ` Martin Liška
2023-03-02 23:05 ` Gerald Pfeifer
2023-03-02 23:16 ` Jakub Jelinek
2023-03-09 7:09 ` Gerald Pfeifer
2023-03-09 8:05 ` Jakub Jelinek [this message]
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