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Date: Thu, 9 Feb 2023 17:20:50 +0100
To: gcc-patches@gcc.gnu.org, Gerald Pfeifer
Subject: [wwwdocs] gcc-13/changes.html: Document C++
-fexcess-precision=standard
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From: Jakub Jelinek
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Hi!
Martin Liska mentioned that porting_to.html doesn't mention
the C++ excess precision changes. Not really sure if porting_to
should document those, but I think changes.html certainly should.
And perhaps porting_to could have some examples and link to this
spot in changes.
Ok for wwwdocs?
Jakub
--- a/htdocs/gcc-13/changes.html
+++ b/htdocs/gcc-13/changes.html
@@ -230,6 +230,21 @@ a work-in-progress.
C++
+ - Excess precision support (which has been available in C since GCC 4.5)
+ has been implemented for C++ as well. It is enabled by default
+ in strict standard modes like
-std=c++17
, where it
+ defaults to -fexcess-precision=standard
, while in GNU
+ standard modes like -std=gnu++20
it defaults to
+ -fexcess-precision=fast
. The option affects mainly
+ IA-32/x86-64 where when defaulting to x87 math and in some cases on
+ Motorola 68000 float
and double
expressions
+ are evaluated in long double
precision and S/390, System z,
+ IBM z Systems where float
expressions are evaluated in
+ double
precision. Also, on several architectures where
+ std::float16_t
or std::bfloat16_t
types
+ are supported those are evaluated in float
precision.
+ -fexcess-precision=fast
restores previous behavior.
+
- Several C++23 features have been implemented: