From: liuhongt <hongtao.liu@intel.com>
To: gcc-patches@gcc.gnu.org
Subject: [PATCH] Adjust the wording for x86 _Float16 type.
Date: Mon, 6 Sep 2021 17:24:54 +0800 [thread overview]
Message-ID: <20210906092454.61611-1-hongtao.liu@intel.com> (raw)
Hi:
As discussed in [1], adjust the layout for x86 _Float16 description.
Bootstrappedn and regtested on x86_64-linux-gnu{-m32,}.
Ok for trunk?
gcc/ChangeLog:
* doc/extend.texi: (@node Floating Types): Adjust the wording.
(@node Half-Precision): Ditto.
---
gcc/doc/extend.texi | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 7fb22ed8063..1aa0118bb1f 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -1076,9 +1076,11 @@ systems where @code{__float128} is supported. The @code{_Float32}
type is supported on all systems supporting IEEE binary32; the
@code{_Float64} and @code{_Float32x} types are supported on all systems
supporting IEEE binary64. The @code{_Float16} type is supported on AArch64
-systems by default, and on ARM systems when the IEEE format for 16-bit
-floating-point types is selected with @option{-mfp16-format=ieee}.
-GCC does not currently support @code{_Float128x} on any systems.
+systems by default, and also on x86 systems with @code{target("sse2")}
+for both C and C++.
+On ARM systems when the IEEE format for 16-bit floating-point types is
+selected with @option{-mfp16-format=ieee}. GCC does not currently support
+@code{_Float128x} on any systems.
On the i386, x86_64, IA-64, and HP-UX targets, you can declare complex
types using the corresponding internal complex type, @code{XCmode} for
@@ -1108,6 +1110,10 @@ On ARM and AArch64 targets, GCC supports half-precision (16-bit) floating
point via the @code{__fp16} type defined in the ARM C Language Extensions.
On ARM systems, you must enable this type explicitly with the
@option{-mfp16-format} command-line option in order to use it.
+On x86 targets with @code{target("sse2")} and above, GCC supports
+half-precision (16-bit) floating point via the @code{_Float16} type.
+For C++, x86 provide a builtin type named @code{_Float16} which contains
+same data format as C.
ARM targets support two incompatible representations for half-precision
floating-point values. You must choose one of the representations and
@@ -1151,16 +1157,11 @@ calls.
It is recommended that portable code use the @code{_Float16} type defined
by ISO/IEC TS 18661-3:2015. @xref{Floating Types}.
-On x86 targets with @code{target("sse2")} and above, GCC supports half-precision
-(16-bit) floating point via the @code{_Float16} type which is defined by
-18661-3:2015. For C++, x86 provide a builtin type named @code{_Float16}
-which contains same data format as C.
-
-Without @option{-mavx512fp16}, @code{_Float16} type is storage only, all
-operations will be emulated by software emulation and the @code{float}
-instructions. The default behavior for @code{FLT_EVAL_METHOD} is to keep
-the intermediate result of the operation as 32-bit precision. This may lead
-to inconsistent behavior between software emulation and AVX512-FP16
+On x86 targets, without @option{-mavx512fp16}, @code{_Float16} type is
+storage only, all operations will be emulated by software emulation and the
+@code{float} instructions. The default behavior for @code{FLT_EVAL_METHOD} is
+to keep the intermediate result of the operation as 32-bit precision. This may
+lead to inconsistent behavior between software emulation and AVX512-FP16
instructions.
@node Decimal Float
--
2.18.1
reply other threads:[~2021-09-06 9:24 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210906092454.61611-1-hongtao.liu@intel.com \
--to=hongtao.liu@intel.com \
--cc=gcc-patches@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).