On Wed, Jan 10, 2018 at 11:48:30PM +0000, Joseph Myers wrote:
> On Wed, 10 Jan 2018, Michael Meissner wrote:
>
> > This patch is next in my series of patches to enable us to configure the
> > long
> > double type on PowerPC systems. This patch is only about the configuration
> > option. A future patch will contain the multilib support.
>
> In general we expect configure options to be documented in install.texi.
> Is this one being deliberately omitted because it is only actually usable
> for toolchain development at present, with various ways in which the
> support for IEEE long double is not yet completely functional and library
> support is missing - with documentation intended to be added later once
> fully functional?
Here is the first pass at documentation. Segher is this ok?
2018-01-11 Michael Meissner <meiss...@linux.vnet.ibm.com>
* doc/install.texi (--with-long-double-format=): Document the
switch, and note it isn't for general use at the moment.
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meiss...@linux.vnet.ibm.com, phone: +1 (978) 899-4797
Index: gcc/doc/install.texi
===================================================================
--- gcc/doc/install.texi (revision 256556)
+++ gcc/doc/install.texi (working copy)
@@ -1877,6 +1877,18 @@ When neither of these configure options
128-bit @code{long double} when built against GNU C Library 2.4 and later,
64-bit @code{long double} otherwise.
+@item --with-long-double-format=ibm
+@itemx --with-long-double-format=ieee
+Specify what format 128-bit @code{long double} should use on PowerPC
+VSX systems, If you use @code{--with-long-double-format=ibm},
+@code{long double} will be IBM extended double, which consists of a
+pair of @code{double} values to give a larger mantissa range. If you
+use @code{--with-long-double-format=ieee}, @code{long double} will use
+the IEEE 128-bit floating point format. At the present time, this
+option is only useful for people adding support to the compiler and
+libraries to ultimately switch to the IEEE 128-bit floating point
+format in the future.
+
@item --enable-fdpic
On SH Linux systems, generate ELF FDPIC code.
