This patch udpates the GCC installation documentation to document the
configuration options to set the long double type on the PowerPC: I verified
that the documentation builds. Can I install this on to the trunk?
2018-02-07 Michael Meissner <meiss...@linux.vnet.ibm.com>
* doc/install.texi (Configuration): Document the
--with-long-double-format={ibm,eee} PowerPC configuration
options.
--
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 257455)
+++ gcc/doc/install.texi (working copy)
@@ -1877,6 +1877,35 @@ 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 whether @code{long double} uses the IBM extended double format
+or the IEEE 128-bit floating point format on PowerPC Linux systems.
+This configuration switch will only work on little endian PowerPC
+Linux systems and on big endian 64-bit systems where the default cpu
+is at least power7 (i.e. @option{--with-cpu=power7},
+@option{--with-cpu=power8}, or @option{--with-cpu=power9} is used).
+
+If you use the @option{--with-long-double-64} configuration option,
+the @option{--with-long-double-format=ibm} and
+@option{--with-long-double-format=ieee} options are ignored.
+
+The default @code{long double} format is to use IBM extended double.
+Until all of the libraries are converted to use IEEE 128-bit floating
+point, it is not recommended to use
+@option{--with-long-double-format=ieee}.
+
+On little endian PowerPC Linux systems, if you explicitly set the
+@code{long double} type, it will build multilibs to allow you to
+select either @code{long double} format, unless you disable multilibs
+with the @code{--disable-multilib} option. At present,
+@code{long double} multilibs are not built on big endian PowerPC Linux
+systems. If you are building multilibs, you will need to configure
+the compiler using the @option{--with-system-zlib} option.
+
+If you do not set the @code{long double} type explicitly, no multilibs
+will be generated.
+
@item --enable-fdpic
On SH Linux systems, generate ELF FDPIC code.
