[gcc r12-8298] doc: Document Solaris D bootstrap requirements [PR 103528]

[Rainer Orth <ro@gcc.gnu.org>]

https://gcc.gnu.org/g:4e4f550a5bc588a76452941cb3fb887a20f8a6cc

commit r12-8298-g4e4f550a5bc588a76452941cb3fb887a20f8a6cc
Author: Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
Date:   Thu Apr 28 10:27:32 2022 +0200

    doc: Document Solaris D bootstrap requirements [PR 103528]
    
    This patch documents the Solaris-specific D bootstrap requirements.
    
    Tested by building and inspecting gccinstall.{pdf,info}.
    
    
    2022-03-16  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
    
            gcc:
            PR d/103528
            * doc/install.texi (Tools/packages necessary for building GCC)
            (GDC): Document libphobos requirement.
            (Host/target specific installation notes for GCC, *-*-solaris2*):
            Document libphobos and GDC specifics.

Diff:
---
 gcc/doc/install.texi | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 2bb2d2315de..3192824bdc4 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -287,7 +287,8 @@ section.
 @item @anchor{GDC-prerequisite}GDC
 
 In order to build GDC, the D compiler, you need a working GDC
-compiler (GCC version 9.1 or later), as the D front end is written in D.
+compiler (GCC version 9.1 or later) and D runtime library,
+@samp{libphobos}, as the D front end is written in D.
 
 Versions of GDC prior to 12 can be built with an ISO C++11 compiler, which can
 then be installed and used to bootstrap newer versions of the D front end.
@@ -303,6 +304,10 @@ front end does not make use of any GDC-specific extensions, or novel features
 of the D language, if too old a GDC version is installed and
 @option{--enable-languages=d} is used, the build will fail.
 
+On some targets, @samp{libphobos} isn't enabled by default, but compiles
+and works if @option{--enable-libphobos} is used.  Specifics are
+documented for affected targets.
+
 @item A ``working'' POSIX compatible shell, or GNU bash
 
 Necessary when running @command{configure} because some
@@ -4875,6 +4880,12 @@ GNU binutils.  @samp{libstdc++} symbol versioning will be disabled if no
 appropriate version is found.  Solaris @command{c++filt} from the Solaris
 Studio compilers does @emph{not} work.
 
+In order to build the GNU D compiler, GDC, a working @samp{libphobos} is
+needed.  That library wasn't built by default in GCC 9--11 on SPARC, or
+on x86 when the Solaris assembler is used, but can be enabled by
+configuring with @option{--enable-libphobos}.  Also, GDC 9.4.0 is
+required on x86, while GDC 9.3.0 is known to work on SPARC.
+
 The versions of the GNU Multiple Precision Library (GMP), the MPFR
 library and the MPC library bundled with Solaris 11.3 and later are
 usually recent enough to match GCC's requirements.  There are two
@@ -4888,6 +4899,7 @@ need to configure with @option{--with-gmp-include=/usr/include/gmp}.
 @item
 The version of the MPFR libary included in Solaris 11.3 is too old; you
 need to provide a more recent one.
+
 @end itemize
 
 @html