Distribute prebuilt bootstraps for common hosts

* am/bootstrap.am: New file, factored out of bootstrap/Makefile.am.
* bootstrap/Makefile.am: Use bootstrap.am.

* prebuilt/Makefile.am:
* prebuilt/i686-pc-linux-gnu/Makefile.am:
* prebuilt/mips-unknown-linux-gnu/Makefile.am:
* prebuilt/x86_64-unknown-linux-gnu/Makefile.am: New files.

* configure.ac: Output the prebuilt/ makefiles.
* Makefile.am: Descend into prebuilt/ when making dist.

* meta/uninstalled-env.in: Arrange to put prebuilt/ in the beginning of
  the GUILE_LOAD_COMPILED_PATH.  Also fix a case where bootstrap/ wasn't
  being correctly added to the load path.

1 files changed, 56 insertions, 0 deletions

diff --git a/prebuilt/Makefile.am b/prebuilt/Makefile.am
new file mode 100644
index 000000000..b0a24d023
--- /dev/null
+++ b/prebuilt/Makefile.am
@@ -0,0 +1,56 @@
+## Process this file with automake to produce Makefile.in.
+##
+##  	Copyright (C) 2016 Free Software Foundation, Inc.
+##
+##   This file is part of GNU Guile.
+##
+##   GNU Guile is free software; you can redistribute it and/or modify
+##   it under the terms of the GNU Lesser General Public License as
+##   published by the Free Software Foundation; either version 3, or (at
+##   your option) any later version.
+##
+##   GNU Guile is distributed in the hope that it will be useful, but
+##   WITHOUT ANY WARRANTY; without even the implied warranty of
+##   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+##   GNU Lesser General Public License for more details.
+##
+##   You should have received a copy of the GNU Lesser General Public
+##   License along with GNU Guile; see the file COPYING.LESSER.  If not,
+##   write to the Free Software Foundation, Inc., 51 Franklin Street,
+##   Fifth Floor, Boston, MA 02110-1301 USA
+
+# Guile Scheme is mostly written in Guile Scheme.  Its compiler is
+# written in Guile Scheme, and its interpreter too.  However, it is not
+# bootstrapped from itself: Guile includes a minimal interpreter written
+# in C as well which can load the compiler, enough to compile the
+# interpreter written in Scheme.  That compiled interpreter written in
+# Scheme is then used to compile the rest of Guile, including the
+# compiler itself.
+#
+# The problem is, this process takes a long time, and for people
+# installing Guile from source, it's their first experience of Guile: an
+# hour-long bootstrap.  It's not the nicest experience.  To avoid this,
+# in our tarballs we pre-build object files for the essential parts of
+# the compiler.
+#
+# In the future we will do native compilation and so we will need to
+# precompile object files for all common host types.  Still, since we
+# use ELF everywhere, there will be many host types whose compiled files
+# are the same: because Guile incorporates its own linker and loader for
+# compiled Scheme files, any AArch64 machine, for example, is going to
+# have the same compiled files.  So, for the variants that will be the
+# same, we compile one target triple, and symlink the similar targets to
+# that directory.
+#
+# The current situation though is that we compile to bytecode, and there
+# are only four variants of that bytecode: big- or little-endian, and
+# 32- or 64-bit.  The strategy is the same, only that now
+# arm64-unknown-linux-gnu will link to x86_64-unknown-linux-gnu, as they
+# have the same word size and endianness.  A pending issue to resolve is
+# how this wil deal with architectures where longs are 32 bits and
+# pointers are 64 bits; we'll let the x32 people deal with that.
+
+SUBDIRS = \
+  x86_64-unknown-linux-gnu \
+  i686-pc-linux-gnu \
+  mips-unknown-linux-gnu