Rework the way SCons recurses into subdirectories, making it

automatic.  The point is that now a subdirectory can be added
to the build process just by creating a SConscript file in it.
The process has two passes.  On the first pass, all subdirs
of the root of the tree are searched for SConsopts files.
These files contain any command line options that ought to be
added for a particular subdirectory.  On the second pass,
all subdirs of the src directory are searched for SConscript
files.  These files describe how to build any given subdirectory.
I have added a Source() function.  Any file (relative to the
directory in which the SConscript resides) passed to that
function is added to the build.  Clean up everything to take
advantage of Source().
function is added to the list of files to be built.

--HG--
extra : convert_revision : 103f6b490d2eb224436688c89cdc015211c4fd30

SConstruct

@@ -63,10 +63,10 @@
 #
 ###################################################
 
-# Python library imports
 import sys
 import os
 import subprocess
+
 from os.path import join as joinpath
 
 # Check for recent-enough Python and SCons versions.  If your system's
@@ -182,6 +182,7 @@ for t in abs_targets:
 env = Environment(ENV = os.environ,  # inherit user's environment vars
                   ROOT = ROOT,
                   SRCDIR = SRCDIR)
+Export('env')
 
 #Parse CC/CXX early so that we use the correct compiler for 
 # to test for dependencies/versions/libraries/includes
@@ -363,30 +364,42 @@ if have_mysql:
 env = conf.Finish()
 
 # Define the universe of supported ISAs
-env['ALL_ISA_LIST'] = ['alpha', 'sparc', 'mips', 'x86']
+all_isa_list = [ ]
+Export('all_isa_list')
 
 # Define the universe of supported CPU models
-env['ALL_CPU_LIST'] = ['AtomicSimpleCPU', 'TimingSimpleCPU',
-                       'O3CPU', 'OzoneCPU']
-
-if os.path.isdir(joinpath(SRCDIR, 'encumbered/cpu/full')):
-    env['ALL_CPU_LIST'] += ['FullCPU']
+all_cpu_list = [ ]
+default_cpus = [ ]
+Export('all_cpu_list', 'default_cpus')
 
 # Sticky options get saved in the options file so they persist from
 # one invocation to the next (unless overridden, in which case the new
 # value becomes sticky).
 sticky_opts = Options(args=ARGUMENTS)
+Export('sticky_opts')
+
+# Non-sticky options only apply to the current build.
+nonsticky_opts = Options(args=ARGUMENTS)
+Export('nonsticky_opts')
+
+# Walk the tree and execute all SConsopts scripts that wil add to the
+# above options
+for root, dirs, files in os.walk('.'):
+    if 'SConsopts' in files:
+        SConscript(os.path.join(root, 'SConsopts'))
+
+all_isa_list.sort()
+all_cpu_list.sort()
+default_cpus.sort()
+
 sticky_opts.AddOptions(
-    EnumOption('TARGET_ISA', 'Target ISA', 'alpha', env['ALL_ISA_LIST']),
+    EnumOption('TARGET_ISA', 'Target ISA', 'alpha', all_isa_list),
     BoolOption('FULL_SYSTEM', 'Full-system support', False),
     # There's a bug in scons 0.96.1 that causes ListOptions with list
     # values (more than one value) not to be able to be restored from
     # a saved option file.  If this causes trouble then upgrade to
     # scons 0.96.90 or later.
-    ListOption('CPU_MODELS', 'CPU models', 'AtomicSimpleCPU,TimingSimpleCPU,O3CPU',
-               env['ALL_CPU_LIST']),
-    BoolOption('ALPHA_TLASER',
-               'Model Alpha TurboLaser platform (vs. Tsunami)', False),
+    ListOption('CPU_MODELS', 'CPU models', default_cpus, all_cpu_list),
     BoolOption('NO_FAST_ALLOC', 'Disable fast object allocator', False),
     BoolOption('EFENCE', 'Link with Electric Fence malloc debugger',
                False),
@@ -408,8 +421,6 @@ sticky_opts.AddOptions(
      '%s:%s' % (sys.prefix, sys.exec_prefix))
     )
 
-# Non-sticky options only apply to the current build.
-nonsticky_opts = Options(args=ARGUMENTS)
 nonsticky_opts.AddOptions(
     BoolOption('update_ref', 'Update test reference outputs', False)
     )
@@ -514,6 +525,7 @@ env.SConscript('ext/libelf/SConscript',
 #
 ###################################################
 
+env['ALL_ISA_LIST'] = all_isa_list
 def make_switching_dir(dirname, switch_headers, env):
     # Generate the header.  target[0] is the full path of the output
     # header to generate.  'source' is a dummy variable, since we get the
@@ -524,7 +536,7 @@ def make_switching_dir(dirname, switch_headers, env):
 	f = open(fname, 'w')
 	f.write('#include "arch/isa_specific.hh"\n')
 	cond = '#if'
-	for isa in env['ALL_ISA_LIST']:
+	for isa in all_isa_list:
 	    f.write('%s THE_ISA == %s_ISA\n#include "%s/%s/%s"\n'
 		    % (cond, isa.upper(), dirname, isa, basename))
 	    cond = '#elif'
@@ -545,8 +557,7 @@ def make_switching_dir(dirname, switch_headers, env):
     # Instantiate actions for each header
     for hdr in switch_headers:
         env.Command(hdr, [], switch_hdr_action)
-
-env.make_switching_dir = make_switching_dir
+Export('make_switching_dir')
 
 ###################################################
 #