path: root/src/SConscript

# -*- mode:python -*-

# Copyright (c) 2004-2005 The Regents of The University of Michigan
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met: redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer;
# redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution;
# neither the name of the copyright holders nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# Authors: Nathan Binkert

import array
import bisect
import imp
import marshal
import os
import re
import sys
import zlib

from os.path import basename, dirname, exists, isdir, isfile, join as joinpath

import SCons

# This file defines how to build a particular configuration of gem5
# based on variable settings in the 'env' build environment.

Import('*')

# Children need to see the environment
Export('env')

build_env = [(opt, env[opt]) for opt in export_vars]

from m5.util import code_formatter, compareVersions

########################################################################
# Code for adding source files of various types
#
# When specifying a source file of some type, a set of guards can be
# specified for that file.  When get() is used to find the files, if
# get specifies a set of filters, only files that match those filters
# will be accepted (unspecified filters on files are assumed to be
# false).  Current filters are:
#     main -- specifies the gem5 main() function
#     skip_lib -- do not put this file into the gem5 library
#     <unittest> -- unit tests use filters based on the unit test name
#
# A parent can now be specified for a source file and default filter
# values will be retrieved recursively from parents (children override
# parents).
#
class SourceMeta(type):
    '''Meta class for source files that keeps track of all files of a
    particular type and has a get function for finding all functions
    of a certain type that match a set of guards'''
    def __init__(cls, name, bases, dict):
        super(SourceMeta, cls).__init__(name, bases, dict)
        cls.all = []
        
    def get(cls, **guards):
        '''Find all files that match the specified guards.  If a source
        file does not specify a flag, the default is False'''
        for src in cls.all:
            for flag,value in guards.iteritems():
                # if the flag is found and has a different value, skip
                # this file
                if src.all_guards.get(flag, False) != value:
                    break
            else:
                yield src

class SourceFile(object):
    '''Base object that encapsulates the notion of a source file.
    This includes, the source node, target node, various manipulations
    of those.  A source file also specifies a set of guards which
    describing which builds the source file applies to.  A parent can
    also be specified to get default guards from'''
    __metaclass__ = SourceMeta
    def __init__(self, source, parent=None, **guards):
        self.guards = guards
        self.parent = parent

        tnode = source
        if not isinstance(source, SCons.Node.FS.File):
            tnode = File(source)

        self.tnode = tnode
        self.snode = tnode.srcnode()

        for base in type(self).__mro__:
            if issubclass(base, SourceFile):
                base.all.append(self)

    @property
    def filename(self):
        return str(self.tnode)

    @property
    def dirname(self):
        return dirname(self.filename)

    @property
    def basename(self):
        return basename(self.filename)

    @property
    def extname(self):
        index = self.basename.rfind('.')
        if index <= 0:
            # dot files aren't extensions
            return self.basename, None

        return self.basename[:index], self.basename[index+1:]

    @property
    def all_guards(self):
        '''find all guards for this object getting default values
        recursively from its parents'''
        guards = {}
        if self.parent:
            guards.update(self.parent.guards)
        guards.update(self.guards)
        return guards

    def __lt__(self, other): return self.filename < other.filename
    def __le__(self, other): return self.filename <= other.filename
    def __gt__(self, other): return self.filename > other.filename
    def __ge__(self, other): return self.filename >= other.filename
    def __eq__(self, other): return self.filename == other.filename
    def __ne__(self, other): return self.filename != other.filename
        
class Source(SourceFile):
    '''Add a c/c++ source file to the build'''
    def __init__(self, source, Werror=True, swig=False, **guards):
        '''specify the source file, and any guards'''
        super(Source, self).__init__(source, **guards)

        self.Werror = Werror
        self.swig = swig

class PySource(SourceFile):
    '''Add a python source file to the named package'''
    invalid_sym_char = re.compile('[^A-z0-9_]')
    modules = {}
    tnodes = {}
    symnames = {}
    
    def __init__(self, package, source, **guards):
        '''specify the python package, the source file, and any guards'''
        super(PySource, self).__init__(source, **guards)

        modname,ext = self.extname
        assert ext == 'py'

        if package:
            path = package.split('.')
        else:
            path = []

        modpath = path[:]
        if modname != '__init__':
            modpath += [ modname ]
        modpath = '.'.join(modpath)

        arcpath = path + [ self.basename ]
        abspath = self.snode.abspath
        if not exists(abspath):
            abspath = self.tnode.abspath

        self.package = package
        self.modname = modname
        self.modpath = modpath
        self.arcname = joinpath(*arcpath)
        self.abspath = abspath
        self.compiled = File(self.filename + 'c')
        self.cpp = File(self.filename + '.cc')
        self.symname = PySource.invalid_sym_char.sub('_', modpath)

        PySource.modules[modpath] = self
        PySource.tnodes[self.tnode] = self
        PySource.symnames[self.symname] = self

class SimObject(PySource):
    '''Add a SimObject python file as a python source object and add
    it to a list of sim object modules'''

    fixed = False
    modnames = []

    def __init__(self, source, **guards):
        '''Specify the source file and any guards (automatically in
        the m5.objects package)'''
        super(SimObject, self).__init__('m5.objects', source, **guards)
        if self.fixed:
            raise AttributeError, "Too late to call SimObject now."

        bisect.insort_right(SimObject.modnames, self.modname)

class SwigSource(SourceFile):
    '''Add a swig file to build'''

    def __init__(self, package, source, **guards):
        '''Specify the python package, the source file, and any guards'''
        super(SwigSource, self).__init__(source, **guards)

        modname,ext = self.extname
        assert ext == 'i'

        self.module = modname
        cc_file = joinpath(self.dirname, modname + '_wrap.cc')
        py_file = joinpath(self.dirname, modname + '.py')

        self.cc_source = Source(cc_file, swig=True, parent=self)
        self.py_source = PySource(package, py_file, parent=self)

class UnitTest(object):
    '''Create a UnitTest'''

    all = []
    def __init__(self, target, *sources, **kwargs):
        '''Specify the target name and any sources.  Sources that are
        not SourceFiles are evalued with Source().  All files are
        guarded with a guard of the same name as the UnitTest
        target.'''

        srcs = []
        for src in sources:
            if not isinstance(src, SourceFile):
                src = Source(src, skip_lib=True)
            src.guards[target] = True
            srcs.append(src)

        self.sources = srcs
        self.target = target
        self.main = kwargs.get('main', False)
        UnitTest.all.append(self)

# Children should have access
Export('Source')
Export('PySource')
Export('SimObject')
Export('SwigSource')
Export('UnitTest')

########################################################################
#
# Debug Flags
#
debug_flags = {}
def DebugFlag(name, desc=None):
    if name in debug_flags:
        raise AttributeError, "Flag %s already specified" % name
    debug_flags[name] = (name, (), desc)

def CompoundFlag(name, flags, desc=None):
    if name in debug_flags:
        raise AttributeError, "Flag %s already specified" % name

    compound = tuple(flags)
    debug_flags[name] = (name, compound, desc)

Export('DebugFlag')
Export('CompoundFlag')

########################################################################
#
# Set some compiler variables
#

# Include file paths are rooted in this directory.  SCons will
# automatically expand '.' to refer to both the source directory and
# the corresponding build directory to pick up generated include
# files.
env.Append(CPPPATH=Dir('.'))

for extra_dir in extras_dir_list:
    env.Append(CPPPATH=Dir(extra_dir))

# Workaround for bug in SCons version > 0.97d20071212
# Scons bug id: 2006 gem5 Bug id: 308
for root, dirs, files in os.walk(base_dir, topdown=True):
    Dir(root[len(base_dir) + 1:])

########################################################################
#
# Walk the tree and execute all SConscripts in subdirectories
#

here = Dir('.').srcnode().abspath
for root, dirs, files in os.walk(base_dir, topdown=True):
    if root == here:
        # we don't want to recurse back into this SConscript
        continue

    if 'SConscript' in files:
        build_dir = joinpath(env['BUILDDIR'], root[len(base_dir) + 1:])
        SConscript(joinpath(root, 'SConscript'), variant_dir=build_dir)

for extra_dir in extras_dir_list:
    prefix_len = len(dirname(extra_dir)) + 1
    for root, dirs, files in os.walk(extra_dir, topdown=True):
        # if build lives in the extras directory, don't walk down it
        if 'build' in dirs:
            dirs.remove('build')

        if 'SConscript' in files:
            build_dir = joinpath(env['BUILDDIR'], root[prefix_len:])
            SConscript(joinpath(root, 'SConscript'), variant_dir=build_dir)

for opt in export_vars:
    env.ConfigFile(opt)

def makeTheISA(source, target, env):
    isas = [ src.get_contents() for src in source ]
    target_isa = env['TARGET_ISA']
    def define(isa):
        return isa.upper() + '_ISA'
    
    def namespace(isa):
        return isa[0].upper() + isa[1:].lower() + 'ISA' 


    code = code_formatter()
    code('''\
#ifndef __CONFIG_THE_ISA_HH__
#define __CONFIG_THE_ISA_HH__

''')

    for i,isa in enumerate(isas):
        code('#define $0 $1', define(isa), i + 1)

    code('''

#define THE_ISA ${{define(target_isa)}}
#define TheISA ${{namespace(target_isa)}}
#define THE_ISA_STR "${{target_isa}}"

#endif // __CONFIG_THE_ISA_HH__''')

    code.write(str(target[0]))

env.Command('config/the_isa.hh', map(Value, all_isa_list),
            MakeAction(makeTheISA, Transform("CFG ISA", 0)))

########################################################################
#
# Prevent any SimObjects from being added after this point, they
# should all have been added in the SConscripts above
#
SimObject.fixed = True

class DictImporter(object):
    '''This importer takes a dictionary of arbitrary module names that
    map to arbitrary filenames.'''
    def __init__(self, modules):
        self.modules = modules
        self.installed = set()

    def __del__(self):
        self.unload()

    def unload(self):
        import sys
        for module in self.installed:
            del sys.modules[module]
        self.installed = set()

    def find_module(self, fullname, path):
        if fullname == 'm5.defines':
            return self

        if fullname == 'm5.objects':
            return self

        if fullname.startswith('m5.internal'):
            return None

        source = self.modules.get(fullname, None)
        if source is not None and fullname.startswith('m5.objects'):
            return self

        return None

    def load_module(self, fullname):
        mod = imp.new_module(fullname)
        sys.modules[fullname] = mod
        self.installed.add(fullname)

        mod.__loader__ = self
        if fullname == 'm5.objects':
            mod.__path__ = fullname.split('.')
            return mod

        if fullname == 'm5.defines':
            mod.__dict__['buildEnv'] = m5.util.SmartDict(build_env)
            return mod

        source = self.modules[fullname]
        if source.modname == '__init__':
            mod.__path__ = source.modpath
        mod.__file__ = source.abspath

        exec file(source.abspath, 'r') in mod.__dict__

        return mod

import m5.SimObject
import m5.params
from m5.util import code_formatter

m5.SimObject.clear()
m5.params.clear()

# install the python importer so we can grab stuff from the source
# tree itself.  We can't have SimObjects added after this point or
# else we won't know about them for the rest of the stuff.
importer = DictImporter(PySource.modules)
sys.meta_path[0:0] = [ importer ]

# import all sim objects so we can populate the all_objects list
# make sure that we're working with a list, then let's sort it
for modname in SimObject.modnames:
    exec('from m5.objects import %s' % modname)

# we need to unload all of the currently imported modules so that they
# will be re-imported the next time the sconscript is run
importer.unload()
sys.meta_path.remove(importer)

sim_objects = m5.SimObject.allClasses
all_enums = m5.params.allEnums

# Find param types that need to be explicitly wrapped with swig.
# These will be recognized because the ParamDesc will have a
# swig_decl() method.  Most param types are based on types that don't
# need this, either because they're based on native types (like Int)
# or because they're SimObjects (which get swigged independently).
# For now the only things handled here are VectorParam types.
params_to_swig = {}
for name,obj in sorted(sim_objects.iteritems()):
    for param in obj._params.local.values():
        # load the ptype attribute now because it depends on the
        # current version of SimObject.allClasses, but when scons
        # actually uses the value, all versions of
        # SimObject.allClasses will have been loaded
        param.ptype

        if not hasattr(param, 'swig_decl'):
            continue
        pname = param.ptype_str
        if pname not in params_to_swig:
            params_to_swig[pname] = param

########################################################################
#
# calculate extra dependencies
#
module_depends = ["m5", "m5.SimObject", "m5.params"]
depends = [ PySource.modules[dep].snode for dep in module_depends ]

########################################################################
#
# Commands for the basic automatically generated python files
#

# Generate Python file containing a dict specifying the current
# buildEnv flags.
def makeDefinesPyFile(target, source, env):
    build_env = source[0].get_contents()

    code = code_formatter()
    code("""
import m5.internal
import m5.util

buildEnv = m5.util.SmartDict($build_env)

compileDate = m5.internal.core.compileDate
_globals = globals()
for key,val in m5.internal.core.__dict__.iteritems():
    if key.startswith('flag_'):
        flag = key[5:]
        _globals[flag] = val
del _globals
""")
    code.write(target[0].abspath)

defines_info = Value(build_env)
# Generate a file with all of the compile options in it
env.Command('python/m5/defines.py', defines_info,
            MakeAction(makeDefinesPyFile, Transform("DEFINES", 0)))
PySource('m5', 'python/m5/defines.py')

# Generate python file containing info about the M5 source code
def makeInfoPyFile(target, source, env):
    code = code_formatter()
    for src in source:
        data = ''.join(file(src.srcnode().abspath, 'r').xreadlines())
        code('$src = ${{repr(data)}}')
    code.write(str(target[0]))

# Generate a file that wraps the basic top level files
env.Command('python/m5/info.py',
            [ '#/COPYING', '#/LICENSE', '#/README', ],
            MakeAction(makeInfoPyFile, Transform("INFO")))
PySource('m5', 'python/m5/info.py')

########################################################################
#
# Create all of the SimObject param headers and enum headers
#

def createSimObjectParamStruct(target, source, env):
    assert len(target) == 1 and len(source) == 1

    name = str(source[0].get_contents())
    obj = sim_objects[name]

    code = code_formatter()
    obj.cxx_param_decl(code)
    code.write(target[0].abspath)

def createParamSwigWrapper(target, source, env):
    assert len(target) == 1 and len(source) == 1

    name = str(source[0].get_contents())
    param = params_to_swig[name]

    code = code_formatter()
    param.swig_decl(code)
    code.write(target[0].abspath)

def createEnumStrings(target, source, env):
    assert len(target) == 1 and len(source) == 1

    name = str(source[0].get_contents())
    obj = all_enums[name]

    code = code_formatter()
    obj.cxx_def(code)
    code.write(target[0].abspath)

def createEnumDecls(target, source, env):
    assert len(target) == 1 and len(source) == 1

    name = str(source[0].get_contents())
    obj = all_enums[name]

    code = code_formatter()
    obj.cxx_decl(code)
    code.write(target[0].abspath)

def createEnumSwigWrapper(target, source, env):
    assert len(target) == 1 and len(source) == 1

    name = str(source[0].get_contents())
    obj = all_enums[name]

    code = code_formatter()
    obj.swig_decl(code)
    code.write(target[0].abspath)

def createSimObjectSwigWrapper(target, source, env):
    name = source[0].get_contents()
    obj = sim_objects[name]

    code = code_formatter()
    obj.swig_decl(code)
    code.write(target[0].abspath)

# Generate all of the SimObject param C++ struct header files
params_hh_files = []
for name,simobj in sorted(sim_objects.iteritems()):
    py_source = PySource.modules[simobj.__module__]
    extra_deps = [ py_source.tnode ]

    hh_file = File('params/%s.hh' % name)
    params_hh_files.append(hh_file)
    env.Command(hh_file, Value(name),
                MakeAction(createSimObjectParamStruct, Transform("SO PARAM")))
    env.Depends(hh_file, depends + extra_deps)

# Generate any needed param SWIG wrapper files
params_i_files = []
for name,param in params_to_swig.iteritems():
    i_file = File('python/m5/internal/%s.i' % (param.swig_module_name()))
    params_i_files.append(i_file)
    env.Command(i_file, Value(name),
                MakeAction(createParamSwigWrapper, Transform("SW PARAM")))
    env.Depends(i_file, depends)
    SwigSource('m5.internal', i_file)

# Generate all enum header files
for name,enum in sorted(all_enums.iteritems()):
    py_source = PySource.modules[enum.__module__]
    extra_deps = [ py_source.tnode ]

    cc_file = File('enums/%s.cc' % name)
    env.Command(cc_file, Value(name),
                MakeAction(createEnumStrings, Transform("ENUM STR")))
    env.Depends(cc_file, depends + extra_deps)
    Source(cc_file)

    hh_file = File('enums/%s.hh' % name)
    env.Command(hh_file, Value(name),
                MakeAction(createEnumDecls, Transform("ENUMDECL")))
    env.Depends(hh_file, depends + extra_deps)

    i_file = File('python/m5/internal/enum_%s.i' % name)
    env.Command(i_file, Value(name),
                MakeAction(createEnumSwigWrapper, Transform("ENUMSWIG")))
    env.Depends(i_file, depends + extra_deps)
    SwigSource('m5.internal', i_file)

# Generate SimObject SWIG wrapper files
for name,simobj in sim_objects.iteritems():
    py_source = PySource.modules[simobj.__module__]
    extra_deps = [ py_source.tnode ]

    i_file = File('python/m5/internal/param_%s.i' % name)
    env.Command(i_file, Value(name),
                MakeAction(createSimObjectSwigWrapper, Transform("SO SWIG")))
    env.Depends(i_file, depends + extra_deps)
    SwigSource('m5.internal', i_file)

# Generate the main swig init file
def makeEmbeddedSwigInit(target, source, env):
    code = code_formatter()
    module = source[0].get_contents()
    code('''\
#include "sim/init.hh"

extern "C" {
    void init_${module}();
}

EmbeddedSwig embed_swig_${module}(init_${module});
''')
    code.write(str(target[0]))
    
# Build all swig modules
for swig in SwigSource.all:
    env.Command([swig.cc_source.tnode, swig.py_source.tnode], swig.tnode,
                MakeAction('$SWIG $SWIGFLAGS -outdir ${TARGETS[1].dir} '
                '-o ${TARGETS[0]} $SOURCES', Transform("SWIG")))
    cc_file = str(swig.tnode)
    init_file = '%s/%s_init.cc' % (dirname(cc_file), basename(cc_file))
    env.Command(init_file, Value(swig.module),
                MakeAction(makeEmbeddedSwigInit, Transform("EMBED SW")))
    Source(init_file, **swig.guards)

#
# Handle debug flags
#
def makeDebugFlagCC(target, source, env):
    assert(len(target) == 1 and len(source) == 1)

    val = eval(source[0].get_contents())
    name, compound, desc = val
    compound = list(sorted(compound))

    code = code_formatter()

    # file header
    code('''
/*
 * DO NOT EDIT THIS FILE! Automatically generated
 */

#include "base/debug.hh"
''')

    for flag in compound:
        code('#include "debug/$flag.hh"')
    code()
    code('namespace Debug {')
    code()

    if not compound:
        code('SimpleFlag $name("$name", "$desc");')
    else:
        code('CompoundFlag $name("$name", "$desc",')
        code.indent()
        last = len(compound) - 1
        for i,flag in enumerate(compound):
            if i != last:
                code('$flag,')
            else:
                code('$flag);')
        code.dedent()

    code()
    code('} // namespace Debug')

    code.write(str(target[0]))

def makeDebugFlagHH(target, source, env):
    assert(len(target) == 1 and len(source) == 1)

    val = eval(source[0].get_contents())
    name, compound, desc = val

    code = code_formatter()

    # file header boilerplate
    code('''\
/*
 * DO NOT EDIT THIS FILE!
 *
 * Automatically generated by SCons
 */

#ifndef __DEBUG_${name}_HH__
#define __DEBUG_${name}_HH__

namespace Debug {
''')

    if compound:
        code('class CompoundFlag;')
    code('class SimpleFlag;')

    if compound:
        code('extern CompoundFlag $name;')
        for flag in compound:
            code('extern SimpleFlag $flag;')
    else:
        code('extern SimpleFlag $name;')

    code('''
}

#endif // __DEBUG_${name}_HH__
''')

    code.write(str(target[0]))

for name,flag in sorted(debug_flags.iteritems()):
    n, compound, desc = flag
    assert n == name

    env.Command('debug/%s.hh' % name, Value(flag),
                MakeAction(makeDebugFlagHH, Transform("TRACING", 0)))
    env.Command('debug/%s.cc' % name, Value(flag),
                MakeAction(makeDebugFlagCC, Transform("TRACING", 0)))
    Source('debug/%s.cc' % name)

# Embed python files.  All .py files that have been indicated by a
# PySource() call in a SConscript need to be embedded into the M5
# library.  To do that, we compile the file to byte code, marshal the
# byte code, compress it, and then generate a c++ file that
# inserts the result into an array.
def embedPyFile(target, source, env):
    def c_str(string):
        if string is None:
            return "0"
        return '"%s"' % string

    '''Action function to compile a .py into a code object, marshal
    it, compress it, and stick it into an asm file so the code appears
    as just bytes with a label in the data section'''

    src = file(str(source[0]), 'r').read()

    pysource = PySource.tnodes[source[0]]
    compiled = compile(src, pysource.abspath, 'exec')
    marshalled = marshal.dumps(compiled)
    compressed = zlib.compress(marshalled)
    data = compressed
    sym = pysource.symname

    code = code_formatter()
    code('''\
#include "sim/init.hh"

namespace {

const uint8_t data_${sym}[] = {
''')
    code.indent()
    step = 16
    for i in xrange(0, len(data), step):
        x = array.array('B', data[i:i+step])
        code(''.join('%d,' % d for d in x))
    code.dedent()
    
    code('''};

EmbeddedPython embedded_${sym}(
    ${{c_str(pysource.arcname)}},
    ${{c_str(pysource.abspath)}},
    ${{c_str(pysource.modpath)}},
    data_${sym},
    ${{len(data)}},
    ${{len(marshalled)}});

} // anonymous namespace
''')
    code.write(str(target[0]))

for source in PySource.all:
    env.Command(source.cpp, source.tnode, 
                MakeAction(embedPyFile, Transform("EMBED PY")))
    Source(source.cpp)

########################################################################
#
# Define binaries.  Each different build type (debug, opt, etc.) gets
# a slightly different build environment.
#

# List of constructed environments to pass back to SConstruct
envList = []

date_source = Source('base/date.cc', skip_lib=True)

# Function to create a new build environment as clone of current
# environment 'env' with modified object suffix and optional stripped
# binary.  Additional keyword arguments are appended to corresponding
# build environment vars.
def makeEnv(label, objsfx, strip = False, **kwargs):
    # SCons doesn't know to append a library suffix when there is a '.' in the
    # name.  Use '_' instead.
    libname = 'gem5_' + label
    exename = 'gem5.' + label
    secondary_exename = 'm5.' + label

    new_env = env.Clone(OBJSUFFIX=objsfx, SHOBJSUFFIX=objsfx + 's')
    new_env.Label = label
    new_env.Append(**kwargs)

    swig_env = new_env.Clone()
    swig_env.Append(CCFLAGS='-Werror')
    if env['GCC']:
        swig_env.Append(CCFLAGS=['-Wno-uninitialized', '-Wno-sign-compare',
                                 '-Wno-parentheses', '-Wno-unused-label',
                                 '-Wno-unused-value'])
        if compareVersions(env['GCC_VERSION'], '4.6') >= 0:
            swig_env.Append(CCFLAGS='-Wno-unused-but-set-variable')
    if env['CLANG']:
        swig_env.Append(CCFLAGS=['-Wno-unused-label', '-Wno-unused-value'])

    werror_env = new_env.Clone()
    werror_env.Append(CCFLAGS='-Werror')

    def make_obj(source, static, extra_deps = None):
        '''This function adds the specified source to the correct
        build environment, and returns the corresponding SCons Object
        nodes'''

        if source.swig:
            env = swig_env
        elif source.Werror:
            env = werror_env
        else:
            env = new_env

        if static:
            obj = env.StaticObject(source.tnode)
        else:
            obj = env.SharedObject(source.tnode)

        if extra_deps:
            env.Depends(obj, extra_deps)

        return obj

    static_objs = \
        [ make_obj(s, True) for s in Source.get(main=False, skip_lib=False) ]
    shared_objs = \
        [ make_obj(s, False) for s in Source.get(main=False, skip_lib=False) ]

    static_date = make_obj(date_source, static=True, extra_deps=static_objs)
    static_objs.append(static_date)
    
    shared_date = make_obj(date_source, static=False, extra_deps=shared_objs)
    shared_objs.append(shared_date)

    # First make a library of everything but main() so other programs can
    # link against m5.
    static_lib = new_env.StaticLibrary(libname, static_objs)
    shared_lib = new_env.SharedLibrary(libname, shared_objs)

    # Now link a stub with main() and the static library.
    main_objs = [ make_obj(s, True) for s in Source.get(main=True) ]

    for test in UnitTest.all:
        flags = { test.target : True }
        test_sources = Source.get(**flags)
        test_objs = [ make_obj(s, static=True) for s in test_sources ]
        if test.main:
            test_objs += main_objs
        testname = "unittest/%s.%s" % (test.target, label)
        new_env.Program(testname, test_objs + static_objs)

    progname = exename
    if strip:
        progname += '.unstripped'

    targets = new_env.Program(progname, main_objs + static_objs)

    if strip:
        if sys.platform == 'sunos5':
            cmd = 'cp $SOURCE $TARGET; strip $TARGET'
        else:
            cmd = 'strip $SOURCE -o $TARGET'
        targets = new_env.Command(exename, progname,
                    MakeAction(cmd, Transform("STRIP")))

    new_env.Command(secondary_exename, exename,
            MakeAction('ln $SOURCE $TARGET', Transform("HARDLINK")))

    new_env.M5Binary = targets[0]
    envList.append(new_env)

# Start out with the compiler flags common to all compilers,
# i.e. they all use -g for opt and -g -pg for prof
ccflags = {'debug' : [], 'opt' : ['-g'], 'fast' : [], 'prof' : ['-g', '-pg'],
           'perf' : ['-g']}

# Start out with the linker flags common to all linkers, i.e. -pg for
# prof, and -lprofiler for perf. The -lprofile flag is surrounded by
# no-as-needed and as-needed as the binutils linker is too clever and
# simply doesn't link to the library otherwise.
ldflags = {'debug' : [], 'opt' : [], 'fast' : [], 'prof' : ['-pg'],
           'perf' : ['-Wl,--no-as-needed', '-lprofiler', '-Wl,--as-needed']}

# For Link Time Optimization, the optimisation flags used to compile
# individual files are decoupled from those used at link time
# (i.e. you can compile with -O3 and perform LTO with -O0), so we need
# to also update the linker flags based on the target.
if env['GCC']:
    if sys.platform == 'sunos5':
        ccflags['debug'] += ['-gstabs+']
    else:
        ccflags['debug'] += ['-ggdb3']
    ldflags['debug'] += ['-O0']
    # opt, fast, prof and perf all share the same cc flags, also add
    # the optimization to the ldflags as LTO defers the optimization
    # to link time
    for target in ['opt', 'fast', 'prof', 'perf']:
        ccflags[target] += ['-O3']
        ldflags[target] += ['-O3']

    ccflags['fast'] += env['LTO_CCFLAGS']
    ldflags['fast'] += env['LTO_LDFLAGS']

elif env['SUNCC']:
    ccflags['debug'] += ['-g0']
    ccflags['opt'] += ['-O']
    for target in ['fast', 'prof', 'perf']:
        ccflags[target] += ['-fast']
elif env['ICC']:
    ccflags['debug'] += ['-g', '-O0']
    ccflags['opt'] += ['-O']
    for target in ['fast', 'prof', 'perf']:
        ccflags[target] += ['-fast']
elif env['CLANG']:
    ccflags['debug'] += ['-g', '-O0']
    # opt, fast, prof and perf all share the same cc flags
    for target in ['opt', 'fast', 'prof', 'perf']:
        ccflags[target] += ['-O3']
else:
    print 'Unknown compiler, please fix compiler options'
    Exit(1)


# To speed things up, we only instantiate the build environments we
# need.  We try to identify the needed environment for each target; if
# we can't, we fall back on instantiating all the environments just to
# be safe.
target_types = ['debug', 'opt', 'fast', 'prof', 'perf']
obj2target = {'do': 'debug', 'o': 'opt', 'fo': 'fast', 'po': 'prof',
              'gpo' : 'perf'}

def identifyTarget(t):
    ext = t.split('.')[-1]
    if ext in target_types:
        return ext
    if obj2target.has_key(ext):
        return obj2target[ext]
    match = re.search(r'/tests/([^/]+)/', t)
    if match and match.group(1) in target_types:
        return match.group(1)
    return 'all'

needed_envs = [identifyTarget(target) for target in BUILD_TARGETS]
if 'all' in needed_envs:
    needed_envs += target_types

# Debug binary
if 'debug' in needed_envs:
    makeEnv('debug', '.do',
            CCFLAGS = Split(ccflags['debug']),
            CPPDEFINES = ['DEBUG', 'TRACING_ON=1'],
            LINKFLAGS = Split(ldflags['debug']))

# Optimized binary
if 'opt' in needed_envs:
    makeEnv('opt', '.o',
            CCFLAGS = Split(ccflags['opt']),
            CPPDEFINES = ['TRACING_ON=1'],
            LINKFLAGS = Split(ldflags['opt']))

# "Fast" binary
if 'fast' in needed_envs:
    makeEnv('fast', '.fo', strip = True,
            CCFLAGS = Split(ccflags['fast']),
            CPPDEFINES = ['NDEBUG', 'TRACING_ON=0'],
            LINKFLAGS = Split(ldflags['fast']))

# Profiled binary using gprof
if 'prof' in needed_envs:
    makeEnv('prof', '.po',
            CCFLAGS = Split(ccflags['prof']),
            CPPDEFINES = ['NDEBUG', 'TRACING_ON=0'],
            LINKFLAGS = Split(ldflags['prof']))

# Profiled binary using google-pprof
if 'perf' in needed_envs:
    makeEnv('perf', '.gpo',
            CCFLAGS = Split(ccflags['perf']),
            CPPDEFINES = ['NDEBUG', 'TRACING_ON=0'],
            LINKFLAGS = Split(ldflags['perf']))

Return('envList')