scons: Pull the code which generates debug/flags.cc into a helper script.

Change-Id: Ib4ce51ae0311428e3bcd2dae431cfb0abe185c5d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49401
Reviewed-by: Yu-hsin Wang <yuhsingw@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

build_tools/debugflagcc.py

@@ -0,0 +1,123 @@
+# Copyright (c) 2018, 2020 ARM Limited
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
+# 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.
+
+import collections
+import sys
+
+from code_formatter import code_formatter
+
+def usage():
+    print(f"Usage: {sys.argv[0]} CC [NAME DESC FMT COMPONENTS]...",
+            file=sys.stderr)
+    sys.exit(1)
+
+if len(sys.argv) < 2:
+    usage()
+
+cc = sys.argv[1]
+
+
+FlagInfo = collections.namedtuple('FlagInfo',
+        ['name', 'desc', 'fmt', 'components'])
+
+flags = []
+
+pos = 2
+# Extract groups of arguments for each flag.
+while pos < len(sys.argv):
+    if len(sys.argv) < pos + 4:
+        usage()
+
+    name, desc, fmt, components = sys.argv[pos:pos+4]
+    pos += 4
+    fmt = fmt.lower()
+    if fmt == 'true':
+        fmt = True
+    elif fmt == 'false':
+        fmt = False
+    else:
+        print(f'Unrecognized "FMT" value {fmt}', file=sys.stderr)
+        sys.exit(1)
+    components = components.split(':') if components else []
+    flags.append(FlagInfo(name, desc, fmt, components))
+
+
+code = code_formatter()
+
+# File header.
+code('''
+#include "base/compiler.hh" // For namespace deprecation
+#include "base/debug.hh"
+
+namespace gem5
+{
+
+GEM5_DEPRECATED_NAMESPACE(Debug, debug);
+namespace debug
+{
+''')
+
+# Group the flags into either simple flags or compound flags.
+simple_flags = sorted(filter(lambda f: not f.components, flags))
+compound_flags = sorted(filter(lambda f: f.components, flags))
+
+# We intentionally make flag a reference to a heap allocated object so
+# (1) It has a similar interface to a global object like before
+# (2) It does not get destructed at the end of simulation
+# The second property is desirable as global objects from different
+# translation units do not have a defined destruction order, so it'll
+# be unsafe to access debug flags in their destructor in such cases.
+for flag in simple_flags:
+    name, desc, components, fmt = \
+            flag.name, flag.desc, flag.components, flag.fmt
+    fmt = 'true' if fmt else 'false'
+    code('''
+SimpleFlag& $name = *(
+    new SimpleFlag("$name", "$desc", $fmt));''')
+
+for flag in compound_flags:
+    name, desc, components = flag.name, flag.desc, flag.components
+    code('''
+CompoundFlag& $name = *(new CompoundFlag("$name", "$desc", {
+    ${{', '.join('&' + simple for simple in components)}}
+}));''')
+
+code('''
+} // namespace debug
+} // namespace gem5''')
+
+code.write(cc)