scons: Define the rules for building debug flag hdrs in place.

Define the rules for building debug flag header files in place, instead
of looping over them all after they've been accumulated.

Change-Id: I02113a21529958c3f971b5462ea340d70d1b18d7
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48372
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>

src/SConscript

@@ -54,7 +54,7 @@ import zlib
 
 import SCons
 
-from gem5_scons import Transform, warning, error
+from gem5_scons import Transform, warning, error, ToValue, FromValue
 
 # This file defines how to build a particular configuration of gem5
 # based on variable settings in the 'env' build environment.
@@ -677,13 +677,58 @@ Export('GTest')
 #
 # Debug Flags
 #
+
+def makeDebugFlagHH(target, source, env):
+    assert len(target) == 1 and len(source) == 1
+
+    name, components, desc, fmt = FromValue(source[0])
+
+    code = code_formatter()
+
+    typename = "CompoundFlag" if components else "SimpleFlag"
+    component_flag_decls = \
+            ''.join('extern SimpleFlag& %s;\n' % flag for flag in components)
+
+    # file header boilerplate
+    code('''\
+#ifndef __DEBUG_${name}_HH__
+#define __DEBUG_${name}_HH__
+
+#include "base/compiler.hh" // For namespace deprecation
+
+namespace gem5
+{
+
+GEM5_DEPRECATED_NAMESPACE(Debug, debug);
+namespace debug
+{
+
+class SimpleFlag;
+class CompoundFlag;
+extern ${typename}& ${name};
+${component_flag_decls}
+
+} // namespace debug
+} // namespace gem5
+
+#endif // __DEBUG_${name}_HH__
+''')
+
+    code.write(str(target[0]))
+
 debug_flags = {}
 def DebugFlag(name, desc=None, fmt=False):
     if name == "All":
         raise AttributeError('The "All" flag name is reserved')
     if name in debug_flags:
-        raise AttributeError('Flag {} already specified'.format(name))
-    debug_flags[name] = (name, (), desc, fmt)
+        raise AttributeError("Flag {} already specified".format(name))
+
+    flag = (name, (), desc, fmt)
+    debug_flags[name] = flag
+
+    hh_file = Dir(env['BUILDDIR']).Dir('debug').File('%s.hh' % name)
+    env.Command(hh_file, ToValue(flag),
+            MakeAction(makeDebugFlagHH, Transform("TRACING", 0)))
 
 def CompoundFlag(name, flags, desc=None):
     if name == "All":
@@ -691,8 +736,12 @@ def CompoundFlag(name, flags, desc=None):
     if name in debug_flags:
         raise AttributeError('Flag {} already specified'.format(name))
 
-    compound = tuple(flags)
-    debug_flags[name] = (name, compound, desc, False)
+    flag = (name, flags, desc, False)
+    debug_flags[name] = flag
+
+    env.Command(Dir(env['BUILDDIR']).Dir('debug').File('%s.hh' % name),
+            ToValue(flag),
+            MakeAction(makeDebugFlagHH, Transform("TRACING", 0)))
 
 def DebugFormatFlag(name, desc=None):
     DebugFlag(name, desc, True)
@@ -1188,58 +1237,7 @@ 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, fmt = val
-
-    code = code_formatter()
-
-    # file header boilerplate
-    code('''\
-#ifndef __DEBUG_${name}_HH__
-#define __DEBUG_${name}_HH__
-
-#include "base/compiler.hh" // For namespace deprecation
-
-namespace gem5
-{
-
-GEM5_DEPRECATED_NAMESPACE(Debug, debug);
-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& $name;')
-
-    code('''
-} // namespace debug
-} // namespace gem5
-
-#endif // __DEBUG_${name}_HH__
-''')
-
-    code.write(str(target[0]))
-
 # Generate the files for the debug and debug-format flags
-for name,flag in sorted(debug_flags.items()):
-    n, compound, desc, fmt = flag
-    assert n == name
-
-    hh_file = 'debug/%s.hh' % name
-    env.Command(hh_file, Value(flag),
-                MakeAction(makeDebugFlagHH, Transform("TRACING", 0)))
-
 env.Command('debug/flags.cc', Value(debug_flags),
             MakeAction(makeDebugFlagCC, Transform("TRACING", 0)))
 Source('debug/flags.cc', add_tags='gem5 trace')