The --optimize-for-size flag should imply a small semi-space

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
 // a mode defined before it's included.  The modes are FLAG_MODE_... below:
 
+#define DEFINE_IMPLICATION(whenflag, thenflag)              \
+  DEFINE_VALUE_IMPLICATION(whenflag, thenflag, true)
+
+#define DEFINE_NEG_IMPLICATION(whenflag, thenflag)          \
+  DEFINE_VALUE_IMPLICATION(whenflag, thenflag, false)
+
 // We want to declare the names of the variables for the header file.  Normally
 // this will just be an extern declaration, but for a readonly flag we let the
 // compiler make better optimizations by giving it the value.
 #if defined(FLAG_MODE_DECLARE)
 #define FLAG_FULL(ftype, ctype, nam, def, cmt) extern ctype FLAG_##nam;
 #define FLAG_READONLY(ftype, ctype, nam, def, cmt) \
   static ctype const FLAG_##nam = def;
 
 // We want to supply the actual storage and value for the flag variable in the
 // .cc file.  We only do this for writable flags.
@@ skipping 15 matching lines @@
   ,
 #define FLAG_ALIAS(ftype, ctype, alias, nam)                     \
   {                                                              \
     Flag::TYPE_##ftype, #alias, &FLAG_##nam, &FLAGDEFAULT_##nam, \
         "alias for --" #nam, false                               \
   }                                                              \
   ,
 
 // We produce the code to set flags when it is implied by another flag.
 #elif defined(FLAG_MODE_DEFINE_IMPLICATIONS)
-#define DEFINE_IMPLICATION(whenflag, thenflag) \
-  if (FLAG_##whenflag) FLAG_##thenflag = true;
-
-#define DEFINE_NEG_IMPLICATION(whenflag, thenflag) \
-  if (FLAG_##whenflag) FLAG_##thenflag = false;
+#define DEFINE_VALUE_IMPLICATION(whenflag, thenflag, value) \
+  if (FLAG_##whenflag) FLAG_##thenflag = value;
 
 #else
 #error No mode supplied when including flags.defs
 #endif
 
 // Dummy defines for modes where it is not relevant.
 #ifndef FLAG_FULL
 #define FLAG_FULL(ftype, ctype, nam, def, cmt)
 #endif
 
 #ifndef FLAG_READONLY
 #define FLAG_READONLY(ftype, ctype, nam, def, cmt)
 #endif
 
 #ifndef FLAG_ALIAS
 #define FLAG_ALIAS(ftype, ctype, alias, nam)
 #endif
 
-#ifndef DEFINE_IMPLICATION
-#define DEFINE_IMPLICATION(whenflag, thenflag)
-#endif
-
-#ifndef DEFINE_NEG_IMPLICATION
-#define DEFINE_NEG_IMPLICATION(whenflag, thenflag)
+#ifndef DEFINE_VALUE_IMPLICATION
+#define DEFINE_VALUE_IMPLICATION(whenflag, thenflag, value)
 #endif
 
 #define COMMA ,
 
 #ifdef FLAG_MODE_DECLARE
 // Structure used to hold a collection of arguments to the JavaScript code.
 struct JSArguments {
  public:
   inline const char*& operator[](int idx) const { return argv[idx]; }
   static JSArguments Create(int argc, const char** argv) {
@@ skipping 120 matching lines @@
 DEFINE_IMPLICATION(track_field_types, track_fields)
 DEFINE_IMPLICATION(track_field_types, track_heap_object_fields)
 DEFINE_BOOL(smi_binop, true, "support smi representation in binary operations")
 DEFINE_BOOL(vector_ics, false, "support vector-based ics")
 
 // Flags for optimization types.
 DEFINE_BOOL(optimize_for_size, false,
             "Enables optimizations which favor memory size over execution "
             "speed.")
 
+DEFINE_VALUE_IMPLICATION(optimize_for_size, max_semi_space_size, 1)
+
 // Flags for data representation optimizations
 DEFINE_BOOL(unbox_double_arrays, true, "automatically unbox arrays of doubles")
 DEFINE_BOOL(string_slices, true, "use string slices")
 
 // Flags for Crankshaft.
 DEFINE_BOOL(crankshaft, true, "use crankshaft")
 DEFINE_STRING(hydrogen_filter, "*", "optimization filter")
 DEFINE_BOOL(use_gvn, true, "use hydrogen global value numbering")
 DEFINE_INT(gvn_iterations, 3, "maximum number of GVN fix-point iterations")
 DEFINE_BOOL(use_canonicalizing, true, "use hydrogen instruction canonicalizing")
@@ skipping 695 matching lines @@
 #undef FLAG_ALIAS
 
 #undef DEFINE_BOOL
 #undef DEFINE_MAYBE_BOOL
 #undef DEFINE_INT
 #undef DEFINE_STRING
 #undef DEFINE_FLOAT
 #undef DEFINE_ARGS
 #undef DEFINE_IMPLICATION
 #undef DEFINE_NEG_IMPLICATION
+#undef DEFINE_VALUE_IMPLICATION
 #undef DEFINE_ALIAS_BOOL
 #undef DEFINE_ALIAS_INT
 #undef DEFINE_ALIAS_STRING
 #undef DEFINE_ALIAS_FLOAT
 #undef DEFINE_ALIAS_ARGS
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 
 #undef COMMA