Use data driven code when registering constructors.

Source/build/scripts/templates/ElementFactory.cpp.tmpl

Index: Source/build/scripts/templates/ElementFactory.cpp.tmpl
diff --git a/Source/build/scripts/templates/ElementFactory.cpp.tmpl b/Source/build/scripts/templates/ElementFactory.cpp.tmpl
index 1eca356b5b8cecf14501064c6f9d6725ab44b4a8..56398570ec707adfc991b69f21f474d3f49a146e 100644
--- a/Source/build/scripts/templates/ElementFactory.cpp.tmpl
+++ b/Source/build/scripts/templates/ElementFactory.cpp.tmpl
@@ -58,18 +58,21 @@ static PassRefPtr<{{namespace}}Element> {{tag|symbol}}Constructor(
 }
 {%- endfor %}
 
-static void addTag(const QualifiedName& tag, ConstructorFunction func)
-{
-    g_constructors->set(tag.localName(), func);
-}
-
 static void createFunctionMap()
 {
     ASSERT(!g_constructors);
     g_constructors = new FunctionMap;
+    struct CreateFunctionMapData {
+        const QualifiedName& tag;
+        ConstructorFunction func;
+    };
+    const CreateFunctionMapData data[] = {

[adamk, 2014/02/18 18:28:41]

Not sure if it matters (since this is only called once), but shouldn't this be
static?

[Daniel Bratell, 2014/02/19 13:41:05]

It's a tricky question. For a compile time constant "static const" is the right
thing to do. For an array of function and data pointers? Making it static will
create a data block where all the pointers will have to be resolved at a later
time (at worst, when the function is called and then nothing has been gained).

I wasn't sure when I wrote the code what was correct but since I wanted to avoid
the startup cost of resolving pointers I skipped static. Now I've tried with
both (in clang) and it seems static might be better for code size and the extra
cost for loading the binary will be offset by less work when calling this
function.

Short answer: "Yes".

 {%- for tag in tags|sort if not tag.noConstructor %}
-    addTag({{tag|symbol}}Tag, {{tag|symbol}}Constructor);
+        { {{tag|symbol}}Tag, {{tag|symbol}}Constructor },
 {%- endfor %}
+    };
+    for (size_t i = 0; i < sizeof(data) / sizeof(*data); i++)

[adamk, 2014/02/18 18:28:41]

Nit: you can use WTF_ARRAY_LENGTH() (from wtf/StdLibExtras.h) here instead of
doing sizeof arithmetic.

[Daniel Bratell, 2014/02/19 13:41:05]

Thanks!

+        g_constructors->set(data[i].tag.localName(), data[i].func);
 }
 
 PassRefPtr<{{namespace}}Element> {{namespace}}ElementFactory::create{{namespace}}Element(