Performance dmd vs ldc2

[Chris]

On Tuesday, 30 July 2013 at 09:10:24 UTC, Temtaime wrote:
> I have a little question..
> Why Digital Mars doesn't uses LLVM for backend and develops 
> their own performance killer ?
> Is someone contact with them to drop out their backend ?

I checked it once more to make sure my code is not the problem. I 
used the xml parsing example on this page 
http://dlang.org/phobos/std_xml.html (the second example). I 
created a dummy "books.xml" file with one entry (see below for 
source). The result:

Loop: 0..100

DMD 2.063
dmd -release -noboundscheck -O -inline
Average time: 41.88 msecs

LDC2 (latest version, no flags)
ldc2 [files]
Average time: 0.01 msecs

------ D Code -------

import std.xml;
import std.stdio;
import std.string;
import std.datetime;

void main() {
	StopWatch sw;
   enum n = 100;
   TickDuration[n] times;
   TickDuration last = TickDuration.from!"seconds"(0);

   foreach (i; 0..n) {
   	sw.start();
   	parse();
   	//writeln("Time ", sw.peek().msecs, " [ms]");
   	sw.stop();
   	times[i] = sw.peek() - last;
     last = sw.peek();
   }
    real sum = 0;
    // To know the number of seconds,
     // use properties of TickDuration.
     // (seconds, msecs, usecs, hnsecs)
    foreach(t; times) {
    	sum += t.msecs;
    }
    writeln("Average time: ", sum/n, " msecs");
}

struct Book
{
     string id;
     string author;
     string title;
     string genre;
     string price;
     string pubDate;
     string description;
}

void parse() {
	string s = cast(string)std.file.read("books.xml");

     // Check for well-formedness
     check(s);

     // Take it apart
     Book[] books;

     auto xml = new DocumentParser(s);
     xml.onStartTag["book"] = (ElementParser xml)
     {
         Book book;
         book.id = xml.tag.attr["id"];
				
         xml.onEndTag["author"]       = (in Element e) { 
book.author      = e.text(); };
         xml.onEndTag["title"]        = (in Element e) { 
book.title       = e.text(); };
         xml.onEndTag["genre"]        = (in Element e) { 
book.genre       = e.text(); };
         xml.onEndTag["price"]        = (in Element e) { 
book.price       = e.text(); };
         xml.onEndTag["publish-date"] = (in Element e) { 
book.pubDate     = e.text(); };
         xml.onEndTag["description"]  = (in Element e) { 
book.description = e.text(); };

         xml.parse();

         books ~= book;
     };
     xml.parse();

     // Put it back together again;
     auto doc = new Document(new Tag("catalog"));
     foreach(book;books)
     {
         auto element = new Element("book");
         element.tag.attr["id"] = book.id;

         element ~= new Element("author",      book.author);
         element ~= new Element("title",       book.title);
         element ~= new Element("genre",       book.genre);
         element ~= new Element("price",       book.price);
         element ~= new Element("publish-date",book.pubDate);
         element ~= new Element("description", book.description);

         doc ~= element;
     }

     // Pretty-print it
     //writefln(join(doc.pretty(3),"\n"));
}

------ XML FILE ------

<?xml version="1.0" encoding="UTF-8"?>
<books>
	<book id="1-23456789">
		<author>Count Dracula</author>
		<title>D for Vampires</title>
		<genre>Programming</genre>
		<price>66.6</price>
		<publish-date>1897</publish-date>
		<description>Tomb programming with D</description>
	</book>
</books>