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   <img src="dragoneggsmall.png" alt="DragonEgg logo" width="136" height="136" align="left" hspace="30">

   <!--*********************************************************************-->
   <h1>DragonEgg - Using LLVM as a GCC backend</h1>
   <!--*********************************************************************-->

   <p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a gcc plugin
   <tt>dragonegg.so</tt> that replaces gcc's optimizers and code generators with
   those from the <a href="http://llvm.org">LLVM project</a>.</p>
   <p>It is a reimplementation of
   <a href="http://llvm.org/docs/CommandGuide/">llvm-gcc</a>
   that works with <a href="http://gcc.gnu.org">gcc-4.5</a> or later.</p>

   <br clear="all">

   <!--=====================================================================-->
   <h2>Goals</h2>
   <!--=====================================================================-->

   <ul>
   <li>Work with unmodified gcc</li>
   <li>Support all gcc languages</li>
   </ul>

   <!--=====================================================================-->
   <h2>Current Status</h2>
   <!--=====================================================================-->

   <ul>
   <li>C works well, for example you can build a working gcc using it</li>
   <li>C++ works fairly well, for example you can build LLVM, clang and boost
   with it (the resulting LLVM and clang work correctly; I did not test whether
   boost actually works)</li>
   <li>A lot of Fortran compiles, but the compiled code has not been tested for
   correctness</li>
   <li>It can compile quite a lot of Ada, but the compiled code may not work
   right</li>
   <li>It can compile a small amount of Obj-C and Obj-C++</li>
   <li>It fails to compile any Java</li>
   <li>Exception handling does not work</li>
   <li>Limited debug info</li>
   <li>Requires one gcc patch</li>
   <li>Only supports x86-32 and x86-64</li>
   <li>Only supports linux and darwin (darwin hasn't been tested recently though)</li>
   </ul>

   <p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is under heavy
   development and is not mature - it may crash or produce wrong code.  It works
   with <a href="http://gcc.gnu.org">gcc-4.5</a> which is nowhere near being
   released yet and is changing rapidly.  This is an additional source of
   instability, and means that
   <a href="http://dragonegg.llvm.org/">DragonEgg</a> may fail to build from
   time-to-time if it has not caught up with the latest gcc changes.
   <a href="http://dragonegg.llvm.org/">DragonEgg</a> uses the development
   version of <a href="http://llvm.org">LLVM</a> which creates similar problems.</p>

   <!--=====================================================================-->
   <h2>DragonEgg in action</h2>
   <!--=====================================================================-->

   <p>Here is the result of compiling a simple "hello world" program with gcc-4.5.</p>
   <pre>
 $ gcc hello.c -S -O1 -o -
 	.file	"hello.c"
 	.section	.rodata.str1.1,"aMS",@progbits,1
 .LC0:
 	.string	"Hello world!"
 	.text
 .globl main
 	.type	main, @function
 main:
 	subq	$8, %rsp
 	movl	$.LC0, %edi
 	call	puts
 	movl	$0, %eax
 	addq	$8, %rsp
 	ret
 	.size	main, .-main
 	.ident	"GCC: (GNU) 4.5.0 20090928 (experimental)"
 	.section	.note.GNU-stack,"",@progbits
   </pre>

   <p>Adding <tt>-fplugin=path/dragonegg.so</tt> to the gcc command line causes
   the program to be optimized and codegened by LLVM instead.</p>
   <pre>
 $ gcc hello.c -S -O1 -o - -fplugin=./dragonegg.so
 	.file	"hello.c"
 # Start of file scope inline assembly
 	.ident	"GCC: (GNU) 4.5.0 20090928 (experimental) LLVM: 82450:82981"
 # End of file scope inline assembly


 	.text
 	.align	16
 	.globl	main
 	.type	main,@function
 main:
 	subq	$8, %rsp
 	movl	$.L.str, %edi
 	call	puts
 	xorl	%eax, %eax
 	addq	$8, %rsp
 	ret
 	.size	main, .-main
 	.type	.L.str,@object
 	.section	.rodata.str1.1,"aMS",@progbits,1
 .L.str:
 	.asciz	"Hello world!"
 	.size	.L.str, 13

 	.section	.note.GNU-stack,"",@progbits
   </pre>

   <p>Adding <tt>-fplugin-arg-dragonegg-emit-ir</tt> causes LLVM IR to be output.</p>
   <pre>
 $ gcc hello.c -S -O1 -o - -fplugin=./dragonegg.so -fplugin-arg-dragonegg-emit-ir
 ; ModuleID = 'hello.c'
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
 target triple = "x86_64-unknown-linux-gnu"

 module asm "\09.ident\09\22GCC: (GNU) 4.5.0 20090928 (experimental) LLVM: 82450:82981\22"

 @.str = private constant [13 x i8] c"Hello world!\00", align 1 ; &lt;[13 x i8]*&gt; [#uses=1]

 define i32 @main() nounwind {
 entry:
   %0 = tail call i32 @puts(i8* getelementptr inbounds ([13 x i8]* @.str, i64 0, i64 0)) nounwind ; &lt;i32&gt; [#uses=0]
   ret i32 0
 }

 declare i32 @puts(i8* nocapture) nounwind
 </pre>
   <!--=====================================================================-->
   <h2>Getting it</h2>
   <!--=====================================================================-->

   <p>Get <a href="http://dragonegg.llvm.org/">DragonEgg</a>:</p>
      <pre>	svn co http://llvm.org/svn/llvm-project/dragonegg/trunk dragonegg</pre>
   <p>Get the development version of <a href="http://llvm.org">LLVM</a>:</p>
      <pre>	svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</pre>
   <p>Build <a href="http://llvm.org">LLVM</a> in the usual way.
      You do not need to install it.</p>
   <p>Get the development version of <a href="http://gcc.gnu.org">gcc</a>:</p>
      <pre>	svn co http://gcc.gnu.org/svn/gcc/trunk gcc</pre>
   <p>Apply all of the patches in <tt>dragonegg/gcc-patches/</tt>, if any, to
      <a href="http://gcc.gnu.org">gcc</a>.
      You need to pass the <tt>-p1</tt> option to <tt>patch</tt>.
      Build and install <a href="http://gcc.gnu.org">gcc</a> in the usual way.</p>
   <p>Doing</p>
      <pre>	GCC=path_to_just_installed_gcc make</pre>
   <p>in the <tt>dragonegg</tt> directory should then build <tt>dragonegg.so</tt>.
      See the <tt>README</tt> file for more details.</p>
   <p>To use <tt>dragonegg.so</tt>, compile something with your just-installed
      version of <tt>gcc</tt>, adding <tt>-fplugin=path_to_dragonegg/dragonegg.so</tt>
      to the command line.  See the <tt>README</tt> file for more details and useful
      command line options.</p>

   <!--=====================================================================-->
   <h2>It doesn't work!</h2>
   <!--=====================================================================-->
   <p>Sorry about that!  Please report bugs and problems to the LLVM developers'
      <a href="http://llvm.org/docs/#maillist">mailing list</a>, or using LLVM's
      <a href="http://llvm.org/bugs/">bugzilla</a>.</p>
   <p>Suggestions for improvement are welcome.  Patches are even more welcome!</p>

   <!--=====================================================================-->
   <h2>More information</h2>
   <!--=====================================================================-->
   There was a talk "Reimplementing llvm-gcc as a gcc plugin" about
   <a href="http://dragonegg.llvm.org/">DragonEgg</a> at the
   <a href="http://llvm.org/devmtg/2009-10/">2009 llvm developers meeting</a>.
   At that time, <a href="http://dragonegg.llvm.org/">DragonEgg</a> was known as
   "the gcc plugin".
   <p>[<a href="http://llvm.org/devmtg/2009-10/Sands_LLVMGCCPlugin.pdf">Slides</a>]</p>
   <p>[<a href="http://llvm.org/devmtg/2009-10/Sands_LLVMGCCPlugin-700kbps.mov">Video</a>]&nbsp;<font size="-1">(Computer)</font></p>
   <p>[<a href="http://llvm.org/devmtg/2009-10/Sands_LLVMGCCPlugin-mobile.m4v">Video</a>]&nbsp;<font size="-1">(Mobile)</font></p>
 </div>
 </body>
 </html>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
	<html>
	<head>
	<META http-equiv="Content-Type" content="text/html; charset=utf-8">
	<title>DragonEgg</title>
	</head>
	<body>
	<div>

	<img src="dragoneggsmall.png" alt="DragonEgg logo" width="136" height="136" align="left" hspace="30">

	<!--*********************************************************************-->
	<h1>DragonEgg - Using LLVM as a GCC backend</h1>
	<!--*********************************************************************-->

	<p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a gcc plugin
	<tt>dragonegg.so</tt> that replaces gcc's optimizers and code generators with
	those from the <a href="http://llvm.org">LLVM project</a>.</p>
	<p>It is a reimplementation of
	<a href="http://llvm.org/docs/CommandGuide/">llvm-gcc</a>
	that works with <a href="http://gcc.gnu.org">gcc-4.5</a> or later.</p>

	<br clear="all">

	<!--=====================================================================-->
	<h2>Goals</h2>
	<!--=====================================================================-->

	<ul>
	<li>Work with unmodified gcc</li>
	<li>Support all gcc languages</li>
	</ul>

	<!--=====================================================================-->
	<h2>Current Status</h2>
	<!--=====================================================================-->

	<ul>
	<li>C works well, for example you can build a working gcc using it</li>
	<li>C++ works fairly well, for example you can build LLVM, clang and boost
	with it (the resulting LLVM and clang work correctly; I did not test whether
	boost actually works)</li>
	<li>A lot of Fortran compiles, but the compiled code has not been tested for
	correctness</li>
	<li>It can compile quite a lot of Ada, but the compiled code may not work
	right</li>
	<li>It can compile a small amount of Obj-C and Obj-C++</li>
	<li>It fails to compile any Java</li>
	<li>Exception handling does not work</li>
	<li>Limited debug info</li>
	<li>Requires one gcc patch</li>
	<li>Only supports x86-32 and x86-64</li>
	<li>Only supports linux and darwin (darwin hasn't been tested recently though)</li>
	</ul>

	<p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is under heavy
	development and is not mature - it may crash or produce wrong code. It works
	with <a href="http://gcc.gnu.org">gcc-4.5</a> which is nowhere near being
	released yet and is changing rapidly. This is an additional source of
	instability, and means that
	<a href="http://dragonegg.llvm.org/">DragonEgg</a> may fail to build from
	time-to-time if it has not caught up with the latest gcc changes.
	<a href="http://dragonegg.llvm.org/">DragonEgg</a> uses the development
	version of <a href="http://llvm.org">LLVM</a> which creates similar problems.</p>

	<!--=====================================================================-->
	<h2>DragonEgg in action</h2>
	<!--=====================================================================-->

	<p>Here is the result of compiling a simple "hello world" program with gcc-4.5.</p>
	<pre>
	$ gcc hello.c -S -O1 -o -
	.file "hello.c"
	.section .rodata.str1.1,"aMS",@progbits,1
	.LC0:
	.string "Hello world!"
	.text
	.globl main
	.type main, @function
	main:
	subq $8, %rsp
	movl $.LC0, %edi
	call puts
	movl $0, %eax
	addq $8, %rsp
	ret
	.size main, .-main
	.ident "GCC: (GNU) 4.5.0 20090928 (experimental)"
	.section .note.GNU-stack,"",@progbits
	</pre>

	<p>Adding <tt>-fplugin=path/dragonegg.so</tt> to the gcc command line causes
	the program to be optimized and codegened by LLVM instead.</p>
	<pre>
	$ gcc hello.c -S -O1 -o - -fplugin=./dragonegg.so
	.file "hello.c"
	# Start of file scope inline assembly
	.ident "GCC: (GNU) 4.5.0 20090928 (experimental) LLVM: 82450:82981"
	# End of file scope inline assembly


	.text
	.align 16
	.globl main
	.type main,@function
	main:
	subq $8, %rsp
	movl $.L.str, %edi
	call puts
	xorl %eax, %eax
	addq $8, %rsp
	ret
	.size main, .-main
	.type .L.str,@object
	.section .rodata.str1.1,"aMS",@progbits,1
	.L.str:
	.asciz "Hello world!"
	.size .L.str, 13

	.section .note.GNU-stack,"",@progbits
	</pre>

	<p>Adding <tt>-fplugin-arg-dragonegg-emit-ir</tt> causes LLVM IR to be output.</p>
	<pre>
	$ gcc hello.c -S -O1 -o - -fplugin=./dragonegg.so -fplugin-arg-dragonegg-emit-ir
	; ModuleID = 'hello.c'
	target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
	target triple = "x86_64-unknown-linux-gnu"

	module asm "\09.ident\09\22GCC: (GNU) 4.5.0 20090928 (experimental) LLVM: 82450:82981\22"

	@.str = private constant [13 x i8] c"Hello world!\00", align 1 ; <[13 x i8]*> [#uses=1]

	define i32 @main() nounwind {
	entry:
	%0 = tail call i32 @puts(i8* getelementptr inbounds ([13 x i8]* @.str, i64 0, i64 0)) nounwind ; <i32> [#uses=0]
	ret i32 0
	}

	declare i32 @puts(i8* nocapture) nounwind
	</pre>
	<!--=====================================================================-->
	<h2>Getting it</h2>
	<!--=====================================================================-->

	<p>Get <a href="http://dragonegg.llvm.org/">DragonEgg</a>:</p>
	<pre> svn co http://llvm.org/svn/llvm-project/dragonegg/trunk dragonegg</pre>
	<p>Get the development version of <a href="http://llvm.org">LLVM</a>:</p>
	<pre> svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</pre>
	<p>Build <a href="http://llvm.org">LLVM</a> in the usual way.
	You do not need to install it.</p>
	<p>Get the development version of <a href="http://gcc.gnu.org">gcc</a>:</p>
	<pre> svn co http://gcc.gnu.org/svn/gcc/trunk gcc</pre>
	<p>Apply all of the patches in <tt>dragonegg/gcc-patches/</tt>, if any, to
	<a href="http://gcc.gnu.org">gcc</a>.
	You need to pass the <tt>-p1</tt> option to <tt>patch</tt>.
	Build and install <a href="http://gcc.gnu.org">gcc</a> in the usual way.</p>
	<p>Doing</p>
	<pre> GCC=path_to_just_installed_gcc make</pre>
	<p>in the <tt>dragonegg</tt> directory should then build <tt>dragonegg.so</tt>.
	See the <tt>README</tt> file for more details.</p>
	<p>To use <tt>dragonegg.so</tt>, compile something with your just-installed
	version of <tt>gcc</tt>, adding <tt>-fplugin=path_to_dragonegg/dragonegg.so</tt>
	to the command line. See the <tt>README</tt> file for more details and useful
	command line options.</p>

	<!--=====================================================================-->
	<h2>It doesn't work!</h2>
	<!--=====================================================================-->
	<p>Sorry about that! Please report bugs and problems to the LLVM developers'
	<a href="http://llvm.org/docs/#maillist">mailing list</a>, or using LLVM's
	<a href="http://llvm.org/bugs/">bugzilla</a>.</p>
	<p>Suggestions for improvement are welcome. Patches are even more welcome!</p>

	<!--=====================================================================-->
	<h2>More information</h2>
	<!--=====================================================================-->
	There was a talk "Reimplementing llvm-gcc as a gcc plugin" about
	<a href="http://dragonegg.llvm.org/">DragonEgg</a> at the
	<a href="http://llvm.org/devmtg/2009-10/">2009 llvm developers meeting</a>.
	At that time, <a href="http://dragonegg.llvm.org/">DragonEgg</a> was known as
	"the gcc plugin".
	<p>[<a href="http://llvm.org/devmtg/2009-10/Sands_LLVMGCCPlugin.pdf">Slides</a>]</p>
	<p>[<a href="http://llvm.org/devmtg/2009-10/Sands_LLVMGCCPlugin-700kbps.mov">Video</a>] <font size="-1">(Computer)</font></p>
	<p>[<a href="http://llvm.org/devmtg/2009-10/Sands_LLVMGCCPlugin-mobile.m4v">Video</a>] <font size="-1">(Mobile)</font></p>
	</div>
	</body>
	</html>