docs/CFEBuildInstrs.html - platform/external/llvm - Gitiles

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 <html><head><title>Bootstrapping the C/C++ Front-End</title></head>

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 <center><h1><font size=7>Bootstrapping the C/C++ Front-End</font></h1></center>

 <br><br>

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 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
 <a name="instructions">Instructions
 </b></font></td></tr></table><ul>
 <!-- *********************************************************************** -->

 <p>This document is intended to explain the process of building the LLVM
 C/C++ front-end, based on GCC 3.4, from source.</p>

 <p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
 process, and you should only try to do it if (A) you really, really,
 really can't use the binaries we distribute, and (B) you are a wicked
 good GCC hacker.</p>

 <p>We welcome patches to help make this process simpler.</p>

 <ol>
 <li><p>Configure and build the LLVM libraries and tools using:</p>
 <pre>
  % cd llvm
  % ./configure [options...]
  % gmake tools-only
 </pre>
     <p>The use of the non-default target "tools-only" means that the
     LLVM tools and libraries will build, and the binaries will be
     deposited in llvm/tools/Debug, but the runtime (bytecode)
     libraries will not build.</p>

 <li><p>Add the directory containing the tools to your PATH.</p>
 <pre>
  % set path = ( `cd llvm/tools/Debug && pwd` $path )
 </pre>

 <li><p>Unpack the C/C++ front-end source into cfrontend/src.</p>

 <li><p>Edit src/configure.  Change the first line (starting w/ #!) to
        contain the correct full pathname of sh.</p>

 <li><p>Make "build" and "install" directories as siblings of the "src"
        tree.</p>
 <pre>
  % pwd
  /usr/local/example/cfrontend/src
  % cd ..
  % mkdir build install
  % set CFEINSTALL = `pwd`/install
 </pre>

 <li><p>Configure, build and install the C front-end:</p>
 <pre>
  % cd build
  % ../src/configure --prefix=$CFEINSTALL --disable-nls --disable-shared \
    --enable-languages=c,c++
  % gmake all-gcc
  % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
  % gmake all; gmake install
 </pre>

  <p><b>Common Problem 1:</b> You may get error messages regarding the fact
  that LLVM does not support inline assembly. Here are two common
  fixes:</p>

  <ul>
   <li><p><b>Fix 1:</b> If you have system header files that include
    inline assembly, you may have to modify them to remove the inline
    assembly, and install the modified versions in
    <code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code>.</p>

   <li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
    haven't tried yet, you will probably have to edit the appropriate
    version of atomicity.h under
    <code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
    and apply a patch so that it does not use inline assembly.</p>
  </ul>

  <p><b>Common Problem 2:</b> <b>FIXME:</b> Chris should add a section about
  common problems porting to a new architecture, including changes you
  might have to make to the gcc/gcc/config/<i>name-of-cpu</i>
  directory. For example (expand these):</p>

  <ul>
   <li>Munge linker flags so they are compatible with gccld.
   <li>Change the target so it doesn't have long double; just use double
       instead.
   <li>No inline assembly for position independent code.
   <li>We handle init and fini differently.
   <li>Do not include inline assembly map things for SPARC, or profile things.
  </ul>

 <li><p>Go back into the LLVM source tree proper. Edit Makefile.config
 to redefine <code>LLVMGCCDIR</code> to the full pathname of the
 <code>$CFEINSTALL</code> directory, which is the directory you just
 installed the C front-end into. (The ./configure script is likely to
 have set this to a directory which does not exist on your system.)</p>

 <li><p>If you edited header files during the C/C++ front-end build as
 described in "Fix 1" above, you must now copy those header files from
 <code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code> to
 <code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.
 (This should be the "include" directory in the same directory as the
 libgcc.a library, which you can find by running
 <code>$CFEINSTALL/bin/gcc --print-libgcc-file-name</code>.)</p>

 <li><p>Build and install the runtime (bytecode) libraries by running:</p>
 <pre>
  % gmake -C runtime
  % mkdir $CFEINSTALL/bytecode-libs
  % gmake -C runtime install
  % setenv LLVM_LIB_SEARCH_PATH $CFEINSTALL/bytecode-libs
 </pre>

 <li><p>Test the newly-installed C frontend by one or more of the
 following means:</p>
  <ul>
   <li> compiling and running a "hello, world" program in C or C++.
   <li> running the tests under test/Programs using <code>gmake -C
    test/Programs</code>;
  </ul>

 </p>
 </ol>

 <!-- *********************************************************************** -->
 </ul>
 <!-- *********************************************************************** -->

 <hr><font size-1>
 <address><a href="mailto:gaeke -at- uiuc.edu">Brian Gaeke</a></address>
 Last modified: $Date$
 </font></body></html>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
	<html><head><title>Bootstrapping the C/C++ Front-End</title></head>

	<body bgcolor=white>
	<center><h1><font size=7>Bootstrapping the C/C++ Front-End</font></h1></center>

	<br><br>

	<!-- *********************************************************************** -->
	<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
	<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
	<a name="instructions">Instructions
	</b></font></td></tr></table><ul>
	<!-- *********************************************************************** -->

	<p>This document is intended to explain the process of building the LLVM
	C/C++ front-end, based on GCC 3.4, from source.</p>

	<p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
	process, and you should only try to do it if (A) you really, really,
	really can't use the binaries we distribute, and (B) you are a wicked
	good GCC hacker.</p>

	<p>We welcome patches to help make this process simpler.</p>

	<ol>
	<li><p>Configure and build the LLVM libraries and tools using:</p>
	<pre>
	% cd llvm
	% ./configure [options...]
	% gmake tools-only
	</pre>
	<p>The use of the non-default target "tools-only" means that the
	LLVM tools and libraries will build, and the binaries will be
	deposited in llvm/tools/Debug, but the runtime (bytecode)
	libraries will not build.</p>

	<li><p>Add the directory containing the tools to your PATH.</p>
	<pre>
	% set path = ( `cd llvm/tools/Debug && pwd` $path )
	</pre>

	<li><p>Unpack the C/C++ front-end source into cfrontend/src.</p>

	<li><p>Edit src/configure. Change the first line (starting w/ #!) to
	contain the correct full pathname of sh.</p>

	<li><p>Make "build" and "install" directories as siblings of the "src"
	tree.</p>
	<pre>
	% pwd
	/usr/local/example/cfrontend/src
	% cd ..
	% mkdir build install
	% set CFEINSTALL = `pwd`/install
	</pre>

	<li><p>Configure, build and install the C front-end:</p>
	<pre>
	% cd build
	% ../src/configure --prefix=$CFEINSTALL --disable-nls --disable-shared \
	--enable-languages=c,c++
	% gmake all-gcc
	% setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
	% gmake all; gmake install
	</pre>

	<p><b>Common Problem 1:</b> You may get error messages regarding the fact
	that LLVM does not support inline assembly. Here are two common
	fixes:</p>

	<ul>
	<li><p><b>Fix 1:</b> If you have system header files that include
	inline assembly, you may have to modify them to remove the inline
	assembly, and install the modified versions in
	<code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code>.</p>

	<li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
	haven't tried yet, you will probably have to edit the appropriate
	version of atomicity.h under
	<code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
	and apply a patch so that it does not use inline assembly.</p>
	</ul>

	<p><b>Common Problem 2:</b> <b>FIXME:</b> Chris should add a section about
	common problems porting to a new architecture, including changes you
	might have to make to the gcc/gcc/config/<i>name-of-cpu</i>
	directory. For example (expand these):</p>

	<ul>
	<li>Munge linker flags so they are compatible with gccld.
	<li>Change the target so it doesn't have long double; just use double
	instead.
	<li>No inline assembly for position independent code.
	<li>We handle init and fini differently.
	<li>Do not include inline assembly map things for SPARC, or profile things.
	</ul>

	<li><p>Go back into the LLVM source tree proper. Edit Makefile.config
	to redefine <code>LLVMGCCDIR</code> to the full pathname of the
	<code>$CFEINSTALL</code> directory, which is the directory you just
	installed the C front-end into. (The ./configure script is likely to
	have set this to a directory which does not exist on your system.)</p>

	<li><p>If you edited header files during the C/C++ front-end build as
	described in "Fix 1" above, you must now copy those header files from
	<code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code> to
	<code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.
	(This should be the "include" directory in the same directory as the
	libgcc.a library, which you can find by running
	<code>$CFEINSTALL/bin/gcc --print-libgcc-file-name</code>.)</p>

	<li><p>Build and install the runtime (bytecode) libraries by running:</p>
	<pre>
	% gmake -C runtime
	% mkdir $CFEINSTALL/bytecode-libs
	% gmake -C runtime install
	% setenv LLVM_LIB_SEARCH_PATH $CFEINSTALL/bytecode-libs
	</pre>

	<li><p>Test the newly-installed C frontend by one or more of the
	following means:</p>
	<ul>
	<li> compiling and running a "hello, world" program in C or C++.
	<li> running the tests under test/Programs using <code>gmake -C
	test/Programs</code>;
	</ul>

	</p>
	</ol>

	<!-- *********************************************************************** -->
	</ul>
	<!-- *********************************************************************** -->

	<hr><font size-1>
	<address><a href="mailto:gaeke -at- uiuc.edu">Brian Gaeke</a></address>
	Last modified: $Date$
	</font></body></html>