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2<html><head><title>Bootstrapping the C/C++ Front-End</title></head>
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4<body bgcolor=white>
5<center><h1><font size=7>Bootstrapping the C/C++ Front-End</font></h1></center>
6
7<br><br>
8
9<!-- *********************************************************************** -->
10<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
11<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
12<a name="instructions">Instructions
13</b></font></td></tr></table><ul>
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15
16<p>This document is intended to explain the process of building the LLVM
17C/C++ front-end, based on GCC 3.4, from source.</p>
18
19<p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
20process, and you should only try to do it if (A) you really, really,
21really can't use the binaries we distribute, and (B) you are a wicked
22good GCC hacker.</p>
23
24<p>We welcome patches to help make this process simpler.</p>
25
26<ol>
27<li><p>Configure and build the LLVM libraries and tools using:</p>
28<pre>
29 % cd llvm
30 % ./configure [options...]
31 % gmake tools-only
32</pre>
33 <p>The use of the non-default target "tools-only" means that the
34 LLVM tools and libraries will build, and the binaries will be
35 deposited in llvm/tools/Debug, but the runtime (bytecode)
36 libraries will not build.</p>
37
38<li><p>Add the directory containing the tools to your PATH.</p>
39<pre>
40 % set path = ( `cd llvm/tools/Debug && pwd` $path )
41</pre>
42
43<li><p>Unpack the C/C++ front-end source into cfrontend/src.</p>
44
45<li><p>Edit src/configure. Change the first line (starting w/ #!) to
46 contain the correct full pathname of sh.</p>
47
48<li><p>Make "build" and "install" directories as siblings of the "src"
49 tree.</p>
50<pre>
51 % pwd
52 /usr/local/example/cfrontend/src
53 % cd ..
54 % mkdir build install
55 % set CFEINSTALL = `pwd`/install
56</pre>
57
58<li><p>Configure, build and install the C front-end:</p>
59<pre>
60 % cd build
61 % ../src/configure --prefix=$CFEINSTALL --disable-nls --disable-shared \
62 --enable-languages=c,c++
63 % gmake all-gcc
64 % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
65 % gmake all; gmake install
66</pre>
67
68 <p><b>Common Problem 1:</b> You may get error messages regarding the fact
69 that LLVM does not support inline assembly. Here are two common
70 fixes:</p>
71
72 <ul>
73 <li><p><b>Fix 1:</b> If you have system header files that include
74 inline assembly, you may have to modify them to remove the inline
75 assembly, and install the modified versions in
76 <code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code>.</p>
77
78 <li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
79 haven't tried yet, you will probably have to edit the appropriate
80 version of atomicity.h under
81 <code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
82 and apply a patch so that it does not use inline assembly.</p>
83 </ul>
84
85 <p><b>Common Problem 2:</b> <b>FIXME:</b> Chris should add a section about
86 common problems porting to a new architecture, including changes you
87 might have to make to the gcc/gcc/config/<i>name-of-cpu</i>
88 directory. For example (expand these):</p>
89
90 <ul>
91 <li>Munge linker flags so they are compatible with gccld.
92 <li>Change the target so it doesn't have long double; just use double
93 instead.
94 <li>No inline assembly for position independent code.
95 <li>We handle init and fini differently.
96 <li>Do not include inline assembly map things for SPARC, or profile things.
97 </ul>
98
99<li><p>Go back into the LLVM source tree proper. Edit Makefile.config
100to redefine <code>LLVMGCCDIR</code> to the full pathname of the
101<code>$CFEINSTALL</code> directory, which is the directory you just
102installed the C front-end into. (The ./configure script is likely to
103have set this to a directory which does not exist on your system.)</p>
104
105<li><p>If you edited header files during the C/C++ front-end build as
106described in "Fix 1" above, you must now copy those header files from
107<code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code> to
108<code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.
109(This should be the "include" directory in the same directory as the
110libgcc.a library, which you can find by running
111<code>$CFEINSTALL/bin/gcc --print-libgcc-file-name</code>.)</p>
112
113<li><p>Build and install the runtime (bytecode) libraries by running:</p>
114<pre>
115 % gmake -C runtime
116 % mkdir $CFEINSTALL/bytecode-libs
117 % gmake -C runtime install
118 % setenv LLVM_LIB_SEARCH_PATH $CFEINSTALL/bytecode-libs
119</pre>
120
121<li><p>Test the newly-installed C frontend by one or more of the
122following means:</p>
123 <ul>
124 <li> compiling and running a "hello, world" program in C or C++.
125 <li> running the tests under test/Programs using <code>gmake -C
126 test/Programs</code>;
127 </ul>
128
129</p>
130</ol>
131
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133</ul>
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135
136<hr><font size-1>
137<address><a href="mailto:gaeke -at- uiuc.edu">Brian Gaeke</a></address>
138Last modified: $Date$
139</font></body></html>
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