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Update "Getting Started" with more current information about 'clang-cc' and 'clang'. 

llvm-svn: 67850
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Ted Kremenek 2009-03-27 16:32:57 +00:00
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clang/www/get_started.html
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@ -15,14 +15,12 @@
<h1>Getting Started: Building and Running Clang</h1>
<p>This page gives you the shortest path to checking out clang and demos a few
<p>This page gives you the shortest path to checking out Clang and demos a few
options. This should get you up and running with the minimum of muss and fuss.
If you like what you see, please consider <a href="get_involved.html">getting
involved</a> with the clang community.</p>
involved</a> with the Clang community.</p>
<h2>A word of warning</h2>
<h2>A Word of Warning</h2>
<p>While this work aims to provide a fully functional C/C++/ObjC front-end, it
is <em>still early work</em> and is under heavy development. In particular,
@ -43,10 +41,10 @@ href="http://llvm.org/bugs/">LLVM Bugzilla</a> or bring up the issue on the
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang development
mailing list</a>.</p>
<h2 id="build">Building clang / working with the code</h2>
<h2 id="build">Building Clang and Working with the Code</h2>
<p>If you would like to check out and build the project, the current scheme
is:</p>
<p>If you would like to check out and build Clang, the current procedure is as
follows:</p>
<ol>
<li><a href="http://www.llvm.org/docs/GettingStarted.html#checkout">Checkout
@ -57,7 +55,7 @@ is:</p>
<li><tt>cd llvm</tt></li>
<li><tt>./configure; make</tt></li>
</ul>
<li>Checkout clang:</li>
<li>Checkout Clang:</li>
<ul>
<li>From within the <tt>llvm</tt> directory (where you
built llvm):</li>
@ -65,8 +63,8 @@ is:</p>
<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
</ul>
<li>If you intend to work on clang C++ support, you may need to tell it how
to find your C++ standard library headers. If clang can't find your
<li>If you intend to work on Clang C++ support, you may need to tell it how
to find your C++ standard library headers. If Clang cannot find your
system libstdc++ headers, please follow these instructions:</li>
<ul>
@ -77,7 +75,7 @@ is:</p>
change the lines below to include that path.</li>
</ul>
<li>Build clang:</li>
<li>Build Clang:</li>
<ul>
<li><tt>cd clang</tt> (assuming that you are in <tt>llvm/tools</tt>)</li>
<li><tt>make</tt> (this will give you a debug build)</li>
@ -85,45 +83,69 @@ is:</p>
<li>Try it out (assuming you add llvm/Debug/bin to your path):</li>
<ul>
<li><tt>clang --help</tt></li>
<li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li>
<li><tt>clang file.c -ast-dump</tt> (internal debug dump of ast)</li>
<li><tt>clang file.c -ast-view</tt> (<a
<li><tt>clang-cc --help</tt></li>
<li><tt>clang-cc file.c -fsyntax-only</tt> (check for correctness)</li>
<li><tt>clang-cc file.c -ast-dump</tt> (internal debug dump of ast)</li>
<li><tt>clang-cc file.c -ast-view</tt> (<a
href="http://llvm.org/docs/ProgrammersManual.html#ViewGraph">set up graphviz
and rebuild llvm first</a>)</li>
<li><tt>clang file.c -emit-llvm</tt> (print out unoptimized llvm code)</li>
<li><tt>clang file.c -emit-llvm -o - | llvm-as | opt -std-compile-opts |
<li><tt>clang-cc file.c -emit-llvm</tt> (print out unoptimized llvm code)</li>
<li><tt>clang-cc file.c -emit-llvm -o - | llvm-as | opt -std-compile-opts |
llvm-dis</tt> (print out optimized llvm code)</li>
<li><tt>clang file.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc
<li><tt>clang-cc file.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc
&gt; file.s</tt> (output native machine code)</li>
</ul>
<p><em>Note</em>: Here <tt>clang-cc</tt> is the "low-level" frontend
executable that is similar in purpose to <tt>cc1</tt>. Clang also has a <a
href="#driver">high-level compiler driver</a> that acts as a drop-in
replacement for <tt>gcc</tt>.
</ol>
<p>Note that the C front-end uses LLVM, but does not depend on
llvm-gcc. If you encounter problems with building clang, make
sure you have the latest SVN version of LLVM. LLVM contains
support libraries for clang that will be updated as well as
development on clang progresses.</p>
<p>Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you
encounter problems with building Clang, make sure you have the latest SVN
version of LLVM. LLVM contains support libraries for Clang that will be updated
as well as development on Clang progresses.</p>
<h3>Building clang while building llvm:</h3>
<p>Since you've checked out clang into the llvm source tree you can
build them all at once with a simple Makefile change. This moves
Step 1 above to Step 4.</p>
<ul>
<li><tt>cd llvm/tools</tt></li>
<li>then edit <tt>Makefile</tt> to have a clang target in <tt>PARALLEL_DIRS</tt>
just like <tt>llvm-config</tt></li>
<li>then just build llvm normally as above and clang will build at
the same time</li>
<li><em>Note:</em> you can update your toplevel project and all (possibly unrelated)
projects inside it with <tt><b>make update</b></tt>. This will run
<tt>svn update</tt> on all subdirectories related to subversion.</li>
</ul>
<h3>Simultaneously Building Clang and LLVM:</h3>
<h2>Examples of using clang</h2>
<p>Once you have checked out Clang into the llvm source tree it will build along
with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at
once simply run <tt>make</tt> from the root LLVM directory.</p>
<p><em>Note:</em> Observe that Clang is technically part of a separate
Subversion repository. As mentioned above, the latest Clang sources are tied to
the latest sources in the LLVM tree. You can update your toplevel LLVM project
and all (possibly unrelated) projects inside it with <tt><b>make
update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related
to subversion. </p>
<a name="driver"><h2>High-Level Compiler Driver (Drop-in Substitute for GCC)</h2></a>
<p>While the <tt>clang-cc</tt> executable is a low-level frontend executable
that can perform code generation, program analysis, and other actions, it is not
designed to be a drop-in replacement for GCC's <tt>cc</tt>. For this purpose,
use the high-level driver, aptly named <tt>clang</tt>. Here are some
examples of how to use the high-level driver:
</p>
<pre class="code">
$ <b>cat t.c</b>
#include &lt;stdio.h&gt;
int main(int argc, char **argv) { printf("hello world\n"); }
$ <b>clang t.c</b>
$ <b>./a.out</b>
hello world
</pre>
<h2>Examples of using Clang</h2>
<p>The high-level driver <tt>clang</tt> is designed to understand most of GCC's
options, and the lower-level <tt>clang-cc</tt> executable also directly takes
many of GCC's options. You can see which options <tt>clang-cc</tt> accepts with
'<tt>clang-cc --help</tt>'. Here are a few examples of using <tt>clang</tt> and
<tt>clang-cc</tt>:</p>
<p>The clang driver takes a lot of GCC compatible options, which you can see
with 'clang --help'. Here are a few examples:</p>
<!-- Thanks to
http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings
Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre>
@ -169,7 +191,7 @@ typedef float V __attribute__((vector_size(16)));
<h3>Pretty printing from the AST:</h3>
<pre class="code">
$ <b>clang ~/t.c -ast-print</b>
$ <b>clang-cc ~/t.c -ast-print</b>
typedef float V __attribute__(( vector_size(16) ));
V foo(V a, V b) {
return a + b * a;
@ -180,19 +202,19 @@ V foo(V a, V b) {
<h3>Code generation with LLVM:</h3>
<pre class="code">
$ <b>clang ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llvm-dis</b>
$ <b>clang-cc ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llvm-dis</b>
define &lt;4 x float&gt; @foo(&lt;4 x float&gt; %a, &lt;4 x float&gt; %b) {
entry:
%mul = mul &lt;4 x float&gt; %b, %a
%add = add &lt;4 x float&gt; %mul, %a
ret &lt;4 x float&gt; %add
}
$ <b>clang ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc -march=ppc32 -mcpu=g5</b>
$ <b>clang-cc ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc -march=ppc32 -mcpu=g5</b>
..
_foo:
vmaddfp v2, v3, v2, v2
blr
$ <b>clang ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc -march=x86 -mcpu=yonah</b>
$ <b>clang-cc ~/t.c -emit-llvm -o - | llvm-as | opt -std-compile-opts | llc -march=x86 -mcpu=yonah</b>
..
_foo:
mulps %xmm0, %xmm1
@ -201,30 +223,6 @@ _foo:
ret
</pre>
<a name="ccc"><h3>GCC "Emulation" Driver</h3></a>
<p>While the <tt>clang</tt> executable is a compiler driver that can perform
code generation, program analysis, and other actions, it is not designed to be a
drop-in replacement for GCC's <tt>cc</tt>. There is interest in developing such
a driver for clang, but in the interim the clang source tree includes a Python
script <tt>ccc</tt> in the <tt>utils</tt> subdirectory that provides some of
this functionality (the script is intended to be used where GCC's <tt>cc</tt>
could be used). It is currently a work in progress, and eventually will likely
be replaced by a more complete driver.</p>
<p>Example use:</p>
<pre class="code">
$ <b>ccc t.c</b>
clang -emit-llvm-bc -o t.o -U__GNUC__ t.c
llvm-ld -native -o a.out t.o
$ <b>ls</b>
a.out a.out.bc t.c t.o
</pre>
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