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Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]7 <title>LLVM 2.4 Release Notes</title>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]8</head>
9<body>
10
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]11<div class="doc_title">LLVM 2.4 Release Notes</div>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]12
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]13<ol>
14 <li><a href="#intro">Introduction</a></li>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]15 <li><a href="#subproj">Sub-project Status Update</a></li>
16 <li><a href="#whatsnew">What's New in LLVM?</a></li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]17 <li><a href="GettingStarted.html">Installation Instructions</a></li>
18 <li><a href="#portability">Portability and Supported Platforms</a></li>
19 <li><a href="#knownproblems">Known Problems</a>
20 <li><a href="#additionalinfo">Additional Information</a></li>
21</ol>
22
23<div class="doc_author">
24 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
25</div>
26
27<!-- *********************************************************************** -->
28<div class="doc_section">
29 <a name="intro">Introduction</a>
30</div>
31<!-- *********************************************************************** -->
32
33<div class="doc_text">
34
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]35<p>This document contains the release notes for the LLVM Compiler
36Infrastructure, release 2.4. Here we describe the status of LLVM, including
37major improvements from the previous release and significant known problems.
38All LLVM releases may be downloaded from the <a
39href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]40
41<p>For more information about LLVM, including information about the latest
42release, please check out the <a href="http://llvm.org/">main LLVM
43web site</a>. If you have questions or comments, the <a
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]44href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
45List</a> is a good place to send them.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]46
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]47<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]48main LLVM web page, this document applies to the <i>next</i> release, not the
49current one. To see the release notes for a specific releases, please see the
50<a href="http://llvm.org/releases/">releases page</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]51
52</div>
53
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]54<!-- Unfinished features in 2.4:
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]55 Machine LICM
56 Machine Sinking
57 LegalizeDAGTypes
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]58 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
59 one MBB to another
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]60 -->
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]61
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]62 <!-- for announcement email:
63 mention dev mtg
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]64 Xcode 3.1 and 3.1.1.
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]65 -->
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]66
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]67<!-- *********************************************************************** -->
68<div class="doc_section">
69 <a name="subproj">Sub-project Status Update</a>
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]70</div>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]71<!-- *********************************************************************** -->
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]72
73<div class="doc_text">
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]74<p>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]75The LLVM 2.4 distribution currently consists of code from the core LLVM
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]76repository (which roughly includes the LLVM optimizers, code generators and
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]77supporting tools) and the llvm-gcc repository. In addition to this code, the
78LLVM Project includes other sub-projects that are in development. The two which
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]79are the most actively developed are the <a href="#clang">Clang Project</a> and
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]80the <a href="#vmkit">vmkit Project</a>.
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]81</p>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]82
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]83</div>
84
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]85
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]86<!--=========================================================================-->
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]87<div class="doc_subsection">
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]88<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]89</div>
90
91<div class="doc_text">
92
93<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
94a set of new 'LLVM native' front-end technologies for the LLVM optimizer
95and code generator. Clang is continuing to make major strides forward in all
96areas. Its C and Objective-C parsing support is very solid, and the code
97generation support is far enough along to build many C applications. While not
98yet production quality, it is progressing very nicely. In addition, C++
99front-end work has started to make significant progress.</p>
100
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]101<p>Codegen progress/state
102</p>
103
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]104</div>
105
106<!--=========================================================================-->
107<div class="doc_subsection">
108<a name="clangsa">Clang Static Analyzer</a>
109</div>
110
111<div class="doc_text">
112
113<p>The
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]114<a href="http://clang.llvm.org/StaticAnalysis.html">static analysis tool</a>
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]115.</p>
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]116
117</div>
118
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]119<!--=========================================================================-->
120<div class="doc_subsection">
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]121<a name="vmkit">vmkit: JVM/CLI Virtual Machine Implementation</a>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]122</div>
123
124<div class="doc_text">
125<p>
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]126The <a href="http://vmkit.llvm.org/">vmkit project</a> is an implementation of
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]127a JVM and a CLI Virtual Machines (Microsoft .NET is an
128implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
129
130<p>...</p>
131
132</div>
133
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]134
135<!-- *********************************************************************** -->
136<div class="doc_section">
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]137 <a name="whatsnew">What's New in LLVM?</a>
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]138</div>
139<!-- *********************************************************************** -->
140
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]141<div class="doc_text">
142
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]143<p>This release includes a huge number of bug fixes, performance tweaks and
144minor improvements. Some of the major improvements and new features are listed
145in this section.
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]146</p>
147</div>
148
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]149<!--=========================================================================-->
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]150<div class="doc_subsection">
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]151<a name="majorfeatures">Major New Features</a>
152</div>
153
154<div class="doc_text">
155
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]156<p>LLVM 2.4 includes several major new capabilities:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]157
158<ul>
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame^]159<li><p>The most visible end-user change in LLVM 2.4 is that it includes many
160optimizations and changes ot make -O0 compile times much faster. You should see
161improvements on the order of 30% or more faster than LLVM 2.3. There are many
162pieces to this change, described in more detail below. The speedups and new
163components can also be used for JIT compilers that want fast compilation as
164well.</p></li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]165
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame^]166<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which
167were introduced in LLVM 2.3) have been generalized to full support for "First
168Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using
169structs and arrays as values in a function. This capability is mostly useful
170for front-end authors, who prefer to treat things like complex numbers, simple
171tuples, dope vectors, etc as Value*'s instead of as a tuple of Value*'s or as
172memory values.</p></li>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]173
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame^]174<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This
175is the LLVM targer that only has support for 8 bit registers, and a number of
176other crazy constraints. While the port is still in early development stages,
177it shows some interesting things you can do with LLVM.</p></li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]178
Chris Lattner5ba16862008-02-10 08:18:42 +0000[diff] [blame]179</ul>
180
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]181</div>
182
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]183
184<!--=========================================================================-->
185<div class="doc_subsection">
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]186<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]187</div>
188
189<div class="doc_text">
190
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame^]191<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
192front-ends and driver with the LLVM optimizer and code generator. It currently
193includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]194
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]195<ul>
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame^]196<li>LLVM 2.4 supports the full set of atomic __sync builtins. LLVM 2.3 only
197supported those used by OpenMP, but 2.4 supports them all. Not all targets
198support all builtins, but X86 and PowerPC do.</li>
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]199
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame^]200<li>llvm-gcc now supports an -flimited-precision option, which tells the
201compiler that it is ok to use low-precision approximations of certain libm
202functions (like tan, log, etc). This allows you to get high performance if you
203only need (say) 14-bits of precision.</li>
204
205<li>llvm-gcc now supports a C language extension known as "<a
206href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks
207</a>. This feature is similar to nested functions and closures, but does not
208require stack trampolines (with most ABIs) and supports returning closures
209from functions that define them. Note that actually <em>using</em> Blocks
210requires a small runtime that is not included with llvm-gcc.</li>
211
212<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
213transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
214later) this allows the use of LTO with other optimization levels like -Os.
215Previously, LTO could only be used with -O4, which implied optimizations in
216-O3 that can increase code size.</li>
Gabor Greif0e49cc82008-06-09 06:06:18 +0000[diff] [blame]217</ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]218
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]219</div>
220
221
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]222<!--=========================================================================-->
223<div class="doc_subsection">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]224<a name="coreimprovements">LLVM Core Improvements</a>
225</div>
226
227<div class="doc_text">
228<p>New features include:
229</p>
230
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]231<ul>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]232<li>vector shifts in the IR: no codegen support yet</li>
Chris Lattnera5a49382008-10-12 18:30:33 +0000[diff] [blame]233<li>use diet patch landed: saved 15% IR memory footprint</li>
234<li>LLVM IR now directly represents "common" linkage, instead of
235 representing it as a form of weak linkage.</li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]236<li>DebugInfoBuilder</li>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]237<li>.ll printing format change: %3 = add i32 4, 2</li>
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]238<li>opt-size, noinline, alwaysinline function attributes</li>
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame^]239<li>Attrs: function, return, param.</p></li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]240<li>...</li>
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]241</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]242
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]243</div>
244
245<!--=========================================================================-->
246<div class="doc_subsection">
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]247<a name="optimizer">Optimizer Improvements</a>
248</div>
249
250<div class="doc_text">
251
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]252<p>In addition to a huge array of bug fixes and minor performance tweaks, the
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]253LLVM 2.4 optimizers support a few major enhancements:</p>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]254
255<ul>
256
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]257<li>GVN now does local PRE?</li>
258
259<li>Matthijs' Dead argument elimination rewrite</li>
260
Chris Lattnera5a49382008-10-12 18:30:33 +0000[diff] [blame]261<li>Old-ADCE used control dependence and deleted output-free infinite loops.
262Added a new Loop deletion pass (for deleting output free provably-finite loops)
263and rewrote ADCE to be simpler faster, and not need control dependence.</li>
264
265<li>SparsePropagation framework for lattice-based dataflow solvers.</li>
266
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]267<li>Tail duplication was removed from the standard optimizer sequence.</li>
Chris Lattnera5a49382008-10-12 18:30:33 +0000[diff] [blame]268
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]269<li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
270pulled out of instcombine and put into a new ValueTracking.h file, where they
271can be reused by other passes.</li>
272
Duncan Sands2aecc3f2008-10-13 18:42:43 +0000[diff] [blame]273<li>The new AddReadAttrs pass works out which functions are read-only or
274read-none (these correspond to 'pure' and 'const' in C) and marks them
275with the appropriate attribute.</li>
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]276</ul>
277
278</div>
279
280<!--=========================================================================-->
281<div class="doc_subsection">
282<a name="codegen">Code Generator Improvements</a>
283</div>
284
285<div class="doc_text">
286
287<p>We put a significant amount of work into the code generator infrastructure,
288which allows us to implement more aggressive algorithms and make it run
289faster:</p>
290
291<ul>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]292<li>asm writers split out to their own library to avoid JITs having to link
293 them in.</li>
294<li>Big asm writer refactoring + TargetAsmInfo</li>
295<li>2-addr pass and coalescer can now remat trivial insts to avoid a copy.</li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]296<li>spiller to commute instructions in order to fold a reload</li>
297<li>Stack slot coloring?</li>
298<li>Live intervals renumbering? Is this useful to external people?</li>
299<li>'is as cheap as a move' instruction flag</li>
300<li>Improvements to selection dag viewing</li>
301<li>fast isel</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]302<li>Selection dag speedups</li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]303<li>asmwriter + raw_ostream -> fastah</li>
Chris Lattner72c8a252008-10-13 17:12:51 +0000[diff] [blame]304<li>Partitioned Boolean Quadratic Programming (PBQP) based register
305allocator.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]306<li>...</li>
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]307
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]308</ul>
309
310</div>
311
312
313<!--=========================================================================-->
314<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]315<a name="x86specific">X86/X86-64 Specific Improvements</a>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]316</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]317
318<div class="doc_text">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]319<p>New target-specific features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]320</p>
321
322<ul>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]323<li>Exception handling is supported by default on Linux/x86-64.</li>
Duncan Sandsd8745a92008-10-13 17:32:15 +0000[diff] [blame]324<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]325<li>...</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]326
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]327</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]328
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]329</div>
330
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]331<!--=========================================================================-->
332<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]333<a name="targetspecific">Other Target Specific Improvements</a>
334</div>
335
336<div class="doc_text">
337<p>New target-specific features include:
338</p>
339
340<ul>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]341<li>MIPS floating point support?</li>
Duncan Sandsd8745a92008-10-13 17:32:15 +0000[diff] [blame]342<li>PowerPC now supports trampolines.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]343<li>....</li>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]344</ul>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]345
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]346</div>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]347
348
349<!--=========================================================================-->
350<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]351<a name="otherimprovements">Other Improvements</a>
352</div>
353
354<div class="doc_text">
355<p>New features include:
356</p>
357
358<ul>
Mikhail Glushenkovcc2d3012008-10-13 02:46:01 +0000[diff] [blame]359<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]360 support. It is now easier to experiment with <tt>llvmc2</tt> and
361 build your own tools based on it. </li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]362<li>raw_ostream + formatting</li>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]363<li>Recycler + pool allocation stuff?</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]364<li>...</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]365</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]366
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]367</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]368
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]369<!--=========================================================================-->
370<div class="doc_subsection">
371<a name="changes">Major Changes and Removed Features</a>
372</div>
373
374<div class="doc_text">
375
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]376<p>If you're already an LLVM user, this section lists some "gotchas" that you
377may run into upgrading from the previous release.</p>
378
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]379<p>The LLVM IR generated by llvm-gcc no longer names all instructions.
380 Use the instnamer pass if you want everything named.</p>
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]381
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]382<li>The LoadVN and GCSE passes have been removed.</li>
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]383
384
385<p>LLVM API Changes:</p>
386
387<ul>
388
389<li>... Attributes changes ... </li>
390
391<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
392<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
393converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
394"llvm/Analysis/ValueTracking.h".</li>
395
396<li>API change: BinaryOperator::create -> Create (CmpInst, CastInst too)</li>
397<li>Various header files like "llvm/ADT/iterator" were given a .h suffix.
398 Change your code to #include "llvm/ADT/iterator.h" instead.</li>
399
400</ul>
401
402</div>
403
404
405
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]406<!-- *********************************************************************** -->
407<div class="doc_section">
408 <a name="portability">Portability and Supported Platforms</a>
409</div>
410<!-- *********************************************************************** -->
411
412<div class="doc_text">
413
414<p>LLVM is known to work on the following platforms:</p>
415
416<ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]417<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]418 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]419<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]420 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]421<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]422<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
423 support is available for native builds with Visual C++).</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]424<li>Sun UltraSPARC workstations running Solaris 10.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]425<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]426<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]427</ul>
428
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]429<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]430to the machine and operating system on which it is built. However, minor
431porting may be required to get LLVM to work on new platforms. We welcome your
432portability patches and reports of successful builds or error messages.</p>
433
434</div>
435
436<!-- *********************************************************************** -->
437<div class="doc_section">
438 <a name="knownproblems">Known Problems</a>
439</div>
440<!-- *********************************************************************** -->
441
442<div class="doc_text">
443
444<p>This section contains all known problems with the LLVM system, listed by
445component. As new problems are discovered, they will be added to these
446sections. If you run into a problem, please check the <a
447href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
448there isn't already one.</p>
449
450</div>
451
452<!-- ======================================================================= -->
453<div class="doc_subsection">
454 <a name="experimental">Experimental features included with this release</a>
455</div>
456
457<div class="doc_text">
458
459<p>The following components of this LLVM release are either untested, known to
460be broken or unreliable, or are in early development. These components should
461not be relied on, and bugs should not be filed against them, but they may be
462useful to some people. In particular, if you would like to work on one of these
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]463components, please contact us on the <a
464href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]465
466<ul>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]467<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]468<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]469 value for this option.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]470</ul>
471
472</div>
473
474<!-- ======================================================================= -->
475<div class="doc_subsection">
476 <a name="x86-be">Known problems with the X86 back-end</a>
477</div>
478
479<div class="doc_text">
480
481<ul>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame]482 <li>The X86 backend does not yet support
483 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
484 floating point stack</a>. It supports the 'f' and 't' constraints, but not
485 'u'.</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]486 <li>The X86 backend generates inefficient floating point code when configured
487 to generate code for systems that don't have SSE2.</li>
Duncan Sands8b4f3772008-06-08 19:38:43 +0000[diff] [blame]488 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame]489 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
490 currently due
491 to <a href="http://llvm.org/PR2255">several</a>
Chris Lattnerf06141a2008-06-08 23:12:47 +0000[diff] [blame]492 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
493 'u' inline assembly constraint and X87 floating point inline assembly.</li>
Dan Gohman3882ecb2008-06-08 23:05:11 +0000[diff] [blame]494 <li>The X86-64 backend does not yet support the LLVM IR instruction
495 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
496 argument constructs on X86-64 by lowering them manually.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]497</ul>
498
499</div>
500
501<!-- ======================================================================= -->
502<div class="doc_subsection">
503 <a name="ppc-be">Known problems with the PowerPC back-end</a>
504</div>
505
506<div class="doc_text">
507
508<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]509<li>The Linux PPC32/ABI support needs testing for the interpreter and static
510compilation, and lacks support for debug information.</li>
511</ul>
512
513</div>
514
515<!-- ======================================================================= -->
516<div class="doc_subsection">
517 <a name="arm-be">Known problems with the ARM back-end</a>
518</div>
519
520<div class="doc_text">
521
522<ul>
523<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]524processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]525results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
526<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
527</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]528<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
529 execute
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]530programs compiled with LLVM. Please use more recent versions of QEMU.</li>
531</ul>
532
533</div>
534
535<!-- ======================================================================= -->
536<div class="doc_subsection">
537 <a name="sparc-be">Known problems with the SPARC back-end</a>
538</div>
539
540<div class="doc_text">
541
542<ul>
543<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
544 support the 64-bit SPARC ABI (-m64).</li>
545</ul>
546
547</div>
548
549<!-- ======================================================================= -->
550<div class="doc_subsection">
551 <a name="alpha-be">Known problems with the Alpha back-end</a>
552</div>
553
554<div class="doc_text">
555
556<ul>
557
558<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
559appropriate nops inserted to ensure restartability.</li>
560
561</ul>
562</div>
563
564<!-- ======================================================================= -->
565<div class="doc_subsection">
566 <a name="ia64-be">Known problems with the IA64 back-end</a>
567</div>
568
569<div class="doc_text">
570
571<ul>
Chris Lattnerf06141a2008-06-08 23:12:47 +0000[diff] [blame]572<li>The Itanium backend is highly experimental, and has a number of known
573 issues. We are looking for a maintainer for the Itanium backend. If you
574 are interested, please contact the llvmdev mailing list.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]575</ul>
576
577</div>
578
579<!-- ======================================================================= -->
580<div class="doc_subsection">
581 <a name="c-be">Known problems with the C back-end</a>
582</div>
583
584<div class="doc_text">
585
586<ul>
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]587<li><a href="http://llvm.org/PR802">The C backend has only basic support for
588 inline assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]589<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
590 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]591 C++ code compiled with llc or native compilers.</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]592<li>The C backend does not support all exception handling constructs.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]593</ul>
594
595</div>
596
597
598<!-- ======================================================================= -->
599<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]600 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]601</div>
602
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]603<div class="doc_text">
604
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]605<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
606Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]607llvmdev mailing list if you are interested.</p>
608
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]609<p>The only major language feature of GCC not supported by llvm-gcc is
610 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
611 are only supported on some targets. For example, trampolines are only
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]612 supported on some targets (these are used when you take the address of a
613 nested function).</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]614
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]615<p>If you run into GCC extensions which are not supported, please let us know.
616</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]617
618</div>
619
620<!-- ======================================================================= -->
621<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]622 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]623</div>
624
625<div class="doc_text">
626
627<p>The C++ front-end is considered to be fully
628tested and works for a number of non-trivial programs, including LLVM
629itself, Qt, Mozilla, etc.</p>
630
631<ul>
Anton Korobeynikovd9a17932008-10-11 18:27:16 +0000[diff] [blame]632<li>Exception handling works well on the X86 and PowerPC targets. Currently
633 only linux and darwin targets are supported (both 32 and 64 bit).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]634</ul>
635
636</div>
637
638
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]639<!-- ======================================================================= -->
640<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]641 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]642</div>
643
644<div class="doc_text">
645The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
646technology and problems should be expected.
647<ul>
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]648<li>The Ada front-end currently only builds on X86-32. This is mainly due
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]649to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]650however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]651which does support trampolines.</li>
652<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
653Workaround: configure with --disable-bootstrap.</li>
Duncan Sands2dbc2e82008-10-13 17:27:23 +0000[diff] [blame]654<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
655and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
656(c380004 also fails with gcc-4.2 mainline).</li>
657<li>Some gcc specific Ada tests continue to crash the compiler.</li>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]658<li>The -E binder option (exception backtraces)
659<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
660crashing if an exception is raised. Workaround: do not use -E.</li>
661<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
662or finish at a non-byte offset</a> in a record. Workaround: do not pack records
663or use representation clauses that result in a field of a non-discrete type
664starting or finishing in the middle of a byte.</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]665<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
666'main' as generated by the Ada binder to be invalid</a>.
667Workaround: hand edit the file to use pointers for <tt>argv</tt> and
668<tt>envp</tt> rather than integers.</li>
669<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
670ignored</a>.</li>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]671</ul>
672</div>
673
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]674<!-- *********************************************************************** -->
675<div class="doc_section">
676 <a name="additionalinfo">Additional Information</a>
677</div>
678<!-- *********************************************************************** -->
679
680<div class="doc_text">
681
682<p>A wide variety of additional information is available on the <a
683href="http://llvm.org">LLVM web page</a>, in particular in the <a
684href="http://llvm.org/docs/">documentation</a> section. The web page also
685contains versions of the API documentation which is up-to-date with the
686Subversion version of the source code.
687You can access versions of these documents specific to this release by going
688into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
689
690<p>If you have any questions or comments about LLVM, please feel free to contact
691us via the <a href="http://llvm.org/docs/#maillist"> mailing
692lists</a>.</p>
693
694</div>
695
696<!-- *********************************************************************** -->
697
698<hr>
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