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Chris Lattner857fb132008-10-11 18:18:28 +00007 <title>LLVM 2.4 Release Notes</title>
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9<body>
Chris Lattner79c3fe12003-10-02 04:57:28 +000010
Chris Lattner857fb132008-10-11 18:18:28 +000011<div class="doc_title">LLVM 2.4 Release Notes</div>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +000012
Chris Lattner79c3fe12003-10-02 04:57:28 +000013<ol>
Misha Brukman500bc302003-11-22 00:38:41 +000014 <li><a href="#intro">Introduction</a></li>
Chris Lattner96a445e2008-10-13 18:01:01 +000015 <li><a href="#subproj">Sub-project Status Update</a></li>
16 <li><a href="#whatsnew">What's New in LLVM?</a></li>
Chris Lattner4b538b92004-04-30 22:17:12 +000017 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +000018 <li><a href="#portability">Portability and Supported Platforms</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +000019 <li><a href="#knownproblems">Known Problems</a>
Misha Brukman500bc302003-11-22 00:38:41 +000020 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +000021</ol>
22
Chris Lattner7911ce22004-05-23 21:07:27 +000023<div class="doc_author">
Chris Lattnerc463b272005-10-29 07:07:09 +000024 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
Misha Brukman500bc302003-11-22 00:38:41 +000025</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000026
27<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +000028<div class="doc_section">
29 <a name="intro">Introduction</a>
30</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000031<!-- *********************************************************************** -->
32
Misha Brukman500bc302003-11-22 00:38:41 +000033<div class="doc_text">
34
Chris Lattnerf6662f92008-10-13 17:57:36 +000035<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>
Chris Lattner19092612003-10-02 16:38:05 +000040
Chris Lattner7506b1d2004-12-07 08:04:13 +000041<p>For more information about LLVM, including information about the latest
Chris Lattnerc463b272005-10-29 07:07:09 +000042release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattner47ad72c2003-10-07 21:38:31 +000043web site</a>. If you have questions or comments, the <a
Chris Lattnerf6662f92008-10-13 17:57:36 +000044href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
45List</a> is a good place to send them.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +000046
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +000047<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattner84977642007-09-21 03:54:09 +000048main 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>
Misha Brukman500bc302003-11-22 00:38:41 +000051
52</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000053
Chris Lattner857fb132008-10-11 18:18:28 +000054<!-- Unfinished features in 2.4:
Chris Lattneracce85d2008-02-10 07:46:44 +000055 Machine LICM
56 Machine Sinking
57 LegalizeDAGTypes
Chris Lattner547a3912008-10-12 19:47:48 +000058 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
59 one MBB to another
Chris Lattneracce85d2008-02-10 07:46:44 +000060 -->
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +000061
Chris Lattner547a3912008-10-12 19:47:48 +000062 <!-- for announcement email:
63 mention dev mtg
Chris Lattnercdb0e4c2008-10-12 22:57:58 +000064 Xcode 3.1 and 3.1.1.
Chris Lattner547a3912008-10-12 19:47:48 +000065 -->
Chris Lattneracce85d2008-02-10 07:46:44 +000066
Chris Lattner96a445e2008-10-13 18:01:01 +000067<!-- *********************************************************************** -->
68<div class="doc_section">
69 <a name="subproj">Sub-project Status Update</a>
Chris Lattnerea34f642008-06-08 21:34:41 +000070</div>
Chris Lattner96a445e2008-10-13 18:01:01 +000071<!-- *********************************************************************** -->
Chris Lattnerea34f642008-06-08 21:34:41 +000072
73<div class="doc_text">
Chris Lattner8348b472008-06-08 21:58:17 +000074<p>
Chris Lattner96a445e2008-10-13 18:01:01 +000075The LLVM 2.4 distribution currently consists of code from the core LLVM
Chris Lattnerfb97b2d2008-10-13 18:11:54 +000076repository (which roughly includes the LLVM optimizers, code generators and
Chris Lattner8348b472008-06-08 21:58:17 +000077supporting 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 Lattner857fb132008-10-11 18:18:28 +000079are the most actively developed are the <a href="#clang">Clang Project</a> and
Duncan Sandsbf8c4f22008-10-13 18:33:28 +000080the <a href="#vmkit">vmkit Project</a>.
Chris Lattner8348b472008-06-08 21:58:17 +000081</p>
Chris Lattner96a445e2008-10-13 18:01:01 +000082
Chris Lattner8348b472008-06-08 21:58:17 +000083</div>
84
Chris Lattner96a445e2008-10-13 18:01:01 +000085
Chris Lattner8348b472008-06-08 21:58:17 +000086<!--=========================================================================-->
Chris Lattner96a445e2008-10-13 18:01:01 +000087<div class="doc_subsection">
Chris Lattnerfb97b2d2008-10-13 18:11:54 +000088<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
Chris Lattner8348b472008-06-08 21:58:17 +000089</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 Lattner857fb132008-10-11 18:18:28 +0000101<p>Codegen progress/state
102</p>
103
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000104</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 Lattner857fb132008-10-11 18:18:28 +0000114<a href="http://clang.llvm.org/StaticAnalysis.html">static analysis tool</a>
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000115.</p>
Chris Lattner8348b472008-06-08 21:58:17 +0000116
117</div>
118
Chris Lattner96a445e2008-10-13 18:01:01 +0000119<!--=========================================================================-->
120<div class="doc_subsection">
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000121<a name="vmkit">vmkit: JVM/CLI Virtual Machine Implementation</a>
Chris Lattner96a445e2008-10-13 18:01:01 +0000122</div>
123
124<div class="doc_text">
125<p>
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000126The <a href="http://vmkit.llvm.org/">vmkit project</a> is an implementation of
Chris Lattner96a445e2008-10-13 18:01:01 +0000127a 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 Lattner8348b472008-06-08 21:58:17 +0000134
135<!-- *********************************************************************** -->
136<div class="doc_section">
Chris Lattner96a445e2008-10-13 18:01:01 +0000137 <a name="whatsnew">What's New in LLVM?</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000138</div>
139<!-- *********************************************************************** -->
140
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000141<div class="doc_text">
142
Chris Lattnerf6662f92008-10-13 17:57:36 +0000143<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 Lattnerf8e0b4e2008-06-08 22:59:35 +0000146</p>
147</div>
148
Chris Lattner8348b472008-06-08 21:58:17 +0000149<!--=========================================================================-->
Chris Lattnerea34f642008-06-08 21:34:41 +0000150<div class="doc_subsection">
Chris Lattner252b83d2008-02-06 18:00:06 +0000151<a name="majorfeatures">Major New Features</a>
152</div>
153
154<div class="doc_text">
155
Chris Lattner857fb132008-10-11 18:18:28 +0000156<p>LLVM 2.4 includes several major new capabilities:</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000157
158<ul>
Chris Lattnerb82eb062008-10-13 20:47:20 +0000159<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 Lattner857fb132008-10-11 18:18:28 +0000165
Chris Lattnerb82eb062008-10-13 20:47:20 +0000166<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 Glushenkovea65d7d2008-10-13 02:08:34 +0000173
Chris Lattnerb82eb062008-10-13 20:47:20 +0000174<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 Lattnerbc5786b2008-06-05 06:57:39 +0000178
Chris Lattner8170c102008-02-10 08:18:42 +0000179</ul>
180
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000181</div>
182
Chris Lattner791f77b2008-06-05 06:25:56 +0000183
184<!--=========================================================================-->
185<div class="doc_subsection">
Chris Lattnerea34f642008-06-08 21:34:41 +0000186<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
Chris Lattner791f77b2008-06-05 06:25:56 +0000187</div>
188
189<div class="doc_text">
190
Chris Lattnerb82eb062008-10-13 20:47:20 +0000191<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 Lattner791f77b2008-06-05 06:25:56 +0000194
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000195<ul>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000196<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM
1972.3 only supported those used by OpenMP, but 2.4 supports them all. While
198llvm-gcc supports all of these builtins, note that not all targets do. X86 and
199PowerPC are known to support them all in both 32-bit and 64-bit mode.</li>
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000200
Chris Lattner7752d1a2008-10-13 20:59:32 +0000201<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells
202the compiler that it is ok to use low-precision approximations of certain libm
Chris Lattnerb82eb062008-10-13 20:47:20 +0000203functions (like tan, log, etc). This allows you to get high performance if you
204only need (say) 14-bits of precision.</li>
205
206<li>llvm-gcc now supports a C language extension known as "<a
207href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks
208</a>. This feature is similar to nested functions and closures, but does not
209require stack trampolines (with most ABIs) and supports returning closures
210from functions that define them. Note that actually <em>using</em> Blocks
211requires a small runtime that is not included with llvm-gcc.</li>
212
213<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
214transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
215later) this allows the use of LTO with other optimization levels like -Os.
216Previously, LTO could only be used with -O4, which implied optimizations in
217-O3 that can increase code size.</li>
Gabor Greifa3bd11d2008-06-09 06:06:18 +0000218</ul>
Chris Lattner791f77b2008-06-05 06:25:56 +0000219
Chris Lattner791f77b2008-06-05 06:25:56 +0000220</div>
221
222
Chris Lattner84977642007-09-21 03:54:09 +0000223<!--=========================================================================-->
224<div class="doc_subsection">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000225<a name="coreimprovements">LLVM Core Improvements</a>
226</div>
227
228<div class="doc_text">
229<p>New features include:
230</p>
231
Chris Lattner791f77b2008-06-05 06:25:56 +0000232<ul>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000233<li>A major change to the "Use" class landed, which shrank it by 25%. Since
234this is a pervasive part of the LLVM, it ended up reducing the memory use of
235LLVM IR in general by 15% for most programs.</li>
236
237<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more
238nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of
239"<tt>add i32 %A, 4 ; &lt;i32&gt;:3</tt>", which makes it much easier to read.
240</li>
241
242<li>LLVM 2.4 includes some changes for better vector support. First, the shift
243operations (<tt>shl</tt>, <tt>ashr</tt>, <tt>lshr</tt>) now all support vectors
244and do an element-by-element shift (shifts of the whole vector can be
245accomplished by bitcasting the vector to &lt;1 x i128&gt; for example). Second,
246there is support in development for vector comparisons. LLVM 2.4 actually
247supports two ways to do vector comparisons: the vicmp/vfcmp instructions and the
248icmp/fcmp instructions. The vicmp/vfcmp instructions are temporary and will be
249removed (do not use them). The icmp/fcmp instructions compare two vectors and
250return a vector of i1's for each result. Note that there is very little codegen
251support available for any of these IR features though.</li>
252
253<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much
254easier for front-ends to create debug info descriptors, similar to the way that
255IRBuilder makes it easier to create LLVM IR.</li>
256
257<li>LLVM now supports "function attributes", which allows us to seperate return
258value attributes from function attributes. LLVM now supports attributes on a
259function itself, a return value, and its parameters. New supported function
260attributes include noinline/alwaysinline and the "opt-size" flag which says the
261function should be optimized for code size.</li>
262
Chris Lattnercce6d4b2008-10-12 18:30:33 +0000263<li>LLVM IR now directly represents "common" linkage, instead of
264 representing it as a form of weak linkage.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000265
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000266</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000267
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000268</div>
269
270<!--=========================================================================-->
271<div class="doc_subsection">
Chris Lattneracce85d2008-02-10 07:46:44 +0000272<a name="optimizer">Optimizer Improvements</a>
273</div>
274
275<div class="doc_text">
276
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000277<p>In addition to a huge array of bug fixes and minor performance tweaks, the
Chris Lattner857fb132008-10-11 18:18:28 +0000278LLVM 2.4 optimizers support a few major enhancements:</p>
Chris Lattneracce85d2008-02-10 07:46:44 +0000279
280<ul>
281
Chris Lattner547a3912008-10-12 19:47:48 +0000282<li>GVN now does local PRE?</li>
283
284<li>Matthijs' Dead argument elimination rewrite</li>
285
Chris Lattnercce6d4b2008-10-12 18:30:33 +0000286<li>Old-ADCE used control dependence and deleted output-free infinite loops.
287Added a new Loop deletion pass (for deleting output free provably-finite loops)
288and rewrote ADCE to be simpler faster, and not need control dependence.</li>
289
290<li>SparsePropagation framework for lattice-based dataflow solvers.</li>
291
Chris Lattnercdb0e4c2008-10-12 22:57:58 +0000292<li>Tail duplication was removed from the standard optimizer sequence.</li>
Chris Lattnercce6d4b2008-10-12 18:30:33 +0000293
Chris Lattner547a3912008-10-12 19:47:48 +0000294<li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
295pulled out of instcombine and put into a new ValueTracking.h file, where they
296can be reused by other passes.</li>
297
Duncan Sands1050d732008-10-13 18:42:43 +0000298<li>The new AddReadAttrs pass works out which functions are read-only or
299read-none (these correspond to 'pure' and 'const' in C) and marks them
300with the appropriate attribute.</li>
Chris Lattner0b832202008-06-08 02:45:07 +0000301</ul>
302
303</div>
304
305<!--=========================================================================-->
306<div class="doc_subsection">
307<a name="codegen">Code Generator Improvements</a>
308</div>
309
310<div class="doc_text">
311
312<p>We put a significant amount of work into the code generator infrastructure,
313which allows us to implement more aggressive algorithms and make it run
314faster:</p>
315
316<ul>
Chris Lattnercdb0e4c2008-10-12 22:57:58 +0000317<li>asm writers split out to their own library to avoid JITs having to link
318 them in.</li>
319<li>Big asm writer refactoring + TargetAsmInfo</li>
320<li>2-addr pass and coalescer can now remat trivial insts to avoid a copy.</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000321<li>spiller to commute instructions in order to fold a reload</li>
322<li>Stack slot coloring?</li>
323<li>Live intervals renumbering? Is this useful to external people?</li>
324<li>'is as cheap as a move' instruction flag</li>
325<li>Improvements to selection dag viewing</li>
326<li>fast isel</li>
Chris Lattner857fb132008-10-11 18:18:28 +0000327<li>Selection dag speedups</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000328<li>asmwriter + raw_ostream -> fastah</li>
Chris Lattner59b5ce42008-10-13 17:12:51 +0000329<li>Partitioned Boolean Quadratic Programming (PBQP) based register
330allocator.</li>
Chris Lattner857fb132008-10-11 18:18:28 +0000331<li>...</li>
Chris Lattner0b832202008-06-08 02:45:07 +0000332
Chris Lattner84977642007-09-21 03:54:09 +0000333</ul>
334
335</div>
336
337
338<!--=========================================================================-->
339<div class="doc_subsection">
Chris Lattner77d29b12008-06-05 08:02:49 +0000340<a name="x86specific">X86/X86-64 Specific Improvements</a>
Chris Lattner84977642007-09-21 03:54:09 +0000341</div>
Chris Lattner60893e52007-05-18 06:33:02 +0000342
Chris Lattner738bd302006-04-18 06:32:08 +0000343<div class="doc_text">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000344<p>New target-specific features include:
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000345</p>
Chris Lattner26299222006-11-18 07:51:14 +0000346
347<ul>
Chris Lattner547a3912008-10-12 19:47:48 +0000348<li>Exception handling is supported by default on Linux/x86-64.</li>
Duncan Sandsbbf379a2008-10-13 17:32:15 +0000349<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
Chris Lattner857fb132008-10-11 18:18:28 +0000350<li>...</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000351
Chris Lattnerbfb17ab2007-05-17 21:41:31 +0000352</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000353
Chris Lattnerbfb17ab2007-05-17 21:41:31 +0000354</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000355
Chris Lattner84977642007-09-21 03:54:09 +0000356<!--=========================================================================-->
357<div class="doc_subsection">
Chris Lattner77d29b12008-06-05 08:02:49 +0000358<a name="targetspecific">Other Target Specific Improvements</a>
359</div>
360
361<div class="doc_text">
362<p>New target-specific features include:
363</p>
364
365<ul>
Chris Lattnercdb0e4c2008-10-12 22:57:58 +0000366<li>MIPS floating point support?</li>
Duncan Sandsbbf379a2008-10-13 17:32:15 +0000367<li>PowerPC now supports trampolines.</li>
Chris Lattner857fb132008-10-11 18:18:28 +0000368<li>....</li>
Chris Lattner77d29b12008-06-05 08:02:49 +0000369</ul>
Chris Lattner77d29b12008-06-05 08:02:49 +0000370
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000371</div>
Chris Lattner77d29b12008-06-05 08:02:49 +0000372
373
374<!--=========================================================================-->
375<div class="doc_subsection">
Chris Lattner84977642007-09-21 03:54:09 +0000376<a name="otherimprovements">Other Improvements</a>
377</div>
378
379<div class="doc_text">
380<p>New features include:
381</p>
382
383<ul>
Mikhail Glushenkov49feb452008-10-13 02:46:01 +0000384<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000385 support. It is now easier to experiment with <tt>llvmc2</tt> and
386 build your own tools based on it. </li>
Chris Lattner547a3912008-10-12 19:47:48 +0000387<li>raw_ostream + formatting</li>
Chris Lattnercdb0e4c2008-10-12 22:57:58 +0000388<li>Recycler + pool allocation stuff?</li>
Chris Lattner857fb132008-10-11 18:18:28 +0000389<li>...</li>
Chris Lattner84977642007-09-21 03:54:09 +0000390</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000391
Chris Lattner84977642007-09-21 03:54:09 +0000392</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000393
Chris Lattnerf6662f92008-10-13 17:57:36 +0000394<!--=========================================================================-->
395<div class="doc_subsection">
396<a name="changes">Major Changes and Removed Features</a>
397</div>
398
399<div class="doc_text">
400
Chris Lattner96a445e2008-10-13 18:01:01 +0000401<p>If you're already an LLVM user, this section lists some "gotchas" that you
402may run into upgrading from the previous release.</p>
403
Duncan Sandsbf8c4f22008-10-13 18:33:28 +0000404<p>The LLVM IR generated by llvm-gcc no longer names all instructions.
405 Use the instnamer pass if you want everything named.</p>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000406
Duncan Sandsbf8c4f22008-10-13 18:33:28 +0000407<li>The LoadVN and GCSE passes have been removed.</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000408
409
410<p>LLVM API Changes:</p>
411
412<ul>
413
414<li>... Attributes changes ... </li>
415
416<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
417<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
418converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
419"llvm/Analysis/ValueTracking.h".</li>
420
421<li>API change: BinaryOperator::create -> Create (CmpInst, CastInst too)</li>
422<li>Various header files like "llvm/ADT/iterator" were given a .h suffix.
423 Change your code to #include "llvm/ADT/iterator.h" instead.</li>
424
425</ul>
426
427</div>
428
429
430
Chris Lattner19092612003-10-02 16:38:05 +0000431<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000432<div class="doc_section">
433 <a name="portability">Portability and Supported Platforms</a>
434</div>
Chris Lattner19092612003-10-02 16:38:05 +0000435<!-- *********************************************************************** -->
436
Misha Brukman500bc302003-11-22 00:38:41 +0000437<div class="doc_text">
438
John Criswell0b5b5e92004-12-08 20:35:47 +0000439<p>LLVM is known to work on the following platforms:</p>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000440
441<ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000442<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Reid Spencer00812e22005-05-17 02:47:27 +0000443 (and probably other unix-like systems).</li>
Chris Lattner000c73b2008-02-06 06:30:34 +0000444<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Chris Lattner26299222006-11-18 07:51:14 +0000445 64-bit modes.</li>
Chris Lattner252b83d2008-02-06 18:00:06 +0000446<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Chris Lattner57a460e2007-05-23 04:39:32 +0000447<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
448 support is available for native builds with Visual C++).</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000449<li>Sun UltraSPARC workstations running Solaris 10.</li>
John Criswell9321fa82005-05-13 20:28:15 +0000450<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000451<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000452</ul>
453
Chris Lattnerbc5786b2008-06-05 06:57:39 +0000454<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Brian Gaekeb0fd7612004-05-09 05:28:35 +0000455to the machine and operating system on which it is built. However, minor
456porting may be required to get LLVM to work on new platforms. We welcome your
457portability patches and reports of successful builds or error messages.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000458
Misha Brukman500bc302003-11-22 00:38:41 +0000459</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000460
461<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000462<div class="doc_section">
463 <a name="knownproblems">Known Problems</a>
464</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000465<!-- *********************************************************************** -->
466
Misha Brukman500bc302003-11-22 00:38:41 +0000467<div class="doc_text">
468
469<p>This section contains all known problems with the LLVM system, listed by
Chris Lattner79c3fe12003-10-02 04:57:28 +0000470component. As new problems are discovered, they will be added to these
Chris Lattner5eccca42003-12-12 21:22:16 +0000471sections. If you run into a problem, please check the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000472href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattner5eccca42003-12-12 21:22:16 +0000473there isn't already one.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000474
Misha Brukman500bc302003-11-22 00:38:41 +0000475</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000476
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000477<!-- ======================================================================= -->
478<div class="doc_subsection">
479 <a name="experimental">Experimental features included with this release</a>
480</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000481
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000482<div class="doc_text">
483
Misha Brukman6df9e2c2004-05-12 21:46:05 +0000484<p>The following components of this LLVM release are either untested, known to
485be broken or unreliable, or are in early development. These components should
486not be relied on, and bugs should not be filed against them, but they may be
487useful to some people. In particular, if you would like to work on one of these
Chris Lattner2b659ef2008-02-12 06:29:45 +0000488components, please contact us on the <a
489href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000490
491<ul>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000492<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
Duncan Sands27aff872008-06-08 20:18:35 +0000493<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattner000c73b2008-02-06 06:30:34 +0000494 value for this option.</li>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000495</ul>
496
497</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000498
Misha Brukman500bc302003-11-22 00:38:41 +0000499<!-- ======================================================================= -->
500<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000501 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswellc0c186d2005-11-08 21:11:33 +0000502</div>
503
504<div class="doc_text">
505
506<ul>
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000507 <li>The X86 backend does not yet support
508 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
509 floating point stack</a>. It supports the 'f' and 't' constraints, but not
510 'u'.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000511 <li>The X86 backend generates inefficient floating point code when configured
512 to generate code for systems that don't have SSE2.</li>
Duncan Sands47eff2b2008-06-08 19:38:43 +0000513 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000514 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
515 currently due
516 to <a href="http://llvm.org/PR2255">several</a>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000517 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
518 'u' inline assembly constraint and X87 floating point inline assembly.</li>
Dan Gohman8207ba92008-06-08 23:05:11 +0000519 <li>The X86-64 backend does not yet support the LLVM IR instruction
520 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
521 argument constructs on X86-64 by lowering them manually.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000522</ul>
523
524</div>
525
526<!-- ======================================================================= -->
527<div class="doc_subsection">
528 <a name="ppc-be">Known problems with the PowerPC back-end</a>
529</div>
530
531<div class="doc_text">
532
533<ul>
Nicolas Geoffraye4285dc2007-05-15 09:21:28 +0000534<li>The Linux PPC32/ABI support needs testing for the interpreter and static
Chris Lattner57a460e2007-05-23 04:39:32 +0000535compilation, and lacks support for debug information.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000536</ul>
537
538</div>
539
540<!-- ======================================================================= -->
541<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000542 <a name="arm-be">Known problems with the ARM back-end</a>
543</div>
544
545<div class="doc_text">
546
547<ul>
Chris Lattner57a460e2007-05-23 04:39:32 +0000548<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sandsc90d68b2007-09-26 15:59:54 +0000549processors, thumb programs can crash or produce wrong
Chris Lattner57a460e2007-05-23 04:39:32 +0000550results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000551<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
552</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000553<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
554 execute
Chris Lattner57a460e2007-05-23 04:39:32 +0000555programs compiled with LLVM. Please use more recent versions of QEMU.</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000556</ul>
557
558</div>
559
560<!-- ======================================================================= -->
561<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000562 <a name="sparc-be">Known problems with the SPARC back-end</a>
563</div>
564
565<div class="doc_text">
566
567<ul>
568<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
569 support the 64-bit SPARC ABI (-m64).</li>
570</ul>
571
572</div>
573
574<!-- ======================================================================= -->
575<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000576 <a name="alpha-be">Known problems with the Alpha back-end</a>
577</div>
578
579<div class="doc_text">
580
581<ul>
582
583<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
584appropriate nops inserted to ensure restartability.</li>
585
John Criswellc0c186d2005-11-08 21:11:33 +0000586</ul>
587</div>
588
Chris Lattner26299222006-11-18 07:51:14 +0000589<!-- ======================================================================= -->
590<div class="doc_subsection">
591 <a name="ia64-be">Known problems with the IA64 back-end</a>
592</div>
593
594<div class="doc_text">
595
596<ul>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000597<li>The Itanium backend is highly experimental, and has a number of known
598 issues. We are looking for a maintainer for the Itanium backend. If you
599 are interested, please contact the llvmdev mailing list.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000600</ul>
601
602</div>
603
604<!-- ======================================================================= -->
605<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000606 <a name="c-be">Known problems with the C back-end</a>
Chris Lattner26299222006-11-18 07:51:14 +0000607</div>
608
609<div class="doc_text">
610
611<ul>
Chris Lattner5733b272008-06-05 06:35:40 +0000612<li><a href="http://llvm.org/PR802">The C backend has only basic support for
613 inline assembly code</a>.</li>
Chris Lattner725a0d82007-09-26 06:01:35 +0000614<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
615 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Duncan Sands27aff872008-06-08 20:18:35 +0000616 C++ code compiled with llc or native compilers.</li>
Duncan Sandsf74c0cc2008-02-10 13:40:55 +0000617<li>The C backend does not support all exception handling constructs.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000618</ul>
619
620</div>
John Criswellc0c186d2005-11-08 21:11:33 +0000621
Misha Brukman500bc302003-11-22 00:38:41 +0000622
623<!-- ======================================================================= -->
624<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000625 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000626</div>
Chris Lattner47588f92003-10-02 05:07:23 +0000627
Misha Brukman500bc302003-11-22 00:38:41 +0000628<div class="doc_text">
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000629
Chris Lattner252b83d2008-02-06 18:00:06 +0000630<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
631Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000632llvmdev mailing list if you are interested.</p>
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000633
Chris Lattner5733b272008-06-05 06:35:40 +0000634<p>The only major language feature of GCC not supported by llvm-gcc is
635 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
636 are only supported on some targets. For example, trampolines are only
Duncan Sands27aff872008-06-08 20:18:35 +0000637 supported on some targets (these are used when you take the address of a
638 nested function).</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000639
Chris Lattner5733b272008-06-05 06:35:40 +0000640<p>If you run into GCC extensions which are not supported, please let us know.
641</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000642
Misha Brukman500bc302003-11-22 00:38:41 +0000643</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000644
Misha Brukman500bc302003-11-22 00:38:41 +0000645<!-- ======================================================================= -->
646<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000647 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000648</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000649
Misha Brukman500bc302003-11-22 00:38:41 +0000650<div class="doc_text">
651
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000652<p>The C++ front-end is considered to be fully
Chris Lattner7506b1d2004-12-07 08:04:13 +0000653tested and works for a number of non-trivial programs, including LLVM
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000654itself, Qt, Mozilla, etc.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000655
Misha Brukman500bc302003-11-22 00:38:41 +0000656<ul>
Anton Korobeynikov0021fc12008-10-11 18:27:16 +0000657<li>Exception handling works well on the X86 and PowerPC targets. Currently
658 only linux and darwin targets are supported (both 32 and 64 bit).</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000659</ul>
Chris Lattnerfcc54b32003-10-07 22:14:37 +0000660
Misha Brukman500bc302003-11-22 00:38:41 +0000661</div>
662
Misha Brukman500bc302003-11-22 00:38:41 +0000663
Chris Lattner2b659ef2008-02-12 06:29:45 +0000664<!-- ======================================================================= -->
665<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000666 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000667</div>
668
669<div class="doc_text">
670The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
671technology and problems should be expected.
672<ul>
Duncan Sands27aff872008-06-08 20:18:35 +0000673<li>The Ada front-end currently only builds on X86-32. This is mainly due
Chris Lattner2b659ef2008-02-12 06:29:45 +0000674to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sands27aff872008-06-08 20:18:35 +0000675however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000676which does support trampolines.</li>
677<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
678Workaround: configure with --disable-bootstrap.</li>
Duncan Sands978bcee2008-10-13 17:27:23 +0000679<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
680and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
681(c380004 also fails with gcc-4.2 mainline).</li>
682<li>Some gcc specific Ada tests continue to crash the compiler.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000683<li>The -E binder option (exception backtraces)
684<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
685crashing if an exception is raised. Workaround: do not use -E.</li>
686<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
687or finish at a non-byte offset</a> in a record. Workaround: do not pack records
688or use representation clauses that result in a field of a non-discrete type
689starting or finishing in the middle of a byte.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000690<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
691'main' as generated by the Ada binder to be invalid</a>.
692Workaround: hand edit the file to use pointers for <tt>argv</tt> and
693<tt>envp</tt> rather than integers.</li>
694<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
695ignored</a>.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000696</ul>
697</div>
698
Chris Lattner79c3fe12003-10-02 04:57:28 +0000699<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000700<div class="doc_section">
701 <a name="additionalinfo">Additional Information</a>
702</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000703<!-- *********************************************************************** -->
704
Misha Brukman500bc302003-11-22 00:38:41 +0000705<div class="doc_text">
706
Chris Lattner416db102005-05-16 17:13:10 +0000707<p>A wide variety of additional information is available on the <a
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000708href="http://llvm.org">LLVM web page</a>, in particular in the <a
709href="http://llvm.org/docs/">documentation</a> section. The web page also
Reid Spencer669ed452007-07-09 08:04:31 +0000710contains versions of the API documentation which is up-to-date with the
711Subversion version of the source code.
Misha Brukman109d9e82005-03-30 19:14:24 +0000712You can access versions of these documents specific to this release by going
713into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000714
Misha Brukman500bc302003-11-22 00:38:41 +0000715<p>If you have any questions or comments about LLVM, please feel free to contact
Chris Lattnerc463b272005-10-29 07:07:09 +0000716us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattner5eccca42003-12-12 21:22:16 +0000717lists</a>.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000718
Misha Brukman500bc302003-11-22 00:38:41 +0000719</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000720
721<!-- *********************************************************************** -->
Chris Lattner79c3fe12003-10-02 04:57:28 +0000722
Misha Brukman500bc302003-11-22 00:38:41 +0000723<hr>
Misha Brukman2061e892003-11-22 01:23:39 +0000724<address>
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Misha Brukman2061e892003-11-22 01:23:39 +0000729
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000730 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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