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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 Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame^]196<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 Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]200
Chris Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame^]201<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 Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame]203functions (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 Greif0e49cc82008-06-09 06:06:18 +0000[diff] [blame]218</ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]219
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]220</div>
221
222
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]223<!--=========================================================================-->
224<div class="doc_subsection">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]225<a name="coreimprovements">LLVM Core Improvements</a>
226</div>
227
228<div class="doc_text">
229<p>New features include:
230</p>
231
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]232<ul>
Chris Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame^]233<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 Lattnera5a49382008-10-12 18:30:33 +0000[diff] [blame]263<li>LLVM IR now directly represents "common" linkage, instead of
264 representing it as a form of weak linkage.</li>
Chris Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame^]265
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]266</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]267
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]268</div>
269
270<!--=========================================================================-->
271<div class="doc_subsection">
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]272<a name="optimizer">Optimizer Improvements</a>
273</div>
274
275<div class="doc_text">
276
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]277<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]278LLVM 2.4 optimizers support a few major enhancements:</p>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]279
280<ul>
281
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]282<li>GVN now does local PRE?</li>
283
284<li>Matthijs' Dead argument elimination rewrite</li>
285
Chris Lattnera5a49382008-10-12 18:30:33 +0000[diff] [blame]286<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 Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]292<li>Tail duplication was removed from the standard optimizer sequence.</li>
Chris Lattnera5a49382008-10-12 18:30:33 +0000[diff] [blame]293
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]294<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 Sands2aecc3f2008-10-13 18:42:43 +0000[diff] [blame]298<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 Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]301</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 Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]317<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 Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]321<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 Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]327<li>Selection dag speedups</li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]328<li>asmwriter + raw_ostream -> fastah</li>
Chris Lattner72c8a252008-10-13 17:12:51 +0000[diff] [blame]329<li>Partitioned Boolean Quadratic Programming (PBQP) based register
330allocator.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]331<li>...</li>
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]332
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]333</ul>
334
335</div>
336
337
338<!--=========================================================================-->
339<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]340<a name="x86specific">X86/X86-64 Specific Improvements</a>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]341</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]342
343<div class="doc_text">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]344<p>New target-specific features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]345</p>
346
347<ul>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]348<li>Exception handling is supported by default on Linux/x86-64.</li>
Duncan Sandsd8745a92008-10-13 17:32:15 +0000[diff] [blame]349<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]350<li>...</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]351
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]352</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]353
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]354</div>
355
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]356<!--=========================================================================-->
357<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]358<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 Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]366<li>MIPS floating point support?</li>
Duncan Sandsd8745a92008-10-13 17:32:15 +0000[diff] [blame]367<li>PowerPC now supports trampolines.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]368<li>....</li>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]369</ul>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]370
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]371</div>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]372
373
374<!--=========================================================================-->
375<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]376<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 Glushenkovcc2d3012008-10-13 02:46:01 +0000[diff] [blame]384<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]385 support. It is now easier to experiment with <tt>llvmc2</tt> and
386 build your own tools based on it. </li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]387<li>raw_ostream + formatting</li>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]388<li>Recycler + pool allocation stuff?</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]389<li>...</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]390</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]391
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]392</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]393
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]394<!--=========================================================================-->
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 Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]401<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 Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]404<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 Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]406
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]407<li>The LoadVN and GCSE passes have been removed.</li>
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]408
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
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]431<!-- *********************************************************************** -->
432<div class="doc_section">
433 <a name="portability">Portability and Supported Platforms</a>
434</div>
435<!-- *********************************************************************** -->
436
437<div class="doc_text">
438
439<p>LLVM is known to work on the following platforms:</p>
440
441<ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]442<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]443 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]444<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]445 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]446<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]447<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 Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]449<li>Sun UltraSPARC workstations running Solaris 10.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]450<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]451<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]452</ul>
453
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]454<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]455to 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>
458
459</div>
460
461<!-- *********************************************************************** -->
462<div class="doc_section">
463 <a name="knownproblems">Known Problems</a>
464</div>
465<!-- *********************************************************************** -->
466
467<div class="doc_text">
468
469<p>This section contains all known problems with the LLVM system, listed by
470component. As new problems are discovered, they will be added to these
471sections. If you run into a problem, please check the <a
472href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
473there isn't already one.</p>
474
475</div>
476
477<!-- ======================================================================= -->
478<div class="doc_subsection">
479 <a name="experimental">Experimental features included with this release</a>
480</div>
481
482<div class="doc_text">
483
484<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 Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]488components, please contact us on the <a
489href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]490
491<ul>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]492<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]493<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]494 value for this option.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]495</ul>
496
497</div>
498
499<!-- ======================================================================= -->
500<div class="doc_subsection">
501 <a name="x86-be">Known problems with the X86 back-end</a>
502</div>
503
504<div class="doc_text">
505
506<ul>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame]507 <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 Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]511 <li>The X86 backend generates inefficient floating point code when configured
512 to generate code for systems that don't have SSE2.</li>
Duncan Sands8b4f3772008-06-08 19:38:43 +0000[diff] [blame]513 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame]514 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 Lattnerf06141a2008-06-08 23:12:47 +0000[diff] [blame]517 <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 Gohman3882ecb2008-06-08 23:05:11 +0000[diff] [blame]519 <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>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]522</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>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]534<li>The Linux PPC32/ABI support needs testing for the interpreter and static
535compilation, and lacks support for debug information.</li>
536</ul>
537
538</div>
539
540<!-- ======================================================================= -->
541<div class="doc_subsection">
542 <a name="arm-be">Known problems with the ARM back-end</a>
543</div>
544
545<div class="doc_text">
546
547<ul>
548<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]549processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]550results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
551<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
552</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]553<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
554 execute
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]555programs compiled with LLVM. Please use more recent versions of QEMU.</li>
556</ul>
557
558</div>
559
560<!-- ======================================================================= -->
561<div class="doc_subsection">
562 <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">
576 <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
586</ul>
587</div>
588
589<!-- ======================================================================= -->
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 Lattnerf06141a2008-06-08 23:12:47 +0000[diff] [blame]597<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>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]600</ul>
601
602</div>
603
604<!-- ======================================================================= -->
605<div class="doc_subsection">
606 <a name="c-be">Known problems with the C back-end</a>
607</div>
608
609<div class="doc_text">
610
611<ul>
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]612<li><a href="http://llvm.org/PR802">The C backend has only basic support for
613 inline assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]614<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 Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]616 C++ code compiled with llc or native compilers.</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]617<li>The C backend does not support all exception handling constructs.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]618</ul>
619
620</div>
621
622
623<!-- ======================================================================= -->
624<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]625 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]626</div>
627
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]628<div class="doc_text">
629
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]630<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
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]632llvmdev mailing list if you are interested.</p>
633
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]634<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 Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]637 supported on some targets (these are used when you take the address of a
638 nested function).</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]639
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]640<p>If you run into GCC extensions which are not supported, please let us know.
641</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]642
643</div>
644
645<!-- ======================================================================= -->
646<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]647 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]648</div>
649
650<div class="doc_text">
651
652<p>The C++ front-end is considered to be fully
653tested and works for a number of non-trivial programs, including LLVM
654itself, Qt, Mozilla, etc.</p>
655
656<ul>
Anton Korobeynikovd9a17932008-10-11 18:27:16 +0000[diff] [blame]657<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>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]659</ul>
660
661</div>
662
663
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]664<!-- ======================================================================= -->
665<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]666 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]667</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 Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]673<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]674to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]675however 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]676which 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 Sands2dbc2e82008-10-13 17:27:23 +0000[diff] [blame]679<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 Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]683<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 Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]690<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 Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]696</ul>
697</div>
698
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]699<!-- *********************************************************************** -->
700<div class="doc_section">
701 <a name="additionalinfo">Additional Information</a>
702</div>
703<!-- *********************************************************************** -->
704
705<div class="doc_text">
706
707<p>A wide variety of additional information is available on the <a
708href="http://llvm.org">LLVM web page</a>, in particular in the <a
709href="http://llvm.org/docs/">documentation</a> section. The web page also
710contains versions of the API documentation which is up-to-date with the
711Subversion version of the source code.
712You can access versions of these documents specific to this release by going
713into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
714
715<p>If you have any questions or comments about LLVM, please feel free to contact
716us via the <a href="http://llvm.org/docs/#maillist"> mailing
717lists</a>.</p>
718
719</div>
720
721<!-- *********************************************************************** -->
722
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