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Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]7 <title>LLVM 2.0 Release Notes</title>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]8</head>
9<body>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]10
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]11<div class="doc_title">LLVM 2.0 Release Notes</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]12
13<ol>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]14 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#whatsnew">What's New?</a></li>
Chris Lattner4b538b92004-04-30 22:17:12 +0000[diff] [blame]16 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]17 <li><a href="#portability">Portability and Supported Platforms</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]18 <li><a href="#knownproblems">Known Problems</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]19 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]20</ol>
21
Chris Lattner7911ce22004-05-23 21:07:27 +0000[diff] [blame]22<div class="doc_author">
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]23 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]24</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]25
26<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]27<div class="doc_section">
28 <a name="intro">Introduction</a>
29</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]30<!-- *********************************************************************** -->
31
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]32<div class="doc_text">
33
34<p>This document contains the release notes for the LLVM compiler
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]35infrastructure, release 2.0. Here we describe the status of LLVM, including any
36known problems and major improvements from the previous release. All LLVM
37releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
38releases web site</a>.
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]39
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]40<p>For more information about LLVM, including information about the latest
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]41release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattner47ad72c2003-10-07 21:38:31 +0000[diff] [blame]42web site</a>. If you have questions or comments, the <a
43href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]44list</a> is a good place to send them.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]45
Chris Lattner78bf32b2004-12-09 22:22:58 +0000[diff] [blame]46<p>Note that if you are reading this file from CVS or the main LLVM web page,
47this document applies to the <i>next</i> release, not the current one. To see
48the release notes for the current or previous releases, see the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]49href="http://llvm.org/releases/">releases page</a>.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]50
51</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]52
53<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]54<div class="doc_section">
55 <a name="whatsnew">What's New?</a>
56</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]57<!-- *********************************************************************** -->
58
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]59<div class="doc_text">
60
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]61<p>This is the eleventh public release of the LLVM Compiler Infrastructure.
Chris Lattnerf01b0b52007-05-09 05:27:05 +0000[diff] [blame]62Being the first major release since 1.0, this release is different in several
63ways from our previous releases:</p>
64
65<ol>
66<li>We took this as an opportunity to
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]67break backwards compatibility with the LLVM 1.x bytecode and .ll file format.
68If you have LLVM 1.9 .ll files that you would like to upgrade to LLVM 2.x, we
Lauro Ramos Venanciobe1b1b12007-05-12 02:36:41 +0000[diff] [blame]69recommend the use of the stand alone <a href="#llvm-upgrade">llvm-upgrade</a>
Chris Lattnerbf8abe32007-05-17 19:58:57 +0000[diff] [blame]70tool (which is included with 2.0). We intend to keep compatibility with .ll
71and .bc formats within the 2.x release series, like we did within the 1.x
72series.</li>
Chris Lattnerf01b0b52007-05-09 05:27:05 +0000[diff] [blame]73<li>There are several significant change to the LLVM IR and internal APIs, such
74 as a major overhaul of the type system, the completely new bitcode file
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]75 format, etc (described below).</li>
Chris Lattnerf01b0b52007-05-09 05:27:05 +0000[diff] [blame]76<li>We designed the release around a 6 month release cycle instead of the usual
77 3-month cycle. This gave us extra time to develop and test some of the
78 more invasive features in this release.</li>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]79<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end. Users are required to
80 upgrade to llvm-gcc4. llvm-gcc4 includes many features over
81 llvm-gcc3, is faster, and is <a href="CFEBuildInstrs.html">much easier to
82 build from source</a>.</li>
Chris Lattnerf01b0b52007-05-09 05:27:05 +0000[diff] [blame]83</ol>
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]84
Chris Lattnerf01b0b52007-05-09 05:27:05 +0000[diff] [blame]85<p>Note that while this is a major version bump, this release has been
86 extensively tested on a wide range of software. It is easy to say that this
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]87 is our best release yet, in terms of both features and correctness. This is
88 the first LLVM release to correctly compile and optimize major software like
89 LLVM itself, Mozilla/Seamonkey, Qt 4.3rc1, kOffice, etc out of the box on
90 linux/x86.
91 </p>
Chris Lattnera5099962003-12-06 20:22:41 +0000[diff] [blame]92
Chris Lattner80453c92004-05-24 04:50:25 +0000[diff] [blame]93</div>
94
Chris Lattnera5099962003-12-06 20:22:41 +0000[diff] [blame]95<!--=========================================================================-->
Chris Lattner8a458762005-05-15 05:44:51 +0000[diff] [blame]96<div class="doc_subsection">
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]97<a name="newfeatures">New Features in LLVM 2.0</a>
Chris Lattner44c933e2006-04-18 06:18:36 +0000[diff] [blame]98</div>
99
Chris Lattner738bd302006-04-18 06:32:08 +0000[diff] [blame]100<!--_________________________________________________________________________-->
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]101<div class="doc_subsubsection"><a name="majorchanges">Major Changes</a></div>
102<div class="doc_text">
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]103
104<p>Changes to the LLVM IR itself:</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]105
106<ul>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]107
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]108<li>Integer types are now completely signless. This means that we
109 have types like i8/i16/i32 instead of ubyte/sbyte/short/ushort/int
110 etc. LLVM operations that depend on sign have been split up into
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]111 separate instructions (<a href="http://llvm.org/PR950">PR950</a>). This
112 eliminates cast instructions that just change the sign of the operands (e.g.
113 int -> uint), which reduces the size of the IR and makes optimizers
114 simpler to write.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]115
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]116<li>Integer types with arbitrary bitwidths (e.g. i13, i36, i42, i1057, etc) are
117 now supported in the LLVM IR and optimizations (<a
118 href="http://llvm.org/PR1043">PR1043</a>). However, neither llvm-gcc
119 (<a href="http://llvm.org/PR1284">PR1284</a>) nor the native code generators
120 (<a href="http://llvm.org/PR1270">PR1270</a>) support non-standard width
121 integers yet.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]122
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]123<li>'Type planes' have been removed (<a href="http://llvm.org/PR411">PR411</a>).
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]124 It is no longer possible to have two values with the same name in the
125 same symbol table. This simplifies LLVM internals, allowing significant
126 speedups.</li>
127
128<li>Global variables and functions in .ll files are now prefixed with
129 @ instead of % (<a href="http://llvm.org/PR645">PR645</a>).</li>
130
131<li>The LLVM 1.x "bytecode" format has been replaced with a
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]132 completely new binary representation, named 'bitcode'. The <a
133 href="BitCodeFormat.html">Bitcode Format</a> brings a
134 number of advantages to the LLVM over the old bytecode format: it is denser
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]135 (files are smaller), more extensible, requires less memory to read,
136 is easier to keep backwards compatible (so LLVM 2.5 will read 2.0 .bc
137 files), and has many other nice features.</li>
138
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]139<li>Load and store instructions now track the alignment of their pointer
140 (<a href="http://www.llvm.org/PR400">PR400</a>). This allows the IR to
141 express loads that are not sufficiently aligned (e.g. due to '<tt>#pragma
142 packed</tt>') or to capture extra alignment information.</li>
143</ul>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]144
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]145<p>Major new features:</p>
146
147<ul>
148
149<li>A number of ELF features are now supported by LLVM, including 'visibility',
150 extern weak linkage, Thread Local Storage (TLS) with the <tt>__thread</tt>
151 keyword, and symbol aliases.
152 Among other things, this means that many of the special options needed to
153 configure llvm-gcc on linux are no longer needed, and special hacks to build
154 large C++ libraries like Qt are not needed.</li>
155
156<li>LLVM now has a new MSIL backend. llc -march=msil will now turn LLVM
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]157 into MSIL (".net") bytecode. This is still fairly early development
158 with a number of limitations.</li>
159
Chris Lattner46ccdbf2007-05-18 06:38:51 +0000[diff] [blame]160<li>A new <a href="CommandGuide/html/llvm-upgrade.html">llvm-upgrade</a> tool
161 exists to migrates LLVM 1.9 .ll files to LLVM 2.0 syntax.</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]162</ul>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]163
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]164</div>
165
166
167<!--_________________________________________________________________________-->
168<div class="doc_subsubsection"><a name="llvmgccfeatures">llvm-gcc
169Improvements</a></div>
170<div class="doc_text">
171<p>New features include:
172</p>
173
174<ul>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]175<li>Precompiled Headers (PCH) are now supported.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]176
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]177<li>"<tt>#pragma packed</tt>" is now supported, as are the various features
178 described above (visibility, extern weak linkage, __thread, aliases,
179 etc).</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]180
181<li>Tracking function parameter/result attributes is now possible.</li>
182
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]183<li>Many internal enhancements have been added, such as improvements to
184 NON_LVALUE_EXPR, arrays with non-zero base, structs with variable sized
185 fields, VIEW_CONVERT_EXPR, CEIL_DIV_EXPR, nested functions, and many other
186 things. This is primarily to supports non-C GCC front-ends, like Ada.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]187
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]188<li>It is simpler to configure llvm-gcc for linux.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]189
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]190</ul>
191
192</div>
193
194<!--_________________________________________________________________________-->
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]195<div class="doc_subsubsection"><a name="optimizer">Optimizer
196Improvements</a></div>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]197
Chris Lattner738bd302006-04-18 06:32:08 +0000[diff] [blame]198<div class="doc_text">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]199<p>New features include:
200</p>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]201
202<ul>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]203<li>The <a href="WritingAnLLVMPass.html">pass manager</a> has been entirely
204 rewritten, making it significantly smaller, simpler, and more extensible.
205 Support has been added to run FunctionPasses interlaced with
206 CallGraphSCCPasses, and we now support loop transformations explicitly with
207 LoopPass.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]208
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]209<li>The <tt>-scalarrepl</tt> pass can now promote unions containing FP values
210 into a register, it can also handle unions of vectors of the same
211 size.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]212
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]213<li>LLVM 2.0 includes a new loop rotation pass, which converts "for loops" into
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]214 "do/while loops", where the condition is at the bottom of the loop.</li>
215
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]216<li>The Loop Strength Reduction pass has been improved, and support added
217 for sinking expressions across blocks to reduce register pressure.</li>
218
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]219<li>ModulePasses may now use the result of FunctionPasses.</li>
220
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]221<li>The [Post]DominatorSet classes have been removed from LLVM and clients
222 switched to use the far-more-efficient ETForest class instead.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]223
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]224<li>The ImmediateDominator class has also been removed, and clients have been
225 switched to use DominatorTree instead.</li>
226
227<li>The predicate simplifier pass has been improved, making it able to do
228 simple value range propagation and eliminate more conditionals.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]229
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]230</ul>
231
Chris Lattner738bd302006-04-18 06:32:08 +0000[diff] [blame]232</div>
233
Chris Lattner1c1a85c2006-04-19 04:02:47 +0000[diff] [blame]234<!--_________________________________________________________________________-->
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]235<div class="doc_subsubsection"><a name="codegen">Code
236Generator Enhancements</a></div>
237
Chris Lattner1c1a85c2006-04-19 04:02:47 +0000[diff] [blame]238<div class="doc_text">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]239<p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]240New features include:
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]241</p>
242
243<ul>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]244
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]245<li>Support was added for software floating point, which allows LLVM to target
246 chips that don't have hardware FPUs (e.g. ARM thumb mode).</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]247
248<li>A new register scavenger has been implemented, which is useful for
249 finding free registers after register allocation. This is useful when
250 rewriting frame references on RISC targets, for example.</li>
251
252<li>Heuristics have been added to avoid coalescing vregs with very large live
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]253 ranges to physregs. This was bad because it effectively pinned the physical
254 register for the entire lifetime of the virtual register (<a
255 href="http://llvm.org/PR711">PR711</a>).</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]256
257<li>Support now exists for very simple (but still very useful)
258 rematerialization the register allocator, enough to move
259 instructions like "load immediate" and constant pool loads.</li>
260
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]261<li>Switch statement lowering is significantly better, improving codegen for
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]262 sparse switches that have dense subregions, and implemented support
263 for the shift/and trick.</li>
264
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]265<li>Added support for tracking physreg sub-registers and super-registers
266 in the code generator, as well as extensive register
267 allocator changes to track them.</li>
268
269<li>There is initial support for virtreg sub-registers
270 (<a href="http://llvm.org/PR1350">PR1350</a>).</li>
271
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]272</ul>
273
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]274<p>
275Other improvements include:
276</p>
277
278<ul>
279
280<li>Inline assembly support is much more solid that before.
281 The two primary features still missing are support for 80-bit floating point
282 stack registers on X86 (<a href="http://llvm.org/PR879">PR879</a>), and
283 support for inline asm in the C backend (<a
284 href="http://llvm.org/PR802">PR802</a>).</li>
285
286<li>DWARF debug information generation has been improved. LLVM now passes
287 most of the GDB testsuite on MacOS and debug info is more dense.</li>
288
289<li>Codegen support for Zero-cost DWARF exception handling has been added (<a
290 href="http://llvm.org/PR592">PR592</a>). It is mostly
291 complete and just in need of continued bug fixes and optimizations at
292 this point. However, support in llvm-g++ is disabled with an
293 #ifdef for the 2.0 release (<a
294 href="http://llvm.org/PR870">PR870</a>).</li>
295
296<li>The code generator now has more accurate and general hooks for
297 describing addressing modes ("isLegalAddressingMode") to
298 optimizations like loop strength reduction and code sinking.</li>
299
300<li>Progress has been made on a direct Mach-o .o file writer. Many small
301 apps work, but it is still not quite complete.</li>
302
303</ul>
304
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]305<p>In addition, the LLVM target description format has itself been extended in
306 several ways:</p>
307
308<ul>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]309<li>Extended TargetData to support better target parameterization in
310 the .ll/.bc files, eliminating the 'pointersize/endianness' attributes
311 in the files (<a href="http://llvm.org/PR761">PR761</a>).</li>
312
313<li>TargetData was generalized for finer grained alignment handling,
314 handling of vector alignment, and handling of preferred alignment</li>
315
316<li>LLVM now supports describing target calling conventions
317 explicitly in .td files, reducing the amount of C++ code that needs
318 to be written for a port.</li>
319
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]320</ul>
321
Chris Lattner1c1a85c2006-04-19 04:02:47 +0000[diff] [blame]322</div>
Chris Lattner44c933e2006-04-18 06:18:36 +0000[diff] [blame]323
324<!--_________________________________________________________________________-->
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]325<div class="doc_subsubsection"><a name="specifictargets">Target-Specific
326Improvements</a></div>
327
328<div class="doc_text">
329
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]330<p>X86-specific Code Generator Enhancements:
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]331</p>
332
333<ul>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]334<li>The MMX instruction set is now supported through intrinsics.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]335<li>The scheduler was improved to better reduce register pressure on
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]336 X86 and other targets that are register pressure sensitive.</li>
337<li>Linux/x86-64 support is much better.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]338<li>PIC support for linux/x86 has been added.</li>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]339<li>The X86 backend now supports the GCC regparm attribute.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]340<li>LLVM now supports inline asm with multiple constraint letters per operand
341 (like "ri") which is common in X86 inline asms.</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]342</ul>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]343
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]344<p>ARM-specific Code Generator Enhancements:</p>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]345
346<ul>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]347<li>The ARM code generator is now stable and fully supported.</li>
348
349<li>There are major new features, including support for ARM
350 v4-v6 chips, vfp support, soft float point support, pre/postinc support,
351 load/store multiple generation, constant pool entry motion (to support
352 large functions), and inline asm support, weak linkage support, static
353 ctor/dtor support and many bug fixes.</li>
354<li>Added support for Thumb code generation (<tt>llc -march=thumb</tt>).</li>
355
356<li>The ARM backend now supports the ARM AAPCS/EABI ABI and PIC codegen on
357 arm/linux.</li>
358
359<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]360</ul>
361
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]362<p>PowerPC-specific Code Generator Enhancements:</p>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]363
364<ul>
365<li>The PowerPC 64 JIT now supports addressing code loaded above the 2G
366 boundary.</li>
367
368<li>Improved support for the Linux/ppc ABI and the linux/ppc JIT is fully
369 functional now. llvm-gcc and static compilation are not fully supported
Chris Lattnerbf8abe32007-05-17 19:58:57 +0000[diff] [blame]370 yet though.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]371
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]372<li>Many PowerPC 64 bug fixes.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]373
374</ul>
375
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]376</div>
377
378
379<!--_________________________________________________________________________-->
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000[diff] [blame]380<div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
Chris Lattner58504a62006-02-05 06:39:36 +0000[diff] [blame]381<div class="doc_text">
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]382
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000[diff] [blame]383<p>More specific changes include:</p>
384
Chris Lattner58504a62006-02-05 06:39:36 +0000[diff] [blame]385<ul>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]386<li>LLVM no longer relies on static destructors to shut itself down. Instead,
Chris Lattner46ccdbf2007-05-18 06:38:51 +0000[diff] [blame]387 it lazily initializes itself and shuts down when <tt>llvm_shutdown()</tt> is
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]388 explicitly called.</li>
389
390<li>LLVM now has significantly fewer static constructors, reducing startup time.
391 </li>
392
393<li>Several classes have been refactored to reduce the amount of code that
394 gets linked into apps that use the JIT.</li>
395
396<li>Construction of intrinsic function declarations has been simplified.</li>
397
Chris Lattner46ccdbf2007-05-18 06:38:51 +0000[diff] [blame]398<li>The gccas/gccld tools have been replaced with small shell scripts.</li>
Tanya Lattnerb6ec3a92007-05-16 23:25:46 +0000[diff] [blame]399
400<li>Support has been added to llvm-test for running on low-memory
401 or slow machines (make SMALL_PROBLEM_SIZE=1).</li>
402
Chris Lattner58504a62006-02-05 06:39:36 +0000[diff] [blame]403</ul>
404</div>
John Criswelle531ec52005-06-29 16:22:34 +0000[diff] [blame]405
Chris Lattnerbfb17ab2007-05-17 21:41:31 +0000[diff] [blame]406<!--_________________________________________________________________________-->
407<div class="doc_subsubsection"><a name="apichanges">API Changes</a></div>
408<div class="doc_text">
409
410<p>LLVM 2.0 contains a revamp of the type system and several other significant
411internal changes. If you are programming to the C++ API, be aware of the
412following major changes:</p>
413
414<ul>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]415<li>Pass registration is slightly different in LLVM 2.0 (you now need an
Chris Lattnerbfb17ab2007-05-17 21:41:31 +0000[diff] [blame]416 intptr_t in your constructor), as explained in the <a
417 href="WritingAnLLVMPass.html#basiccode">Writing an LLVM Pass</a>
418 document.</li>
419
420<li><tt>ConstantBool</tt>, <tt>ConstantIntegral</tt> and <tt>ConstantInt</tt>
421 classes have been merged together, we now just have
422 <tt>ConstantInt</tt>.</li>
423
424<li><tt>Type::IntTy</tt>, <tt>Type::UIntTy</tt>, <tt>Type::SByteTy</tt>, ... are
425 replaced by <tt>Type::Int8Ty</tt>, <tt>Type::Int16Ty</tt>, etc. LLVM types
426 have always corresponded to fixed size types
427 (e.g. long was always 64-bits), but the type system no longer includes
428 information about the sign of the type.</li>
429
430<li>Several classes (<tt>CallInst</tt>, <tt>GetElementPtrInst</tt>,
431 <tt>ConstantArray</tt>, etc), that once took <tt>std::vector</tt> as
432 arguments now take ranges instead. For example, you can create a
433 <tt>GetElementPtrInst</tt> with code like:
434
435 <pre>
436 Value *Ops[] = { Op1, Op2, Op3 };
437 GEP = new GetElementPtrInst(BasePtr, Ops, 3);
438 </pre>
439
440 This avoids creation of a temporary vector (and a call to malloc/free). If
441 you have an std::vector, use code like this:
442 <pre>
443 std::vector&lt;Value*&gt; Ops = ...;
444 GEP = new GetElementPtrInst(BasePtr, &amp;Ops[0], Ops.size());
445 </pre>
446
447 </li>
448
449<li>CastInst is now abstract and its functionality is split into several parts,
450 one for each of the <a href="LangRef.html#convertops">new cast
451 instructions</a>.</li>
452
453<li><tt>Instruction::getNext()/getPrev()</tt> are now private (along with
454 <tt>BasicBlock::getNext</tt>, etc), for efficiency reasons (they are now no
455 longer just simple pointers). Please use BasicBlock::iterator, etc instead.
456</li>
457
458<li><tt>Module::getNamedFunction()</tt> is now called
459 <tt>Module::getFunction()</tt>.</li>
460
461<li><tt>SymbolTable.h</tt> has been split into <tt>ValueSymbolTable.h</tt> and
462<tt>TypeSymbolTable.h</tt>.</li>
463</ul>
464</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]465
466
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]467<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]468<div class="doc_section">
469 <a name="portability">Portability and Supported Platforms</a>
470</div>
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]471<!-- *********************************************************************** -->
472
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]473<div class="doc_text">
474
John Criswell0b5b5e92004-12-08 20:35:47 +0000[diff] [blame]475<p>LLVM is known to work on the following platforms:</p>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]476
477<ul>
Reid Spencer00812e22005-05-17 02:47:27 +0000[diff] [blame]478 <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
479 (and probably other unix-like systems).</li>
Chris Lattner7ea41e32006-08-09 04:10:32 +0000[diff] [blame]480<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]481<li>Sun UltraSPARC workstations running Solaris 8.</li>
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]482<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
483 support is available for native builds with Visual C++).</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]484<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
485 64-bit modes.</li>
John Criswell9321fa82005-05-13 20:28:15 +0000[diff] [blame]486<li>Alpha-based machines running Debian GNU/Linux.</li>
487<li>Itanium-based machines running Linux and HP-UX.</li>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]488</ul>
489
Brian Gaekeb0fd7612004-05-09 05:28:35 +0000[diff] [blame]490<p>The core LLVM infrastructure uses
491<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
492to the machine and operating system on which it is built. However, minor
493porting may be required to get LLVM to work on new platforms. We welcome your
494portability patches and reports of successful builds or error messages.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]495
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]496</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]497
498<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]499<div class="doc_section">
500 <a name="knownproblems">Known Problems</a>
501</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]502<!-- *********************************************************************** -->
503
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]504<div class="doc_text">
505
506<p>This section contains all known problems with the LLVM system, listed by
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]507component. As new problems are discovered, they will be added to these
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]508sections. If you run into a problem, please check the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]509href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]510there isn't already one.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]511
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]512</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]513
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]514<!-- ======================================================================= -->
515<div class="doc_subsection">
516 <a name="experimental">Experimental features included with this release</a>
517</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]518
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]519<div class="doc_text">
520
Misha Brukman6df9e2c2004-05-12 21:46:05 +0000[diff] [blame]521<p>The following components of this LLVM release are either untested, known to
522be broken or unreliable, or are in early development. These components should
523not be relied on, and bugs should not be filed against them, but they may be
524useful to some people. In particular, if you would like to work on one of these
Chris Lattner49e693e2006-08-09 04:08:52 +0000[diff] [blame]525components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]526
527<ul>
Chris Lattner44c933e2006-04-18 06:18:36 +0000[diff] [blame]528<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a
529 future release.</li>
Chris Lattner0d77e052007-05-09 06:23:58 +0000[diff] [blame]530<li>C++ EH support</li>
Chris Lattner58504a62006-02-05 06:39:36 +0000[diff] [blame]531<li>The IA64 code generator is experimental.</li>
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]532<li>The Alpha JIT is experimental.</li>
Chris Lattner44c933e2006-04-18 06:18:36 +0000[diff] [blame]533<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
534 <tt>-filetype</tt> llc option.</li>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]535</ul>
536
537</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]538
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]539<!-- ======================================================================= -->
540<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]541 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]542</div>
543
544<div class="doc_text">
545
546<ul>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]547<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]548 assembly that uses the X86 floating point stack</a>.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]549</ul>
550
551</div>
552
553<!-- ======================================================================= -->
554<div class="doc_subsection">
555 <a name="ppc-be">Known problems with the PowerPC back-end</a>
556</div>
557
558<div class="doc_text">
559
560<ul>
561<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
562implement ordered FP comparisons</a>.</li>
Nicolas Geoffraye4285dc2007-05-15 09:21:28 +0000[diff] [blame]563<li>The Linux PPC32/ABI support needs testing for the interpreter and static
564compilation, and lacks Dwarf debugging informations.
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]565</ul>
566
567</div>
568
569<!-- ======================================================================= -->
570<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]571 <a name="arm-be">Known problems with the ARM back-end</a>
572</div>
573
574<div class="doc_text">
575
576<ul>
577<li>The Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
578processors, any thumb program compiled with LLVM crashes or produces wrong
579results. (<a href="http://llvm.org/PR1388">PR1388</a>)</li>
580<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
581</li>
582<li>QEMU-ARM (<= 0.9.0) wrongly executes programs compiled with LLVM. A non-affected QEMU version must be used or this
Chris Lattnerbcd10f12007-05-17 22:03:43 +0000[diff] [blame]583<a href="http://cvs.savannah.nongnu.org/viewcvs/qemu/target-arm/translate.c?root=qemu&amp;r1=1.46&amp;r2=1.47&amp;makepatch=1&amp;diff_format=h">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]584patch</a> must be applied on QEMU.</li>
585</ul>
586
587</div>
588
589<!-- ======================================================================= -->
590<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]591 <a name="sparc-be">Known problems with the SPARC back-end</a>
592</div>
593
594<div class="doc_text">
595
596<ul>
597<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
598 support the 64-bit SPARC ABI (-m64).</li>
599</ul>
600
601</div>
602
603<!-- ======================================================================= -->
604<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]605 <a name="alpha-be">Known problems with the Alpha back-end</a>
606</div>
607
608<div class="doc_text">
609
610<ul>
611
612<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
613appropriate nops inserted to ensure restartability.</li>
614
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]615</ul>
616</div>
617
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]618<!-- ======================================================================= -->
619<div class="doc_subsection">
620 <a name="ia64-be">Known problems with the IA64 back-end</a>
621</div>
622
623<div class="doc_text">
624
625<ul>
626
627<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
628made where the argument is not 16-byte aligned, as required on IA64. (Strictly
629speaking this is not a bug in the IA64 back-end; it will also be encountered
630when building C++ programs using the C back-end.)</li>
631
632<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
633ABI compliant layout of v-tables</a>. In particular, it just stores function
634pointers instead of function descriptors in the vtable. This bug prevents
635mixing C++ code compiled with LLVM with C++ objects compiled by other C++
636compilers.</li>
637
638<li>There are a few ABI violations which will lead to problems when mixing LLVM
639output with code built with other compilers, particularly for floating-point
640programs.</li>
641
642<li>Defining vararg functions is not supported (but calling them is ok).</li>
643
Chris Lattnercaf06342007-05-09 04:58:11 +0000[diff] [blame]644<li>The Itanium backend has bitrotted somewhat.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]645</ul>
646
647</div>
648
649<!-- ======================================================================= -->
650<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]651 <a name="c-be">Known problems with the C back-end</a>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]652</div>
653
654<div class="doc_text">
655
656<ul>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]657<li><a href="http://llvm.org/PR802">The C backend does not support inline
658 assembly code</a>.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]659</ul>
660
661</div>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]662
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]663
664<!-- ======================================================================= -->
665<div class="doc_subsection">
666 <a name="c-fe">Known problems with the C front-end</a>
667</div>
Chris Lattner47588f92003-10-02 05:07:23 +0000[diff] [blame]668
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]669<!-- _______________________________________________________________________ -->
Chris Lattnerb40efb32003-12-14 05:03:43 +0000[diff] [blame]670<div class="doc_subsubsection">Bugs</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]671
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]672<div class="doc_text">
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]673
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]674<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
675Optimization</a> on most platforms "out-of-the-box". Please inquire on the
676llvmdev mailing list if you are interested.</p>
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000[diff] [blame]677
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]678</div>
679
680<!-- _______________________________________________________________________ -->
681<div class="doc_subsubsection">
682 Notes
683</div>
684
685<div class="doc_text">
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]686<ul>
687
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]688<li><p>"long double" is silently transformed by the front-end into "double". There
689is no support for floating point data types of any size other than 32 and 64
690bits.</p></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]691
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]692<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
693 See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
694</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]695
Duncan Sands32a83442007-05-18 09:04:20 +0000[diff] [blame^]696<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]697 <ol>
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]698 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.<br>
699 Nested functions are supported, but llvm-gcc does not support non-local
700 gotos or taking the address of a nested function.</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]701
702 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]703
John Criswelld000e1d2003-12-18 16:43:17 +0000[diff] [blame]704 Declaring that functions have no side effects or that they can never
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]705 return.<br>
706
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]707 <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
708 <tt>constructor</tt>, <tt>destructor</tt>,
Anton Korobeynikov9413de32006-11-18 08:04:48 +0000[diff] [blame]709 <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
Anton Korobeynikov9ec81372007-05-10 08:26:24 +0000[diff] [blame]710 <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, <tt>regparm</tt>
Anton Korobeynikov8cea37b2007-01-23 12:35:46 +0000[diff] [blame]711 <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
712 <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]713
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]714 <b>Ignored:</b> <tt>noinline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
715 <tt>malloc</tt>, <tt>no_instrument_function</tt></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]716 </ol>
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]717</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]718
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]719<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]720
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]721 <ol>
Chris Lattnerd09c4ec2007-05-17 22:02:24 +0000[diff] [blame]722 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
723 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
724 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
725 Other built-in functions.</li>
726 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
727 Specifying attributes of variables.</li>
728 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
729 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
730 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
731 Arrays whose length is computed at run time.</li>
Chris Lattner7fe97dd2004-03-16 08:54:07 +0000[diff] [blame]732 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]733 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
734 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li>
Tanya Lattnerca26c3e2004-06-22 03:48:17 +0000[diff] [blame]735 <li><a href="http://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]736 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
737 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
738 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
739 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
740 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
741 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
742 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li>
743 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]744 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li>
745 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
746 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li>
747 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li>
748 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li>
749 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]750 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li>
Misha Brukmanc4b7bee2003-12-12 04:37:31 +0000[diff] [blame]751 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]752 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
John Criswelld000e1d2003-12-18 16:43:17 +0000[diff] [blame]753 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
754or arrays as values.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]755 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
Misha Brukmanc4b7bee2003-12-12 04:37:31 +0000[diff] [blame]756 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]757 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
758 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
759 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
Tanya Lattner78537e42004-12-08 18:29:38 +0000[diff] [blame]760 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Comments.html#C_002b_002b-Comments">C++ Comments</a>: C++ comments are recognized.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]761 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
762 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character &lt;ESC&gt;.</li>
763 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
764 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
765 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li>
766 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li>
767 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li>
Chris Lattner25795bc2004-02-14 04:08:29 +0000[diff] [blame]768 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]769 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li>
770 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
Misha Brukmane0c891c2003-11-22 01:00:11 +0000[diff] [blame]771 </ol></li>
772
773</ul>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]774
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]775<p>If you run into GCC extensions which have not been included in any of these
776lists, please let us know (also including whether or not they work).</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]777
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]778</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]779
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]780<!-- ======================================================================= -->
781<div class="doc_subsection">
782 <a name="c++-fe">Known problems with the C++ front-end</a>
783</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]784
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]785<div class="doc_text">
786
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]787<p>The C++ front-end is considered to be fully
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]788tested and works for a number of non-trivial programs, including LLVM
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]789itself, Qt, Mozilla, etc.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]790
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]791<ul>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]792<li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++
793Exception Handling</a>, and it is not enabled by default.</li>
794
795<!-- NO EH Support!
Chris Lattnere01fcfb2003-10-27 18:30:37 +0000[diff] [blame]796
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]797<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]798 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]799 function and in the <tt>setjmp</tt> receiver function may not be run.
John Criswelld000e1d2003-12-18 16:43:17 +0000[diff] [blame]800 Objects in intervening stack frames will be destroyed, however (which is
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]801 better than most compilers).</li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]802
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]803<li>The LLVM C++ front-end follows the <a
804 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
805 This document, which is not Itanium specific, specifies a standard for name
806 mangling, class layout, v-table layout, RTTI formats, and other C++
807 representation issues. Because we use this API, code generated by the LLVM
808 compilers should be binary compatible with machine code generated by other
809 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]810 <i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]811 different from the model used in the Itanium ABI, so <b>exceptions will not
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]812 interact correctly</b>. </li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]813-->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]814</ul>
Chris Lattnerfcc54b32003-10-07 22:14:37 +0000[diff] [blame]815
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]816</div>
817
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]818
Chris Lattner98a493c2005-05-15 16:01:20 +0000[diff] [blame]819
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]820<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]821<div class="doc_section">
822 <a name="additionalinfo">Additional Information</a>
823</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]824<!-- *********************************************************************** -->
825
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]826<div class="doc_text">
827
Chris Lattner416db102005-05-16 17:13:10 +0000[diff] [blame]828<p>A wide variety of additional information is available on the <a
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]829href="http://llvm.org">LLVM web page</a>, in particular in the <a
830href="http://llvm.org/docs/">documentation</a> section. The web page also
831contains versions of the API documentation which is up-to-date with the CVS
832version of the source code.
Misha Brukman109d9e82005-03-30 19:14:24 +0000[diff] [blame]833You can access versions of these documents specific to this release by going
834into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]835
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]836<p>If you have any questions or comments about LLVM, please feel free to contact
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]837us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]838lists</a>.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]839
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]840</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]841
842<!-- *********************************************************************** -->
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]843
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]844<hr>
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]845<address>
Misha Brukman38847d52003-12-21 22:53:21 +0000[diff] [blame]846 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]847 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
848 <a href="http://validator.w3.org/check/referer"><img
849 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
850
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]851 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]852 Last modified: $Date$
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]853</address>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]854
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]855</body>
856</html>