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Dan Gohmanb44f6c62010-05-03 23:51:05 +00007 <title>LLVM 2.8 Release Notes</title>
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9<body>
Chris Lattner79c3fe12003-10-02 04:57:28 +000010
Dan Gohmanb44f6c62010-05-03 23:51:05 +000011<div class="doc_title">LLVM 2.8 Release Notes</div>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +000012
Chris Lattner0e464a92010-03-17 04:02:39 +000013<img align=right src="http://llvm.org/img/DragonSmall.png"
Gabor Greifee2187a2010-04-22 10:21:43 +000014 width="136" height="136" alt="LLVM Dragon Logo">
Chris Lattner0e464a92010-03-17 04:02:39 +000015
Chris Lattner79c3fe12003-10-02 04:57:28 +000016<ol>
Misha Brukman500bc302003-11-22 00:38:41 +000017 <li><a href="#intro">Introduction</a></li>
Chris Lattner96a445e2008-10-13 18:01:01 +000018 <li><a href="#subproj">Sub-project Status Update</a></li>
Dan Gohmanb44f6c62010-05-03 23:51:05 +000019 <li><a href="#externalproj">External Projects Using LLVM 2.8</a></li>
20 <li><a href="#whatsnew">What's New in LLVM 2.8?</a></li>
Chris Lattner4b538b92004-04-30 22:17:12 +000021 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Dan Gohman44aa9212008-10-14 16:23:02 +000022 <li><a href="#knownproblems">Known Problems</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +000023 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +000024</ol>
25
Chris Lattner7911ce22004-05-23 21:07:27 +000026<div class="doc_author">
Dan Gohman44aa9212008-10-14 16:23:02 +000027 <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
Misha Brukman500bc302003-11-22 00:38:41 +000028</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000029
Chris Lattnere07043c2010-09-29 05:30:03 +000030<!--
Chris Lattner7b91eda2010-04-22 05:41:35 +000031<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
Jeffrey Yasskinbec48772010-01-28 01:14:43 +000032release.<br>
33You may prefer the
Dan Gohmanb44f6c62010-05-03 23:51:05 +000034<a href="http://llvm.org/releases/2.7/docs/ReleaseNotes.html">LLVM 2.7
35Release Notes</a>.</h1>
Chris Lattnere07043c2010-09-29 05:30:03 +000036-->
Jeffrey Yasskinbec48772010-01-28 01:14:43 +000037
Chris Lattner79c3fe12003-10-02 04:57:28 +000038<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +000039<div class="doc_section">
40 <a name="intro">Introduction</a>
41</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +000042<!-- *********************************************************************** -->
43
Misha Brukman500bc302003-11-22 00:38:41 +000044<div class="doc_text">
45
Chris Lattnerf6662f92008-10-13 17:57:36 +000046<p>This document contains the release notes for the LLVM Compiler
Dan Gohman7ae3ac82010-05-03 23:52:21 +000047Infrastructure, release 2.8. Here we describe the status of LLVM, including
Chris Lattnerf6662f92008-10-13 17:57:36 +000048major improvements from the previous release and significant known problems.
Mikhail Glushenkovf795ef02009-03-01 18:09:47 +000049All LLVM releases may be downloaded from the <a
Chris Lattnerf6662f92008-10-13 17:57:36 +000050href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
Chris Lattner19092612003-10-02 16:38:05 +000051
Chris Lattner7506b1d2004-12-07 08:04:13 +000052<p>For more information about LLVM, including information about the latest
Chris Lattnerc463b272005-10-29 07:07:09 +000053release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattner47ad72c2003-10-07 21:38:31 +000054web site</a>. If you have questions or comments, the <a
Chris Lattnerc66bfef2010-03-17 04:41:49 +000055href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
56Mailing List</a> is a good place to send them.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +000057
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +000058<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattner84977642007-09-21 03:54:09 +000059main LLVM web page, this document applies to the <i>next</i> release, not the
Gabor Greiffa933f82008-10-14 11:00:32 +000060current one. To see the release notes for a specific release, please see the
Chris Lattner84977642007-09-21 03:54:09 +000061<a href="http://llvm.org/releases/">releases page</a>.</p>
Misha Brukman500bc302003-11-22 00:38:41 +000062
63</div>
Chris Lattner61358ab2009-10-13 17:48:04 +000064
Chris Lattner79c3fe12003-10-02 04:57:28 +000065
Chris Lattner61358ab2009-10-13 17:48:04 +000066<!--
67Almost dead code.
68 include/llvm/Analysis/LiveValues.h => Dan
69 lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
70 llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
Chris Lattner61c70e92010-08-28 04:09:24 +000071 GEPSplitterPass
Chris Lattner61358ab2009-10-13 17:48:04 +000072-->
73
74
Chris Lattnere07043c2010-09-29 05:30:03 +000075<!-- Features that need text if they're finished for 2.9:
Chris Lattner914ce462010-04-22 06:28:20 +000076 combiner-aa?
Chris Lattner61358ab2009-10-13 17:48:04 +000077 strong phi elim
Chris Lattner61358ab2009-10-13 17:48:04 +000078 loop dependence analysis
Chris Lattner885b6612010-08-28 16:33:36 +000079 TBAA
Chris Lattnere07043c2010-09-29 05:30:03 +000080 CorrelatedValuePropagation
Chris Lattneracce85d2008-02-10 07:46:44 +000081 -->
Chris Lattnere07043c2010-09-29 05:30:03 +000082
83 <!-- Announcement, lldb, libc++ -->
Chris Lattnerafa41632010-09-29 07:25:03 +000084
85 <!-- to write:
86 MachineCSE tuned and on by default.
87 llvm.dbg.value: variable debug info for optimized code
88 MC Assembler backend is now real, does relaxation and is bitwise identical
89 with darwin assembler in huge majority of all cases.
90 new GHC calling convention
91 New half float intrinsics LangRef.html#int_fp16
92 Rewrote tblgen's type inference for backends to be more consistent and
93 diagnose more target bugs. This also allows limited support for writing
94 patterns for instructions that return multiple results, e.g. a virtual
95 register and a flag result. Stuff that used 'parallel' before should use
96 this.
97 New ARM/Thumb disassembler support in MC.
98 New SSEDomainFix pass:
99 On Nehalem and newer CPUs there is a 2 cycle latency penalty on using a
100 register in a different domain than where it was defined. Some instructions
101 have equvivalents for different domains, like por/orps/orpd. The
102 SSEDomainFix pass tries to minimize the number of domain crossings by
103 changing between equvivalent opcodes where possible.
104 Support for the Intel AES instructions in the assembler.
105 memcpy, memmove, and memset now take address space qualified pointers + volatile.
Chris Lattner4ba2b652010-09-30 16:31:33 +0000106 per-instruction debug info metadata is much faster and uses less space (new DebugLoc class).
107 -ffunction-sections and -fdata-sections are supported on ELF targets.
108 Now iterate function passes when a cgsccpassmanager detects a devirtualization
109 -momit-leaf-frame-pointer now supported.
110 New -regalloc=fast, =local got removed
111 New -regalloc=default option that chooses a register allocator based on the -O optimization level.
112 New "trap values" concept: http://llvm.org/docs/LangRef.html#trapvalues
113 Improved trip count analysis for <= and >= loops, and uses sign overflow info.
114 REMOVED: SCCVN pass.
115 X86 backend attempts to promote 16-bit integer operations to 32-bits to avoid
116 0x66 prefixes, which are slow on some microarchitectures and bloat the code
117 on others.
118 X87 fp stackifier is global!
119 LTO debug info support?
120 NEON: Better performance for QQQQ (4-consecutive Q register) instructions. New reg sequence abstraction?
121 New support for X86 "thiscall" calling convention (x86_thiscallcc in IR).
122 ARM: Better scheduling (list-hybrid, hybrid?)
123 New SubRegIndex tblgen class for targets -> jakob
124 ARM: Tail call support.
125 AVX support in the MC assembler. Full compiler support not done yet.
126 Atomics now get legalized when not natively supported (jim g)
127 ARM: General performance work and tuning.
Chris Lattnerafa41632010-09-29 07:25:03 +0000128 -->
129
Chris Lattneracce85d2008-02-10 07:46:44 +0000130
Chris Lattner96a445e2008-10-13 18:01:01 +0000131<!-- *********************************************************************** -->
132<div class="doc_section">
133 <a name="subproj">Sub-project Status Update</a>
Chris Lattnerea34f642008-06-08 21:34:41 +0000134</div>
Chris Lattner96a445e2008-10-13 18:01:01 +0000135<!-- *********************************************************************** -->
Chris Lattnerea34f642008-06-08 21:34:41 +0000136
137<div class="doc_text">
Chris Lattner8348b472008-06-08 21:58:17 +0000138<p>
Dan Gohmanb44f6c62010-05-03 23:51:05 +0000139The LLVM 2.8 distribution currently consists of code from the core LLVM
Chris Lattner61358ab2009-10-13 17:48:04 +0000140repository (which roughly includes the LLVM optimizers, code generators
141and supporting tools), the Clang repository and the llvm-gcc repository. In
142addition to this code, the LLVM Project includes other sub-projects that are in
143development. Here we include updates on these subprojects.
Bill Wendling63d8c552009-03-02 04:28:57 +0000144</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000145
Chris Lattner8348b472008-06-08 21:58:17 +0000146</div>
147
Chris Lattner96a445e2008-10-13 18:01:01 +0000148
Chris Lattner8348b472008-06-08 21:58:17 +0000149<!--=========================================================================-->
Chris Lattner96a445e2008-10-13 18:01:01 +0000150<div class="doc_subsection">
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000151<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000152</div>
153
154<div class="doc_text">
155
Chris Lattner095539f2010-04-26 17:42:18 +0000156<p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
157C++, and Objective-C languages. Clang aims to provide a better user experience
158through expressive diagnostics, a high level of conformance to language
159standards, fast compilation, and low memory use. Like LLVM, Clang provides a
160modular, library-based architecture that makes it suitable for creating or
161integrating with other development tools. Clang is considered a
Chris Lattnere07043c2010-09-29 05:30:03 +0000162production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
163(32- and 64-bit), and for darwin-arm targets.</p>
Chris Lattner61358ab2009-10-13 17:48:04 +0000164
Chris Lattner922d00f2010-07-21 15:57:40 +0000165<p>In the LLVM 2.8 time-frame, the Clang team has made many improvements:</p>
Bill Wendling741748a2008-10-27 09:27:33 +0000166
Daniel Dunbar13739432008-10-14 23:25:09 +0000167<ul>
Chris Lattnere07043c2010-09-29 05:30:03 +0000168<li>Surely these guys have done something</li>
Chris Lattner4ba2b652010-09-30 16:31:33 +0000169<li>X86-64 abi improvements? Did they make it in?</li>
Bill Wendling6bc15282009-03-02 04:28:18 +0000170</ul>
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000171</div>
172
173<!--=========================================================================-->
174<div class="doc_subsection">
175<a name="clangsa">Clang Static Analyzer</a>
176</div>
177
178<div class="doc_text">
179
Chris Lattner8cdd7932010-04-22 06:38:11 +0000180<p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a>
181 project is an effort to use static source code analysis techniques to
182 automatically find bugs in C and Objective-C programs (and hopefully <a
183 href="http://clang-analyzer.llvm.org/dev_cxx.html">C++ in the
184 future</a>!). The tool is very good at finding bugs that occur on specific
185 paths through code, such as on error conditions.</p>
Chris Lattnercc042612008-10-14 00:52:49 +0000186
Chris Lattner2e38c7f2010-09-30 00:34:43 +0000187<p>The LLVM 2.8 release fixes a number of bugs and slightly improves precision
188 over 2.7, but there are no major new features in the release.
Chris Lattner8cdd7932010-04-22 06:38:11 +0000189</p>
Chris Lattner8348b472008-06-08 21:58:17 +0000190
191</div>
192
Chris Lattner96a445e2008-10-13 18:01:01 +0000193<!--=========================================================================-->
194<div class="doc_subsection">
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000195<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
Chris Lattner96a445e2008-10-13 18:01:01 +0000196</div>
197
198<div class="doc_text">
199<p>
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000200The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
Chris Lattner61358ab2009-10-13 17:48:04 +0000201a JVM and a CLI Virtual Machine (Microsoft .NET is an
202implementation of the CLI) using LLVM for static and just-in-time
203compilation.</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000204
Chris Lattner922d00f2010-07-21 15:57:40 +0000205<p>With the release of LLVM 2.8, ...</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000206
207</div>
208
Chris Lattner61358ab2009-10-13 17:48:04 +0000209
210<!--=========================================================================-->
211<div class="doc_subsection">
212<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
213</div>
214
215<div class="doc_text">
216<p>
217The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
218is a simple library that provides an implementation of the low-level
219target-specific hooks required by code generation and other runtime components.
220For example, when compiling for a 32-bit target, converting a double to a 64-bit
221unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
222function. The compiler-rt library provides highly optimized implementations of
223this and other low-level routines (some are 3x faster than the equivalent
224libgcc routines).</p>
225
226<p>
227All of the code in the compiler-rt project is available under the standard LLVM
Chris Lattner922d00f2010-07-21 15:57:40 +0000228License, a "BSD-style" license. New in LLVM 2.8:
229
230Soft float support
231</p>
Chris Lattner61358ab2009-10-13 17:48:04 +0000232
233</div>
234
235<!--=========================================================================-->
236<div class="doc_subsection">
Duncan Sands749fd832010-04-02 09:23:15 +0000237<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
Chris Lattner61358ab2009-10-13 17:48:04 +0000238</div>
239
240<div class="doc_text">
241<p>
Duncan Sands749fd832010-04-02 09:23:15 +0000242<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
243gcc-4.5. Unlike llvm-gcc, which makes many intrusive changes to the underlying
244gcc-4.2 code, dragonegg in theory does not require any gcc-4.5 modifications
245whatsoever (currently one small patch is needed). This is thanks to the new
246<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>, which
247makes it possible to modify the behaviour of gcc at runtime by loading a plugin,
248which is nothing more than a dynamic library which conforms to the gcc plugin
249interface. DragonEgg is a gcc plugin that causes the LLVM optimizers to be run
250instead of the gcc optimizers, and the LLVM code generators instead of the gcc
251code generators, just like llvm-gcc. To use it, you add
252"-fplugin=path/dragonegg.so" to the gcc-4.5 command line, and gcc-4.5 magically
253becomes llvm-gcc-4.5!
254</p>
255
256<p>
257DragonEgg is still a work in progress. Currently C works very well, while C++,
258Ada and Fortran work fairly well. All other languages either don't work at all,
259or only work poorly. For the moment only the x86-32 and x86-64 targets are
Duncan Sands51a51742010-04-20 19:40:58 +0000260supported, and only on linux and darwin (darwin needs an additional gcc patch).
Duncan Sands749fd832010-04-02 09:23:15 +0000261</p>
262
263<p>
Chris Lattner922d00f2010-07-21 15:57:40 +00002642.8 status here.
Chris Lattner61358ab2009-10-13 17:48:04 +0000265</p>
266
267</div>
268
269
270<!--=========================================================================-->
271<div class="doc_subsection">
Chris Lattnere07043c2010-09-29 05:30:03 +0000272<a name="lldb">LLDB: Low Level Debugger</a>
273</div>
274
275<div class="doc_text">
276<p>
277<a href="http://lldb.llvm.org/">LLDB</a> is</p>
278
279<p>
280</p>
281
282<p>
2832.8 status here.
284</p>
285
286</div>
287
288<!--=========================================================================-->
289<div class="doc_subsection">
290<a name="libc++">libc++: C++ Standard Library</a>
291</div>
292
293<div class="doc_text">
294<p>
295<a href="http://libc++.llvm.org/">libc++</a> is</p>
296
297<p>
298</p>
299
300<p>
3012.8 status here.
302</p>
303
304</div>
305
Chris Lattner61358ab2009-10-13 17:48:04 +0000306
Chris Lattnerab68e9e2009-02-26 22:33:38 +0000307<!-- *********************************************************************** -->
308<div class="doc_section">
Chris Lattner922d00f2010-07-21 15:57:40 +0000309 <a name="externalproj">External Open Source Projects Using LLVM 2.8</a>
Chris Lattnerab68e9e2009-02-26 22:33:38 +0000310</div>
311<!-- *********************************************************************** -->
312
Chris Lattner61358ab2009-10-13 17:48:04 +0000313<div class="doc_text">
314
315<p>An exciting aspect of LLVM is that it is used as an enabling technology for
316 a lot of other language and tools projects. This section lists some of the
Chris Lattner922d00f2010-07-21 15:57:40 +0000317 projects that have already been updated to work with LLVM 2.8.</p>
Chris Lattner7c8e7962010-04-26 17:38:10 +0000318</div>
319
Chris Lattner2e38c7f2010-09-30 00:34:43 +0000320<!--=========================================================================-->
321<div class="doc_subsection">
322<a name="tce">TTA-based Codesign Environment (TCE)</a>
323</div>
324
325<div class="doc_text">
326<p>
327<a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
328application-specific processors (ASP) based on the Transport triggered
329architecture (TTA). The toolset provides a complete co-design flow from C/C++
330programs down to synthesizable VHDL and parallel program binaries. Processor
331customization points include the register files, function units, supported
332operations, and the interconnection network.</p>
333
334<p>TCE uses llvm-gcc/Clang and LLVM for C/C++ language support, target
335independent optimizations and also for parts of code generation. It generates
336new LLVM-based code generators "on the fly" for the designed TTA processors and
337loads them in to the compiler backend as runtime libraries to avoid per-target
338recompilation of larger parts of the compiler chain.</p>
339
340</div>
341
342<!--=========================================================================-->
343<div class="doc_subsection">
344<a name="Horizon">Horizon Bytecode Compiler</a>
345</div>
346
347<div class="doc_text">
348<p>
349<a href="http://www.quokforge.org/projects/horizon">Horizon</a> is a bytecode
350language and compiler written on top of LLVM, intended for producing
351single-address-space managed code operating systems that
352run faster than the equivalent multiple-address-space C systems.
353More in-depth blurb is available on <a
354href="http://www.quokforge.org/projects/horizon/wiki/Wiki">the wiki</a>.</p>
355
356</div>
357
358<!--=========================================================================-->
359<div class="doc_subsection">
360<a name="clamav">Clam AntiVirus</a>
361</div>
362
363<div class="doc_text">
364<p>
365<a href=http://www.clamav.net>Clam AntiVirus</a> is an open source (GPL)
366anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail
367gateways. Since version 0.96 it has <a
368href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
369signatures</a> that allow writing detections for complex malware. It
370uses LLVM's JIT to speed up the execution of bytecode on
371X86,X86-64,PPC32/64, falling back to its own interpreter otherwise.
372The git version was updated to work with LLVM 2.8
373</p>
374
375<p>The <a
376href="http://git.clamav.net/gitweb?p=clamav-bytecode-compiler.git;a=blob_plain;f=docs/user/clambc-user.pdf">
377ClamAV bytecode compiler</a> uses Clang and LLVM to compile a C-like
378language, insert runtime checks, and generate ClamAV bytecode.</p>
379
380</div>
381
382<!--=========================================================================-->
383<div class="doc_subsection">
384<a name="pure">Pure</a>
385</div>
386
387<div class="doc_text">
388<p>
389<a href="http://pure-lang.googlecode.com/">Pure</a>
390is an algebraic/functional
391programming language based on term rewriting. Programs are collections
392of equations which are used to evaluate expressions in a symbolic
393fashion. Pure offers dynamic typing, eager and lazy evaluation, lexical
394closures, a hygienic macro system (also based on term rewriting),
395built-in list and matrix support (including list and matrix
396comprehensions) and an easy-to-use C interface. The interpreter uses
397LLVM as a backend to JIT-compile Pure programs to fast native code.</p>
398
399<p>Pure versions 0.44 and later have been tested and are known to work with
400LLVM 2.8 (and continue to work with older LLVM releases >= 2.5).</p>
401
402</div>
403
404<!--=========================================================================-->
405<div class="doc_subsection">
406<a name="GHC">Glasgow Haskell Compiler (GHC)</a>
407</div>
408
409<div class="doc_text">
410<p>
411<a href="http://www.haskell.org/ghc/">GHC</a> is an open source,
412state-of-the-art programming suite for
413Haskell, a standard lazy functional programming language. It includes
414an optimizing static compiler generating good code for a variety of
415platforms, together with an interactive system for convenient, quick
416development.</p>
417
418<p>In addition to the existing C and native code generators, GHC 7.0 now
419supports an <a
420href="http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVM">LLVM
421code generator</a>. GHC supports LLVM 2.7 and later.</p>
422
423</div>
424
425<!--=========================================================================-->
426<div class="doc_subsection">
427<a name="Clay">Clay Programming Language</a>
428</div>
429
430<div class="doc_text">
431<p>
Chris Lattner97fe6452010-09-30 01:12:09 +0000432<a href="http://tachyon.in/clay/">Clay</a> is a new systems programming
Chris Lattner2e38c7f2010-09-30 00:34:43 +0000433language that is specifically designed for generic programming. It makes
434generic programming very concise thanks to whole program type propagation. It
435uses LLVM as its backend.</p>
436
437</div>
Chris Lattner3a1d4cf2010-04-22 21:34:16 +0000438
Chris Lattner8348b472008-06-08 21:58:17 +0000439<!-- *********************************************************************** -->
440<div class="doc_section">
Chris Lattner922d00f2010-07-21 15:57:40 +0000441 <a name="whatsnew">What's New in LLVM 2.8?</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000442</div>
443<!-- *********************************************************************** -->
444
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000445<div class="doc_text">
446
Chris Lattner61358ab2009-10-13 17:48:04 +0000447<p>This release includes a huge number of bug fixes, performance tweaks and
Chris Lattnerf6662f92008-10-13 17:57:36 +0000448minor improvements. Some of the major improvements and new features are listed
449in this section.
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000450</p>
Chris Lattner61358ab2009-10-13 17:48:04 +0000451
Chris Lattner914ce462010-04-22 06:28:20 +0000452</div>
453
454<!--=========================================================================-->
455<div class="doc_subsection">
456<a name="orgchanges">LLVM Community Changes</a>
457</div>
458
459<div class="doc_text">
460
Chris Lattner922d00f2010-07-21 15:57:40 +0000461<p>In addition to changes to the code, between LLVM 2.7 and 2.8, a number of
Chris Lattnerb7c85b42010-04-21 05:17:40 +0000462organization changes have happened:
463</p>
464
465<ul>
Chris Lattnere07043c2010-09-29 05:30:03 +0000466<li>libc++ and lldb are new</li>
Chris Lattnerafa41632010-09-29 07:25:03 +0000467<li>Debugging optimized code support.</li>
Chris Lattnerb7c85b42010-04-21 05:17:40 +0000468</ul>
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000469</div>
470
Chris Lattner8348b472008-06-08 21:58:17 +0000471<!--=========================================================================-->
Chris Lattnerea34f642008-06-08 21:34:41 +0000472<div class="doc_subsection">
Chris Lattner252b83d2008-02-06 18:00:06 +0000473<a name="majorfeatures">Major New Features</a>
474</div>
475
476<div class="doc_text">
477
Chris Lattner922d00f2010-07-21 15:57:40 +0000478<p>LLVM 2.8 includes several major new capabilities:</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000479
480<ul>
Chris Lattner8dc5faf2010-09-05 20:49:45 +0000481<li>atomic lowering pass.</li>
482<li>RegionInfo pass: opt -regions analyze" or "opt -view-regions".
483<!-- Tobias Grosser --></li>
484<li>ARMGlobalMerge: <!-- Anton --> </li>
Chris Lattner702f2d42010-09-06 19:14:40 +0000485<li>llvm-diff</li>
Chris Lattner8170c102008-02-10 08:18:42 +0000486</ul>
Chris Lattnerdc910082010-03-17 06:41:58 +0000487
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000488</div>
489
Chris Lattner84977642007-09-21 03:54:09 +0000490<!--=========================================================================-->
491<div class="doc_subsection">
Chris Lattner917cc712009-03-02 02:37:32 +0000492<a name="coreimprovements">LLVM IR and Core Improvements</a>
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000493</div>
494
495<div class="doc_text">
Chris Lattner61358ab2009-10-13 17:48:04 +0000496<p>LLVM IR has several new features for better support of new targets and that
497expose new optimization opportunities:</p>
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000498
Chris Lattner791f77b2008-06-05 06:25:56 +0000499<ul>
Gabor Greif17b59fe2010-07-21 10:20:08 +0000500
501<li>LLVM 2.8 changes the internal order of operands in <a
502 href="http://llvm.org/doxygen/classllvm_1_1InvokeInst.html"><tt>InvokeInst</tt></a>
503 and <a href="http://llvm.org/doxygen/classllvm_1_1CallInst.html"><tt>CallInst</tt></a>.
504 To be portable across releases, resort to <tt>CallSite</tt> and the
Gabor Greif50fb3302010-07-21 10:22:41 +0000505 high-level accessors, such as <tt>getCalledValue</tt> and <tt>setUnwindDest</tt>.
Gabor Greif17b59fe2010-07-21 10:20:08 +0000506</li>
Gabor Greif05006e22010-07-26 18:48:07 +0000507<li>
508 You can no longer pass use_iterators directly to cast<> (and similar), because
509 these routines tend to perform costly dereference operations more than once. You
510 have to dereference the iterators yourself and pass them in.
511</li>
Torok Edwin7c46cf02010-08-04 12:43:22 +0000512<li>
513 llvm.memcpy.*, llvm.memset.*, llvm.memmove.* (and possibly other?) intrinsics
514 take an extra parameter now (i1 isVolatile), totaling 5 parameters.
515 If you were creating these intrinsic calls and prototypes yourself (as opposed
516 to using Intrinsic::getDeclaration), you can use UpgradeIntrinsicFunction/UpgradeIntrinsicCall
517 to be portable accross releases.
518 Note that you cannot use Intrinsic::getDeclaration() in a backwards compatible
519 way (needs 2/3 types now, in 2.7 it needed just 1).
520</li>
521<li>
522 SetCurrentDebugLocation takes a DebugLoc now instead of a MDNode.
523 Change your code to use
524 SetCurrentDebugLocation(DebugLoc::getFromDILocation(...)).
525</li>
526<li>
527 VISIBILITY_HIDDEN is gone.
528</li>
529<li>
Owen Anderson87ebbc02010-08-04 18:27:08 +0000530 The <tt>RegisterPass</tt> and <tt>RegisterAnalysisGroup</tt> templates are
531 considered deprecated, but continue to function in LLVM 2.8. Clients are
532 strongly advised to use the upcoming <tt>INITIALIZE_PASS()</tt> and
533 <tt>INITIALIZE_AG_PASS()</tt> macros instead.
534<li>
Torok Edwin7c46cf02010-08-04 12:43:22 +0000535 SMDiagnostic takes different parameters now. //FIXME: how to upgrade?
536</li>
537<li>
Duncan Sands12881e72010-08-30 10:57:54 +0000538 The constructor for the Triple class no longer tries to understand odd triple
539 specifications. Frontends should ensure that they only pass valid triples to
540 LLVM. The Triple::normalize utility method has been added to help front-ends
541 deal with funky triples.
542<li>
Torok Edwin7c46cf02010-08-04 12:43:22 +0000543 Some APIs got renamed:
544 <ul>
545 <li>llvm_report_error -&gt; report_fatal_error</li>
546 <li>llvm_install_error_handler -&gt; install_fatal_error_handler</li>
547 <li>llvm::DwarfExceptionHandling -&gt; llvm::JITExceptionHandling</li>
548 </ul>
549</li>
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000550</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000551
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000552</div>
553
554<!--=========================================================================-->
555<div class="doc_subsection">
Chris Lattneracce85d2008-02-10 07:46:44 +0000556<a name="optimizer">Optimizer Improvements</a>
557</div>
558
559<div class="doc_text">
560
Chris Lattner61358ab2009-10-13 17:48:04 +0000561<p>In addition to a large array of minor performance tweaks and bug fixes, this
Chris Lattnerf3013872008-10-13 21:50:36 +0000562release includes a few major enhancements and additions to the optimizers:</p>
Chris Lattneracce85d2008-02-10 07:46:44 +0000563
564<ul>
565
Chris Lattner922d00f2010-07-21 15:57:40 +0000566<li></li>
Chris Lattnera54c1f72010-04-21 06:42:24 +0000567
Chris Lattner61358ab2009-10-13 17:48:04 +0000568</ul>
Chris Lattner917cc712009-03-02 02:37:32 +0000569
Chris Lattner61358ab2009-10-13 17:48:04 +0000570</div>
Chris Lattner917cc712009-03-02 02:37:32 +0000571
Chris Lattner917cc712009-03-02 02:37:32 +0000572
Chris Lattner61358ab2009-10-13 17:48:04 +0000573<!--=========================================================================-->
574<div class="doc_subsection">
575<a name="executionengine">Interpreter and JIT Improvements</a>
576</div>
Chris Lattnerf3013872008-10-13 21:50:36 +0000577
Chris Lattner61358ab2009-10-13 17:48:04 +0000578<div class="doc_text">
579
580<ul>
Chris Lattner922d00f2010-07-21 15:57:40 +0000581<li></li>
Chris Lattnerb7c85b42010-04-21 05:17:40 +0000582
Chris Lattner0b832202008-06-08 02:45:07 +0000583</ul>
584
585</div>
586
587<!--=========================================================================-->
588<div class="doc_subsection">
Chris Lattner4ba2b652010-09-30 16:31:33 +0000589<a name="mc">MC Level Improvements</a>
590</div>
591
592<div class="doc_text">
593<p>
594FIXME: Rewrite.
595
596The LLVM Machine Code (aka MC) sub-project of LLVM was created to solve a number
597of problems in the realm of assembly, disassembly, object file format handling,
598and a number of other related areas that CPU instruction-set level tools work
599in. It is a sub-project of LLVM which provides it with a number of advantages
600over other compilers that do not have tightly integrated assembly-level tools.
601For a gentle introduction, please see the <a
602href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
603LLVM MC Project Blog Post</a>.
604</p>
605
606<p>2.8 status here. Basic correctness, some obscure missing instructions on
607 mainline, on by default in clang.
608 Entire compiler backend converted to use mcstreamer.
609 </p>
610</div>
611
612
613
614<!--=========================================================================-->
615<div class="doc_subsection">
Chris Lattner511433e2009-03-02 03:24:11 +0000616<a name="codegen">Target Independent Code Generator Improvements</a>
Chris Lattner0b832202008-06-08 02:45:07 +0000617</div>
618
619<div class="doc_text">
620
Mikhail Glushenkovf795ef02009-03-01 18:09:47 +0000621<p>We have put a significant amount of work into the code generator
622infrastructure, which allows us to implement more aggressive algorithms and make
623it run faster:</p>
Chris Lattner0b832202008-06-08 02:45:07 +0000624
625<ul>
Chris Lattner922d00f2010-07-21 15:57:40 +0000626<li>MachO writer works.</li>
Chris Lattner84977642007-09-21 03:54:09 +0000627</ul>
Chris Lattner84977642007-09-21 03:54:09 +0000628</div>
629
Chris Lattner917cc712009-03-02 02:37:32 +0000630<!--=========================================================================-->
631<div class="doc_subsection">
632<a name="x86">X86-32 and X86-64 Target Improvements</a>
633</div>
634
635<div class="doc_text">
636<p>New features of the X86 target include:
637</p>
638
639<ul>
Chris Lattner922d00f2010-07-21 15:57:40 +0000640<li>The X86 backend now supports holding X87 floating point stack values
641 in registers across basic blocks, dramatically improving performance of code
642 that uses long double, and when targetting CPUs that don't support SSE.</li>
Chris Lattner511433e2009-03-02 03:24:11 +0000643
Chris Lattner917cc712009-03-02 02:37:32 +0000644</ul>
645
Chris Lattner917cc712009-03-02 02:37:32 +0000646</div>
Chris Lattner84977642007-09-21 03:54:09 +0000647
648<!--=========================================================================-->
649<div class="doc_subsection">
Chris Lattner61358ab2009-10-13 17:48:04 +0000650<a name="ARM">ARM Target Improvements</a>
Chris Lattnerc441fb82009-03-01 02:30:21 +0000651</div>
652
653<div class="doc_text">
Chris Lattner61358ab2009-10-13 17:48:04 +0000654<p>New features of the ARM target include:
655</p>
Chris Lattnerc441fb82009-03-01 02:30:21 +0000656
657<ul>
Chris Lattnerc441fb82009-03-01 02:30:21 +0000658
Bob Wilson5b2fb952010-09-13 17:37:55 +0000659<li>
660 All of the NEON load and store intrinsics (llvm.arm.neon.vld* and
661 llvm.arm.neon.vst*) take an extra parameter to specify the alignment in bytes
662 of the memory being accessed.
663</li>
664<li>
665 The llvm.arm.neon.vaba intrinsic (vector absolute difference and
666 accumulate) has been removed. This operation is now represented using
667 the llvm.arm.neon.vabd intrinsic (vector absolute difference) followed by a
668 vector add.
Bob Wilsone8472772010-09-13 17:39:35 +0000669</li>
Bob Wilson5b2fb952010-09-13 17:37:55 +0000670<li>
671 The llvm.arm.neon.vabdl and llvm.arm.neon.vabal intrinsics (lengthening
672 vector absolute difference with and without accumlation) have been removed.
673 They are represented using the llvm.arm.neon.vabd intrinsic (vector absolute
674 difference) followed by a vector zero-extend operation, and for vabal,
675 a vector add.
676</li>
677<li>
678 The llvm.arm.neon.vmovn intrinsic has been removed. Calls of this intrinsic
679 are now replaced by vector truncate operations.
680</li>
681<li>
682 The llvm.arm.neon.vmovls and llvm.arm.neon.vmovlu intrinsics have been
683 removed. They are now represented as vector sign-extend (vmovls) and
684 zero-extend (vmovlu) operations.
685</li>
686<li>
687 The llvm.arm.neon.vaddl*, llvm.arm.neon.vaddw*, llvm.arm.neon.vsubl*, and
688 llvm.arm.neon.vsubw* intrinsics (lengthening vector add and subtract) have
689 been removed. They are replaced by vector add and vector subtract operations
690 where one (vaddw, vsubw) or both (vaddl, vsubl) of the operands are either
691 sign-extended or zero-extended.
692</li>
693<li>
694 The llvm.arm.neon.vmulls, llvm.arm.neon.vmullu, llvm.arm.neon.vmlal*, and
695 llvm.arm.neon.vmlsl* intrinsics (lengthening vector multiply with and without
696 accumulation and subtraction) have been removed. These operations are now
697 represented as vector multiplications where the operands are either
698 sign-extended or zero-extended, followed by a vector add for vmlal or a
699 vector subtract for vmlsl. Note that the polynomial vector multiply
700 intrinsic, llvm.arm.neon.vmullp, remains unchanged.
701</li>
Bob Wilsone8472772010-09-13 17:39:35 +0000702
703</ul>
Chris Lattner61358ab2009-10-13 17:48:04 +0000704</div>
Chris Lattnerc441fb82009-03-01 02:30:21 +0000705
Chris Lattner61358ab2009-10-13 17:48:04 +0000706<!--=========================================================================-->
707<div class="doc_subsection">
Chris Lattner61358ab2009-10-13 17:48:04 +0000708<a name="newapis">New Useful APIs</a>
709</div>
710
711<div class="doc_text">
712
713<p>This release includes a number of new APIs that are used internally, which
714 may also be useful for external clients.
715</p>
716
717<ul>
Chris Lattner922d00f2010-07-21 15:57:40 +0000718<li></li>
Chris Lattner61358ab2009-10-13 17:48:04 +0000719</ul>
720
721
722</div>
723
724<!--=========================================================================-->
725<div class="doc_subsection">
726<a name="otherimprovements">Other Improvements and New Features</a>
727</div>
728
729<div class="doc_text">
730<p>Other miscellaneous features include:</p>
731
732<ul>
Chris Lattner922d00f2010-07-21 15:57:40 +0000733<li></li>
Chris Lattnerc441fb82009-03-01 02:30:21 +0000734</ul>
735
736</div>
737
Chris Lattner77d29b12008-06-05 08:02:49 +0000738
739<!--=========================================================================-->
740<div class="doc_subsection">
Chris Lattnerf6662f92008-10-13 17:57:36 +0000741<a name="changes">Major Changes and Removed Features</a>
742</div>
743
744<div class="doc_text">
745
Chris Lattnereeb4da02008-10-13 22:06:31 +0000746<p>If you're already an LLVM user or developer with out-of-tree changes based
Chris Lattner922d00f2010-07-21 15:57:40 +0000747on LLVM 2.7, this section lists some "gotchas" that you may run into upgrading
Chris Lattnereeb4da02008-10-13 22:06:31 +0000748from the previous release.</p>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000749
750<ul>
Chris Lattner2295b5a2010-09-02 23:22:50 +0000751<li>.ll file doesn't produce #uses comments anymore, to get them, run a .bc file
752 through "llvm-dis --show-annotations".</li>
Chris Lattner885b6612010-08-28 16:33:36 +0000753<li>MSIL Backend removed.</li>
754<li>ABCD and SSI passes removed.</li>
755<li>'Union' LLVM IR feature removed.</li>
Chris Lattnerb7c85b42010-04-21 05:17:40 +0000756</ul>
Chris Lattnereeb4da02008-10-13 22:06:31 +0000757
758<p>In addition, many APIs have changed in this release. Some of the major LLVM
759API changes are:</p>
760
761<ul>
Devang Patelb34dd132008-10-14 20:03:43 +0000762</ul>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000763
Chris Lattnerf6662f92008-10-13 17:57:36 +0000764</div>
765
766
Chris Lattner79c3fe12003-10-02 04:57:28 +0000767<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000768<div class="doc_section">
769 <a name="knownproblems">Known Problems</a>
770</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000771<!-- *********************************************************************** -->
772
Misha Brukman500bc302003-11-22 00:38:41 +0000773<div class="doc_text">
774
Mikhail Glushenkovf795ef02009-03-01 18:09:47 +0000775<p>This section contains significant known problems with the LLVM system,
Chris Lattnere18b32e2008-11-10 05:40:34 +0000776listed by component. If you run into a problem, please check the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000777href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattner5eccca42003-12-12 21:22:16 +0000778there isn't already one.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000779
Misha Brukman500bc302003-11-22 00:38:41 +0000780</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000781
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000782<!-- ======================================================================= -->
783<div class="doc_subsection">
784 <a name="experimental">Experimental features included with this release</a>
785</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000786
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000787<div class="doc_text">
788
Misha Brukman6df9e2c2004-05-12 21:46:05 +0000789<p>The following components of this LLVM release are either untested, known to
790be broken or unreliable, or are in early development. These components should
791not be relied on, and bugs should not be filed against them, but they may be
792useful to some people. In particular, if you would like to work on one of these
Chris Lattner2b659ef2008-02-12 06:29:45 +0000793components, please contact us on the <a
794href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000795
796<ul>
Chris Lattner885b6612010-08-28 16:33:36 +0000797<li>The Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze
Wesley Peck7c4a1212010-03-18 14:31:30 +0000798 backends are experimental.</li>
Chris Lattner914ce462010-04-22 06:28:20 +0000799<li><tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
Chris Lattner922d00f2010-07-21 15:57:40 +0000800 supported value for this option. XXX Update me</li>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000801</ul>
802
803</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000804
Misha Brukman500bc302003-11-22 00:38:41 +0000805<!-- ======================================================================= -->
806<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000807 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswellc0c186d2005-11-08 21:11:33 +0000808</div>
809
810<div class="doc_text">
811
812<ul>
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000813 <li>The X86 backend does not yet support
814 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
815 floating point stack</a>. It supports the 'f' and 't' constraints, but not
816 'u'.</li>
Duncan Sands47eff2b2008-06-08 19:38:43 +0000817 <li>Win64 code generation wasn't widely tested. Everything should work, but we
John Criswell524a5dd2009-03-02 15:28:15 +0000818 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
Chris Lattner914ce462010-04-22 06:28:20 +0000819 runtime currently due to lack of support for the 'u' inline assembly
820 constraint and for X87 floating point inline assembly.</li>
Dan Gohman8207ba92008-06-08 23:05:11 +0000821 <li>The X86-64 backend does not yet support the LLVM IR instruction
Chris Lattner914ce462010-04-22 06:28:20 +0000822 <tt>va_arg</tt>. Currently, front-ends support variadic
Dan Gohman8207ba92008-06-08 23:05:11 +0000823 argument constructs on X86-64 by lowering them manually.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000824</ul>
825
826</div>
827
828<!-- ======================================================================= -->
829<div class="doc_subsection">
830 <a name="ppc-be">Known problems with the PowerPC back-end</a>
831</div>
832
833<div class="doc_text">
834
835<ul>
Nicolas Geoffraye4285dc2007-05-15 09:21:28 +0000836<li>The Linux PPC32/ABI support needs testing for the interpreter and static
Chris Lattner57a460e2007-05-23 04:39:32 +0000837compilation, and lacks support for debug information.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000838</ul>
839
840</div>
841
842<!-- ======================================================================= -->
843<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000844 <a name="arm-be">Known problems with the ARM back-end</a>
845</div>
846
847<div class="doc_text">
848
849<ul>
Chris Lattner57a460e2007-05-23 04:39:32 +0000850<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sandsc90d68b2007-09-26 15:59:54 +0000851processors, thumb programs can crash or produce wrong
Chris Lattner57a460e2007-05-23 04:39:32 +0000852results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
John Criswell524a5dd2009-03-02 15:28:15 +0000853<li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000854</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000855</ul>
856
857</div>
858
859<!-- ======================================================================= -->
860<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000861 <a name="sparc-be">Known problems with the SPARC back-end</a>
862</div>
863
864<div class="doc_text">
865
866<ul>
John Criswell524a5dd2009-03-02 15:28:15 +0000867<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
Chris Lattner26299222006-11-18 07:51:14 +0000868 support the 64-bit SPARC ABI (-m64).</li>
869</ul>
870
871</div>
872
873<!-- ======================================================================= -->
874<div class="doc_subsection">
Bruno Cardoso Lopesb7e1a4f2008-10-25 14:56:26 +0000875 <a name="mips-be">Known problems with the MIPS back-end</a>
876</div>
877
878<div class="doc_text">
879
880<ul>
Bruno Cardoso Lopesb7e1a4f2008-10-25 14:56:26 +0000881<li>64-bit MIPS targets are not supported yet.</li>
882</ul>
883
884</div>
885
886<!-- ======================================================================= -->
887<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000888 <a name="alpha-be">Known problems with the Alpha back-end</a>
889</div>
890
891<div class="doc_text">
892
893<ul>
894
895<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
896appropriate nops inserted to ensure restartability.</li>
897
John Criswellc0c186d2005-11-08 21:11:33 +0000898</ul>
899</div>
900
Chris Lattner26299222006-11-18 07:51:14 +0000901<!-- ======================================================================= -->
902<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000903 <a name="c-be">Known problems with the C back-end</a>
Chris Lattner26299222006-11-18 07:51:14 +0000904</div>
905
906<div class="doc_text">
907
Chris Lattner3016ee92010-09-29 05:34:42 +0000908<p>The C backend has numerous problems and is not being actively maintained.
909Depending on it for anything serious is not advised.</p>
910
Chris Lattner26299222006-11-18 07:51:14 +0000911<ul>
Chris Lattner5733b272008-06-05 06:35:40 +0000912<li><a href="http://llvm.org/PR802">The C backend has only basic support for
913 inline assembly code</a>.</li>
Chris Lattner725a0d82007-09-26 06:01:35 +0000914<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
915 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Gabor Greif4906abe2009-03-02 12:02:51 +0000916 C++ code compiled with <tt>llc</tt> or native compilers.</li>
Duncan Sandsf74c0cc2008-02-10 13:40:55 +0000917<li>The C backend does not support all exception handling constructs.</li>
Duncan Sands50723a92009-02-25 11:51:54 +0000918<li>The C backend does not support arbitrary precision integers.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000919</ul>
920
921</div>
John Criswellc0c186d2005-11-08 21:11:33 +0000922
Misha Brukman500bc302003-11-22 00:38:41 +0000923
924<!-- ======================================================================= -->
925<div class="doc_subsection">
Chris Lattner3016ee92010-09-29 05:34:42 +0000926 <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000927</div>
Chris Lattner47588f92003-10-02 05:07:23 +0000928
Misha Brukman500bc302003-11-22 00:38:41 +0000929<div class="doc_text">
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000930
Chris Lattner3016ee92010-09-29 05:34:42 +0000931<p>llvm-gcc is generally very stable for the C family of languages. The only
932 major language feature of GCC not supported by llvm-gcc is the
933 <tt>__builtin_apply</tt> family of builtins. However, some extensions
934 are only supported on some targets. For example, trampolines are only
935 supported on some targets (these are used when you take the address of a
936 nested function).</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000937
Chris Lattner3016ee92010-09-29 05:34:42 +0000938<p>Fortran support generally works, but there are still several unresolved bugs
939 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
940 tools/gfortran component for details. Note that llvm-gcc is missing major
941 Fortran performance work in the frontend and library that went into GCC after
942 4.2. If you are interested in Fortran, we recommend that you consider using
943 <a href="#dragonegg">dragonegg</a> instead.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000944
Chris Lattner3016ee92010-09-29 05:34:42 +0000945<p>The llvm-gcc 4.2 Ada compiler has basic functionality. However, this is not a
946mature technology, and problems should be expected. For example:</p>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000947<ul>
Duncan Sands27aff872008-06-08 20:18:35 +0000948<li>The Ada front-end currently only builds on X86-32. This is mainly due
John Criswell524a5dd2009-03-02 15:28:15 +0000949to lack of trampoline support (pointers to nested functions) on other platforms.
950However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000951which does support trampolines.</li>
952<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
Duncan Sands326a4982009-02-25 11:59:06 +0000953This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
954exception handling, which is used internally by the compiler.
Chris Lattner61358ab2009-10-13 17:48:04 +0000955Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
Duncan Sands978bcee2008-10-13 17:27:23 +0000956<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
957and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
Duncan Sands326a4982009-02-25 11:59:06 +0000958(c380004 also fails with gcc-4.2 mainline).
959If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
960causes the compiler to go into an infinite loop, using up all system memory.</li>
Duncan Sandsdd3e6722009-03-02 16:35:57 +0000961<li>Some GCC specific Ada tests continue to crash the compiler.</li>
Chris Lattner61358ab2009-10-13 17:48:04 +0000962<li>The <tt>-E</tt> binder option (exception backtraces)
Chris Lattner2b659ef2008-02-12 06:29:45 +0000963<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
Chris Lattner61358ab2009-10-13 17:48:04 +0000964crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000965<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
966or finish at a non-byte offset</a> in a record. Workaround: do not pack records
967or use representation clauses that result in a field of a non-discrete type
968starting or finishing in the middle of a byte.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000969<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
970'main' as generated by the Ada binder to be invalid</a>.
971Workaround: hand edit the file to use pointers for <tt>argv</tt> and
972<tt>envp</tt> rather than integers.</li>
973<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
974ignored</a>.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000975</ul>
976</div>
977
Chris Lattner79c3fe12003-10-02 04:57:28 +0000978<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000979<div class="doc_section">
980 <a name="additionalinfo">Additional Information</a>
981</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000982<!-- *********************************************************************** -->
983
Misha Brukman500bc302003-11-22 00:38:41 +0000984<div class="doc_text">
985
Chris Lattner416db102005-05-16 17:13:10 +0000986<p>A wide variety of additional information is available on the <a
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000987href="http://llvm.org">LLVM web page</a>, in particular in the <a
988href="http://llvm.org/docs/">documentation</a> section. The web page also
Reid Spencer669ed452007-07-09 08:04:31 +0000989contains versions of the API documentation which is up-to-date with the
990Subversion version of the source code.
Misha Brukman109d9e82005-03-30 19:14:24 +0000991You can access versions of these documents specific to this release by going
992into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000993
Misha Brukman500bc302003-11-22 00:38:41 +0000994<p>If you have any questions or comments about LLVM, please feel free to contact
Chris Lattnerc463b272005-10-29 07:07:09 +0000995us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattner5eccca42003-12-12 21:22:16 +0000996lists</a>.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000997
Misha Brukman500bc302003-11-22 00:38:41 +0000998</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000999
1000<!-- *********************************************************************** -->
Chris Lattner79c3fe12003-10-02 04:57:28 +00001001
Misha Brukman500bc302003-11-22 00:38:41 +00001002<hr>
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Chris Lattnerb4b0ce72007-05-18 00:44:29 +00001009 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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