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Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]7 <title>LLVM 2.4 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 Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]11<div class="doc_title">LLVM 2.4 Release Notes</div>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]12
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]13<ol>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]14 <li><a href="#intro">Introduction</a></li>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]15 <li><a href="#subproj">Sub-project Status Update</a></li>
16 <li><a href="#whatsnew">What's New in LLVM?</a></li>
Chris Lattner4b538b92004-04-30 22:17:12 +0000[diff] [blame]17 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]18 <li><a href="#portability">Portability and Supported Platforms</a></li>
Dan Gohman44aa9212008-10-14 16:23:02 +0000[diff] [blame]19 <li><a href="#knownproblems">Known Problems</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]20 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]21</ol>
22
Chris Lattner7911ce22004-05-23 21:07:27 +0000[diff] [blame]23<div class="doc_author">
Dan Gohman44aa9212008-10-14 16:23:02 +0000[diff] [blame]24 <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]25</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]26
27<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]28<div class="doc_section">
29 <a name="intro">Introduction</a>
30</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]31<!-- *********************************************************************** -->
32
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]33<div class="doc_text">
34
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]35<p>This document contains the release notes for the LLVM Compiler
36Infrastructure, release 2.4. Here we describe the status of LLVM, including
37major improvements from the previous release and significant known problems.
38All LLVM releases may be downloaded from the <a
39href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]40
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]41<p>For more information about LLVM, including information about the latest
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]42release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattner47ad72c2003-10-07 21:38:31 +0000[diff] [blame]43web site</a>. If you have questions or comments, the <a
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]44href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
45List</a> is a good place to send them.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]46
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]47<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]48main LLVM web page, this document applies to the <i>next</i> release, not the
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]49current one. To see the release notes for a specific release, please see the
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]50<a href="http://llvm.org/releases/">releases page</a>.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]51
52</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]53
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]54<!-- Unfinished features in 2.4:
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]55 Machine LICM
56 Machine Sinking
57 LegalizeDAGTypes
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]58 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
59 one MBB to another
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]60 -->
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]61
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]62 <!-- for announcement email:
63 mention dev mtg
Chris Lattnercdb0e4c2008-10-12 22:57:58 +0000[diff] [blame]64 Xcode 3.1 and 3.1.1.
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]65 -->
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]66
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]67<!-- *********************************************************************** -->
68<div class="doc_section">
69 <a name="subproj">Sub-project Status Update</a>
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]70</div>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]71<!-- *********************************************************************** -->
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]72
73<div class="doc_text">
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]74<p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]75The LLVM 2.4 distribution currently consists of code from the core LLVM
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]76repository (which roughly includes the LLVM optimizers, code generators and
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]77supporting tools) and the llvm-gcc repository. In addition to this code, the
78LLVM Project includes other sub-projects that are in development. The two which
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]79are the most actively developed are the <a href="#clang">Clang Project</a> and
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]80the <a href="#vmkit">VMKit Project</a>.
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]81</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]82
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]83</div>
84
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]85
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]86<!--=========================================================================-->
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]87<div class="doc_subsection">
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]88<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]89</div>
90
91<div class="doc_text">
92
93<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
94a set of new 'LLVM native' front-end technologies for the LLVM optimizer
95and code generator. Clang is continuing to make major strides forward in all
96areas. Its C and Objective-C parsing support is very solid, and the code
97generation support is far enough along to build many C applications. While not
98yet production quality, it is progressing very nicely. In addition, C++
99front-end work has started to make significant progress.</p>
100
Chris Lattnercc042612008-10-14 00:52:49 +0000[diff] [blame]101<p>Codegen progress/state [DANIEL]</p>
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]102
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]103</div>
104
105<!--=========================================================================-->
106<div class="doc_subsection">
107<a name="clangsa">Clang Static Analyzer</a>
108</div>
109
110<div class="doc_text">
111
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]112<p>The Clang project also includes an early stage static source code analysis
113tool for <a href="http://clang.llvm.org/StaticAnalysis.html">automatically
114finding bugs</a> in C and Objective-C programs. The tool performs a growing set
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]115of checks to find bugs that occur on a specific path within a program. Examples
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]116of bugs the tool finds include logic errors such as null dereferences,
117violations of various API rules, dead code, and potential memory leaks in
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]118Objective-C programs. Since its inception, public feedback on the tool has been
119extremely positive, and conservative estimates put the number of real bugs it
120has found in industrial-quality software on the order of thousands.</p>
Chris Lattnercc042612008-10-14 00:52:49 +0000[diff] [blame]121
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]122<p>The tool also provides a simple web GUI to inspect potential bugs found by
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]123the tool. While still early in development, the GUI illustrates some of the key
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]124features of Clang: accurate source location information, which is used by the
125GUI to highlight specific code expressions that relate to a bug (including those
126that span multiple lines) and built-in knowledge of macros, which is used to
127perform inline expansion of macros within the GUI itself.</p>
128
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]129<p>The set of checks performed by the static analyzer is gradually expanding,
130and
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]131future plans for the tool include full source-level inter-procedural analysis
132and deeper checks such as buffer overrun detection. There are many opportunities
133to extend and enhance the static analyzer, and anyone interested in working on
134this project is encouraged to get involved!</p>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]135
136</div>
137
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]138<!--=========================================================================-->
139<div class="doc_subsection">
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]140<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]141</div>
142
143<div class="doc_text">
144<p>
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]145The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]146a JVM and a CLI Virtual Machines (Microsoft .NET is an
147implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
148
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]149<p>Following LLVM 2.4, VMKit has its first release 0.24 that you can find on
150the <a href="http://llvm.org/releases/">release page</a>. The release includes
151bug fixes, cleanup and new features. The major changes include:</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]152
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]153<ul>
154
155<li><p>Support for generics in the .Net virtual machine. This was implemented
156by Tilmann Scheller during his Google Summer of Code project.</li></p>
157<li><p>Initial support for the Mono class libraries.</p></li>
158<li><p>Support for MacOSX/x86, following LLVM's support for exceptions in
159JIT on MacOSX/x86.
160<li><p>A new vmkit driver: a program to run java or .net applications. The
161driver supports llvm command line arguments including the new "-fast" option.
162</p></li>
163<li><p>A new memory allocation scheme in the JVM that makes unloading a
164class loader very fast.</p></li>
165<li><p>VMKit now follows the LLVM Makefile machinery.</p></li>
166
167
168</ul>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]169</div>
170
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]171
172<!-- *********************************************************************** -->
173<div class="doc_section">
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]174 <a name="whatsnew">What's New in LLVM?</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]175</div>
176<!-- *********************************************************************** -->
177
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]178<div class="doc_text">
179
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]180<p>This release includes a huge number of bug fixes, performance tweaks and
181minor improvements. Some of the major improvements and new features are listed
182in this section.
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]183</p>
184</div>
185
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]186<!--=========================================================================-->
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]187<div class="doc_subsection">
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]188<a name="majorfeatures">Major New Features</a>
189</div>
190
191<div class="doc_text">
192
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]193<p>LLVM 2.4 includes several major new capabilities:</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]194
195<ul>
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]196<li><p>The most visible end-user change in LLVM 2.4 is that it includes many
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]197optimizations and changes to make -O0 compile times much faster. You should see
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]198improvements on the order of 30% (or more) faster than LLVM 2.3. There are many
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]199pieces to this change, described in more detail below. The speedups and new
200components can also be used for JIT compilers that want fast compilation as
201well.</p></li>
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]202
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]203<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which
204were introduced in LLVM 2.3) have been generalized to full support for "First
205Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using
206structs and arrays as values in a function. This capability is mostly useful
207for front-end authors, who prefer to treat things like complex numbers, simple
208tuples, dope vectors, etc as Value*'s instead of as a tuple of Value*'s or as
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]209memory values. Bitcode files from LLVM 2.3 will automatically migrate to the
210general representation.</p></li>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]211
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]212<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This
Duncan Sands9ba23792008-10-14 07:06:37 +0000[diff] [blame]213is the LLVM target that only has support for 8 bit registers, and a number of
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]214other crazy constraints. While the port is still in early development stages,
215it shows some interesting things you can do with LLVM.</p></li>
Chris Lattnerbc5786b2008-06-05 06:57:39 +0000[diff] [blame]216
Chris Lattner8170c102008-02-10 08:18:42 +0000[diff] [blame]217</ul>
218
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]219</div>
220
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]221
222<!--=========================================================================-->
223<div class="doc_subsection">
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]224<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]225</div>
226
227<div class="doc_text">
228
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]229<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
230front-ends and driver with the LLVM optimizer and code generator. It currently
231includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]232
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]233<ul>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]234<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM
2352.3 only supported those used by OpenMP, but 2.4 supports them all. While
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]236llvm-gcc supports all of these builtins, note that not all targets do. X86
237support them all in both 32-bit and 64-bit mode and PowerPC supports them all
238except for the 64-bit operations when in 32-bit mode.</li>
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]239
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]240<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells
241the compiler that it is ok to use low-precision approximations of certain libm
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]242functions (like tan, log, etc). This allows you to get high performance if you
243only need (say) 14-bits of precision.</li>
244
245<li>llvm-gcc now supports a C language extension known as "<a
246href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]247</a>". This feature is similar to nested functions and closures, but does not
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]248require stack trampolines (with most ABIs) and supports returning closures
249from functions that define them. Note that actually <em>using</em> Blocks
250requires a small runtime that is not included with llvm-gcc.</li>
251
252<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
253transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
254later) this allows the use of LTO with other optimization levels like -Os.
255Previously, LTO could only be used with -O4, which implied optimizations in
256-O3 that can increase code size.</li>
Gabor Greifa3bd11d2008-06-09 06:06:18 +0000[diff] [blame]257</ul>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]258
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]259</div>
260
261
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]262<!--=========================================================================-->
263<div class="doc_subsection">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]264<a name="coreimprovements">LLVM Core Improvements</a>
265</div>
266
267<div class="doc_text">
268<p>New features include:
269</p>
270
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]271<ul>
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]272<li>A major change to the <tt>Use</tt> class landed, which shrank it by 25%. Since
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]273this is a pervasive part of the LLVM, it ended up reducing the memory use of
274LLVM IR in general by 15% for most programs.</li>
275
276<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more
277nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of
278"<tt>add i32 %A, 4 ; &lt;i32&gt;:3</tt>", which makes it much easier to read.
279</li>
280
281<li>LLVM 2.4 includes some changes for better vector support. First, the shift
282operations (<tt>shl</tt>, <tt>ashr</tt>, <tt>lshr</tt>) now all support vectors
283and do an element-by-element shift (shifts of the whole vector can be
284accomplished by bitcasting the vector to &lt;1 x i128&gt; for example). Second,
Chris Lattnercc042612008-10-14 00:52:49 +0000[diff] [blame]285there is initial support in development for vector comparisons with the
286<a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a>
287instructions. These instructions compare two vectors and return a vector of
288i1's for each result. Note that there is very little codegen support available
289for any of these IR features though.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]290
291<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much
292easier for front-ends to create debug info descriptors, similar to the way that
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]293<tt>IRBuilder</tt> makes it easier to create LLVM IR.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]294
Dan Gohman1bbddce2008-10-14 16:13:59 +0000[diff] [blame]295<li>The <tt>IRBuilder</tt> class is now parameterized by a class responsible
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]296for constant folding. The default <tt>ConstantFolder</tt> class does target independent
297constant folding. The <tt>NoFolder</tt> class does no constant folding at all, which is
298useful when learning how LLVM works. The <tt>TargetFolder</tt> class folds the most,
Duncan Sands9ba23792008-10-14 07:06:37 +0000[diff] [blame]299doing target dependent constant folding.</li>
300
301<li>LLVM now supports "function attributes", which allows us to separate return
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]302value attributes from function attributes. LLVM now supports attributes on a
303function itself, a return value, and its parameters. New supported function
304attributes include noinline/alwaysinline and the "opt-size" flag which says the
305function should be optimized for code size.</li>
306
Chris Lattnercce6d4b2008-10-12 18:30:33 +0000[diff] [blame]307<li>LLVM IR now directly represents "common" linkage, instead of
308 representing it as a form of weak linkage.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]309
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]310</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]311
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]312</div>
313
314<!--=========================================================================-->
315<div class="doc_subsection">
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]316<a name="optimizer">Optimizer Improvements</a>
317</div>
318
319<div class="doc_text">
320
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]321<p>In addition to a huge array of bug fixes and minor performance tweaks, this
322release includes a few major enhancements and additions to the optimizers:</p>
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]323
324<ul>
325
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]326<li>The Global Value Numbering (GVN) pass now does local Partial Redundancy
327Elimination (PRE) to eliminate some partially redundant expressions in cases
328where doing so won't grow code size.</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]329
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]330<li>LLVM 2.4 includes a new loop deletion pass (which removes output-free
331provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE)
332pass that no longer uses control dependence information. These changes speed up
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]333the optimizer and also prevent it from deleting output-free infinite
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]334loops.</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]335
Duncan Sands1050d732008-10-13 18:42:43 +0000[diff] [blame]336<li>The new AddReadAttrs pass works out which functions are read-only or
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]337read-none (these correspond to 'pure' and 'const' in GCC) and marks them
Duncan Sands1050d732008-10-13 18:42:43 +0000[diff] [blame]338with the appropriate attribute.</li>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]339
340<li>LLVM 2.4 now includes a new SparsePropagation framework, which makes it
341trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using
342this interface means that you just define objects to represent your lattice
343values and the transfer functions that operate on them. It handles the
344mechanics of worklist processing, liveness tracking, handling PHI nodes,
345etc.</li>
346
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]347<li>The Loop Strength Reduction and induction variable optimization passes have
348several improvements to avoid inserting MAX expressions, to optimize simple
349floating point induction variables and to analyze trip counts of more
350loops.</li>
351
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]352<li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
353pulled out of the Instruction Combining pass and put into a new
354<tt>ValueTracking.h</tt> header, where they can be reused by other passes.</li>
355
356<li>The tail duplication pass has been removed from the standard optimizer
357sequence used by llvm-gcc. This pass still exists, but the benefits it once
358provided are now achieved by other passes.</li>
359
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]360</ul>
361
362</div>
363
364<!--=========================================================================-->
365<div class="doc_subsection">
366<a name="codegen">Code Generator Improvements</a>
367</div>
368
369<div class="doc_text">
370
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]371<p>We have put a significant amount of work into the code generator infrastructure,
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]372which allows us to implement more aggressive algorithms and make it run
373faster:</p>
374
375<ul>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]376<li>The target-independent code generator supports (and the X86 backend
377 currently implements) a new interface for "fast" instruction selection. This
378 interface is optimized to produce code as quickly as possible, sacrificing
379 code quality to do it. This is used by default at -O0 or when using
380 "llc -fast" on X86. It is straight-forward to add support for
381 other targets if faster -O0 compilation is desired.</li>
382
383<li>In addition to the new 'fast' instruction selection path, many existing
384 pieces of the code generator have been optimized in significant ways.
385 SelectionDAG's are now pool allocated and use better algorithms in many
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]386 places, the ".s" file printers now use <tt>raw_ostream</tt> to emit text much faster,
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]387 etc. The end result of these improvements is that the compiler also takes
388 substantially less time to generate code that is just as good (and often
389 better) than before.</li>
390
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]391<li>Each target has been split to separate the ".s" file printing logic from the
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]392 rest of the target. This enables JIT compilers that don't link in the
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]393 (somewhat large) code and data tables used for printing a ".s" file.</li>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]394
395<li>The code generator now includes a "stack slot coloring" pass, which packs
396 together individual spilled values into common stack slots. This reduces
397 the size of stack frames with many spills, which tends to increase L1 cache
398 effectiveness.</li>
399
400<li>Various pieces of the register allocator (e.g. the coalescer and two-address
401 operation elimination pass) now know how to rematerialize trivial operations
402 to avoid copies and include several other optimizations.</li>
403
404<li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by
405 the <tt>llc -view-*-dags</tt> options are now significantly prettier and
406 easier to read.</li>
407
408<li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean
409 Quadratic Programming (PBQP). This register allocator is still in
410 development, but is very simple and clean.</li>
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]411
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]412</ul>
413
414</div>
415
416
417<!--=========================================================================-->
418<div class="doc_subsection">
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]419<a name="targetspecific">Target Specific Improvements</a>
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]420</div>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]421
Chris Lattner738bd302006-04-18 06:32:08 +0000[diff] [blame]422<div class="doc_text">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]423<p>New target-specific features include:
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]424</p>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]425
426<ul>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]427<li>Exception handling is supported by default on Linux/x86-64.</li>
Duncan Sandsbbf379a2008-10-13 17:32:15 +0000[diff] [blame]428<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]429<li>@llvm.frameaddress now supports getting the frame address of stack frames
430 &gt; 0 on x86/x86-64.</li>
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]431<li>MIPS floating point support? [BRUNO]</li>
432<li>The PowerPC backend now supports trampolines.</li>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]433</ul>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]434
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]435</div>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]436
437
438<!--=========================================================================-->
439<div class="doc_subsection">
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]440<a name="otherimprovements">Other Improvements</a>
441</div>
442
443<div class="doc_text">
444<p>New features include:
445</p>
446
447<ul>
Mikhail Glushenkov49feb452008-10-13 02:46:01 +0000[diff] [blame]448<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]449 support. It is now easier to experiment with <tt>llvmc2</tt> and
450 build your own tools based on it.</li>
451
452<li>LLVM 2.4 includes a number of new generic algorithms and data structures,
Dan Gohmanbd9f9af2008-10-14 15:14:55 +0000[diff] [blame]453 include a scoped hash table, 'immutable' data structures, a simple
454 free-list manager, and a <tt>raw_ostream</tt> class.
455 The <tt>raw_ostream</tt> class and
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]456 <tt>format</tt> allow for efficient file output, and various pieces of LLVM
457 have switched over to use it. The eventual goal is to eliminate
458 std::ostream in favor of it.</li>
459
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]460</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]461
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]462</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]463
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]464<!--=========================================================================-->
465<div class="doc_subsection">
466<a name="changes">Major Changes and Removed Features</a>
467</div>
468
469<div class="doc_text">
470
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]471<p>If you're already an LLVM user or developer with out-of-tree changes based
472on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading
473from the previous release.</p>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]474
475<ul>
476
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]477<li>The LLVM IR generated by llvm-gcc no longer names all instructions. This
478 makes it run faster, but may be more confusing to some people. If you
479 prefer to have names, the '<tt>opt -instnamer</tt>' pass will add names to
480 all instructions.</li>
481
482<li>The LoadVN and GCSE passes have been removed from the tree. They are
483 obsolete and have been replaced with the GVN and MemoryDependence passes.
484 </li>
485</ul>
486
487
488<p>In addition, many APIs have changed in this release. Some of the major LLVM
489API changes are:</p>
490
491<ul>
492
Devang Patelb34dd132008-10-14 20:03:43 +0000[diff] [blame^]493<li>Now, function attributes and return value attributes are managed
494sepearately. Interface exported by <tt>ParameterAttributes.h</tt> header is now
495experted by <tt>Attributes.h</tt> header. The new attributes interface changes are:
496<ul>
497<li><tt>getParamAttrs</tt> method is now replaced by
498<tt>getParamAttributes</tt>, <tt>getRetAttributes</tt> and
499<tt>getFnAttributes</tt> methods.</li>
500<li> Return value attributes are stored at index 0. Function attributes are
501stored at index ~0U. Parameter attributes are stored at index that matches
502parameter number.</li>
503<li> <tt>ParamAttr</tt> namespace is now renamed as <tt>Attribute</tt>.</li>
504<li> The name of the class</tt> that manages reference count of opaque
505attributes is changed from <tt>PAListPtr</tt> to <tt>AttrListPtr</tt>.</li>
506<li> <tt>ParamAttrsWithIndex</tt> is now renamed as <tt>AttributeWithIndex</tt>.
507</li>
508</ul>
509</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]510
511<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
512<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
513converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]514"<tt>llvm/Analysis/ValueTracking.h</tt>".</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]515
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]516<li>The APIs to create various instructions have changed from lower case
517 "create" methods to upper case "Create" methods (e.g.
518 <tt>BinaryOperator::create</tt>). LLVM 2.4 includes both cases, but the
519 lower case ones are removed in mainline, please migrate.</li>
520
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]521<li>Various header files like "<tt>llvm/ADT/iterator</tt>" were given a ".h" suffix.
522 Change your code to #include "<tt>llvm/ADT/iterator.h</tt>" instead.</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]523
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]524<li>In the code generator, many <tt>MachineOperand</tt> predicates were renamed to be
Chris Lattnerf1796b62008-10-14 06:37:11 +0000[diff] [blame]525 shorter (e.g. <tt>isFrameIndex()</tt> -&gt; <tt>isFI()</tt>),
526 <tt>SDOperand</tt> was renamed to <tt>SDValue</tt> (and the "<tt>Val</tt>"
527 member was changed to be the <tt>getNode()</tt> accessor), and the
528 <tt>MVT::ValueType</tt> enum has been replaced with an "<tt>MVT</tt>"
Dan Gohman9aeea5b2008-10-14 17:06:44 +0000[diff] [blame]529 struct. The <tt>getSignExtended</tt> and <tt>getValue</tt> methods in the
530 ConstantSDNode class were renamed to <tt>getSExtValue</tt> and
531 <tt>getZExtValue</tt> respectively, to be more consistent with
532 the <tt>ConstantInt</tt> class.</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]533</ul>
534
535</div>
536
537
538
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]539<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]540<div class="doc_section">
541 <a name="portability">Portability and Supported Platforms</a>
542</div>
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]543<!-- *********************************************************************** -->
544
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]545<div class="doc_text">
546
John Criswell0b5b5e92004-12-08 20:35:47 +0000[diff] [blame]547<p>LLVM is known to work on the following platforms:</p>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]548
549<ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]550<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Reid Spencer00812e22005-05-17 02:47:27 +0000[diff] [blame]551 (and probably other unix-like systems).</li>
Chris Lattner000c73b2008-02-06 06:30:34 +0000[diff] [blame]552<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]553 64-bit modes.</li>
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]554<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]555<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
556 support is available for native builds with Visual C++).</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000[diff] [blame]557<li>Sun UltraSPARC workstations running Solaris 10.</li>
John Criswell9321fa82005-05-13 20:28:15 +0000[diff] [blame]558<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000[diff] [blame]559<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]560</ul>
561
Chris Lattnerbc5786b2008-06-05 06:57:39 +0000[diff] [blame]562<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Brian Gaekeb0fd7612004-05-09 05:28:35 +0000[diff] [blame]563to the machine and operating system on which it is built. However, minor
564porting may be required to get LLVM to work on new platforms. We welcome your
565portability patches and reports of successful builds or error messages.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]566
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]567</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]568
569<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]570<div class="doc_section">
571 <a name="knownproblems">Known Problems</a>
572</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]573<!-- *********************************************************************** -->
574
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]575<div class="doc_text">
576
577<p>This section contains all known problems with the LLVM system, listed by
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]578component. As new problems are discovered, they will be added to these
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]579sections. If you run into a problem, please check the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]580href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]581there isn't already one.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]582
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]583</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]584
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]585<!-- ======================================================================= -->
586<div class="doc_subsection">
587 <a name="experimental">Experimental features included with this release</a>
588</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]589
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]590<div class="doc_text">
591
Misha Brukman6df9e2c2004-05-12 21:46:05 +0000[diff] [blame]592<p>The following components of this LLVM release are either untested, known to
593be broken or unreliable, or are in early development. These components should
594not be relied on, and bugs should not be filed against them, but they may be
595useful to some people. In particular, if you would like to work on one of these
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]596components, please contact us on the <a
597href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]598
599<ul>
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]600<li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]601<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattner000c73b2008-02-06 06:30:34 +0000[diff] [blame]602 value for this option.</li>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]603</ul>
604
605</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]606
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]607<!-- ======================================================================= -->
608<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]609 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]610</div>
611
612<div class="doc_text">
613
614<ul>
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000[diff] [blame]615 <li>The X86 backend does not yet support
616 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
617 floating point stack</a>. It supports the 'f' and 't' constraints, but not
618 'u'.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]619 <li>The X86 backend generates inefficient floating point code when configured
620 to generate code for systems that don't have SSE2.</li>
Duncan Sands47eff2b2008-06-08 19:38:43 +0000[diff] [blame]621 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000[diff] [blame]622 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
623 currently due
624 to <a href="http://llvm.org/PR2255">several</a>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000[diff] [blame]625 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
626 'u' inline assembly constraint and X87 floating point inline assembly.</li>
Dan Gohman8207ba92008-06-08 23:05:11 +0000[diff] [blame]627 <li>The X86-64 backend does not yet support the LLVM IR instruction
628 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
629 argument constructs on X86-64 by lowering them manually.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]630</ul>
631
632</div>
633
634<!-- ======================================================================= -->
635<div class="doc_subsection">
636 <a name="ppc-be">Known problems with the PowerPC back-end</a>
637</div>
638
639<div class="doc_text">
640
641<ul>
Nicolas Geoffraye4285dc2007-05-15 09:21:28 +0000[diff] [blame]642<li>The Linux PPC32/ABI support needs testing for the interpreter and static
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]643compilation, and lacks support for debug information.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]644</ul>
645
646</div>
647
648<!-- ======================================================================= -->
649<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]650 <a name="arm-be">Known problems with the ARM back-end</a>
651</div>
652
653<div class="doc_text">
654
655<ul>
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]656<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sandsc90d68b2007-09-26 15:59:54 +0000[diff] [blame]657processors, thumb programs can crash or produce wrong
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]658results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]659<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
660</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]661<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
662 execute
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]663programs compiled with LLVM. Please use more recent versions of QEMU.</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]664</ul>
665
666</div>
667
668<!-- ======================================================================= -->
669<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]670 <a name="sparc-be">Known problems with the SPARC back-end</a>
671</div>
672
673<div class="doc_text">
674
675<ul>
676<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
677 support the 64-bit SPARC ABI (-m64).</li>
678</ul>
679
680</div>
681
682<!-- ======================================================================= -->
683<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]684 <a name="alpha-be">Known problems with the Alpha back-end</a>
685</div>
686
687<div class="doc_text">
688
689<ul>
690
691<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
692appropriate nops inserted to ensure restartability.</li>
693
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]694</ul>
695</div>
696
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]697<!-- ======================================================================= -->
698<div class="doc_subsection">
699 <a name="ia64-be">Known problems with the IA64 back-end</a>
700</div>
701
702<div class="doc_text">
703
704<ul>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000[diff] [blame]705<li>The Itanium backend is highly experimental, and has a number of known
706 issues. We are looking for a maintainer for the Itanium backend. If you
707 are interested, please contact the llvmdev mailing list.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]708</ul>
709
710</div>
711
712<!-- ======================================================================= -->
713<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]714 <a name="c-be">Known problems with the C back-end</a>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]715</div>
716
717<div class="doc_text">
718
719<ul>
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]720<li><a href="http://llvm.org/PR802">The C backend has only basic support for
721 inline assembly code</a>.</li>
Chris Lattner725a0d82007-09-26 06:01:35 +0000[diff] [blame]722<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
723 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]724 C++ code compiled with llc or native compilers.</li>
Duncan Sandsf74c0cc2008-02-10 13:40:55 +0000[diff] [blame]725<li>The C backend does not support all exception handling constructs.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]726</ul>
727
728</div>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]729
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]730
731<!-- ======================================================================= -->
732<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]733 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]734</div>
Chris Lattner47588f92003-10-02 05:07:23 +0000[diff] [blame]735
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]736<div class="doc_text">
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]737
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]738<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
739Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]740llvmdev mailing list if you are interested.</p>
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000[diff] [blame]741
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]742<p>The only major language feature of GCC not supported by llvm-gcc is
743 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
744 are only supported on some targets. For example, trampolines are only
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]745 supported on some targets (these are used when you take the address of a
746 nested function).</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]747
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]748<p>If you run into GCC extensions which are not supported, please let us know.
749</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]750
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]751</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]752
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]753<!-- ======================================================================= -->
754<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]755 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]756</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]757
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]758<div class="doc_text">
759
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]760<p>The C++ front-end is considered to be fully
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]761tested and works for a number of non-trivial programs, including LLVM
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]762itself, Qt, Mozilla, etc.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]763
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]764<ul>
Anton Korobeynikov0021fc12008-10-11 18:27:16 +0000[diff] [blame]765<li>Exception handling works well on the X86 and PowerPC targets. Currently
766 only linux and darwin targets are supported (both 32 and 64 bit).</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]767</ul>
Chris Lattnerfcc54b32003-10-07 22:14:37 +0000[diff] [blame]768
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]769</div>
770
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]771
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]772<!-- ======================================================================= -->
773<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]774 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]775</div>
776
777<div class="doc_text">
778The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
779technology and problems should be expected.
780<ul>
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]781<li>The Ada front-end currently only builds on X86-32. This is mainly due
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]782to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]783however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]784which does support trampolines.</li>
785<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
786Workaround: configure with --disable-bootstrap.</li>
Duncan Sands978bcee2008-10-13 17:27:23 +0000[diff] [blame]787<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
788and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
789(c380004 also fails with gcc-4.2 mainline).</li>
790<li>Some gcc specific Ada tests continue to crash the compiler.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]791<li>The -E binder option (exception backtraces)
792<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
793crashing if an exception is raised. Workaround: do not use -E.</li>
794<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
795or finish at a non-byte offset</a> in a record. Workaround: do not pack records
796or use representation clauses that result in a field of a non-discrete type
797starting or finishing in the middle of a byte.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]798<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
799'main' as generated by the Ada binder to be invalid</a>.
800Workaround: hand edit the file to use pointers for <tt>argv</tt> and
801<tt>envp</tt> rather than integers.</li>
802<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
803ignored</a>.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]804</ul>
805</div>
806
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]807<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]808<div class="doc_section">
809 <a name="additionalinfo">Additional Information</a>
810</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]811<!-- *********************************************************************** -->
812
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]813<div class="doc_text">
814
Chris Lattner416db102005-05-16 17:13:10 +0000[diff] [blame]815<p>A wide variety of additional information is available on the <a
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]816href="http://llvm.org">LLVM web page</a>, in particular in the <a
817href="http://llvm.org/docs/">documentation</a> section. The web page also
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]818contains versions of the API documentation which is up-to-date with the
819Subversion version of the source code.
Misha Brukman109d9e82005-03-30 19:14:24 +0000[diff] [blame]820You can access versions of these documents specific to this release by going
821into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]822
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]823<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]824us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]825lists</a>.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]826
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]827</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]828
829<!-- *********************************************************************** -->
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]830
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]831<hr>
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]832<address>
Misha Brukman38847d52003-12-21 22:53:21 +0000[diff] [blame]833 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]834 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
835 <a href="http://validator.w3.org/check/referer"><img
Chris Lattner8170c102008-02-10 08:18:42 +0000[diff] [blame]836 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]837
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]838 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]839 Last modified: $Date$
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]840</address>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]841
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]842</body>
843</html>