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Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]7 <title>LLVM 2.4 Release Notes</title>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]8</head>
9<body>
10
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]11<div class="doc_title">LLVM 2.4 Release Notes</div>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]12
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]13<ol>
14 <li><a href="#intro">Introduction</a></li>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]15 <li><a href="#subproj">Sub-project Status Update</a></li>
16 <li><a href="#whatsnew">What's New in LLVM?</a></li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]17 <li><a href="GettingStarted.html">Installation Instructions</a></li>
18 <li><a href="#portability">Portability and Supported Platforms</a></li>
19 <li><a href="#knownproblems">Known Problems</a>
20 <li><a href="#additionalinfo">Additional Information</a></li>
21</ol>
22
23<div class="doc_author">
24 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
25</div>
26
27<!-- *********************************************************************** -->
28<div class="doc_section">
29 <a name="intro">Introduction</a>
30</div>
31<!-- *********************************************************************** -->
32
33<div class="doc_text">
34
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]35<p>This document contains the release notes for the LLVM Compiler
36Infrastructure, release 2.4. Here we describe the status of LLVM, including
37major improvements from the previous release and significant known problems.
38All LLVM releases may be downloaded from the <a
39href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]40
41<p>For more information about LLVM, including information about the latest
42release, please check out the <a href="http://llvm.org/">main LLVM
43web site</a>. If you have questions or comments, the <a
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]44href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
45List</a> is a good place to send them.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]46
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]47<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]48main LLVM web page, this document applies to the <i>next</i> release, not the
49current one. To see the release notes for a specific releases, please see the
50<a href="http://llvm.org/releases/">releases page</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]51
52</div>
53
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]54<!-- Unfinished features in 2.4:
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]55 Machine LICM
56 Machine Sinking
57 LegalizeDAGTypes
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]58 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
59 one MBB to another
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]60 -->
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]61
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]62 <!-- for announcement email:
63 mention dev mtg
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]64 Xcode 3.1 and 3.1.1.
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]65 -->
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]66
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]67<!-- *********************************************************************** -->
68<div class="doc_section">
69 <a name="subproj">Sub-project Status Update</a>
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]70</div>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]71<!-- *********************************************************************** -->
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]72
73<div class="doc_text">
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]74<p>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]75The LLVM 2.4 distribution currently consists of code from the core LLVM
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]76repository (which roughly includes the LLVM optimizers, code generators and
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]77supporting tools) and the llvm-gcc repository. In addition to this code, the
78LLVM Project includes other sub-projects that are in development. The two which
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]79are the most actively developed are the <a href="#clang">Clang Project</a> and
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]80the <a href="#vmkit">vmkit Project</a>.
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]81</p>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]82
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]83</div>
84
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]85
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]86<!--=========================================================================-->
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]87<div class="doc_subsection">
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]88<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]89</div>
90
91<div class="doc_text">
92
93<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
94a set of new 'LLVM native' front-end technologies for the LLVM optimizer
95and code generator. Clang is continuing to make major strides forward in all
96areas. Its C and Objective-C parsing support is very solid, and the code
97generation support is far enough along to build many C applications. While not
98yet production quality, it is progressing very nicely. In addition, C++
99front-end work has started to make significant progress.</p>
100
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]101<p>Codegen progress/state
102</p>
103
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]104</div>
105
106<!--=========================================================================-->
107<div class="doc_subsection">
108<a name="clangsa">Clang Static Analyzer</a>
109</div>
110
111<div class="doc_text">
112
113<p>The
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]114<a href="http://clang.llvm.org/StaticAnalysis.html">static analysis tool</a>
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]115.</p>
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]116
117</div>
118
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]119<!--=========================================================================-->
120<div class="doc_subsection">
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]121<a name="vmkit">vmkit: JVM/CLI Virtual Machine Implementation</a>
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]122</div>
123
124<div class="doc_text">
125<p>
Chris Lattnera3c683b2008-10-13 18:11:54 +0000[diff] [blame]126The <a href="http://vmkit.llvm.org/">vmkit project</a> is an implementation of
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]127a JVM and a CLI Virtual Machines (Microsoft .NET is an
128implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
129
130<p>...</p>
131
132</div>
133
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]134
135<!-- *********************************************************************** -->
136<div class="doc_section">
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]137 <a name="whatsnew">What's New in LLVM?</a>
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]138</div>
139<!-- *********************************************************************** -->
140
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]141<div class="doc_text">
142
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]143<p>This release includes a huge number of bug fixes, performance tweaks and
144minor improvements. Some of the major improvements and new features are listed
145in this section.
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]146</p>
147</div>
148
Chris Lattnerf6a0d382008-06-08 21:58:17 +0000[diff] [blame]149<!--=========================================================================-->
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]150<div class="doc_subsection">
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]151<a name="majorfeatures">Major New Features</a>
152</div>
153
154<div class="doc_text">
155
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]156<p>LLVM 2.4 includes several major new capabilities:</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]157
158<ul>
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame]159<li><p>The most visible end-user change in LLVM 2.4 is that it includes many
Chris Lattnerea9c2242008-10-13 21:50:36 +0000[diff] [blame^]160optimizations and changes to make -O0 compile times much faster. You should see
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame]161improvements on the order of 30% or more faster than LLVM 2.3. There are many
162pieces to this change, described in more detail below. The speedups and new
163components can also be used for JIT compilers that want fast compilation as
164well.</p></li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]165
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame]166<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which
167were introduced in LLVM 2.3) have been generalized to full support for "First
168Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using
169structs and arrays as values in a function. This capability is mostly useful
170for front-end authors, who prefer to treat things like complex numbers, simple
171tuples, dope vectors, etc as Value*'s instead of as a tuple of Value*'s or as
172memory values.</p></li>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]173
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame]174<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This
175is the LLVM targer that only has support for 8 bit registers, and a number of
176other crazy constraints. While the port is still in early development stages,
177it shows some interesting things you can do with LLVM.</p></li>
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]178
Chris Lattner5ba16862008-02-10 08:18:42 +0000[diff] [blame]179</ul>
180
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]181</div>
182
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]183
184<!--=========================================================================-->
185<div class="doc_subsection">
Chris Lattnerf65224f2008-06-08 21:34:41 +0000[diff] [blame]186<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]187</div>
188
189<div class="doc_text">
190
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame]191<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
192front-ends and driver with the LLVM optimizer and code generator. It currently
193includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]194
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]195<ul>
Chris Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame]196<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM
1972.3 only supported those used by OpenMP, but 2.4 supports them all. While
Chris Lattnerea9c2242008-10-13 21:50:36 +0000[diff] [blame^]198llvm-gcc supports all of these builtins, note that not all targets do. X86
199support them all in both 32-bit and 64-bit mode and PowerPC supports them all
200except for the 64-bit operations when in 32-bit mode.</li>
Chris Lattner5cce7a52008-06-08 22:59:35 +0000[diff] [blame]201
Chris Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame]202<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells
203the compiler that it is ok to use low-precision approximations of certain libm
Chris Lattner4352cc82008-10-13 20:47:20 +0000[diff] [blame]204functions (like tan, log, etc). This allows you to get high performance if you
205only need (say) 14-bits of precision.</li>
206
207<li>llvm-gcc now supports a C language extension known as "<a
208href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks
209</a>. This feature is similar to nested functions and closures, but does not
210require stack trampolines (with most ABIs) and supports returning closures
211from functions that define them. Note that actually <em>using</em> Blocks
212requires a small runtime that is not included with llvm-gcc.</li>
213
214<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
215transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
216later) this allows the use of LTO with other optimization levels like -Os.
217Previously, LTO could only be used with -O4, which implied optimizations in
218-O3 that can increase code size.</li>
Gabor Greif0e49cc82008-06-09 06:06:18 +0000[diff] [blame]219</ul>
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]220
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]221</div>
222
223
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]224<!--=========================================================================-->
225<div class="doc_subsection">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]226<a name="coreimprovements">LLVM Core Improvements</a>
227</div>
228
229<div class="doc_text">
230<p>New features include:
231</p>
232
Chris Lattnerc5a4e312008-06-05 06:25:56 +0000[diff] [blame]233<ul>
Chris Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame]234<li>A major change to the "Use" class landed, which shrank it by 25%. Since
235this is a pervasive part of the LLVM, it ended up reducing the memory use of
236LLVM IR in general by 15% for most programs.</li>
237
238<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more
239nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of
240"<tt>add i32 %A, 4 ; &lt;i32&gt;:3</tt>", which makes it much easier to read.
241</li>
242
243<li>LLVM 2.4 includes some changes for better vector support. First, the shift
244operations (<tt>shl</tt>, <tt>ashr</tt>, <tt>lshr</tt>) now all support vectors
245and do an element-by-element shift (shifts of the whole vector can be
246accomplished by bitcasting the vector to &lt;1 x i128&gt; for example). Second,
247there is support in development for vector comparisons. LLVM 2.4 actually
248supports two ways to do vector comparisons: the vicmp/vfcmp instructions and the
249icmp/fcmp instructions. The vicmp/vfcmp instructions are temporary and will be
250removed (do not use them). The icmp/fcmp instructions compare two vectors and
251return a vector of i1's for each result. Note that there is very little codegen
252support available for any of these IR features though.</li>
253
254<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much
255easier for front-ends to create debug info descriptors, similar to the way that
256IRBuilder makes it easier to create LLVM IR.</li>
257
258<li>LLVM now supports "function attributes", which allows us to seperate return
259value attributes from function attributes. LLVM now supports attributes on a
260function itself, a return value, and its parameters. New supported function
261attributes include noinline/alwaysinline and the "opt-size" flag which says the
262function should be optimized for code size.</li>
263
Chris Lattnera5a49382008-10-12 18:30:33 +0000[diff] [blame]264<li>LLVM IR now directly represents "common" linkage, instead of
265 representing it as a form of weak linkage.</li>
Chris Lattnerf7bae6d2008-10-13 20:59:32 +0000[diff] [blame]266
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]267</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]268
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]269</div>
270
271<!--=========================================================================-->
272<div class="doc_subsection">
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]273<a name="optimizer">Optimizer Improvements</a>
274</div>
275
276<div class="doc_text">
277
Chris Lattnerea9c2242008-10-13 21:50:36 +0000[diff] [blame^]278<p>In addition to a huge array of bug fixes and minor performance tweaks, this
279release includes a few major enhancements and additions to the optimizers:</p>
Chris Lattner8fda4952008-02-10 07:46:44 +0000[diff] [blame]280
281<ul>
282
Chris Lattnerea9c2242008-10-13 21:50:36 +0000[diff] [blame^]283<li>The Global Value Numbering (GVN) pass now does local Partial Redundancy
284Elimination (PRE) to eliminate some partially redundant expressions in cases
285where doing so won't grow code size.</li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]286
Chris Lattnerea9c2242008-10-13 21:50:36 +0000[diff] [blame^]287<li>LLVM 2.4 includes a new loop deletion pass (which removes output-free
288provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE)
289pass that no longer uses control dependence information. These changes speed up
290the optimizer and also prevents it from deleting output-free infinite
291loops.</li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]292
Duncan Sands2aecc3f2008-10-13 18:42:43 +0000[diff] [blame]293<li>The new AddReadAttrs pass works out which functions are read-only or
294read-none (these correspond to 'pure' and 'const' in C) and marks them
295with the appropriate attribute.</li>
Chris Lattnerea9c2242008-10-13 21:50:36 +0000[diff] [blame^]296
297<li>LLVM 2.4 now includes a new SparsePropagation framework, which makes it
298trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using
299this interface means that you just define objects to represent your lattice
300values and the transfer functions that operate on them. It handles the
301mechanics of worklist processing, liveness tracking, handling PHI nodes,
302etc.</li>
303
304<li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
305pulled out of the Instruction Combining pass and put into a new
306<tt>ValueTracking.h</tt> header, where they can be reused by other passes.</li>
307
308<li>The tail duplication pass has been removed from the standard optimizer
309sequence used by llvm-gcc. This pass still exists, but the benefits it once
310provided are now achieved by other passes.</li>
311
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]312</ul>
313
314</div>
315
316<!--=========================================================================-->
317<div class="doc_subsection">
318<a name="codegen">Code Generator Improvements</a>
319</div>
320
321<div class="doc_text">
322
323<p>We put a significant amount of work into the code generator infrastructure,
324which allows us to implement more aggressive algorithms and make it run
325faster:</p>
326
327<ul>
Chris Lattnerea9c2242008-10-13 21:50:36 +0000[diff] [blame^]328<li>The target-independent code generator supports (and the X86 backend
329 currently implements) a new interface for "fast" instruction selection. This
330 interface is optimized to produce code as quickly as possible, sacrificing
331 code quality to do it. This is used by default at -O0 or when using
332 "llc -fast" on X86. It is straight-forward to add support for
333 other targets if faster -O0 compilation is desired.</li>
334
335<li>In addition to the new 'fast' instruction selection path, many existing
336 pieces of the code generator have been optimized in significant ways.
337 SelectionDAG's are now pool allocated and use better algorithms in many
338 places, the ".s" file printers now use raw_ostream to emit text much faster,
339 etc. The end result of these improvements is that the compiler also takes
340 substantially less time to generate code that is just as good (and often
341 better) than before.</li>
342
343<li>Each target has been split to separate the .s file printing logic from the
344 rest of the target. This enables JIT compilers that don't link in the
345 (somewhat large) code and data tables used for printing a .s file.</li>
346
347<li>The code generator now includes a "stack slot coloring" pass, which packs
348 together individual spilled values into common stack slots. This reduces
349 the size of stack frames with many spills, which tends to increase L1 cache
350 effectiveness.</li>
351
352<li>Various pieces of the register allocator (e.g. the coalescer and two-address
353 operation elimination pass) now know how to rematerialize trivial operations
354 to avoid copies and include several other optimizations.</li>
355
356<li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by
357 the <tt>llc -view-*-dags</tt> options are now significantly prettier and
358 easier to read.</li>
359
360<li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean
361 Quadratic Programming (PBQP). This register allocator is still in
362 development, but is very simple and clean.</li>
Chris Lattner0eef6e42008-06-08 02:45:07 +0000[diff] [blame]363
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]364</ul>
365
366</div>
367
368
369<!--=========================================================================-->
370<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]371<a name="x86specific">X86/X86-64 Specific Improvements</a>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]372</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]373
374<div class="doc_text">
Chris Lattnerc3649452008-02-10 08:17:19 +0000[diff] [blame]375<p>New target-specific features include:
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]376</p>
377
378<ul>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]379<li>Exception handling is supported by default on Linux/x86-64.</li>
Duncan Sandsd8745a92008-10-13 17:32:15 +0000[diff] [blame]380<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]381<li>...</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]382
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]383</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]384
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]385</div>
386
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]387<!--=========================================================================-->
388<div class="doc_subsection">
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]389<a name="targetspecific">Other Target Specific Improvements</a>
390</div>
391
392<div class="doc_text">
393<p>New target-specific features include:
394</p>
395
396<ul>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]397<li>MIPS floating point support?</li>
Duncan Sandsd8745a92008-10-13 17:32:15 +0000[diff] [blame]398<li>PowerPC now supports trampolines.</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]399<li>....</li>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]400</ul>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]401
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]402</div>
Chris Lattnere45f18b2008-06-05 08:02:49 +0000[diff] [blame]403
404
405<!--=========================================================================-->
406<div class="doc_subsection">
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]407<a name="otherimprovements">Other Improvements</a>
408</div>
409
410<div class="doc_text">
411<p>New features include:
412</p>
413
414<ul>
Mikhail Glushenkovcc2d3012008-10-13 02:46:01 +0000[diff] [blame]415<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]416 support. It is now easier to experiment with <tt>llvmc2</tt> and
417 build your own tools based on it. </li>
Chris Lattner4f076402008-10-12 19:47:48 +0000[diff] [blame]418<li>raw_ostream + formatting</li>
Chris Lattner548493b2008-10-12 22:57:58 +0000[diff] [blame]419<li>Recycler + pool allocation stuff?</li>
Chris Lattner2c3ef982008-10-11 18:18:28 +0000[diff] [blame]420<li>...</li>
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]421</ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]422
Chris Lattnerb0d6c502007-09-21 03:54:09 +0000[diff] [blame]423</div>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]424
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]425<!--=========================================================================-->
426<div class="doc_subsection">
427<a name="changes">Major Changes and Removed Features</a>
428</div>
429
430<div class="doc_text">
431
Chris Lattner78a130b2008-10-13 18:01:01 +0000[diff] [blame]432<p>If you're already an LLVM user, this section lists some "gotchas" that you
433may run into upgrading from the previous release.</p>
434
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]435<p>The LLVM IR generated by llvm-gcc no longer names all instructions.
436 Use the instnamer pass if you want everything named.</p>
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]437
Duncan Sands275d1e02008-10-13 18:33:28 +0000[diff] [blame]438<li>The LoadVN and GCSE passes have been removed.</li>
Chris Lattner92eacf82008-10-13 17:57:36 +0000[diff] [blame]439
440
441<p>LLVM API Changes:</p>
442
443<ul>
444
445<li>... Attributes changes ... </li>
446
447<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
448<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
449converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
450"llvm/Analysis/ValueTracking.h".</li>
451
452<li>API change: BinaryOperator::create -> Create (CmpInst, CastInst too)</li>
453<li>Various header files like "llvm/ADT/iterator" were given a .h suffix.
454 Change your code to #include "llvm/ADT/iterator.h" instead.</li>
455
456</ul>
457
458</div>
459
460
461
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]462<!-- *********************************************************************** -->
463<div class="doc_section">
464 <a name="portability">Portability and Supported Platforms</a>
465</div>
466<!-- *********************************************************************** -->
467
468<div class="doc_text">
469
470<p>LLVM is known to work on the following platforms:</p>
471
472<ul>
Mikhail Glushenkov808cd3e2008-10-13 02:08:34 +0000[diff] [blame]473<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]474 (and probably other unix-like systems).</li>
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]475<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]476 64-bit modes.</li>
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]477<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]478<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
479 support is available for native builds with Visual C++).</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]480<li>Sun UltraSPARC workstations running Solaris 10.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]481<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif5e75e652008-06-05 18:39:01 +0000[diff] [blame]482<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]483</ul>
484
Chris Lattnerba948522008-06-05 06:57:39 +0000[diff] [blame]485<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]486to the machine and operating system on which it is built. However, minor
487porting may be required to get LLVM to work on new platforms. We welcome your
488portability patches and reports of successful builds or error messages.</p>
489
490</div>
491
492<!-- *********************************************************************** -->
493<div class="doc_section">
494 <a name="knownproblems">Known Problems</a>
495</div>
496<!-- *********************************************************************** -->
497
498<div class="doc_text">
499
500<p>This section contains all known problems with the LLVM system, listed by
501component. As new problems are discovered, they will be added to these
502sections. If you run into a problem, please check the <a
503href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
504there isn't already one.</p>
505
506</div>
507
508<!-- ======================================================================= -->
509<div class="doc_subsection">
510 <a name="experimental">Experimental features included with this release</a>
511</div>
512
513<div class="doc_text">
514
515<p>The following components of this LLVM release are either untested, known to
516be broken or unreliable, or are in early development. These components should
517not be relied on, and bugs should not be filed against them, but they may be
518useful to some people. In particular, if you would like to work on one of these
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]519components, please contact us on the <a
520href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]521
522<ul>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]523<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]524<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattnerbd633de92008-02-06 06:30:34 +0000[diff] [blame]525 value for this option.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]526</ul>
527
528</div>
529
530<!-- ======================================================================= -->
531<div class="doc_subsection">
532 <a name="x86-be">Known problems with the X86 back-end</a>
533</div>
534
535<div class="doc_text">
536
537<ul>
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame]538 <li>The X86 backend does not yet support
539 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
540 floating point stack</a>. It supports the 'f' and 't' constraints, but not
541 'u'.</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]542 <li>The X86 backend generates inefficient floating point code when configured
543 to generate code for systems that don't have SSE2.</li>
Duncan Sands8b4f3772008-06-08 19:38:43 +0000[diff] [blame]544 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikov77d15e22008-06-08 10:24:13 +0000[diff] [blame]545 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
546 currently due
547 to <a href="http://llvm.org/PR2255">several</a>
Chris Lattnerf06141a2008-06-08 23:12:47 +0000[diff] [blame]548 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
549 'u' inline assembly constraint and X87 floating point inline assembly.</li>
Dan Gohman3882ecb2008-06-08 23:05:11 +0000[diff] [blame]550 <li>The X86-64 backend does not yet support the LLVM IR instruction
551 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
552 argument constructs on X86-64 by lowering them manually.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]553</ul>
554
555</div>
556
557<!-- ======================================================================= -->
558<div class="doc_subsection">
559 <a name="ppc-be">Known problems with the PowerPC back-end</a>
560</div>
561
562<div class="doc_text">
563
564<ul>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]565<li>The Linux PPC32/ABI support needs testing for the interpreter and static
566compilation, and lacks support for debug information.</li>
567</ul>
568
569</div>
570
571<!-- ======================================================================= -->
572<div class="doc_subsection">
573 <a name="arm-be">Known problems with the ARM back-end</a>
574</div>
575
576<div class="doc_text">
577
578<ul>
579<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sands1827fa62007-09-26 15:59:54 +0000[diff] [blame]580processors, thumb programs can crash or produce wrong
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]581results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
582<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
583</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]584<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
585 execute
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]586programs compiled with LLVM. Please use more recent versions of QEMU.</li>
587</ul>
588
589</div>
590
591<!-- ======================================================================= -->
592<div class="doc_subsection">
593 <a name="sparc-be">Known problems with the SPARC back-end</a>
594</div>
595
596<div class="doc_text">
597
598<ul>
599<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
600 support the 64-bit SPARC ABI (-m64).</li>
601</ul>
602
603</div>
604
605<!-- ======================================================================= -->
606<div class="doc_subsection">
607 <a name="alpha-be">Known problems with the Alpha back-end</a>
608</div>
609
610<div class="doc_text">
611
612<ul>
613
614<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
615appropriate nops inserted to ensure restartability.</li>
616
617</ul>
618</div>
619
620<!-- ======================================================================= -->
621<div class="doc_subsection">
622 <a name="ia64-be">Known problems with the IA64 back-end</a>
623</div>
624
625<div class="doc_text">
626
627<ul>
Chris Lattnerf06141a2008-06-08 23:12:47 +0000[diff] [blame]628<li>The Itanium backend is highly experimental, and has a number of known
629 issues. We are looking for a maintainer for the Itanium backend. If you
630 are interested, please contact the llvmdev mailing list.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]631</ul>
632
633</div>
634
635<!-- ======================================================================= -->
636<div class="doc_subsection">
637 <a name="c-be">Known problems with the C back-end</a>
638</div>
639
640<div class="doc_text">
641
642<ul>
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]643<li><a href="http://llvm.org/PR802">The C backend has only basic support for
644 inline assembly code</a>.</li>
Chris Lattnere0194462007-09-26 06:01:35 +0000[diff] [blame]645<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
646 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]647 C++ code compiled with llc or native compilers.</li>
Duncan Sandsbd0ad6e2008-02-10 13:40:55 +0000[diff] [blame]648<li>The C backend does not support all exception handling constructs.</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]649</ul>
650
651</div>
652
653
654<!-- ======================================================================= -->
655<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]656 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]657</div>
658
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]659<div class="doc_text">
660
Chris Lattnere0798082008-02-06 18:00:06 +0000[diff] [blame]661<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
662Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]663llvmdev mailing list if you are interested.</p>
664
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]665<p>The only major language feature of GCC not supported by llvm-gcc is
666 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
667 are only supported on some targets. For example, trampolines are only
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]668 supported on some targets (these are used when you take the address of a
669 nested function).</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]670
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]671<p>If you run into GCC extensions which are not supported, please let us know.
672</p>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]673
674</div>
675
676<!-- ======================================================================= -->
677<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]678 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]679</div>
680
681<div class="doc_text">
682
683<p>The C++ front-end is considered to be fully
684tested and works for a number of non-trivial programs, including LLVM
685itself, Qt, Mozilla, etc.</p>
686
687<ul>
Anton Korobeynikovd9a17932008-10-11 18:27:16 +0000[diff] [blame]688<li>Exception handling works well on the X86 and PowerPC targets. Currently
689 only linux and darwin targets are supported (both 32 and 64 bit).</li>
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]690</ul>
691
692</div>
693
694
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]695<!-- ======================================================================= -->
696<div class="doc_subsection">
Chris Lattner499c07c2008-06-05 06:35:40 +0000[diff] [blame]697 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]698</div>
699
700<div class="doc_text">
701The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
702technology and problems should be expected.
703<ul>
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]704<li>The Ada front-end currently only builds on X86-32. This is mainly due
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]705to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sandsa73561c2008-06-08 20:18:35 +0000[diff] [blame]706however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]707which does support trampolines.</li>
708<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
709Workaround: configure with --disable-bootstrap.</li>
Duncan Sands2dbc2e82008-10-13 17:27:23 +0000[diff] [blame]710<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
711and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
712(c380004 also fails with gcc-4.2 mainline).</li>
713<li>Some gcc specific Ada tests continue to crash the compiler.</li>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]714<li>The -E binder option (exception backtraces)
715<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
716crashing if an exception is raised. Workaround: do not use -E.</li>
717<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
718or finish at a non-byte offset</a> in a record. Workaround: do not pack records
719or use representation clauses that result in a field of a non-discrete type
720starting or finishing in the middle of a byte.</li>
Chris Lattnerd95b5962008-06-08 21:19:07 +0000[diff] [blame]721<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
722'main' as generated by the Ada binder to be invalid</a>.
723Workaround: hand edit the file to use pointers for <tt>argv</tt> and
724<tt>envp</tt> rather than integers.</li>
725<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
726ignored</a>.</li>
Chris Lattnerdaeb3232008-02-12 06:29:45 +0000[diff] [blame]727</ul>
728</div>
729
Dan Gohmanf17a25c2007-07-18 16:29:46 +0000[diff] [blame]730<!-- *********************************************************************** -->
731<div class="doc_section">
732 <a name="additionalinfo">Additional Information</a>
733</div>
734<!-- *********************************************************************** -->
735
736<div class="doc_text">
737
738<p>A wide variety of additional information is available on the <a
739href="http://llvm.org">LLVM web page</a>, in particular in the <a
740href="http://llvm.org/docs/">documentation</a> section. The web page also
741contains versions of the API documentation which is up-to-date with the
742Subversion version of the source code.
743You can access versions of these documents specific to this release by going
744into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
745
746<p>If you have any questions or comments about LLVM, please feel free to contact
747us via the <a href="http://llvm.org/docs/#maillist"> mailing
748lists</a>.</p>
749
750</div>
751
752<!-- *********************************************************************** -->
753
754<hr>
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