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2 <html><head><title>LLVM 1.0 Release Notes</title></head>
5 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
6 <tr><td> <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM 1.0 Release Notes</b></font></td>
10 <li><a href="#intro">Introduction</a>
11 <li><a href="#whatsnew">What's New?</a>
12 <li><a href="#portability">Portability and Supported Platforms</a>
13 <li><a href="#install-instructions">Installation Instructions</a>
14 <li><a href="#knownproblems">Known Problems</a>
16 <!-- <li><a href="#portabilityprobs">Portability Problems</a> -->
17 <li><a href="#core">Known problems with the LLVM Core</a>
18 <li><a href="#c-fe">Known problems with the C Front-end</a>
19 <li><a href="#c++-fe">Known problems with the C++ Front-end</a>
20 <li><a href="#x86-be">Known problems with the X86 Back-end</a>
21 <li><a href="#sparc-be">Known problems with the Sparc Back-end</a>
22 <li><a href="#c-be">Known problems with the C back-end</a>
24 <li><a href="#additionalinfo">Additional Information</a>
27 <p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
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32 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
33 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
34 <a name="intro">Introduction
35 </b></font></td></tr></table><ul>
36 <!-- *********************************************************************** -->
38 This document contains the release notes for the LLVM compiler infrastructure,
39 release 1.0. Here we describe how to install LLVM, as well as any known
40 problems. The most up-to-date version of this document can be found on the <a
41 href="http://llvm.cs.uiuc.edu/releases/1.0/">LLVM 1.0 web site</a>. If you are
42 not reading this on the LLVM web pages, you should probably go there, because
43 this document may be updated after the release.<p>
45 For more information about LLVM, including information about potentially more
46 current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
47 web site</a>. If you have questions or comments, the <a
48 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
49 list</a> is a good place to send them.<p>
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53 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
54 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
55 <a name="whatsnew">What's New?
56 </b></font></td></tr></table><ul>
57 <!-- *********************************************************************** -->
59 This is the first public release of the LLVM compiler infrastructure. As such,
60 it is all new! In particular, we are providing a stable C compiler, beta C++
61 compiler, a C back-end, stable X86 and Sparc V9 static and JIT code generators,
62 as well as a large suite of scalar and interprocedural optimizations.<p>
64 The default optimizer sequence used by the C/C++ front-ends is:<p>
67 <li>Interprocedural dead code elimination (-globaldce)
68 <li>Exception handling pruning (-prune-eh)
69 <li>Function inlining (-inline)
70 <li>Instruction combining (-instcombine)
71 <li>Cast elimination (-raise)
72 <li>Tail duplication (-tailduplicate)
73 <li>CFG simplification (-simplifycfg)
74 <li>Scalar replacement of aggregates (-scalarrepl)
75 <li>Tail call elimination (-tailcallelim)
76 <li>Instruction combining (-instcombine)
77 <li>Reassociation (-reassociate)
78 <li>Instruction combining (-instcombine)
79 <li>CFG simplification (-simplifycfg)
80 <li>Loop canonnicalization (-preheaders)
81 <li>Loop invariant code motion, with scalar promotion (-licm)
82 <li>Global common subexpression elimination, with load elimination (-gcse)
83 <li>Sparse conditional constant propagation (-sccp)
84 <li>Instruction combining (-instcombine)
85 <li>Induction variable canonicalization (-indvars)
86 <li>Aggressive dead code elimination (-adce)
87 <li>CFG simplication (-simplifycfg)
88 <li>Dead type elimination (-deadtypeelim)
89 <li>Global constant merging (-constmerge)
92 At link-time, the following optimizations are run:<p>
95 <li>Global constant merging (-constmerge)
96 <li>[optional] Internalization [which marks most functions and global variables static] (-internalize)
97 <li>Interprocedural dead argument elimination (-deadargelim)
98 <li>Instruction combining (-instcombine)
99 <li>CFG simplification (-simplifycfg)
100 <li>Interprocedural dead code elimination (-globaldce)
104 TODO: Works on: SPEC CPU 2000<p>
105 TODO: Works on: Olden/Ptrdist benchmarks<p>
107 The What's New section should give a bulletted list of what is
108 included, perhaps a couple of lists (Stable, Beta).<p>
110 It would be useful to give a pointer to a list of the available passes (at least
111 for the standard compiler techniques).<p>
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115 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
116 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
117 <a name="portability">Portability and Supported Platforms
118 </b></font></td></tr></table><ul>
119 <!-- *********************************************************************** -->
121 LLVM has only been extensively tested on ia32-linux and sparc-solaris machines.
122 The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
123 work on more platforms than that. However, it is extremely likely that we
124 missed something. We welcome portability patches and error messages.<p>
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128 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
129 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
130 <a name="install-instructions">Installation Instructions
131 </b></font></td></tr></table><ul>
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137 <!-- *********************************************************************** -->
138 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
139 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
140 <a name="knownproblems">Known Problems
141 </b></font></td></tr></table><ul>
142 <!-- *********************************************************************** -->
144 This section contains all known problems with the LLVM system, listed by
145 component. As new problems are discovered, they will be added to these
149 <!-- _______________________________________________________________________ -->
151 </ul><h4><a name="portability"><hr size=0>Portability Problems</h4><ul>
155 <!-- _______________________________________________________________________ -->
156 </ul><h4><a name="core"><hr size=0>Known problems with the LLVM Core</h4><ul>
158 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not work.<p>
160 <li>The JIT does not use mutexes to protect its internal data structures. As
161 such, execution of a threaded program could cause these data structures to
164 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.<p>
166 <li>Linking in static archive files (.a files) is very slow.
168 <!-- _______________________________________________________________________ -->
169 </ul><h4><a name="c-fe"><hr size=0>Known problems with the C front-end</h4><ul>
171 <li>Inline assembly is not yet supported.<p>
173 <li>"long double" is transformed by the front-end into "double". There is no
174 support for floating point data types of any size other than 32 and 64 bits.
176 <li>C99 Variable sized arrays do not release stack memory when they go out of
177 scope. Thus, the following program may run out of stack space:
179 for (i = 0; i != 1000000; ++i) {
185 <li>The following Unix system functionality has not been tested and may not work:
187 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
188 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions.
189 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
190 - These functions have not been tested.
193 <li>Although many GCC extensions are supported, some are not. In particular,
194 the following extensions are known to <b>not be</b> supported:
196 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.
197 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels, and computed gotos.
198 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.
199 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.
200 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.
201 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands
202 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.
203 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.
204 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.
205 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.
206 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.
207 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.
208 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.
211 The following GCC extensions are <b>partially</b> supported. An ignored
212 attribute means that the LLVM compiler ignores the presence of the attribute,
213 but the code should still work. An unsupported attribute is one which is
214 ignored by the LLVM compiler, which will cause a different interpretation of
218 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
219 Arrays whose length is computed at run time.<br>
220 Supported, but allocated stack space is not freed until the function returns (noted above).
222 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
223 Declaring that functions have no side effects, or that they can never return.<br>
224 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>, <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>, <tt>deprecated</tt>,
225 <tt>warn_unused_result</tt>, <tt>weak</tt><br>
226 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>, <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>, <tt>malloc</tt>
227 <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
228 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>, <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
229 <tt>fastcall</tt>, all other target specific attributes
231 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
232 Specifying attributes of variables.<br>
233 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
234 <tt>deprecated</tt>, <tt>transparent_union</tt>,
235 <tt>unused</tt>, <tt>weak</tt><br>
236 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
237 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
238 <tt>vector_size</tt>, <tt>dllimport</tt>,
239 <tt>dllexport</tt>, all target specific attributes.<br>
241 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.
242 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
243 <tt>deprecated</tt>, <tt>may_alias</tt>
244 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>
245 all target specific attributes.<br>
246 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
247 Other built-in functions.<br>
248 We support all builtins which have a C language equivalent (e.g.,
249 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
250 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
251 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).
255 The following extensions <b>are</b> known to be supported:
257 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.
258 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.
259 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.
260 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.
261 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.
262 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.
263 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.
264 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.
265 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.
266 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.
267 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.
268 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.
269 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>:Arithmetic on <code>void</code>-pointers and function pointers.
270 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.
271 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions or arrays as values.
272 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.
274 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>:Casting to union type from any member of the union.
275 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.
276 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.
278 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.
279 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.
280 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.
281 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character <ESC>.
282 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.
283 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).
284 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.
285 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.
286 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.
287 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.
288 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.
291 If you run into GCC extensions which have not been included in any of these
292 lists, please let us know (also including whether or not they work).
295 <!-- _______________________________________________________________________ -->
296 </ul><h4><a name="c++-fe"><hr size=0>Known problems with the C++ front-end</h4><ul>
298 For this release, the C++ front-end is considered to be of <b>beta</b> quality.
299 It works for a large number of simple programs, but has not been extensively
300 tested. We welcome bug reports though!<p>
302 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
305 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
306 parser is significantly more standards compliant (and picky) than prior GCC
307 versions. For more information, see the C++ section of the <a
308 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.<p>
310 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
311 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
312 function and in the <tt>setjmp</tt> receiver function may not be run.
313 Objects in intervening stack frames will be destroyed however (which is
314 better than most compilers).<p>
316 <li>The LLVM C++ front-end follows the <a
317 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
318 This document, which is not Itanium specific, specifies a standard for name
319 mangling, class layout, v-table layout, RTTI formats, and other C++
320 representation issues. Because we use this API, code generated by the LLVM
321 compilers should be binary compatible with machine code generated by other
322 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
323 <i>However</i>, the exception handling mechanism used by LLVM is very
324 different from the model used in the Itanium ABI, so <b>exceptions will not
325 interact correctly</b> .
327 <!-- _______________________________________________________________________ -->
328 </ul><h4><a name="x86-be"><hr size=0>Known problems with the X86 back-end</h4><ul>
330 <li>The X86 code generator does not currently support the <tt>unwind</tt>
331 instruction, so code that throws a C++ exception or calls the C <tt>longjmp</tt>
332 function will abort.<p>
334 <li>Some executables produced by LLC seem to intermittently crash (extremely
335 infrequently). The cause of the problem has not been diagnosed, and does not
339 <!-- _______________________________________________________________________ -->
340 </ul><h4><a name="sparc-be"><hr size=0>Known problems with the Sparc back-end</h4><ul>
342 <li>The Sparc code generator does not currently support the <tt>unwind</tt>
343 instruction, so code that throws a C++ exception or calls the C <tt>longjmp</tt>
344 function will abort.<p>
347 <!-- _______________________________________________________________________ -->
348 </ul><h4><a name="c-be"><hr size=0>Known problems with the C back-end</h4><ul>
350 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
351 Analysis rules. As such, special options may be necessary to compile the code
352 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
353 problem probably cannot be fixed.<p>
355 <li>Initializers for global variables that include floating point numbers may
356 not be initialized with exactly the right floating point number, if the number
357 is not accurately representable in decimal. This prevents the Olden "power"
358 benchmark from producing exactly the right results with the C back-end.<p>
360 <li>The code produces by the C back-end has only been tested with the Sun CC and
361 GCC compilers. It is possible that it will have to be adjusted to support other
366 <!-- *********************************************************************** -->
367 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
368 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
369 <a name="additionalinfo">Additional Information
370 </b></font></td></tr></table><ul>
371 <!-- *********************************************************************** -->
373 A wide variety of additional information is available on the LLVM web page,
374 including mailing lists publications describing algorithms and components
375 implemented in LLVM. The web page also contains versions of the API
376 documentation which is up-to-date with the CVS version of the source code. You
377 can access versions of these documents specific to this release by going into
378 the "<tt>llvm/www/doc/</tt>" directory in the LLVM tree.<p>
380 If you have any questions or comments about LLVM, please feel free to contact us
381 via the mailing lists.<p>
384 <!-- *********************************************************************** -->
386 <!-- *********************************************************************** -->
390 Maintained By: <a href="http://llvm.cs.uiuc.edu/">The LLVM Team</a><br>
391 <!-- Created: Wed Oct 1 17:38:54 CDT 2003 -->
393 Last modified: Tue Oct 7 16:32:37 CDT 2003