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6 <title>LLVM 1.2 Release Notes</title>
10 <div class="doc_title">
11 LLVM 1.2 Release Notes
15 <li><a href="#intro">Introduction</a></li>
16 <li><a href="#whatsnew">What's New?</a></li>
17 <li><a href="#portability">Portability and Supported Platforms</a></li>
18 <li><a href="#install-instructions">Installation Instructions</a></li>
19 <li><a href="#knownproblems">Known Problems</a>
21 <li><a href="#core">Known problems with the LLVM Core</a>
22 <li><a href="#c-fe">Known problems with the C Front-end</a>
23 <li><a href="#c++-fe">Known problems with the C++ Front-end</a>
24 <li><a href="#x86-be">Known problems with the X86 Back-end</a>
25 <li><a href="#sparc-be">Known problems with the Sparc Back-end</a>
26 <li><a href="#c-be">Known problems with the C back-end</a>
28 <li><a href="#additionalinfo">Additional Information</a></li>
31 <div class="doc_text">
32 <p><b>Written by the <a href="http://llvm.cs.uiuc.edu">LLVM team</a></b><p>
35 <!-- *********************************************************************** -->
36 <div class="doc_section">
37 <a name="intro">Introduction</a>
39 <!-- *********************************************************************** -->
41 <div class="doc_text">
43 <p>This document contains the release notes for the LLVM compiler
44 infrastructure, release 1.2. Here we describe the status of LLVM, including any
45 known problems and bug fixes from the previous release. The most up-to-date
46 version of this document can be found on the <a
47 href="http://llvm.cs.uiuc.edu/releases/1.2/">LLVM 1.2 web site</a>. If you are
48 not reading this on the LLVM web pages, you should probably go there because
49 this document may be updated after the release.</p>
51 <p>For more information about LLVM, including information about potentially more
52 current releases, please check out the <a href="http://llvm.cs.uiuc.edu">main
53 web site</a>. If you have questions or comments, the <a
54 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
55 list</a> is a good place to send them.</p>
57 <p>Note that if you are reading this file from CVS, this document applies
58 to the <i>next</i> release, not the current one. To see the release notes for
59 the current or previous releases, see the <a
60 href="http://llvm.cs.uiuc.edu/releases/">releases page</a>.</p>
64 <!-- *********************************************************************** -->
65 <div class="doc_section">
66 <a name="whatsnew">What's New?</a>
68 <!-- *********************************************************************** -->
70 <div class="doc_text">
73 This is the third public release of the LLVM compiler infrastructure. This
74 release incorporates several <a href="#newfeatures">new features</a> (including
75 exception handling support for the native code generators, the start of a
76 source-level debugger, and profile guided optimizer components), many <a
77 href="#qualityofimp">speedups</a> and <a href="#codequality">code quality</a>
78 improvements, documentation improvements, and a small collection of important <a
79 href="bugfix">bug fixes</a>. Overall, this is our highest quality release to
80 date, and we encourage you to upgrade if you are using LLVM 1.0 or 1.1.
83 <p><B> FIXME: UPDATE: </b>
84 At this time, LLVM is known to correctly compile and run all C
85 & C++ SPEC CPU2000 benchmarks, the Olden benchmarks, and the Ptrdist
86 benchmarks. It has also been used to compile <b>many</b> other programs. LLVM
87 now also works with a broad variety of C++ programs, though it has still
88 received less testing than the C front-end.
91 <!--=========================================================================-->
92 <div class="doc_subsubsection">
93 <a name="newfeatures">This release implements the following new features:</a>
97 <li><a href="SourceLevelDebugging.html">A new LLVM source-level debugger has been started.</a></li>
98 <li>LLVM 1.2 encodes bytecode files for large programs in 10-30% less space.</li>
99 <li>LLVM can now feed profile information back into optimizers for Profile Guided Optimization, includes a simple basic block reordering pass, and supports edge profiling as well as function and block-level profiling.</li>
100 <li>The LLVM JIT lazily initializes global variables, reducing startup time for programs with lots of globals (like C++ programs).</li>
102 <li>The build and installation infrastructure in this release is dramatically
103 improved. There is now an <a
104 href="http://llvm.cs.uiuc.edu/PR105"><tt>autoconf/AutoRegen.sh</tt> script</a>
105 that you can run to rebuild the <tt>configure</tt> script and its associated
106 files as well as beta support for "<a
107 href="http://llvm.cs.uiuc.edu/PR208">make</a> <a
108 href="http://llvm.cs.uiuc.edu/PR220">install</a>" and <a
109 href="http://llvm.cs.uiuc.edu/PR203">RPM package generation</a>.</li>
111 <li>The "tblgen" tool is <a href="TableGenFundamentals.html">now documented</a>.</li>
112 <li>The target-independent code generator got several improvements:
114 <li>It can now fold spill code into instructions (on targets that support it).</li>
115 <li>A generic machine code spiller/rewriter was added. It provides an API for
116 global register allocators to eliminate virtual registers and add the
117 appropriate spill code.</li>
118 <li>The represenation of machine code basic blocks is more efficient and has
119 an easier to use interface.</li>
122 <li><a href="http://llvm.cs.uiuc.edu/PR253">LLVM now no longer depends on the boost library</a>.</li>
123 <li>The X86 backend now generates <b>substantially</b> better native code, and is faster.</li>
124 <li>The C backend has been turned moved from the "llvm-dis" tool to the "llc"
125 tool. You can activate it with "<tt>llc -march=c foo.bc -o foo.c</tt>".</li>
126 <li>LLVM includes a new interprocedural optimization that marks global variables
127 "constant" when they are provably never written to.</li>
128 <li>LLVM now includes a new interprocedural optimization that converts small "by reference" arguments to "by value" arguments, which is often improve the performance of C++ programs substantially.</li>
132 <!--=========================================================================-->
133 <div class="doc_subsubsection">
134 In this release, the following missing features were implemented:
138 <li><a href="http://llvm.cs.uiuc.edu/PR16">Exception handling support in the X86
139 & Sparc native code generators</a></li>
140 <li>The C/C++ front-end now support the GCC <tt>__builtin_return_address</tt> and <tt>__builtin_frame_address</tt> extensions.</li>
141 <li><a href="http://llvm.cs.uiuc.edu/PR249">[X86] Missing cast from ULong -> Double, cast FP -> bool and support for -9223372036854775808</a></li>
145 <!--=========================================================================-->
146 <div class="doc_subsubsection">
147 <a name="qualityofimp">In this release, the following Quality of Implementation issues were fixed:</a>
152 <li><a href="http://llvm.cs.uiuc.edu/PR135">JIT should lazily initialize global variables</a></li>
153 <li><a href="http://llvm.cs.uiuc.edu/PR192">[X86] X86 Backend never releases memory for machine code structures</a></li>
154 <li><a href="http://llvm.cs.uiuc.edu/PR196">[vmcore] OpaqueType objects memory leak</a></li>
155 <li><a href="http://llvm.cs.uiuc.edu/PR182">[llvmgcc] C front-end does not compile "extern inline" into linkonce</a></li>
156 <li><a href="http://llvm.cs.uiuc.edu/PR73">Bytecode format inconsistent</a></li>
157 <li><a href="http://llvm.cs.uiuc.edu/PR209">[loadvn/inline/scalarrepl] Slow optimizations with extremely large basic blocks</a></li>
158 <li><a href="http://llvm.cs.uiuc.edu/PR224">[asmparser] Really slow parsing of types with complex upreferences</a></li>
159 <li><a href="http://llvm.cs.uiuc.edu/PR205">[llvmgcc] C front-end does not emit 'zeroinitializer' when possible</a></li>
160 <li><a href="http://llvm.cs.uiuc.edu/PR233">[llvmgcc] Structure copies result in a LOT of code</a></li>
161 <li><a href="http://llvm.cs.uiuc.edu/PR239">LLVM is now much more memory efficient when handling large zero initialized arrays</a></li>
162 <li><a href="http://llvm.cs.uiuc.edu/PR275">[llvmgcc] Local array initializers are expanded into large amounts of code</a></li>
165 <!--=========================================================================-->
166 <div class="doc_subsubsection">
167 In this release, the following build problems were fixed:
171 <li><a href="http://llvm.cs.uiuc.edu/PR210">[build] Makefiles break if C frontend target string has unexpected value</a></li>
172 <li><a href="http://llvm.cs.uiuc.edu/PR214">[build] hard-wired assumption that shared-library extension is ".so"</a></li>
173 <li><A href="http://llvm.cs.uiuc.edu/PR222">make tools-only doesn't make lib/Support</a></li>
176 <!--=========================================================================-->
177 <div class="doc_subsubsection">
178 <a name="codequality">In this release, the following Code Quality issues were fixed:</a>
182 <li><a href="http://llvm.cs.uiuc.edu/PR187">[loopsimplify] Many pointless phi nodes are created</a></li>
183 <li><a href="http://llvm.cs.uiuc.edu/PR237">[x86] wierd stack/frame pointer manipulation</a></li>
185 <li>The X86 backend now generate <tt>fchs</tt> to negate floating point numbers,
186 compiles memcpy() into the <tt>rep movs</tt> instruction, and makes much better
187 use of powerful addressing modes and instructions.</li>
191 <!--=========================================================================-->
192 <div class="doc_subsubsection">
193 <a name="bugfix">In this release, the following bugs in the previous release were fixed:</a>
196 <p>Bugs in the LLVM Core:</p>
199 <li><a href="http://llvm.cs.uiuc.edu/PR179">[licm] LICM promotes volatile memory
200 locations to registers</a></li>
201 <li><a href="http://llvm.cs.uiuc.edu/PR191">[licm] Memory read after free causes
202 infrequent crash</a></li>
203 <li><a href="http://llvm.cs.uiuc.edu/PR194">[indvars] Induction variable
204 canonicalization always makes 32-bit indvars</a></li>
205 <li><a href="http://llvm.cs.uiuc.edu/PR193">[constantmerge] Merging globals can
206 cause use of invalid pointers!</a></li>
207 <li><a href="http://llvm.cs.uiuc.edu/PR212">[bcreader] Bytecode reader misreads 'long -9223372036854775808'!</a></li>
208 <li><a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=174">Tail duplication does not update SSA form correctly.</a></li>
209 <li><a href="http://llvm.cs.uiuc.edu/PR218">VMCore mishandles double -0.0</a></li>
210 <li><a href="http://llvm.cs.uiuc.edu/PR219">[X86] X86 backend code generates -0.0 as +0.0</a></li>
211 <li><a href="http://llvm.cs.uiuc.edu/PR223">[loopsimplify] Loopsimplify incorrectly updates dominator information</a></li>
212 <li><a href="http://llvm.cs.uiuc.edu/PR225">[pruneeh] -pruneeh pass removes invoke instructions it shouldn't</a></li>
213 <li><a href="http://llvm.cs.uiuc.edu/PR228">[sparc] Boolean constants are emitted as true and false</a></li>
214 <li><a href="http://llvm.cs.uiuc.edu/PR234">[interpreter] va_list values silently corrupted by function calls</a></li>
215 <li><a href="http://llvm.cs.uiuc.edu/PR235">Tablegen aborts on errors</a></li>
216 <li><a href="http://llvm.cs.uiuc.edu/PR236">[inliner] Error inlining intrinsic calls into invoke instructions</a></li>
217 <li><a href="http://llvm.cs.uiuc.edu/PR245">Linking weak and strong global variables is dependent on link order</a></li>
218 <li><a href="http://llvm.cs.uiuc.edu/PR258">Variables used to define non-printable FP constants are externally visible</a></li>
219 <li><a href="http://llvm.cs.uiuc.edu/PR259">CBE gives linkonce functions wrong linkage semantics</a></li>
220 <li><a href="http://llvm.cs.uiuc.edu/PR274">[JIT] Programs cannot resolve the fstat function</a></li>
221 <li><a href="http://llvm.cs.uiuc.edu/PR284">[indvars] Induction variable analysis violates LLVM invariants</a></li>
226 <p>Bugs in the C/C++ front-end:</p>
229 <li><a href="http://llvm.cs.uiuc.edu/PR186">Need weak linkage on memory
230 management functions in libc runtime to allow them to be overriden</a></li>
231 <li><a href="http://llvm.cs.uiuc.edu/PR202">[llvm-gcc] asserts when an extern inline function is redefined</a></li>
232 <li><a href="http://llvm.cs.uiuc.edu/PR204">[llvmg++] Dynamically initialized constants cannot be marked 'constant'</a></li>
233 <li><a href="http://llvm.cs.uiuc.edu/PR216">[llvmgcc] floating-point unary minus is incorrect for +0.0</a></li>
234 <li><a href="http://llvm.cs.uiuc.edu/PR221">[llvm-gcc] miscompilation of 'X = Y = Z' with aggregate values</a></li>
235 <li><a href="http://llvm.cs.uiuc.edu/PR244">[llvm-gcc] miscompilation when a function is re-declared as static</a></li>
236 <li><a href="http://llvm.cs.uiuc.edu/PR272">[llvmgcc] Invalid code created for complex division operation</a></li>
237 <li><a href="http://llvm.cs.uiuc.edu/PR268">[llvmgcc] Incorrect code generation for pointer subtraction</a></li>
238 <li><a href="http://llvm.cs.uiuc.edu/PR261">[llvmg++] Crash assigning pointers-to-members with casted types</a></li>
243 <!-- *********************************************************************** -->
244 <div class="doc_section">
245 <a name="portability">Portability and Supported Platforms</a>
247 <!-- *********************************************************************** -->
249 <div class="doc_text">
251 <p>LLVM has been extensively tested on Intel and AMD machines running Red
252 Hat Linux and FreeBSD. It has also been tested on Sun UltraSPARC workstations running Solaris 8.
254 LLVM works on Mac OS X 10.3 and above, but only with the C backend or
255 interpreter (no native backend for the PowerPC is available yet).
256 The core LLVM infrastructure uses "autoconf" for portability, so hopefully we
257 work on more platforms than that. However, it is likely that we
258 missed something and that minor porting is required to get LLVM to work on
259 new platforms. We welcome portability patches and error messages.</p>
263 <!-- *********************************************************************** -->
264 <div class="doc_section">
265 <a name="knownproblems">Known Problems</a>
267 <!-- *********************************************************************** -->
269 <div class="doc_text">
271 <p>This section contains all known problems with the LLVM system, listed by
272 component. As new problems are discovered, they will be added to these
273 sections. If you run into a problem, please check the <a
274 href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
275 there isn't already one.</p>
279 <!-- _______________________________________________________________________ -->
281 </ul><h4><a name="portability"><hr size=0>Portability Problems</h4><ul>
285 <!-- ======================================================================= -->
286 <div class="doc_subsection">
287 <a name="core">Known problems with the LLVM Core</a>
290 <div class="doc_text">
294 <li>In the JIT, <tt>dlsym</tt> on a symbol compiled by the JIT will not
297 <li>The JIT does not use mutexes to protect its internal data structures. As
298 such, execution of a threaded program could cause these data structures to be
301 <li>It is not possible to <tt>dlopen</tt> an LLVM bytecode file in the JIT.</li>
303 <li>Linking in static archive files (.a files) is very slow (there is no symbol
304 table in the archive).</li>
306 <li><a href="http://llvm.cs.uiuc.edu/PR82">LLVM cannot handle structures with
307 more than 256 elements</a>.</li>
309 <li>The gccld program <a href="http://llvm.cs.uiuc.edu/PR139">does not link objects/archives in the order specified on the command line.</a></li>
311 <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not mark
312 values live across a setjmp as volatile</a>. This missing feature only affects
313 targets whose setjmp/longjmp libraries do not save and restore the entire
318 <!-- ======================================================================= -->
319 <div class="doc_subsection">
320 <a name="c-fe">Known problems with the C front-end</a>
323 <!-- _______________________________________________________________________ -->
324 <div class="doc_subsubsection">Bugs</div>
326 <div class="doc_text">
328 <li>C99 Variable sized arrays do not release stack memory when they go out of
329 scope. Thus, the following program may run out of stack space:
331 for (i = 0; i != 1000000; ++i) {
338 Initialization of global union variables can only be done
339 <a href="http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=162">with the largest
345 <!-- _______________________________________________________________________ -->
346 <div class="doc_subsubsection">
350 <div class="doc_text">
354 <li>Inline assembly is not yet supported.</li>
356 <li>"long double" is transformed by the front-end into "double". There is no
357 support for floating point data types of any size other than 32 and 64
360 <li>The following Unix system functionality has not been tested and may not
363 <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the
364 appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that
365 <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly.
366 <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt>
367 - These functions have not been tested.
370 <li>Although many GCC extensions are supported, some are not. In particular,
371 the following extensions are known to <b>not be</b> supported:
373 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
374 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li>
375 <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.</li>
376 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
377 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li>
378 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
379 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li>
380 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li>
381 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li>
382 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li>
383 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html#Thread-Local">Thread-Local</a>: Per-thread variables.</li>
384 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
387 <p>The following GCC extensions are <b>partially</b> supported. An ignored
388 attribute means that the LLVM compiler ignores the presence of the attribute,
389 but the code should still work. An unsupported attribute is one which is
390 ignored by the LLVM compiler and will cause a different interpretation of
394 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
395 Arrays whose length is computed at run time.<br>
396 Supported, but allocated stack space is not freed until the function returns (noted above).</li>
398 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
400 Declaring that functions have no side effects or that they can never
403 <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
404 <tt>constructor</tt>, <tt>destructor</tt>, <tt>unused</tt>,
405 <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
407 <b>Ignored:</b> <tt>noreturn</tt>, <tt>noinline</tt>,
408 <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
409 <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
411 <b>Unsupported:</b> <tt>used</tt>, <tt>section</tt>, <tt>alias</tt>,
412 <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
413 <tt>fastcall</tt>, all other target specific attributes</li>
415 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
416 Specifying attributes of variables.<br>
417 <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
418 <tt>deprecated</tt>, <tt>transparent_union</tt>,
419 <tt>unused</tt>, <tt>weak</tt><br>
421 <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
422 <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
423 <tt>vector_size</tt>, <tt>dllimport</tt>,
424 <tt>dllexport</tt>, all target specific attributes.</li>
426 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
427 <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
428 <tt>deprecated</tt>, <tt>may_alias</tt><br>
430 <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
431 all target specific attributes.</li>
433 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
434 Other built-in functions.<br>
435 We support all builtins which have a C language equivalent (e.g.,
436 <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
437 <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
438 <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> (ignored).</li>
442 <p>The following extensions <b>are</b> known to be supported:</p>
445 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
446 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li>
447 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
448 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
449 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
450 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
451 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
452 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
453 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
454 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li>
455 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
456 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li>
457 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li>
458 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
459 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
460 or arrays as values.</li>
461 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
462 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li>
463 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
464 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
465 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
466 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C---Comments.html#C++%20Comments">C++ Comments</a>: C++ comments are recognized.</li>
467 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
468 <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>.</li>
469 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
470 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
471 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li>
472 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li>
473 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li>
474 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li>
475 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li>
476 <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
481 <p>If you run into GCC extensions which have not been included in any of these
482 lists, please let us know (also including whether or not they work).</p>
486 <!-- ======================================================================= -->
487 <div class="doc_subsection">
488 <a name="c++-fe">Known problems with the C++ front-end</a>
491 <div class="doc_text">
493 <p>For this release, the C++ front-end is considered to be fully functional but
494 has not been tested as thoroughly as the C front-end. It has been tested and
495 works for a number of non-trivial programs, but there may be lurking bugs.
496 Please report any bugs or problems.</p>
500 <!-- _______________________________________________________________________ -->
501 <div class="doc_subsubsection">Bugs</div>
503 <div class="doc_text">
506 <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
511 <!-- _______________________________________________________________________ -->
512 <div class="doc_subsubsection">
516 <div class="doc_text">
520 <li>The C++ front-end is based on a pre-release of the GCC 3.4 C++ parser. This
521 parser is significantly more standards compliant (and picky) than prior GCC
522 versions. For more information, see the C++ section of the <a
523 href="http://gcc.gnu.org/gcc-3.4/changes.html">GCC 3.4 release notes</a>.</li>
525 <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
526 performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
527 function and in the <tt>setjmp</tt> receiver function may not be run.
528 Objects in intervening stack frames will be destroyed, however (which is
529 better than most compilers).</li>
531 <li>The LLVM C++ front-end follows the <a
532 href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
533 This document, which is not Itanium specific, specifies a standard for name
534 mangling, class layout, v-table layout, RTTI formats, and other C++
535 representation issues. Because we use this API, code generated by the LLVM
536 compilers should be binary compatible with machine code generated by other
537 Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
538 <i>However</i>, the exception handling mechanism used by LLVM is very
539 different from the model used in the Itanium ABI, so <b>exceptions will not
540 interact correctly</b>. </li>
546 <!-- ======================================================================= -->
547 <div class="doc_subsection">
548 <a name="x86-be">Known problems with the X86 back-end</a>
551 <div class="doc_text">
559 <!-- ======================================================================= -->
560 <div class="doc_subsection">
561 <a name="sparc-be">Known problems with the Sparc back-end</a>
564 <div class="doc_text">
572 <!-- ======================================================================= -->
573 <div class="doc_subsection">
574 <a name="c-be">Known problems with the C back-end</a>
577 <div class="doc_text">
581 <li>The C back-end produces code that violates the ANSI C Type-Based Alias
582 Analysis rules. As such, special options may be necessary to compile the code
583 (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
584 problem probably cannot be fixed.</li>
586 <li><a href="http://llvm.cs.uiuc.edu/PR33">Initializers for global variables</a>
587 cannot include special floating point numbers like Not-A-Number or
590 <li><a href="http://llvm.cs.uiuc.edu/PR56">Zero arg vararg functions are not
591 supported</a>. This should not affect LLVM produced by the C or C++
598 <!-- *********************************************************************** -->
599 <div class="doc_section">
600 <a name="additionalinfo">Additional Information</a>
602 <!-- *********************************************************************** -->
604 <div class="doc_text">
606 <p>A wide variety of additional information is available on the LLVM web page,
607 including mailing lists and publications describing algorithms and components
608 implemented in LLVM. The web page also contains versions of the API
609 documentation which is up-to-date with the CVS version of the source code. You
610 can access versions of these documents specific to this release by going into
611 the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
613 <p>If you have any questions or comments about LLVM, please feel free to contact
614 us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
619 <!-- *********************************************************************** -->
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