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| author | Chris Lattner <sabre@nondot.org> | 2007-05-18 06:39:06 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2007-05-18 06:39:06 +0000 |
| commit | 4171182f48248612633966c6a19a1e9ac5a05cee (patch) | |
| tree | c2be5c43f02389ed2ed2832c58d8ed70e8645a55 | |
| parent | 6903edbd7fbdca7f716ff48785ef472acd98769d (diff) | |
first cut of llvm 2.0 release notes
git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_20@37220 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | docs/ReleaseNotes.html | 643 |
1 files changed, 406 insertions, 237 deletions
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html index 279a17906c..abf2582c2f 100644 --- a/docs/ReleaseNotes.html +++ b/docs/ReleaseNotes.html @@ -4,11 +4,11 @@ <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <link rel="stylesheet" href="llvm.css" type="text/css"> - <title>LLVM 1.9 Release Notes</title> + <title>LLVM 2.0 Release Notes</title> </head> <body> -<div class="doc_title">LLVM 1.9 Release Notes</div> +<div class="doc_title">LLVM 2.0 Release Notes</div> <ol> <li><a href="#intro">Introduction</a></li> @@ -32,13 +32,10 @@ <div class="doc_text"> <p>This document contains the release notes for the LLVM compiler -infrastructure, release 1.9. Here we describe the status of LLVM, including any -known problems and major improvements from the previous release. The most -up-to-date version of this document (corresponding to LLVM CVS) can be found -on the <a -href="http://llvm.org/releases/">LLVM releases web site</a>. If you are -not reading this on the LLVM web pages, you should probably go there because -this document may be updated after the release.</p> +infrastructure, release 2.0. Here we describe the status of LLVM, including any +known problems and major improvements from the previous release. All LLVM +releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM +releases web site</a>. <p>For more information about LLVM, including information about the latest release, please check out the <a href="http://llvm.org/">main LLVM @@ -61,67 +58,175 @@ href="http://llvm.org/releases/">releases page</a>.</p> <div class="doc_text"> -<p>This is the tenth public release of the LLVM Compiler Infrastructure. This -release incorporates a large number of enhancements, new features, and bug -fixes. We recommend that all users of previous LLVM versions upgrade. -</p> +<p>This is the eleventh public release of the LLVM Compiler Infrastructure. +Being the first major release since 1.0, this release is different in several +ways from our previous releases:</p> + +<ol> +<li>We took this as an opportunity to +break backwards compatibility with the LLVM 1.x bytecode and .ll file format. +If you have LLVM 1.9 .ll files that you would like to upgrade to LLVM 2.x, we +recommend the use of the stand alone <a href="#llvm-upgrade">llvm-upgrade</a> +tool (which is included with 2.0). We intend to keep compatibility with .ll +and .bc formats within the 2.x release series, like we did within the 1.x +series.</li> +<li>There are several significant change to the LLVM IR and internal APIs, such + as a major overhaul of the type system, the completely new bitcode file + format, etc (described below).</li> +<li>We designed the release around a 6 month release cycle instead of the usual + 3-month cycle. This gave us extra time to develop and test some of the + more invasive features in this release.</li> +<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end. Users are required to + upgrade to llvm-gcc4. llvm-gcc4 includes many features over + llvm-gcc3, is faster, and is <a href="CFEBuildInstrs.html">much easier to + build from source</a>.</li> +</ol> + +<p>Note that while this is a major version bump, this release has been + extensively tested on a wide range of software. It is easy to say that this + is our best release yet, in terms of both features and correctness. This is + the first LLVM release to correctly compile and optimize major software like + LLVM itself, Mozilla/Seamonkey, Qt 4.3rc1, kOffice, etc out of the box on + linux/x86. + </p> </div> <!--=========================================================================--> <div class="doc_subsection"> -<a name="newfeatures">New Features in LLVM 1.9</a> +<a name="newfeatures">New Features in LLVM 2.0</a> </div> <!--_________________________________________________________________________--> -<div class="doc_subsubsection"><a name="x86-64">New X86-64 Backend</a></div> +<div class="doc_subsubsection"><a name="majorchanges">Major Changes</a></div> <div class="doc_text"> -<p>LLVM 1.9 now fully supports the x86-64 instruction set on Mac OS/X, and -supports it on Linux (and other operating systems) when compiling in -static -mode. LLVM includes JIT support for X86-64, and supports both Intel EMT-64T -and AMD-64 architectures. The X86-64 instruction set permits addressing a -64-bit addressing space and provides the compiler with twice the -number of integer registers to use.</p> -</div> -<!--_________________________________________________________________________--> -<div class="doc_subsubsection"><a name="lto">Link-Time Optimization integration -with native linkers</a></div> -<div class="doc_text"> -<p>LLVM now includes <a href="LinkTimeOptimization.html">liblto</a> which can -be used to integrate LLVM Link-Time Optimization support into a native linker. -This allows LLVM .bc to transparently participate with linking an application, -even when some .o files are in LLVM form and some are not.</p> +<p>Changes to the LLVM IR itself:</p> + +<ul> + +<li>Integer types are now completely signless. This means that we + have types like i8/i16/i32 instead of ubyte/sbyte/short/ushort/int + etc. LLVM operations that depend on sign have been split up into + separate instructions (<a href="http://llvm.org/PR950">PR950</a>). This + eliminates cast instructions that just change the sign of the operands (e.g. + int -> uint), which reduces the size of the IR and makes optimizers + simpler to write.</li> + +<li>Integer types with arbitrary bitwidths (e.g. i13, i36, i42, i1057, etc) are + now supported in the LLVM IR and optimizations (<a + href="http://llvm.org/PR1043">PR1043</a>). However, neither llvm-gcc + (<a href="http://llvm.org/PR1284">PR1284</a>) nor the native code generators + (<a href="http://llvm.org/PR1270">PR1270</a>) support non-standard width + integers yet.</li> + +<li>'Type planes' have been removed (<a href="http://llvm.org/PR411">PR411</a>). + It is no longer possible to have two values with the same name in the + same symbol table. This simplifies LLVM internals, allowing significant + speedups.</li> + +<li>Global variables and functions in .ll files are now prefixed with + @ instead of % (<a href="http://llvm.org/PR645">PR645</a>).</li> + +<li>The LLVM 1.x "bytecode" format has been replaced with a + completely new binary representation, named 'bitcode'. The <a + href="BitCodeFormat.html">Bitcode Format</a> brings a + number of advantages to the LLVM over the old bytecode format: it is denser + (files are smaller), more extensible, requires less memory to read, + is easier to keep backwards compatible (so LLVM 2.5 will read 2.0 .bc + files), and has many other nice features.</li> + +<li>Load and store instructions now track the alignment of their pointer + (<a href="http://www.llvm.org/PR400">PR400</a>). This allows the IR to + express loads that are not sufficiently aligned (e.g. due to '<tt>#pragma + packed</tt>') or to capture extra alignment information.</li> +</ul> + +<p>Major new features:</p> + +<ul> + +<li>A number of ELF features are now supported by LLVM, including 'visibility', + extern weak linkage, Thread Local Storage (TLS) with the <tt>__thread</tt> + keyword, and symbol aliases. + Among other things, this means that many of the special options needed to + configure llvm-gcc on linux are no longer needed, and special hacks to build + large C++ libraries like Qt are not needed.</li> + +<li>LLVM now has a new MSIL backend. llc -march=msil will now turn LLVM + into MSIL (".net") bytecode. This is still fairly early development + with a number of limitations.</li> + +<li>A new <a href="CommandGuide/html/llvm-upgrade.html">llvm-upgrade</a> tool + exists to migrates LLVM 1.9 .ll files to LLVM 2.0 syntax.</li> +</ul> + </div> + <!--_________________________________________________________________________--> -<div class="doc_subsubsection"><a name="dwarf">DWARF debugging -support for Linux, Cygwin and MinGW on X86</a></div> +<div class="doc_subsubsection"><a name="llvmgccfeatures">llvm-gcc +Improvements</a></div> <div class="doc_text"> -<p>llvm-gcc4 now supports generating debugging info for Linux, Cygwin and MinGW. -This extends the PPC/Darwin and X86/Darwin debugging support available in the -1.8 release. DWARF is a standard debugging format used on many platforms.</p> +<p>New features include: +</p> + +<ul> +<li>Precompiled Headers (PCH) are now supported.</li> + +<li>"<tt>#pragma packed</tt>" is now supported, as are the various features + described above (visibility, extern weak linkage, __thread, aliases, + etc).</li> + +<li>Tracking function parameter/result attributes is now possible.</li> + +<li>Many internal enhancements have been added, such as improvements to + NON_LVALUE_EXPR, arrays with non-zero base, structs with variable sized + fields, VIEW_CONVERT_EXPR, CEIL_DIV_EXPR, nested functions, and many other + things. This is primarily to supports non-C GCC front-ends, like Ada.</li> + +<li>It is simpler to configure llvm-gcc for linux.</li> + +</ul> + </div> <!--_________________________________________________________________________--> <div class="doc_subsubsection"><a name="optimizer">Optimizer Improvements</a></div> + <div class="doc_text"> -<p>The mid-level optimizer is now faster and produces better code in many cases. - Significant changes include:</p> +<p>New features include: +</p> <ul> -<li>LLVM includes a new 'predicate simplifier' pass, which - currently performs dominator tree-based optimizations.</li> -<li>The complete loop unroll pass now supports unrolling of - multiple basic block loops.</li> -<li>The 'globalopt' pass can now perform the scalar replacement of - aggregates transformation on some heap allocations.</li> -<li>The globalsmodref-aa alias analysis can now track 'indirect pointer - globals' more accurately.</li> -<li>The instruction combiner can now perform element propagation -analysis of vector expressions, eliminating computation of vector elements -that are not used.</li> +<li>The <a href="WritingAnLLVMPass.html">pass manager</a> has been entirely + rewritten, making it significantly smaller, simpler, and more extensible. + Support has been added to run FunctionPasses interlaced with + CallGraphSCCPasses, and we now support loop transformations explicitly with + LoopPass.</li> + +<li>The <tt>-scalarrepl</tt> pass can now promote unions containing FP values + into a register, it can also handle unions of vectors of the same + size.</li> + +<li>LLVM 2.0 includes a new loop rotation pass, which converts "for loops" into + "do/while loops", where the condition is at the bottom of the loop.</li> + +<li>The Loop Strength Reduction pass has been improved, and support added + for sinking expressions across blocks to reduce register pressure.</li> + +<li>ModulePasses may now use the result of FunctionPasses.</li> + +<li>The [Post]DominatorSet classes have been removed from LLVM and clients + switched to use the far-more-efficient ETForest class instead.</li> + +<li>The ImmediateDominator class has also been removed, and clients have been + switched to use DominatorTree instead.</li> + +<li>The predicate simplifier pass has been improved, making it able to do + simple value range propagation and eliminate more conditionals.</li> + </ul> </div> @@ -132,96 +237,229 @@ Generator Enhancements</a></div> <div class="doc_text"> <p> -The LLVM Target-Independent code generator now supports more target features and -optimizes many cases more aggressively. New features include: +New features include: </p> <ul> -<li>LLVM now includes a late branch folding pass which optimizes code - layout, performs several branch optzns, and deletes unreachable code.</li> -<li>The code generator now support targets that have pre/post-increment - addressing modes.</li> -<li>LLVM now supports dynamically-loadable register allocators and - schedulers.</li> -<li>LLVM 1.9 includes several improvements to inline asm support, - including support for new constraints and modifiers.</li> -<li>The register coalescer is now more aggressive than before, - allowing it to eliminate more copies.</li> + +<li>Support was added for software floating point, which allows LLVM to target + chips that don't have hardware FPUs (e.g. ARM thumb mode).</li> + +<li>A new register scavenger has been implemented, which is useful for + finding free registers after register allocation. This is useful when + rewriting frame references on RISC targets, for example.</li> + +<li>Heuristics have been added to avoid coalescing vregs with very large live + ranges to physregs. This was bad because it effectively pinned the physical + register for the entire lifetime of the virtual register (<a + href="http://llvm.org/PR711">PR711</a>).</li> + +<li>Support now exists for very simple (but still very useful) + rematerialization the register allocator, enough to move + instructions like "load immediate" and constant pool loads.</li> + +<li>Switch statement lowering is significantly better, improving codegen for + sparse switches that have dense subregions, and implemented support + for the shift/and trick.</li> + +<li>Added support for tracking physreg sub-registers and super-registers + in the code generator, as well as extensive register + allocator changes to track them.</li> + +<li>There is initial support for virtreg sub-registers + (<a href="http://llvm.org/PR1350">PR1350</a>).</li> + +</ul> + +<p> +Other improvements include: +</p> + +<ul> + +<li>Inline assembly support is much more solid that before. + The two primary features still missing are support for 80-bit floating point + stack registers on X86 (<a href="http://llvm.org/PR879">PR879</a>), and + support for inline asm in the C backend (<a + href="http://llvm.org/PR802">PR802</a>).</li> + +<li>DWARF debug information generation has been improved. LLVM now passes + most of the GDB testsuite on MacOS and debug info is more dense.</li> + +<li>Codegen support for Zero-cost DWARF exception handling has been added (<a + href="http://llvm.org/PR592">PR592</a>). It is mostly + complete and just in need of continued bug fixes and optimizations at + this point. However, support in llvm-g++ is disabled with an + #ifdef for the 2.0 release (<a + href="http://llvm.org/PR870">PR870</a>).</li> + +<li>The code generator now has more accurate and general hooks for + describing addressing modes ("isLegalAddressingMode") to + optimizations like loop strength reduction and code sinking.</li> + +<li>Progress has been made on a direct Mach-o .o file writer. Many small + apps work, but it is still not quite complete.</li> + </ul> <p>In addition, the LLVM target description format has itself been extended in several ways:</p> <ul> -<li>tblgen now allows definition of '<a - href="TableGenFundamentals.html#multiclass">multiclasses</a>' which can be - used to factor instruction patterns more aggressively in .td files.</li> -<li>LLVM has a new TargetAsmInfo class which captures a variety of - information about the target assembly language format.</li> -<li>.td files now support "<tt>${:foo}</tt>" syntax for encoding - subtarget-specific assembler syntax into instruction descriptions.</li> +<li>Extended TargetData to support better target parameterization in + the .ll/.bc files, eliminating the 'pointersize/endianness' attributes + in the files (<a href="http://llvm.org/PR761">PR761</a>).</li> + +<li>TargetData was generalized for finer grained alignment handling, + handling of vector alignment, and handling of preferred alignment</li> + +<li>LLVM now supports describing target calling conventions + explicitly in .td files, reducing the amount of C++ code that needs + to be written for a port.</li> + +</ul> + +</div> + +<!--_________________________________________________________________________--> +<div class="doc_subsubsection"><a name="specifictargets">Target-Specific +Improvements</a></div> + +<div class="doc_text"> + +<p>X86-specific Code Generator Enhancements: +</p> + +<ul> +<li>The MMX instruction set is now supported through intrinsics.</li> +<li>The scheduler was improved to better reduce register pressure on + X86 and other targets that are register pressure sensitive.</li> +<li>Linux/x86-64 support is much better.</li> +<li>PIC support for linux/x86 has been added.</li> +<li>The X86 backend now supports the GCC regparm attribute.</li> +<li>LLVM now supports inline asm with multiple constraint letters per operand + (like "ri") which is common in X86 inline asms.</li> </ul> -<p>Further, several significant target-specific enhancements are included in -LLVM 1.9:</p> +<p>ARM-specific Code Generator Enhancements:</p> <ul> -<li>The LLVM ARM backend now supports more instructions - and the use of a frame pointer. It is now possible to build - libgcc and a simple cross compiler, but it is not considered "complete" yet. - </li> -<li>LLVM supports the Win32 dllimport/dllexport linkage and - stdcall/fastcall calling conventions.</li> +<li>The ARM code generator is now stable and fully supported.</li> + +<li>There are major new features, including support for ARM + v4-v6 chips, vfp support, soft float point support, pre/postinc support, + load/store multiple generation, constant pool entry motion (to support + large functions), and inline asm support, weak linkage support, static + ctor/dtor support and many bug fixes.</li> +<li>Added support for Thumb code generation (<tt>llc -march=thumb</tt>).</li> + +<li>The ARM backend now supports the ARM AAPCS/EABI ABI and PIC codegen on + arm/linux.</li> + +<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li> +</ul> + +<p>PowerPC-specific Code Generator Enhancements:</p> + +<ul> +<li>The PowerPC 64 JIT now supports addressing code loaded above the 2G + boundary.</li> + +<li>Improved support for the Linux/ppc ABI and the linux/ppc JIT is fully + functional now. llvm-gcc and static compilation are not fully supported + yet though.</li> + +<li>Many PowerPC 64 bug fixes.</li> + </ul> </div> + <!--_________________________________________________________________________--> <div class="doc_subsubsection"><a name="other">Other Improvements</a></div> <div class="doc_text"> -<p>This release includes many other improvements, including improvements to - the optimizers and code generators (improving the generated code) changes to - speed up the compiler in many ways (improving algorithms and fine tuning - code), and changes to reduce the code size of the compiler itself.</p> <p>More specific changes include:</p> <ul> -<li>The llvm-test framework now supports SPEC2006.</li> -<li>LLVM now includes a <a href="GetElementPtr.html">FAQ about the -<tt>getelementptr</tt> instruction</a>.</li> -<li>Bugpoint now supports a new "<tt>-find-bugs</tt>" mode. This mode makes - bugpoint permute pass sequences to try to expose bugs due to pass - sequencing.</li> -<li>The JIT now supports lazily streaming code from multiple modules at a - time, implicitly linking the code as it goes.</li> -</ul> -</div> +<li>LLVM no longer relies on static destructors to shut itself down. Instead, + it lazily initializes itself and shuts down when <tt>llvm_shutdown()</tt> is + explicitly called.</li> -<!--=========================================================================--> -<div class="doc_subsection"> -<a name="apichanges">Significant API Changes in LLVM 1.9</a> +<li>LLVM now has significantly fewer static constructors, reducing startup time. + </li> + +<li>Several classes have been refactored to reduce the amount of code that + gets linked into apps that use the JIT.</li> + +<li>Construction of intrinsic function declarations has been simplified.</li> + +<li>The gccas/gccld tools have been replaced with small shell scripts.</li> + +<li>Support has been added to llvm-test for running on low-memory + or slow machines (make SMALL_PROBLEM_SIZE=1).</li> + +</ul> </div> +<!--_________________________________________________________________________--> +<div class="doc_subsubsection"><a name="apichanges">API Changes</a></div> <div class="doc_text"> -<p>Several significant API changes have been made. If you are maintaining -out-of-tree code, please be aware that:</p> +<p>LLVM 2.0 contains a revamp of the type system and several other significant +internal changes. If you are programming to the C++ API, be aware of the +following major changes:</p> <ul> -<li>The ConstantSInt and ConstantUInt classes have been merged into the - ConstantInt class.</li> -<li><p>As a step towards making LLVM's integer types signless, several new -instructions have been added to LLVM. The <tt>Div</tt> instruction is now -<tt>UDiv</tt>, <tt>SDiv</tt>, and <tt>FDiv</tt>. The <tt>Rem</tt> instruction -is now <tt>URem</tt>, <tt>SRem</tt> and <tt>FRem</tt>. See the -<a href="LangRef.html">Language Reference</a> for details on these new -instructions.</p> -<li><p><tt>ConstantBool::True</tt> and <tt>ConstantBool::False</tt> have been - renamed to <tt>ConstantBool::getTrue()</tt> and - <tt>ConstantBool::getFalse()</tt>.</p></li> -<li>The 'analyze' tool has been merged into the 'opt' tool.</li> +<li>Pass registration is slightly different in LLVM 2.0 (you now need an + intptr_t in your constructor), as explained in the <a + href="WritingAnLLVMPass.html#basiccode">Writing an LLVM Pass</a> + document.</li> + +<li><tt>ConstantBool</tt>, <tt>ConstantIntegral</tt> and <tt>ConstantInt</tt> + classes have been merged together, we now just have + <tt>ConstantInt</tt>.</li> + +<li><tt>Type::IntTy</tt>, <tt>Type::UIntTy</tt>, <tt>Type::SByteTy</tt>, ... are + replaced by <tt>Type::Int8Ty</tt>, <tt>Type::Int16Ty</tt>, etc. LLVM types + have always corresponded to fixed size types + (e.g. long was always 64-bits), but the type system no longer includes + information about the sign of the type.</li> + +<li>Several classes (<tt>CallInst</tt>, <tt>GetElementPtrInst</tt>, + <tt>ConstantArray</tt>, etc), that once took <tt>std::vector</tt> as + arguments now take ranges instead. For example, you can create a + <tt>GetElementPtrInst</tt> with code like: + + <pre> + Value *Ops[] = { Op1, Op2, Op3 }; + GEP = new GetElementPtrInst(BasePtr, Ops, 3); + </pre> + + This avoids creation of a temporary vector (and a call to malloc/free). If + you have an std::vector, use code like this: + <pre> + std::vector<Value*> Ops = ...; + GEP = new GetElementPtrInst(BasePtr, &Ops[0], Ops.size()); + </pre> + + </li> + +<li>CastInst is now abstract and its functionality is split into several parts, + one for each of the <a href="LangRef.html#convertops">new cast + instructions</a>.</li> + +<li><tt>Instruction::getNext()/getPrev()</tt> are now private (along with + <tt>BasicBlock::getNext</tt>, etc), for efficiency reasons (they are now no + longer just simple pointers). Please use BasicBlock::iterator, etc instead. +</li> + +<li><tt>Module::getNamedFunction()</tt> is now called + <tt>Module::getFunction()</tt>.</li> +<li><tt>SymbolTable.h</tt> has been split into <tt>ValueSymbolTable.h</tt> and +<tt>TypeSymbolTable.h</tt>.</li> </ul> </div> @@ -289,8 +527,8 @@ components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/l <ul> <li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a future release.</li> +<li>C++ EH support</li> <li>The IA64 code generator is experimental.</li> -<li>The ARM code generator is experimental.</li> <li>The Alpha JIT is experimental.</li> <li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the <tt>-filetype</tt> llc option.</li> @@ -307,9 +545,7 @@ components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/l <ul> <li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline - assembly that uses the X86 floating point stack</a>. See the <a - href="http://llvm.org/PR879">bug</a> for details on workarounds on - Linux.</li> + assembly that uses the X86 floating point stack</a>.</li> </ul> </div> @@ -324,52 +560,42 @@ components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/l <ul> <li><a href="http://llvm.org/PR642">PowerPC backend does not correctly implement ordered FP comparisons</a>.</li> -<li>The 64-bit PowerPC backend is not fully stable. If you desire PPC64 support, - please use mainline CVS LLVM, which has several important bug fixes.</li> +<li>The Linux PPC32/ABI support needs testing for the interpreter and static +compilation, and lacks Dwarf debugging informations. </ul> </div> <!-- ======================================================================= --> <div class="doc_subsection"> - <a name="sparc-be">Known problems with the SPARC back-end</a> + <a name="arm-be">Known problems with the ARM back-end</a> </div> <div class="doc_text"> <ul> -<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not - support the 64-bit SPARC ABI (-m64).</li> +<li>The Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6 +processors, any thumb program compiled with LLVM crashes or produces wrong +results. (<a href="http://llvm.org/PR1388">PR1388</a>)</li> +<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested. +</li> +<li>QEMU-ARM (<= 0.9.0) wrongly executes programs compiled with LLVM. A non-affected QEMU version must be used or this +<a href="http://cvs.savannah.nongnu.org/viewcvs/qemu/target-arm/translate.c?root=qemu&r1=1.46&r2=1.47&makepatch=1&diff_format=h"> +patch</a> must be applied on QEMU.</li> </ul> </div> <!-- ======================================================================= --> <div class="doc_subsection"> - <a name="c-be">Known problems with the C back-end</a> + <a name="sparc-be">Known problems with the SPARC back-end</a> </div> <div class="doc_text"> <ul> - -<li>The C back-end produces code that violates the ANSI C Type-Based Alias -Analysis rules. As such, special options may be necessary to compile the code -(for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This -problem probably cannot be fixed.</li> - -<li><a href="http://llvm.org/PR56">Zero arg vararg functions are not -supported</a>. This should not affect LLVM produced by the C or C++ -frontends.</li> - -<li>The C backend does not correctly implement the <a -href="LangRef.html#int_stacksave"><tt>llvm.stacksave</tt></a> or -<a href="LangRef.html#int_stackrestore"><tt>llvm.stackrestore</tt></a> -intrinsics. This means that some code compiled by it can run out of stack -space if they depend on these (e.g. C99 varargs).</li> - -<li><a href="http://llvm.org/PR802">The C backend does not support inline - assembly code</a>.</li> +<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not + support the 64-bit SPARC ABI (-m64).</li> </ul> </div> @@ -415,36 +641,25 @@ programs.</li> <li>Defining vararg functions is not supported (but calling them is ok).</li> +<li>The Itanium backend has bitrotted somewhat.</li> </ul> </div> <!-- ======================================================================= --> <div class="doc_subsection"> - <a name="arm-be">Known problems with the ARM back-end</a> + <a name="c-be">Known problems with the C back-end</a> </div> <div class="doc_text"> <ul> -<li>The ARM backend is currently in early development stages, it is not -ready for production use.</li> +<li><a href="http://llvm.org/PR802">The C backend does not support inline + assembly code</a>.</li> </ul> </div> -<!-- ======================================================================= --> -<div class="doc_subsection"> - <a name="core">Known problems with the LLVM Core</a> -</div> - -<div class="doc_text"> - -<ul> - <li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not - work.</li> -</ul> -</div> <!-- ======================================================================= --> <div class="doc_subsection"> @@ -456,15 +671,9 @@ ready for production use.</li> <div class="doc_text"> -<p> - -<p>llvm-gcc4 is far more stable and produces better code than llvm-gcc3, but -does not currently support <a href="http://llvm.org/PR869">Link-Time -Optimization</a> or <a href="http://llvm.org/PR870">C++ Exception Handling</a>, -which llvm-gcc3 does.</p> - -<p>llvm-gcc4 does not support the <a href="http://llvm.org/PR947">GCC indirect -goto extension</a>, but llvm-gcc3 does.</p> +<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time +Optimization</a> on most platforms "out-of-the-box". Please inquire on the +llvmdev mailing list if you are interested.</p> </div> @@ -474,86 +683,52 @@ goto extension</a>, but llvm-gcc3 does.</p> </div> <div class="doc_text"> - <ul> -<li>"long double" is transformed by the front-end into "double". There is no -support for floating point data types of any size other than 32 and 64 -bits.</li> +<li><p>"long double" is silently transformed by the front-end into "double". There +is no support for floating point data types of any size other than 32 and 64 +bits.</p></li> -<li>Although many GCC extensions are supported, some are not. In particular, - the following extensions are known to <b>not be</b> supported: - <ol> - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li> - <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> - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li> - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li> - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li> - </ol> - - <p>The following GCC extensions are <b>partially</b> supported. An ignored - attribute means that the LLVM compiler ignores the presence of the attribute, - but the code should still work. An unsupported attribute is one which is - ignored by the LLVM compiler and will cause a different interpretation of - the program.</p> +<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet. + See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p> +</li> +<li><p>llvm-gcc <b>partially</b> supports tthese GCC extensions:</p> <ol> - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>: - Arrays whose length is computed at run time.<br> - Supported, but allocated stack space is not freed until the function returns (noted above).</li> + <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.<br> + Nested functions are supported, but llvm-gcc does not support non-local + gotos or taking the address of a nested function.</li> <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>: Declaring that functions have no side effects or that they can never return.<br> - <b>Supported:</b> <tt>constructor</tt>, <tt>destructor</tt>, + <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>, + <tt>constructor</tt>, <tt>destructor</tt>, <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>, - <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, + <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noreturn</tt>, <tt>regparm</tt> <tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>, <tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br> - <b>Ignored:</b> <tt>noinline</tt>, - <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>, - <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br> - - <b>Unsupported:</b> <tt>alias</tt>, <tt>regparm</tt>, all other target specific - attributes</li> - - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>: - Specifying attributes of variables.<br> - <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>, - <tt>deprecated</tt>, <tt>dllimport</tt>, <tt>dllexport</tt>, - <tt>section</tt>, <tt>transparent_union</tt>, <tt>unused</tt>, - <tt>used</tt>, <tt>weak</tt><br> - - <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>, - <tt>shared</tt>, <tt>tls_model</tt>, - <tt>vector_size</tt>, all target specific attributes. - </li> - - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br> - <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>, - <tt>deprecated</tt>, <tt>may_alias</tt><br> - - <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>, - all target specific attributes.</li> - - <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>: - Other built-in functions.<br> - We support all builtins which have a C language equivalent (e.g., - <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>, - <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>, - <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> - (currently ignored). We also support builtins for ISO C99 floating - point comparison macros (e.g., <tt>__builtin_islessequal</tt>), - <tt>__builtin_prefetch</tt>, <tt>__builtin_popcount[ll]</tt>, - <tt>__builtin_clz[ll]</tt>, and <tt>__builtin_ctz[ll]</tt>.</li> + <b>Ignored:</b> <tt>noinline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>, + <tt>malloc</tt>, <tt>no_instrument_function</tt></li> </ol> +</li> - <p>The following extensions <b>are</b> known to be supported:</p> +<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p> <ol> + <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li> + <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li> + <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>: + Other built-in functions.</li> + <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>: + Specifying attributes of variables.</li> + <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li> + <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li> + <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>: + Arrays whose length is computed at run time.</li> <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> <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li> <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> @@ -609,20 +784,15 @@ lists, please let us know (also including whether or not they work).</p> <div class="doc_text"> -<p>For this release, the C++ front-end is considered to be fully +<p>The C++ front-end is considered to be fully tested and works for a number of non-trivial programs, including LLVM -itself.</p> +itself, Qt, Mozilla, etc.</p> -</div> - -<!-- _______________________________________________________________________ --> -<div class="doc_subsubsection"> - Notes -</div> - -<div class="doc_text"> <ul> -<li>llvm-gcc4 does not support C++ exception handling at all yet.</li> +<li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++ +Exception Handling</a>, and it is not enabled by default.</li> + +<!-- NO EH Support! <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is performed. In particular, destructors for objects in the <tt>longjmp</tt>ing @@ -640,7 +810,7 @@ itself.</p> <i>However</i>, the exception handling mechanism used by llvm-gcc3 is very different from the model used in the Itanium ABI, so <b>exceptions will not interact correctly</b>. </li> - +--> </ul> </div> @@ -656,11 +826,10 @@ itself.</p> <div class="doc_text"> <p>A wide variety of additional information is available on the <a -href="http://llvm.org">LLVM web page</a>, including <a -href="http://llvm.org/docs/">documentation</a> and <a -href="http://llvm.org/pubs/">publications describing algorithms and -components implemented in LLVM</a>. The web page also contains versions of the -API documentation which is up-to-date with the CVS version of the source code. +href="http://llvm.org">LLVM web page</a>, in particular in the <a +href="http://llvm.org/docs/">documentation</a> section. The web page also +contains versions of the API documentation which is up-to-date with the CVS +version of the source code. You can access versions of these documents specific to this release by going into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p> @@ -679,7 +848,7 @@ lists</a>.</p> <a href="http://validator.w3.org/check/referer"><img src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a> - <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br> + <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br> Last modified: $Date$ </address> |