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| author | Tanya Lattner <tonic@nondot.org> | 2008-11-10 05:50:57 +0000 |
|---|---|---|
| committer | Tanya Lattner <tonic@nondot.org> | 2008-11-10 05:50:57 +0000 |
| commit | 607faa54b2ea98f97171b0094e18cc10681b8fde (patch) | |
| tree | 0ae7906eff22f9f8ac93c7d5e9fd1ed62127c86d | |
| parent | 6bd60cd93871905232dd811e1e57e98e32b71d43 (diff) | |
Merge from mainline.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_24@58967 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | docs/ReleaseNotes.html | 765 |
1 files changed, 410 insertions, 355 deletions
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html index 56dd66a21a..15167fe575 100644 --- a/docs/ReleaseNotes.html +++ b/docs/ReleaseNotes.html @@ -1,32 +1,29 @@ - <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <link rel="stylesheet" href="llvm.css" type="text/css"> - <title>LLVM 2.3 Release Notes</title> + <title>LLVM 2.4 Release Notes</title> </head> <body> -<div class="doc_title">LLVM 2.3 Release Notes</div> - +<div class="doc_title">LLVM 2.4 Release Notes</div> + <ol> <li><a href="#intro">Introduction</a></li> - <li><a href="#changes">Major Changes and Sub-project Status</a></li> - <li><a href="#whatsnew">What's New?</a></li> + <li><a href="#subproj">Sub-project Status Update</a></li> + <li><a href="#whatsnew">What's New in LLVM?</a></li> <li><a href="GettingStarted.html">Installation Instructions</a></li> <li><a href="#portability">Portability and Supported Platforms</a></li> - <li><a href="#knownproblems">Known Problems</a> + <li><a href="#knownproblems">Known Problems</a></li> <li><a href="#additionalinfo">Additional Information</a></li> </ol> <div class="doc_author"> - <p>Written by the <a href="http://llvm.org">LLVM Team</a><p> + <p>Written by the <a href="http://llvm.org">LLVM Team</a></p> </div> -<!-- Done through Week-of-Mon-20080324.txt --> - <!-- *********************************************************************** --> <div class="doc_section"> <a name="intro">Introduction</a> @@ -35,174 +32,175 @@ <div class="doc_text"> -<p>This document contains the release notes for the LLVM compiler -infrastructure, release 2.3. Here we describe the status of LLVM, including -major improvements from the previous release and any known problems. All LLVM -releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM -releases web site</a>.</p> +<p>This document contains the release notes for the LLVM Compiler +Infrastructure, release 2.4. Here we describe the status of LLVM, including +major improvements from the previous release and significant known problems. +All LLVM releases may be downloaded from the <a +href="http://llvm.org/releases/">LLVM releases web site</a>.</p> <p>For more information about LLVM, including information about the latest release, please check out the <a href="http://llvm.org/">main LLVM web site</a>. If you have questions or comments, the <a -href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing -list</a> is a good place to send them.</p> +href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing +List</a> is a good place to send them.</p> -<p>Note that if you are reading this file from a Subversion checkout or the +<p>Note that if you are reading this file from a Subversion checkout or the main LLVM web page, this document applies to the <i>next</i> release, not the -current one. To see the release notes for a specific releases, please see the +current one. To see the release notes for a specific release, please see the <a href="http://llvm.org/releases/">releases page</a>.</p> </div> +<!-- Unfinished features in 2.4: + Machine LICM + Machine Sinking + LegalizeDAGTypes + llc -enable-value-prop, propagation of value info (sign/zero ext info) from + one MBB to another + --> + + <!-- for announcement email: + mention dev mtg + Xcode 3.1 and 3.1.1. + --> + <!-- *********************************************************************** --> <div class="doc_section"> - <a name="changes">Major Changes and Sub-project Status</a> + <a name="subproj">Sub-project Status Update</a> </div> <!-- *********************************************************************** --> <div class="doc_text"> - -<p>This is the fourteenth public release of the LLVM Compiler Infrastructure. -It includes a large number of features and refinements from LLVM 2.2.</p> +<p> +The LLVM 2.4 distribution currently consists of code from the core LLVM +repository (which roughly includes the LLVM optimizers, code generators and +supporting tools) and the llvm-gcc repository. In addition to this code, the +LLVM Project includes other sub-projects that are in development. The two which +are the most actively developed are the <a href="#clang">Clang Project</a> and +the <a href="#vmkit">VMKit Project</a>. +</p> </div> -<!-- Unfinished features in 2.3: - Machine LICM - Machine Sinking - LegalizeDAGTypes - --> <!--=========================================================================--> <div class="doc_subsection"> -<a name="changes">Major Changes in LLVM 2.3</a> +<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a> </div> <div class="doc_text"> -<p>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with - llvm-gcc 4.2.</p> +<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build +a set of new 'LLVM native' front-end technologies for the LLVM optimizer +and code generator. Clang is continuing to make major strides forward in all +areas. Its C and Objective-C parsing support is very solid, and the code +generation support is far enough along to build many C applications. While not +yet production quality, it is progressing very nicely. In addition, C++ +front-end work has started to make significant progress.</p> -<p>LLVM 2.3 no longer includes the <tt>llvm-upgrade</tt> tool. It was useful - for upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a - previous LLVM release to do this. One nice impact of this is that the LLVM - regression test suite no longer depends on llvm-upgrade, which makes it run - faster.</p> +<p>Clang, in conjunction with the <tt>ccc</tt> driver, is now usable as a +replacement for gcc for building some small- to medium-sized C applications. +Additionally, Clang now has code generation support for Objective-C on Mac OS X +platform. Major highlights include:</p> -<p>The <tt>llvm2cpp</tt> tool has been folded into llc, use - <tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p> +<ul> + <li> Clang/ccc pass almost all of the LLVM test suite on Mac OS X and Linux +on the 32-bit x86 architecture. This includes significant C +applications such as <a href="http://www.sqlite.org">sqlite3</a>, +<a href="http://www.lua.org">lua</a>, and +<a href="http://www.clamav.net">Clam AntiVirus</a>. </li> + + <li> Clang can build the majority of Objective-C examples shipped with the +Mac OS X Developer Tools. </li> +</ul> -<p>LLVM API Changes:</p> +<p>Clang code generation still needs considerable testing and development, +however. Some areas under active development include:</p> <ul> -<li>Several core LLVM IR classes have migrated to use the - '<tt>FOOCLASS::Create(...)</tt>' pattern instead of '<tt>new - FOOCLASS(...)</tt>' (e.g. where FOOCLASS=<tt>BasicBlock</tt>). We hope to - standardize on <tt>FOOCLASS::Create</tt> for all IR classes in the future, - but not all of them have been moved over yet.</li> -<li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to - <a href="http://llvm.org/doxygen/classllvm_1_1IRBuilder.html">IRBuilder</a>. - </li> -<li>MRegisterInfo was renamed to - <a href="http://llvm.org/doxygen/classllvm_1_1TargetRegisterInfo.html"> - TargetRegisterInfo</a>.</li> -<li>The MappedFile class is gone, please use - <a href="http://llvm.org/doxygen/classllvm_1_1MemoryBuffer.html"> - MemoryBuffer</a> instead.</li> -<li>The '<tt>-enable-eh</tt>' flag to llc has been removed. Now code should - encode whether it is safe to omit unwind information for a function by - tagging the Function object with the '<tt>nounwind</tt>' attribute.</li> -<li>The ConstantFP::get method that uses APFloat now takes one argument - instead of two. The type argument has been removed, and the type is - now inferred from the size of the given APFloat value.</li> - + <li> Improved support for C and Objective-C features, for example + variable-length arrays, va_arg, exception handling (Obj-C), and garbage + collection (Obj-C). </li> + <li> ABI compatibility, especially for platforms other than 32-bit + x86. </li> </ul> + </div> <!--=========================================================================--> <div class="doc_subsection"> -<a name="otherprojects">Other LLVM Sub-Projects</a> +<a name="clangsa">Clang Static Analyzer</a> </div> <div class="doc_text"> -<p> -The core LLVM 2.3 distribution currently consists of code from the core LLVM -repository (which roughly contains the LLVM optimizer, code generators and -supporting tools) and the llvm-gcc repository. In addition to this code, the -LLVM Project includes other sub-projects that are in development. The two which -are the most actively developed are the new <a href="#vmkit">vmkit Project</a> -and the <a href="#clang">Clang Project</a>. -</p> -</div> -<!--=========================================================================--> -<div class="doc_subsubsection"> -<a name="vmkit">vmkit</a> -</div> +<p>The Clang project also includes an early stage static source code analysis +tool for <a href="http://clang.llvm.org/StaticAnalysis.html">automatically +finding bugs</a> in C and Objective-C programs. The tool performs a growing set +of checks to find bugs that occur on a specific path within a program. Examples +of bugs the tool finds include logic errors such as null dereferences, +violations of various API rules, dead code, and potential memory leaks in +Objective-C programs. Since its inception, public feedback on the tool has been +extremely positive, and conservative estimates put the number of real bugs it +has found in industrial-quality software on the order of thousands.</p> -<div class="doc_text"> -<p> -The "vmkit" project is a new addition to the LLVM family. It is an -implementation of a JVM and a CLI Virtual Machines (Microsoft .NET is an -implementation of the CLI) using the Just-In-Time compiler of LLVM.</p> +<p>The tool also provides a simple web GUI to inspect potential bugs found by +the tool. While still early in development, the GUI illustrates some of the key +features of Clang: accurate source location information, which is used by the +GUI to highlight specific code expressions that relate to a bug (including those +that span multiple lines); and built-in knowledge of macros, which is used to +perform inline expansion of macros within the GUI itself.</p> -<p>The JVM, called JnJVM, executes real-world applications such as Apache -projects (e.g. Felix and Tomcat) and the SpecJVM98 benchmark. It uses the GNU -Classpath project for the base classes. The CLI implementation, called N3, is -its in early stages but can execute simple applications and the "pnetmark" -benchmark. It uses the pnetlib project as its core library.</p> - -<p>The 'vmkit' VMs compare in performance with industrial and top open-source -VMs on scientific applications. Besides the JIT, the VMs use many features of -the LLVM framework, including the standard set of optimizations, atomic -operations, custom function provider and memory manager for JITed methods, and -specific virtual machine optimizations. vmkit is not an official part of LLVM -2.3 release. It is publicly available under the LLVM license and can be -downloaded from: -</p> - -<div class="doc_code"> -<pre>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</pre> -</div> +<p>The set of checks performed by the static analyzer is gradually expanding, +and future plans for the tool include full source-level inter-procedural +analysis and deeper checks such as buffer overrun detection. There are many +opportunities to extend and enhance the static analyzer, and anyone interested +in working on this project is encouraged to get involved!</p> </div> <!--=========================================================================--> -<div class="doc_subsubsection"> -<a name="clang">Clang</a> +<div class="doc_subsection"> +<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a> </div> <div class="doc_text"> +<p> +The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of +a JVM and a CLI Virtual Machines (Microsoft .NET is an +implementation of the CLI) using the Just-In-Time compiler of LLVM.</p> -<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build -a set of new 'LLVM native' front-end technologies for the LLVM optimizer -and code generator. Clang is continuing to make major strides forward in all -areas. Its C and Objective-C parsing support is very solid, and the code -generation support is far enough along to build many C applications. While not -yet production quality, it is progressing very nicely. In addition, C++ -front-end work has started to make significant progress.</p> +<p>Following LLVM 2.4, VMKit has its first release 0.24 that you can find on its +<a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes +bug fixes, cleanup and new features. The major changes are:</p> -<p>At this point, Clang is most useful if you are interested in source-to-source -transformations (such as refactoring) and other source-level tools for C and -Objective-C. Clang now also includes tools for turning C code into pretty HTML, -and includes a new <a href="http://clang.llvm.org/StaticAnalysis.html">static -analysis tool</a> in development. This tool focuses on automatically finding -bugs in C and Objective-C code.</p> +<ul> + +<li> Support for generics in the .Net virtual machine.</li> +<li> Initial support for the Mono class libraries. </li> +<li> Support for MacOSX/x86, following LLVM's support for exceptions in +JIT on MacOSX/x86. </li> +<li> A new vmkit driver: a program to run java or .net applications. The driver +supports llvm command line arguments including the new "-fast" option. </li> +<li> A new memory allocation scheme in the JVM that makes unloading a +class loader very fast. </li> +<li> VMKit now follows the LLVM Makefile machinery. </li> +</ul> </div> <!-- *********************************************************************** --> <div class="doc_section"> - <a name="whatsnew">What's New?</a> + <a name="whatsnew">What's New in LLVM?</a> </div> <!-- *********************************************************************** --> <div class="doc_text"> -<p>LLVM 2.3 includes a huge number of bug fixes, performance tweaks and minor -improvements. Some of the major improvements and new features are listed in -this section. +<p>This release includes a huge number of bug fixes, performance tweaks, and +minor improvements. Some of the major improvements and new features are listed +in this section. </p> </div> @@ -213,52 +211,29 @@ this section. <div class="doc_text"> -<p>LLVM 2.3 includes several major new capabilities:</p> +<p>LLVM 2.4 includes several major new capabilities:</p> <ul> -<li><p>The biggest change in LLVM 2.3 is Multiple Return Value (MRV) support. - MRVs allow LLVM IR to directly represent functions that return multiple - values without having to pass them "by reference" in the LLVM IR. This - allows a front-end to generate more efficient code, as MRVs are generally - returned in registers if a target supports them. See the <a - href="LangRef.html#i_getresult">LLVM IR Reference</a> for more details.</p> - - <p>MRVs are fully supported in the LLVM IR, but are not yet fully supported in - on all targets. However, it is generally safe to return up to 2 values from - a function: most targets should be able to handle at least that. MRV - support is a critical requirement for X86-64 ABI support, as X86-64 requires - the ability to return multiple registers from functions, and we use MRVs to - accomplish this in a direct way.</p></li> - -<li><p>LLVM 2.3 includes a complete reimplementation of the "<tt>llvmc</tt>" - tool. It is designed to overcome several problems with the original - <tt>llvmc</tt> and to provide a superset of the features of the - '<tt>gcc</tt>' driver.</p> - - <p>The main features of <tt>llvmc2</tt> are: - <ul> - <li>Extended handling of command line options and smart rules for - dispatching them to different tools.</li> - <li>Flexible (and extensible) rules for defining different tools.</li> - <li>The different intermediate steps performed by tools are represented - as edges in the abstract graph.</li> - <li>The 'language' for driver behavior definition is tablegen and thus - it's relatively easy to add new features.</li> - <li>The definition of driver is transformed into set of C++ classes, thus - no runtime interpretation is needed.</li> - </ul> -</li> - -<li><p>LLVM 2.3 includes a completely rewritten interface for <a - href="LinkTimeOptimization.html">Link Time Optimization</a>. This interface - is written in C, which allows for easier integration with C code bases, and - incorporates improvements we learned about from the first incarnation of the - interface.</p></li> - -<li><p>The <a href="tutorial/LangImpl1.html">Kaleidoscope tutorial</a> now - includes a "port" of the tutorial that <a - href="tutorial/OCamlLangImpl1.html">uses the Ocaml bindings</a> to implement - the Kaleidoscope language.</p></li> +<li><p>The most visible end-user change in LLVM 2.4 is that it includes many +optimizations and changes to make -O0 compile times much faster. You should see +improvements in speed on the order of 30% (or more) than in LLVM 2.3. There are +many pieces to this change described in more detail below. The speedups and new +components can also be used for JIT compilers that want fast +compilation.</p></li> + +<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which +were introduced in LLVM 2.3) have been generalized to full support for "First +Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using +structs and arrays as values in a function. This capability is mostly useful +for front-end authors, who prefer to treat things like complex numbers, simple +tuples, dope vectors, etc., as Value*'s instead of as a tuple of Value*'s or as +memory values. Bitcode files from LLVM 2.3 will automatically migrate to the +general representation.</p></li> + +<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This +target only has support for 8 bit registers, and a number of other crazy +constraints. While the port is still in early development stages, it shows some +interesting things you can do with LLVM.</p></li> </ul> @@ -272,20 +247,34 @@ this section. <div class="doc_text"> -<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support -for the C, C++, Objective-C, Ada, and Fortran front-ends.</p> +<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC +front-ends and driver with the LLVM optimizer and code generator. It currently +includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p> -<p> <ul> -<li>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C -front-end. Objective-C now works very well on Mac OS/X.</li> - -<li>Fortran <tt>EQUIVALENCE</tt>s are now supported by the gfortran -front-end.</li> - -<li>llvm-gcc 4.2 includes many other fixes which improve conformance with the -relevant parts of the GCC testsuite.</li> - +<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM +2.3 only supported those used by OpenMP, but 2.4 supports them all. Note that +while llvm-gcc supports all of these builtins, not all targets do. X86 support +them all in both 32-bit and 64-bit mode and PowerPC supports them all except for +the 64-bit operations when in 32-bit mode.</li> + +<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells +the compiler that it is okay to use low-precision approximations of certain libm +functions (like <tt>exp</tt>, <tt>log</tt>, etc). This allows you to get high +performance if you only need (say) 12-bits of precision.</li> + +<li>llvm-gcc now supports a C language extension known as "<a +href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks</a>". +This feature is similar to nested functions and closures, but does not +require stack trampolines (with most ABIs), and supports returning closures +from functions that define them. Note that actually <em>using</em> Blocks +requires a small runtime that is not included with llvm-gcc.</li> + +<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support +transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and +later) this allows the use of LTO with other optimization levels like -Os. +Previously, LTO could only be used with -O4, which implied optimizations in +-O3 that can increase code size.</li> </ul> </div> @@ -297,23 +286,49 @@ relevant parts of the GCC testsuite.</li> </div> <div class="doc_text"> -<p>New features include: -</p> +<p>New features include:</p> <ul> -<li>LLVM IR now directly represents "common" linkage, instead of representing it -as a form of weak linkage.</li> +<li>A major change to the <tt>Use</tt> class landed, which shrank it by 25%. Since +this is a pervasive part of the LLVM, it ended up reducing the memory use of +LLVM IR in general by 15% for most programs.</li> -<li>LLVM IR now has support for atomic operations, and this functionality can be -accessed through the llvm-gcc "<tt>__sync_synchronize</tt>", -"<tt>__sync_val_compare_and_swap</tt>", and related builtins. Support for -atomics are available in the Alpha, X86, X86-64, and PowerPC backends.</li> +<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more +nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of +"<tt>add i32 %A, 4 ; <i32>:3</tt>", which makes it much easier to read. +</li> -<li>The C and Ocaml bindings have extended to cover pass managers, several -transformation passes, iteration over the LLVM IR, target data, and parameter -attribute lists.</li> +<li>LLVM 2.4 includes some changes for better vector support. First, the shift +operations (<tt>shl</tt>, <tt>ashr</tt>, and <tt>lshr</tt>) now all support +vectors and do an element-by-element shift (shifts of the whole vector can be +accomplished by bitcasting the vector to <tt><1 x i128></tt>, for example). Second, +there is initial support in development for vector comparisons with the +<tt><a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a></tt> +instructions. These instructions compare two vectors and return a vector of +<tt>i1</tt>'s for each result. Note that there is very little codegen support +available for any of these IR features though.</li> + +<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much +easier for front-ends to create debug info descriptors, similar to the way that +<tt>IRBuilder</tt> makes it easier to create LLVM IR.</li> + +<li>The <tt>IRBuilder</tt> class is now parameterized by a class responsible +for constant folding. The default <tt>ConstantFolder</tt> class does target independent +constant folding. The <tt>NoFolder</tt> class does no constant folding at all, which is +useful when learning how LLVM works. The <tt>TargetFolder</tt> class folds the most, +doing target dependent constant folding.</li> + +<li>LLVM now supports "function attributes", which allow us to separate return +value attributes from function attributes. LLVM now supports attributes on a +function itself, a return value, and its parameters. New supported function +attributes include <tt>noinline/alwaysinline</tt> and the <tt>opt-size</tt> flag, +which says the function should be optimized for code size.</li> + +<li>LLVM IR now directly represents "common" linkage, instead of + representing it as a form of weak linkage.</li> + </ul> - + </div> <!--=========================================================================--> @@ -323,66 +338,45 @@ attribute lists.</li> <div class="doc_text"> -<p>In addition to a huge array of bug fixes and minor performance tweaks, the -LLVM 2.3 optimizers support a few major enhancements:</p> +<p>In addition to a huge array of bug fixes and minor performance tweaks, this +release includes a few major enhancements and additions to the optimizers:</p> <ul> -<li><p>Loop index set splitting on by default. -This transformation hoists conditions from loop bodies and reduces a loop's -iteration space to improve performance. For example,</p> +<li>The Global Value Numbering (GVN) pass now does local Partial Redundancy +Elimination (PRE) to eliminate some partially redundant expressions in cases +where doing so won't grow code size.</li> -<div class="doc_code"> -<pre> -for (i = LB; i < UB; ++i) - if (i <= NV) - LOOP_BODY -</pre> -</div> +<li>LLVM 2.4 includes a new loop deletion pass (which removes output-free +provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE) +pass that no longer uses control dependence information. These changes speed up +the optimizer and also prevent it from deleting output-free infinite +loops.</li> -<p>is transformed into:</p> +<li>The new AddReadAttrs pass works out which functions are read-only or +read-none (these correspond to 'pure' and 'const' in GCC) and marks them +with the appropriate attribute.</li> -<p><div class="doc_code"> -<pre> -NUB = min(NV+1, UB) -for (i = LB; i < NUB; ++i) - LOOP_BODY -</pre> -</div> -</p> -</li> +<li>LLVM 2.4 now includes a new SparsePropagation framework, which makes it +trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using +this interface means that you just define objects to represent your lattice +values and the transfer functions that operate on them. It handles the +mechanics of worklist processing, liveness tracking, handling PHI nodes, +etc.</li> -<li>LLVM now includes a new <tt>memcpy</tt> optimization pass which removes -dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs -return slot optimization. The LLVM optimizer now notices long sequences of -consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li> - -<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and -<tt>memset</tt> is now more aggressive.</li> - -<li>The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten -to make it both faster and safer in the presence of code containing infinite -loops. Some of its prior functionality has been factored out into the loop -deletion pass, which <em>is</em> safe for infinite loops. The new ADCE pass is -no longer based on control dependence, making it run faster.</li> - -<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm - functions for C-based languages, has been rewritten to be a FunctionPass - instead a ModulePass. This allows it to be run more often and to be - included at -O1 in llvm-gcc. It was also extended to include more - optimizations and several corner case bugs were fixed.</li> - -<li>LLVM now includes a simple 'Jump Threading' pass, which attempts to simplify - conditional branches using information about predecessor blocks, simplifying - the control flow graph. This pass is pretty basic at this point, but - catches some important cases and provides a foundation to build on.</li> - -<li>Several corner case bugs which could lead to deleting volatile memory - accesses have been fixed.</li> +<li>The Loop Strength Reduction and induction variable optimization passes have +several improvements to avoid inserting MAX expressions, to optimize simple +floating point induction variables and to analyze trip counts of more +loops.</li> + +<li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were +pulled out of the Instruction Combining pass and put into a new +<tt>ValueTracking.h</tt> header, where they can be reused by other passes.</li> + +<li>The tail duplication pass has been removed from the standard optimizer +sequence used by llvm-gcc. This pass still exists, but the benefits it once +provided are now achieved by other passes.</li> -<li>Several optimizations have been sped up, leading to faster code generation - with the same code quality.</li> - </ul> </div> @@ -394,50 +388,47 @@ no longer based on control dependence, making it run faster.</li> <div class="doc_text"> -<p>We put a significant amount of work into the code generator infrastructure, +<p>We have put a significant amount of work into the code generator infrastructure, which allows us to implement more aggressive algorithms and make it run faster:</p> <ul> -<li>The code generator now has support for carrying information about memory - references throughout the entire code generation process, via the - <a href="http://llvm.org/doxygen/classllvm_1_1MachineMemOperand.html"> - MachineMemOperand</a> class. In the future this will be used to improve - both pre-pass and post-pass scheduling, and to improve compiler-debugging - output.</li> - -<li>The target-independent code generator infrastructure now uses LLVM's - <a href="http://llvm.org/doxygen/classllvm_1_1APInt.html">APInt</a> - class to handle integer values, which allows it to support integer types - larger than 64 bits (for example i128). Note that support for such types is - also dependent on target-specific support. Use of APInt is also a step - toward support for non-power-of-2 integer sizes.</li> - -<li>LLVM 2.3 includes several compile time speedups for code with large basic - blocks, particularly in the instruction selection phase, register - allocation, scheduling, and tail merging/jump threading.</li> +<li>The target-independent code generator supports (and the X86 backend + currently implements) a new interface for "fast" instruction selection. This + interface is optimized to produce code as quickly as possible, sacrificing + code quality to do it. This is used by default at -O0 or when using + "llc -fast" on X86. It is straight-forward to add support for + other targets if faster -O0 compilation is desired.</li> + +<li>In addition to the new 'fast' instruction selection path, many existing + pieces of the code generator have been optimized in significant ways. + SelectionDAG's are now pool allocated and use better algorithms in many + places, the ".s" file printers now use <tt>raw_ostream</tt> to emit text much faster, + etc. The end result of these improvements is that the compiler also takes + substantially less time to generate code that is just as good (and often + better) than before.</li> + +<li>Each target has been split to separate the ".s" file printing logic from the + rest of the target. This enables JIT compilers that don't link in the + (somewhat large) code and data tables used for printing a ".s" file.</li> + +<li>The code generator now includes a "stack slot coloring" pass, which packs + together individual spilled values into common stack slots. This reduces + the size of stack frames with many spills, which tends to increase L1 cache + effectiveness.</li> + +<li>Various pieces of the register allocator (e.g. the coalescer and two-address + operation elimination pass) now know how to rematerialize trivial operations + to avoid copies and include several other optimizations.</li> + +<li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by + the <tt>llc -view-*-dags</tt> options are now significantly prettier and + easier to read.</li> + +<li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean + Quadratic Programming (PBQP). This register allocator is still in + development, but is very simple and clean.</li> -<li>LLVM 2.3 includes several improvements which make llc's - <tt>--view-sunit-dags</tt> visualization of scheduling dependency graphs - easier to understand.</li> - -<li>The code generator allows targets to write patterns that generate subreg - references directly in .td files now.</li> - -<li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for - <tt>memcpy</tt> calls introduced by the code generator when handling - pass-by-value structure argument copies.</li> - -<li>Inline assembly with multiple register results now returns those results - directly in the appropriate registers, rather than going through memory. - Inline assembly that uses constraints like "ir" with immediates now use the - 'i' form when possible instead of always loading the value in a register. - This saves an instruction and reduces register use.</li> - -<li>Added support for PIC/GOT style <a - href="CodeGenerator.html#tailcallopt">tail calls</a> on X86/32 and initial - support for tail calls on PowerPC 32 (it may also work on PowerPC 64 but is - not thoroughly tested).</li> </ul> </div> @@ -445,7 +436,7 @@ faster:</p> <!--=========================================================================--> <div class="doc_subsection"> -<a name="x86specific">X86/X86-64 Specific Improvements</a> +<a name="targetspecific">Target Specific Improvements</a> </div> <div class="doc_text"> @@ -453,90 +444,131 @@ faster:</p> </p> <ul> -<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the - area of passing and returning structures by value. llvm-gcc compiled code - now interoperates very well on X86-64 systems with other compilers.</li> - -<li>Support for Win64 was added. This includes code generation itself, JIT - support, and necessary changes to llvm-gcc.</li> - -<li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and - the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various - generic vector operations (insert/extract/shuffle) are much more efficient - when SSE 4.1 is enabled. The JIT automatically takes advantage of these - instructions, but llvm-gcc must be explicitly told to use them, e.g. with - <tt>-march=penryn</tt>.</li> - -<li>The X86 backend now does a number of optimizations that aim to avoid - converting numbers back and forth from SSE registers to the X87 floating - point stack. This is important because most X86 ABIs require return values - to be on the X87 Floating Point stack, but most CPUs prefer computation in - the SSE units.</li> - -<li>The X86 backend supports stack realignment, which is particularly useful for - vector code on OS's without 16-byte aligned stacks, such as Linux and - Windows.</li> - -<li>The X86 backend now supports the "sseregparm" options in GCC, which allow - functions to be tagged as passing floating point values in SSE - registers.</li> +<li>Exception handling is supported by default on Linux/x86-64.</li> +<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li> +<li><tt>@llvm.frameaddress</tt> now supports getting the frame address of stack frames + > 0 on x86/x86-64.</li> +<li>MIPS has improved a lot since last release, the most important changes + are: Little endian support, floating point support, allegrex core and + intrinsics support. O32 ABI is improved but isn't complete. The EABI + was implemented and is fully supported. We also have support for small + sections and gp_rel relocation for its access, a threshold in bytes can be + specified through command line.</li> +<li>The PowerPC backend now supports trampolines.</li> +</ul> -<li>Trampolines (taking the address of a nested function) now work on - Linux/X86-64.</li> +</div> -<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch - instructions instead of being ignored.</li> -<li>128-bit integers are now supported on X86-64 targets. This can be used - through <tt>__attribute__((TImode))</tt> in llvm-gcc.</li> +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="otherimprovements">Other Improvements</a> +</div> -<li>The register allocator can now rematerialize PIC-base computations, which is - an important optimization for register use.</li> +<div class="doc_text"> +<p>New features include: +</p> -<li>The "t" and "f" inline assembly constraints for the X87 floating point stack - now work. However, the "u" constraint is still not fully supported.</li> +<ul> +<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin + support. It is now easier to experiment with <tt>llvmc2</tt> and + build your own tools based on it.</li> + +<li>LLVM 2.4 includes a number of new generic algorithms and data structures, + including a scoped hash table, 'immutable' data structures, a simple + free-list manager, and a <tt>raw_ostream</tt> class. + The <tt>raw_ostream</tt> class and + <tt>format</tt> allow for efficient file output, and various pieces of LLVM + have switched over to use it. The eventual goal is to eliminate + use of <tt>std::ostream</tt> in favor of it.</li> + +<li>LLVM 2.4 includes an optional build system based on CMake. It + still is in its early stages but can be useful for Visual C++ + users who can not use the Visual Studio IDE.</li> </ul> - + </div> <!--=========================================================================--> <div class="doc_subsection"> -<a name="targetspecific">Other Target Specific Improvements</a> +<a name="changes">Major Changes and Removed Features</a> </div> <div class="doc_text"> -<p>New target-specific features include: -</p> + +<p>If you're already an LLVM user or developer with out-of-tree changes based +on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading +from the previous release.</p> <ul> -<li>The LLVM C backend now supports vector code.</li> -<li>The Cell SPU backend includes a number of improvements. It generates better - code and its stability/completeness is improving.</li> -</ul> - -</div> +<li>The LLVM IR generated by llvm-gcc no longer names all instructions. This + makes it run faster, but may be more confusing to some people. If you + prefer to have names, the '<tt>opt -instnamer</tt>' pass will add names to + all instructions.</li> +<li>The LoadVN and GCSE passes have been removed from the tree. They are + obsolete and have been replaced with the GVN and MemoryDependence passes. + </li> +</ul> -<!--=========================================================================--> -<div class="doc_subsection"> -<a name="otherimprovements">Other Improvements</a> -</div> -<div class="doc_text"> -<p>New features include: -</p> +<p>In addition, many APIs have changed in this release. Some of the major LLVM +API changes are:</p> <ul> -<li>LLVM now builds with GCC 4.3.</li> -<li>Bugpoint now supports running custom scripts (with the <tt>-run-custom</tt> - option) to determine how to execute the command and whether it is making - forward process.</li> + +<li>Now, function attributes and return value attributes are managed +separately. Interface exported by <tt>ParameterAttributes.h</tt> header is now +exported by <tt>Attributes.h</tt> header. The new attributes interface changes are: +<ul> +<li><tt>getParamAttrs</tt> method is now replaced by +<tt>getParamAttributes</tt>, <tt>getRetAttributes</tt> and +<tt>getFnAttributes</tt> methods.</li> +<li> Return value attributes are stored at index 0. Function attributes are +stored at index ~0U. Parameter attributes are stored at index that matches +parameter number.</li> +<li> <tt>ParamAttr</tt> namespace is now renamed as <tt>Attribute</tt>.</li> +<li> The name of the class that manages reference count of opaque +attributes is changed from <tt>PAListPtr</tt> to <tt>AttrListPtr</tt>.</li> +<li> <tt>ParamAttrsWithIndex</tt> is now renamed as <tt>AttributeWithIndex</tt>. +</li> </ul> - +</li> + +<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and +<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be +converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via +"<tt>llvm/Analysis/ValueTracking.h</tt>".</li> + +<li>The APIs to create various instructions have changed from lower case + "create" methods to upper case "Create" methods (e.g. + <tt>BinaryOperator::create</tt>). LLVM 2.4 includes both cases, but the + lower case ones are removed in mainline (2.5 and later), please migrate.</li> + +<li>Various header files like "<tt>llvm/ADT/iterator</tt>" were given a ".h" suffix. + Change your code to #include "<tt>llvm/ADT/iterator.h</tt>" instead.</li> + +<li>The <tt>getresult</tt> instruction has been removed and replaced with the + <tt>extractvalue</tt> instruction. This is part of support for first class + aggregates.</li> + +<li>In the code generator, many <tt>MachineOperand</tt> predicates were renamed to be + shorter (e.g. <tt>isFrameIndex()</tt> -> <tt>isFI()</tt>), + <tt>SDOperand</tt> was renamed to <tt>SDValue</tt> (and the "<tt>Val</tt>" + member was changed to be the <tt>getNode()</tt> accessor), and the + <tt>MVT::ValueType</tt> enum has been replaced with an "<tt>MVT</tt>" + struct. The <tt>getSignExtended</tt> and <tt>getValue</tt> methods in the + ConstantSDNode class were renamed to <tt>getSExtValue</tt> and + <tt>getZExtValue</tt> respectively, to be more consistent with + the <tt>ConstantInt</tt> class.</li> +</ul> + </div> + + <!-- *********************************************************************** --> <div class="doc_section"> <a name="portability">Portability and Supported Platforms</a> @@ -548,10 +580,10 @@ faster:</p> <p>LLVM is known to work on the following platforms:</p> <ul> -<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD - (and probably other unix-like systems).</li> -<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and - 64-bit modes.</li> +<li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat +Linux, Fedora Core and FreeBSD (and probably other unix-like systems).</li> +<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit +and 64-bit modes.</li> <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li> <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited support is available for native builds with Visual C++).</li> @@ -575,9 +607,8 @@ portability patches and reports of successful builds or error messages.</p> <div class="doc_text"> -<p>This section contains all known problems with the LLVM system, listed by -component. As new problems are discovered, they will be added to these -sections. If you run into a problem, please check the <a +<p>This section contains significant known problems with the LLVM system, +listed by component. If you run into a problem, please check the <a href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if there isn't already one.</p> @@ -598,7 +629,7 @@ components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p> <ul> -<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li> +<li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li> <li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported value for this option.</li> </ul> @@ -625,8 +656,6 @@ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p> to <a href="http://llvm.org/PR2255">several</a> <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the 'u' inline assembly constraint and X87 floating point inline assembly.</li> - <li>The X86-64 backend does not yet support position-independent code (PIC) - generation on Linux targets.</li> <li>The X86-64 backend does not yet support the LLVM IR instruction <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic argument constructs on X86-64 by lowering them manually.</li> @@ -684,6 +713,20 @@ programs compiled with LLVM. Please use more recent versions of QEMU.</li> <!-- ======================================================================= --> <div class="doc_subsection"> + <a name="mips-be">Known problems with the MIPS back-end</a> +</div> + +<div class="doc_text"> + +<ul> +<li>The O32 ABI is not fully supported.</li> +<li>64-bit MIPS targets are not supported yet.</li> +</ul> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> <a name="alpha-be">Known problems with the Alpha back-end</a> </div> @@ -707,7 +750,7 @@ appropriate nops inserted to ensure restartability.</li> <ul> <li>The Itanium backend is highly experimental, and has a number of known issues. We are looking for a maintainer for the Itanium backend. If you - are interested, please contact the llvmdev mailing list.</li> + are interested, please contact the LLVMdev mailing list.</li> </ul> </div> @@ -740,7 +783,7 @@ appropriate nops inserted to ensure restartability.</li> <p>llvm-gcc 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> +LLVMdev mailing list if you are interested.</p> <p>The only major language feature of GCC not supported by llvm-gcc is the <tt>__builtin_apply</tt> family of builtins. However, some extensions @@ -765,13 +808,26 @@ tested and works for a number of non-trivial programs, including LLVM itself, Qt, Mozilla, etc.</p> <ul> -<li>Exception handling works well on the X86 and PowerPC targets, including -X86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is -supported on X86-64 linux, but that is disabled by default in this release.</li> +<li>Exception handling works well on the X86 and PowerPC targets. Currently + only Linux and Darwin targets are supported (both 32 and 64 bit).</li> </ul> </div> +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a> +</div> + +<div class="doc_text"> +<ul> +<li>Fortran support generally works, but there are still several unresolved bugs + in Bugzilla. Please see the tools/gfortran component for details.</li> + +<li>The Fortran front-end currently does not build on Darwin (without tweaks) + due to unresolved dependencies on the C front-end.</li> +</ul> +</div> <!-- ======================================================================= --> <div class="doc_subsection"> @@ -788,11 +844,10 @@ however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a> which does support trampolines.</li> <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>. Workaround: configure with --disable-bootstrap.</li> -<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests -fail (c380004 also fails with gcc-4.2 mainline). When built at -O3, the -<a href="http://llvm.org/PR2421">cxg2021</a> ACATS test also fails.</li> -<li>Some gcc specific Ada tests continue to crash the compiler. The testsuite -reports most tests as having failed even though they pass.</li> +<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a> +and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail +(c380004 also fails with gcc-4.2 mainline).</li> +<li>Some gcc specific Ada tests continue to crash the compiler.</li> <li>The -E binder option (exception backtraces) <a href="http://llvm.org/PR1982">does not work</a> and will result in programs crashing if an exception is raised. Workaround: do not use -E.</li> |