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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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- <title>LLVM 2.4 Release Notes</title>
+ <title>LLVM 2.5 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.4 Release Notes</div>
+<div class="doc_title">LLVM 2.5 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
<div class="doc_text">
<p>This document contains the release notes for the LLVM Compiler
-Infrastructure, release 2.4. Here we describe the status of LLVM, including
+Infrastructure, release 2.5. 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>
</div>
-<!-- Unfinished features in 2.4:
+<!-- Unfinished features in 2.5:
Machine LICM
Machine Sinking
- LegalizeDAGTypes
+ target-specific intrinsics
+ gold lto plugin
+ pre-alloc splitter, strong phi elim
llc -enable-value-prop, propagation of value info (sign/zero ext info) from
one MBB to another
+ debug info for optimized code
+
-->
<!-- for announcement email:
- mention dev mtg
- Xcode 3.1 and 3.1.1.
- -->
+ -->
<!-- *********************************************************************** -->
<div class="doc_section">
<div class="doc_text">
<p>
-The LLVM 2.4 distribution currently consists of code from the core LLVM
+The LLVM 2.5 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>.
+the <a href="#vmkit">VMKit Project</a>.
</p>
</div>
<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>Codegen progress/state [DANIEL]</p>
+and code generator. While Clang is not included in the LLVM 2.5 release, it
+is continuing to make major strides forward in all areas. Its C and Objective-C
+parsing and code generation support is now very solid. For example, it is
+capable of successfully building many real applications for X86-32 and X86-64,
+including the FreeBSD kernel. C++ is also making <a
+href="http://clang.llvm.org/cxx_status.html">incredible progress</a>, and work
+on templates has recently started.</p>
+
+<p>While Clang is not yet production quality, it is progressing very nicely and
+is quite usable for building many C and Objective-C applications. If you are
+interested in fast compiles and good diagnostics, we encourage you to try it out
+by <a href="http://clang.llvm.org/get_started.html">building from mainline</a>
+and reporting any issues you hit to the <a
+href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
+list</a>.</p>
+
+<p>In the LLVM 2.5 time-frame, the Clang team has made many improvements:</p>
+<ul>
+<li>Clang now has a new driver, which is focused on providing a GCC-compatible
+ interface.</li>
+<li>The X86-64 ABI is now supported.</li>
+<li>Precompiled header support is now implemented.</li>
+<li>Objective-C support is significantly improved beyond LLVM 2.4, supporting
+ many features, such as Objective-C Garbage Collection.</li>
+<li>Many many bugs are fixed.</li>
</div>
<!--=========================================================================-->
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
+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 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>
+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_subsection">
-<a name="vmkit">vmkit: JVM/CLI Virtual Machine Implementation</a>
+<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
+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>[NICOLAS]</p>
+<p>Following LLVM 2.5, VMKit has its first release ? 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>
+
+<ul>
+
+<li>?</li>
+</ul>
</div>
<div class="doc_text">
-<p>This release includes a huge number of bug fixes, performance tweaks and
+<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 class="doc_text">
-<p>LLVM 2.4 includes several major new capabilities:</p>
+<p>LLVM 2.5 includes several major new capabilities:</p>
<ul>
-<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 on the order of 30% (or more) faster than 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 as
-well.</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
-is the LLVM target that 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>
+<li><p>The code generator now supports arbitrary precision integers.
+Types like <tt>i33</tt> have long been valid in the LLVM IR, but previously
+could only be used with the interpreter.
+Now IR using such types can be compiled to native code on all targets.
+All operations are supported if the integer is not bigger than twice the
+target machine word size.
+Simple operations like loads, stores and shifts by a constant amount are
+supported for integers of any size.
+</p></li>
+
+<!--
+Random stuff:
+
+xcore backend!
+fortran on darwin!
+
+.ll parser rewrite.
+GCC inliner off.
+cmake mature?
+x86 backend FS/GS segment address spaces?
+nocapture
+memdep is faster / more aggressive.
+how to write a backend doc docs/WritingAnLLVMBackend.html
+fastisel + exception handling
+vector widening <3 x float> -> <4 x float>
+arm port improvements? arm jit encoding stuff, constant island support?
+JIT TLS support on x86
+mem2reg now faster on code with huge basic blocks
+stack protectors/stack canaries, -fstack-protector, controllable on a
+ per-function basis with attributes.
+shufflevector is generalized to allow different shuffle mask width than its
+ input vectors.
+loop optimizer improves floating point induction variables
+llvm/Analysis/DebugInfo.h classes, llvm-gcc and clang and codegen use them.
+asmprinters seperate from targets for jits
+-->
</ul>
includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
<ul>
-<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. While
-llvm-gcc supports all of these builtins, note that 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 ok to use low-precision approximations of certain libm
-functions (like tan, log, etc). This allows you to get high performance if you
-only need (say) 14-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>
+<li>?</li>
</ul>
</div>
</div>
<div class="doc_text">
-<p>New features include:
-</p>
+<p>New features include:</p>
<ul>
-<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>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>LLVM 2.4 includes some changes for better vector support. First, the shift
-operations (<tt>shl</tt>, <tt>ashr</tt>, <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 <1 x i128> for example). Second,
-there is initial support in development for vector comparisons with the
-<a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a>
-instructions. These instructions compare two vectors and return a vector of
-i1'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 allows 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 noinline/alwaysinline and the "opt-size" 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>
+<li>?</li>
</ul>
<ul>
-<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>
-
-<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>
-
-<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>
-
-<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>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>?</li>
</ul>
faster:</p>
<ul>
-<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>The type legalization logic has been completely rewritten, and is now
+more powerful (it supports arbitrary precision integer types for example)
+and hopefully more correct.
+The type legalizer converts operations on types that are not natively
+supported by the target machine into equivalent code sequences that only use
+natively supported types.
+The old type legalizer is still available and will be used if
+<tt>-disable-legalize-types</tt> is passed to <tt>llc</tt>.
+</li>
+<li>?</li>
</ul>
</p>
<ul>
-<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>@llvm.frameaddress now supports getting the frame address of stack frames
- > 0 on x86/x86-64.</li>
-<li>MIPS floating point support? [BRUNO]</li>
-<li>The PowerPC backend now supports trampolines.</li>
+<li>?</li>
</ul>
</div>
</p>
<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,
- include 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
- std::ostream in favor of it.</li>
+<li>?</li>
</ul>
<div class="doc_text">
<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
+on LLVM 2.4, this section lists some "gotchas" that you may run into upgrading
from the previous release.</p>
<ul>
-<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>
+<li>?</li>
</ul>
API changes are:</p>
<ul>
+<li>?</li>
+</ul>
-<li>Attributes changes [DEVANG] </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, 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>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.</li>
+<li>?</li>
</ul>
</div>
<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>
<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>
</div>
+<!-- ======================================================================= -->
+<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>
<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>
C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
C++ code compiled with llc or native compilers.</li>
<li>The C backend does not support all exception handling constructs.</li>
+<li>The C backend does not support arbitrary precision integers.</li>
</ul>
</div>
<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
<ul>
<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>
+ 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">
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>.
+This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
+exception handling, which is used internally by the compiler.
Workaround: configure with --disable-bootstrap.</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>
+(c380004 also fails with gcc-4.2 mainline).
+If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
+causes the compiler to go into an infinite loop, using up all system memory.</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
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