<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="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#portability">Portability and Supported Platforms</a></li>
<!-- *********************************************************************** -->
<div class="doc_section">
- <a name="whatsnew">What's New?</a>
+ <a name="changes">Major Changes and Sub-project Status</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
-<p>LLVM 2.2 was the last LLVM release to support llvm-gcc 4.0 and llvm-upgrade.
-llvm-gcc 4.0 has been replaced with llvm-gcc 4.2. llvm-upgrade 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>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with
+ llvm-gcc 4.2.</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>The <tt>llvm2cpp</tt> tool has been folded into llc, use
+ <tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p>
<p>LLVM API Changes:</p>
<ul>
-<li>Several core LLVM IR classes have migrated to use 'FOOCLASS::Create(...)'
- instead of 'new FOOCLASS(...)' (e.g. where FOOCLASS=BasicBlock). We hope to
- standardize on FOOCLASS::Create for all IR classes in the future, but not
- all of them have been moved over yet.</li>
+<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
IRBuilder.</li>
<li>MRegisterInfo was renamed to TargetRegisterInfo.</li>
<li>The MappedFile class is gone, please use MemoryBuffer instead.</li>
-<li>The '-enable-eh' flag to llc has been removed. Now code should encode
- whether it is safe to not generate unwind information for a function by
- tagging the Function object with the 'nounwind' attribute.</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>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="majorfeatures">Major New Features</a>
+<a name="otherprojects">Other LLVM Sub-Projects</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>
-<p>LLVM 2.3 includes several major new capabilities:</p>
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="vmkit">vmkit</a>
+</div>
-<ul>
-<li>Multiple Return Value Support.</li>
+<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 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>
+<p>
+<tt>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</tt>
+</p>
-<li><p>LLVM 2.3 includes a complete reimplementation of the "llvmc" tool. It is
-designed to overcome several problems with the original llvmc and to provide a
-superset of the features of the 'gcc' driver.</p>
+</div>
-<p>The main features of llvmc2 is:</p>
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="clang">Clang</a>
+</div>
-<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>
+<div class="doc_text">
+
+<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>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 is automatically focused on finding
+bugs in C and Objective-C code.</p>
+
+</div>
-<li>Reimplemented <a href="LinkTimeOptimization.html">LTO interface</a> in
- C.</li>
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="whatsnew">What's New?</a>
+</div>
+<!-- *********************************************************************** -->
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="majorfeatures">Major New Features</a>
+</div>
-<li>Kaleidoscope tutorial in Ocaml.</li>
+<div class="doc_text">
+
+<p>LLVM 2.3 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></p>
+ </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>
</ul>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="frontends">llvm-gcc 4.2 Improvements and Clang</a>
+<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
</div>
<div class="doc_text">
<p>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.</p>
+<p>Fortran EQUIVALENCEs are now supported by the gfortran front-end.</p>
+
<p>llvm-gcc 4.2 includes many other fixes which improve conformance with the
relevant parts of the GCC testsuite.</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. Currently, its C and Objective-C support is maturing
-nicely, and it has advanced source-to-source analysis and transformation
-capabilities. If you are interested in building source-level tools for C and
-Objective-C (and eventually C++), you should take a look. However, note that
-clang is not an official part of the LLVM 2.3 release. If you are interested in
-this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
-
</div>
This transformation hoists conditions from loop bodies and reduces loop's
iteration space to improve performance. For example, <p>
<pre>
-for (i = LB; i < UB; ++i)
- if (i <= NV)
+for (i = LB; i < UB; ++i)
+ if (i <= NV)
LOOP_BODY
</pre>
is transformed into
<pre>
NUB = min(NV+1, UB)
-for (i = LB; i < NUB; ++i)
+for (i = LB; i < NUB; ++i)
LOOP_BODY
</pre>
</li>
-<li>LLVM includes a new <tt>memcpy</tt> optimization pass removes
+<li>LLVM 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>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>
+ 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>
</ul>
</div>
target-specific support. Use of APInt is also a step toward support for
non-power-of-2 integer sizes.</li>
-<li>Several compile time speedups for code with large basic blocks.</li>
+<li>LLVM 2.3 includes several compile time speedups for code with large basic
+ blocks, particular in the instruction selection phase, register allocation,
+ scheduling, and tail merging/jump threading.</li>
<li>Several improvements which make llc's <tt>--view-sunit-dags</tt>
visualization of scheduling dependency graphs easier to understand.</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 tail calls on x86/32 and initial support
+ for tail calls on PowerPC 32 (it may also work on ppc64 but not
+ thoroughly tested).</li>
</ul>
</div>
<li>The register allocator can now rematerialize PIC-base computations.</li>
+<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>
</div>
<ul>
<li>The LLVM C backend now supports vector code.</li>
-
-
</ul>
</div>
<ul>
<li>LLVM now builds with GCC 4.3.</li>
-<li><tt>llvm2cpp</tt> tool has been folded into llc, use
- <tt>llc -march=cpp</tt></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>
</ul>
</div>
all <a href="http://llvm.org/PR879">inline assembly that uses the X86
floating point stack</a>. It supports the 'f' and 't' constraints, but not
'u'.</li>
- <li>The X86 backend generates inefficient floating point code when configured to
- generate code for systems that don't have SSE2.</li>
+ <li>The X86 backend generates inefficient floating point code when configured
+ to generate code for systems that don't have SSE2.</li>
<li>Win64 code generation wasn't widely tested. Everything should work, but we
expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
currently due
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>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
+<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
+ execute
programs compiled with LLVM. Please use more recent versions of QEMU.</li>
</ul>
or finish at a non-byte offset</a> in a record. Workaround: do not pack records
or use representation clauses that result in a field of a non-discrete type
starting or finishing in the middle of a byte.</li>
-<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers 'main'
-as generated by the Ada binder to be invalid</a>.
-Workaround: hand edit the file to use pointers for <tt>argv</tt> and <tt>envp</tt> rather than
-integers.</li>
-<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is ignored</a>.</li>
+<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
+'main' as generated by the Ada binder to be invalid</a>.
+Workaround: hand edit the file to use pointers for <tt>argv</tt> and
+<tt>envp</tt> rather than integers.</li>
+<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
+ignored</a>.</li>
</ul>
</div>
projects / oota-llvm.git / blobdiff