<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 1.5 Release Notes</title>
+ <title>LLVM 1.6 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 1.5 Release Notes</div>
+<div class="doc_title">LLVM 1.6 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
</ol>
<div class="doc_author">
- <p>Written by the <a href="http://llvm.
cs.uiuc.edu">LLVM Team</a><p>
+ <p>Written by the <a href="http://llvm.
org">LLVM Team</a><p>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
-infrastructure, release 1.5. Here we describe the status of LLVM, including any
-known problems and improvements from the previous release. The most up-to-date
-version of this document can be found on the <a
-href="http://llvm.cs.uiuc.edu/releases/1.5/">LLVM 1.5 web site</a>. If you are
+infrastructure, release 1.6. 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 can be found on the <a
+href="http://llvm.org/releases/1.6/">LLVM 1.6 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>
<p>For more information about LLVM, including information about the latest
-release, please check out the <a href="http://llvm.cs.uiuc.edu">main LLVM
+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>
<p>Note that if you are reading this file from CVS 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 the current or previous releases, see the <a
-href="http://llvm.cs.uiuc.edu/releases/">releases page</a>.</p>
+href="http://llvm.org/releases/">releases page</a>.</p>
</div>
<div class="doc_text">
-<p>This is the sixth public release of the LLVM compiler infrastructure.</p>
-
-<p> At this time, LLVM is known to correctly compile a broad range of C and
-C++ programs, including the SPEC CPU95 & 2000 suite. TODO. It also includes
-bug fixes for those problems found since the 1.4 release.</p>
+<p>This is the seventh public release of the LLVM Compiler Infrastructure. This
+release incorporates a large number of enhancements and additions (primarily in
+the code generator), which combine to improve the quality of the code generated
+by LLVM by up to 30% in some cases. This release is also the first release to
+have first-class support for Mac OS X: all of the major bugs have been shaken
+out and it is now as well supported as Linux on X86.</p>
</div>
<!--=========================================================================-->
-<div class="doc_subsubsection">
-<a name="newfeatures">This release implements the following new features:</a>
+<div class="doc_subsection">
+<a name="newfeatures">New Features in LLVM 1.6</a>
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="iselgen">Instruction Selector
+Generation from Target Description</a></div>
+
<div class="doc_text">
-<ol>
- <li>LLVM now includes an <a href="http://llvm.cs.uiuc.edu/PR415">
- Interprocedural Sparse Conditional Constant Propagation</a> pass, named
- -ipsccp, which is run by default at link-time.</li>
- <li>LLVM 1.5 is now about 15% faster than LLVM 1.4 and its core data structures
- use about 30% less memory.</li>
- <li>LLVM includes new experimental native code generators for SparcV8,
- Alpha, and IA64.</li>
- <li>Support for Microsoft Visual Studio is improved, and <a
- href="GettingStartedVS.html">now documented</a>.</li>
- <li>Configuring LLVM to build targets selectively is now implemented, via the
- <tt>--enable-targets=</tt> option. This feature is documented
- <a href="GettingStarted.html#config">here</a>.</li>
- <li>LLVM now supports <a href="LangRef.html#callingconv">custom and
- target-specific calling conventions</a>.</li>
-</ol>
+<p>LLVM now includes support for auto-generating large portions of the
+instruction selectors from target descriptions. This allows us to
+write patterns in the target .td file, instead of writing lots of
+nasty C++ code. Most of the PowerPC instruction selector is now
+generated from the PowerPC target description files and other targets
+are adding support that will be live for LLVM 1.7.</p>
+
+<p>For example, here are some patterns used by the PowerPC backend. A
+floating-point multiply then subtract instruction (FMSUBS):</p>
+
+<div class="doc_code"><p>
+<tt>(set F4RC:$FRT, (fsub (fmul F4RC:$FRA, F4RC:$FRC), F4RC:$FRB))</tt>
+</p></div>
+
+<p>Exclusive-or by 16-bit immediate (XORI):</p>
+
+<div class="doc_code"><p>
+<tt>(set GPRC:$dst, (xor GPRC:$src1, immZExt16:$src2))</tt>
+</p></div>
+
+<p>Exclusive-or by 16-bit immediate shifted right 16-bits (XORIS):</p>
+
+<div class="doc_code"><p>
+<tt>(set GPRC:$dst, (xor GPRC:$src1, imm16Shifted:$src2))</tt>
+</p></div>
+
+<p>With these definitions, we teach the code generator how to combine these two
+instructions to xor an abitrary 32-bit immediate with the following
+definition. The first line specifies what to match (a xor with an arbitrary
+immediate) the second line specifies what to produce:</p>
+
+<div class="doc_code"><p>
+<pre>def : Pat<(xor GPRC:$in, imm:$imm),
+ (XORIS (XORI GPRC:$in, (LO16 imm:$imm)), (HI16 imm:$imm))>;
+</pre>
+</p></div>
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="sched">Instruction Scheduling
+Support</a></div>
-<!--=========================================================================-->
-<div class="doc_subsubsection">
-In this release, the following missing features were implemented:
+<div class="doc_text">
+
+<p>Instruction selectors using the refined <a
+href="CodeGenerator.html#instselect">instruction selection framework</a> can now
+use a simple pre-pass scheduler included with LLVM 1.6. This scheduler is
+currently simple (cannot be configured much by the targets), but will be
+extended in the future.</p>
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="subtarget">Code Generator Subtarget
+Support</a></div>
+
<div class="doc_text">
+<p>It is now straight-forward to parameterize a target implementation, and
+provide a mapping from CPU names to sets of target parameters. LLC now supports
+a <tt>-mcpu=cpu</tt> option that lets you choose a subtarget by CPU name: use
+"<tt>llvm-as < /dev/null | llc -march=XXX -mcpu=help</tt>" to get a list of
+supported CPUs for target "XXX". It also provides a
+<tt>-mattr=+attr1,-attr2</tt> option that can be used to control individual
+features of a target (the previous command will list available features as
+well).</p>
-<ol>
- <li>LLVM can now create native shared libraries with '<tt>llvm-gcc ...
- -shared -Wl,-native</tt>' (or with <tt>-Wl,-native-cbe</tt>).</li>
- <li>LLVM now supports a new "<a href="LangRef.html#i_prefetch">llvm.prefetch
- </a>" intrinsic, and llvm-gcc now supports __builtin_prefetch.
- <li>LLVM now supports intrinsics for <a href="LangRef.html#int_count">bit
- counting</a> and llvm-gcc now implements the GCC
- <tt>__builtin_popcount</tt>, <tt>__builtin_ctz</tt>, and
- <tt>__builtin_clz</tt> builtins.</li>
-</ol>
+<p>This functionality is nice when you want tell LLC something like "compile to
+code that is specialized for the PowerPC G5, but doesn't use altivec code. In
+this case, using "<tt>llc -march=ppc32 -mcpu=g5 -mattr=-altivec</tt>".</p>
</div>
-<!--=========================================================================-->
-<div class="doc_subsubsection">
-<a name="qualityofimp">In this release, the following Quality of Implementation
-issues were fixed:</a>
-</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="jitlock">Other New Features</a></div>
<div class="doc_text">
-
<ol>
- <li><a href="http://llvm.cs.uiuc.edu/PR448">Building LLVM in optimized mode
- should no longer cause GCC to hit swap in the PowerPC backend.</a></li>
+ <li>The JIT now uses mutexes to protect its internal data structures. This
+ allows multi-threaded programs to be run from the JIT or interpreter without
+ corruption of the internal data structures. See
+ <a href="http://llvm.org/PR418">PR418</a> and
+ <a href="http://llvm.org/PR540">PR540</a> for the details.
+ </li>
+ <li>LLVM on Win32 <a href="http://llvm.org/PR614">no longer requires sed,
+ flex, or bison when compiling with Visual C++</a>.</li>
+ <li>The llvm-test suite can now use the NAG Fortran to C compiler to compile
+ SPEC FP programs if available (allowing us to test all of SPEC'95 &
+ 2000).</li>
+ <li>When bugpoint is grinding away and the user hits ctrl-C, it now
+ gracefully stops and gives what it has reduced so far, instead of
+ giving up completely. In addition, <a href="http://llvm.org/PR576">the JIT
+ debugging mode of bugpoint is much faster</a>.</li>
+ <li>LLVM now includes Xcode project files in the llvm/Xcode directory.</li>
+ <li>LLVM now supports Mac OS X on Intel.</li>
+ <li>LLVM now builds cleanly with GCC 4.1.</li>
</ol>
</div>
<!--=========================================================================-->
-<div class="doc_subsubsection">
-<a name="codequality">This release includes the following Code Quality
-improvements:</a>
+<div class="doc_subsection">
+<a name="codequality">Code Quality Improvements in LLVM 1.6</a>
</div>
<div class="doc_text">
<ol>
- <li>Transition code for 1.0 style varargs was removed. </li>
+ <li>The <tt>-globalopt</tt> pass can now statically evaluate C++ static
+ constructors when they are simple enough. For example, it can
+ now statically initialize "<tt>struct X { int a; X() : a(4) {} } g;</tt>".
+ </li>
+ <li>The Loop Strength Reduction pass has been completely rewritten, is far
+ more aggressive, and is turned on by default in the RISC targets. On PPC,
+ we find that it often speeds up programs from 10-40% depending on the
+ program.</li>
+ <li>The code produced when exception handling is enabled is far more
+ efficient in some cases, particularly on Mac OS X.</li>
</ol>
</div>
+
<!--=========================================================================-->
-<div class="doc_subsubsection">
-<a name="bugfix">In this release, the following bugs in the previous release
-were fixed:</a>
+<div class="doc_subsection">
+<a name="codequality">Code Generator Improvements in LLVM 1.6</a>
</div>
<div class="doc_text">
-
-
-<p>Bugs fixed in the LLVM Core:</p>
<ol>
- <li><a href="http://llvm.cs.uiuc.edu/PR491">[dse] DSE deletes stores that
- are partially overwritten by smaller stores</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR548">[instcombine] miscompilation of
- setcc or setcc in one case</a></li>
+<li>The Alpha backend is substantially more stable and robust than in LLVM 1.5.
+ For example, it now fully supports varargs functions. The Alpha backend
+ also now features beta JIT support.</li>
+<li>The code generator contains a new component, the DAG Combiner. This allows
+ us to optimize lowered code (e.g. after 64-bit operations have been lowered
+ to use 32-bit registers on 32-bit targets) and do fine-grained bit-twiddling
+ optimizations for the backend.</li>
+<li>The SelectionDAG infrastructure is far more capable and mature, able to
+ handle many new target peculiarities in a target-independent way.</li>
+<li>The default <a href="http://llvm.org/PR547">register allocator is now far
+ faster on some testcases</a>,
+ particularly on targets with a large number of registers (e.g. IA64
+ and PPC).</li>
</ol>
+</div>
-<p>Code Generator Bugs:</p>
-<ol>
- <li><a href="http://llvm.cs.uiuc.edu/PR490">[cbackend] Logical constant
- expressions (and/or/xor) not implemented</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR511">[cbackend] C backend does not
- respect 'volatile'</a></li>
-</ol>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="bugfix">Significant Bugs Fixed in LLVM 1.6</a>
+</div>
-<p>Bugs in the C/C++ front-end:</p>
+<div class="doc_text">
<ol>
- <li><a href="http://llvm.cs.uiuc.edu/PR487">[llvmgcc] llvm-gcc incorrectly
- rejects some constant initializers involving the addresses of array
- elements</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR501">[llvm-g++] Crash compiling
- anonymous union</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR509">[llvm-g++] Do not use dynamic
- initialization where static init will do</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR510">[llvmgcc] Field offset
- miscalculated for some structure fields following bit fields</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR513">[llvm-g++] Temporary lifetimes
- incorrect for short circuit logical operations</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR517">[llvm-gcc] Crash compiling
- bitfield <-> aggregate assignment</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR520">[llvm-g++] Error compiling
- virtual function thunk with an unnamed argument</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR522">[llvm-gcc] Crash on certain
- C99 complex number routines</a></li>
- <li><a href="http://llvm.cs.uiuc.edu/PR529">[llvm-g++] Crash using placement
- new on an array type</a></li>
+ <li>A vast number of bugs have been fixed in the PowerPC backend and in
+ llvm-gcc when configured for Mac OS X (particularly relating to ABI
+ issues). For example:
+ <a href="http://llvm.org/PR603">PR449</a>,
+ <a href="http://llvm.org/PR594">PR594</a>,
+ <a href="http://llvm.org/PR603">PR603</a>,
+ <a href="http://llvm.org/PR609">PR609</a>,
+ <a href="http://llvm.org/PR630">PR630</a>,
+ <a href="http://llvm.org/PR643">PR643</a>,
+ and several others without bugzilla bugs.</li>
+ <li>Several bugs in tail call support have been fixed.</li>
+ <li><a href="http://llvm.org/PR608">configure does not correctly detect gcc
+ version on cygwin</a>.</li>
+ <li>Many many other random bugs have been fixed. Query <a
+ href="http://llvm.org/bugs">our bugzilla</a> with a target of 1.6 for more
+ information.</li>
</ol>
-
</div>
<!-- *********************************************************************** -->
<p>LLVM is known to work on the following platforms:</p>
<ul>
-<li>Intel and AMD machines running Red Hat Linux and FreeBSD (and probably
- other unix-like systems).</li>
+ <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
+ (and probably other unix-like systems).</li>
<li>Sun UltraSPARC workstations running Solaris 8.</li>
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
support is available for native builds with Visual C++).</li>
-<li>PowerPC-based Mac OS X systems, running 10.2 and above.</li>
+<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
<li>Itanium-based machines running Linux and HP-UX.</li>
</ul>
<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
-href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug database</a> and submit a bug if
+href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one.</p>
</div>
<ul>
<li>The following passes are incomplete or buggy, and may be removed in future
- releases: <tt>-cee, -branch-combine, -instloops, -paths, -pre</tt></li>
+ releases: <tt>-cee, -pre</tt></li>
<li>The <tt>llvm-db</tt> tool is in a very early stage of development, but can
be used to step through programs and inspect the stack.</li>
-<li>The "iterative scan" register allocator (enabled with
- <tt>-regalloc=iterativescan</tt>) is not stable.</li>
-<li>The SparcV8, Alpha, and IA64 code generators are experimental.</li>
+<li>The SparcV8 and IA64 code generators are experimental.</li>
+<li>The Alpha JIT is experimental.</li>
</ul>
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="build">Known problems with the Build System</a>
+</div>
+
+<div class="doc_text">
+
+<ul>
+ <li>The <a href="http://llvm.org/PR656">configure script sometimes fails on Solaris/Sparc</a>. A work around is documented in <a href="http://llvm.org/PR656">PR656.</a></li>
+</ul>
+</div>
+
+
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="core">Known problems with the LLVM Core</a>
<ul>
<li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not
work.</li>
- <li>The JIT does not use mutexes to protect its internal data structures. As
- such, execution of a threaded program could cause these data structures to be
- corrupted.
- </li>
- <li><a href="http://llvm.cs.uiuc.edu/PR240">The lower-invoke pass does not
- mark values live across a setjmp as volatile</a>. This missing feature
- only affects targets whose setjmp/longjmp libraries do not save and restore
- the entire register file.</li>
</ul>
</div>
</pre></li>
<li>Initialization of global union variables can only be done <a
-href="http://llvm.cs.uiuc.edu/PR162">with the largest union member</a>.</li>
+href="http://llvm.org/PR162">with the largest union member</a>.</li>
</ul>
</div>
<li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C
front-end</a>.</li>
-<li><b>IA-64 specific</b>: The C++ front-end does not use <a
-href="http://llvm.cs.uiuc.edu/PR406">IA64 ABI compliant layout of v-tables</a>.
-In particular, it just stores function pointers instead of function
-descriptors in the vtable. This bug prevents mixing C++ code compiled with
-LLVM with C++ objects compiled by other C++ compilers.</li>
-
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="x86-be">Known problems with the X86 back-end</a>
+ <a name="c-be">Known problems with the C back-end</a>
</div>
<div class="doc_text">
<ul>
- <li>None yet</li>
+
+<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>
+
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="sparcv9-be">Known problems with the SparcV9 back-end</a>
+ <a name="x86-be">Known problems with the X86 back-end</a>
</div>
<div class="doc_text">
<ul>
-<li><a href="http://llvm.cs.uiuc.edu/PR60">[sparcv9] SparcV9 backend miscompiles
-several programs in the LLVM test suite</a></li>
+<li><a href="http://llvm.org/PR566">Memory Mapped I/O Intrinsics do not fence
+memory</a></li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="c-be">Known problems with the C back-end</a>
+ <a name="sparcv9-be">Known problems with the SparcV9 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.cs.uiuc.edu/PR56">Zero arg vararg functions are not
-supported</a>. This should not affect LLVM produced by the C or C++
-frontends.</li>
-
+<li><a href="http://llvm.org/PR60">[sparcv9] SparcV9 backend miscompiles
+several programs in the LLVM test suite</a></li>
</ul>
</div>
<ul>
-<li>On 21164s, some rare FP arithmatic sequences which may trap do not have the appropriate nops inserted to ensure restartability.</li>
-
-<li>Vararg functions are not supported.</li>
-
-<li>Due to the vararg problems, C++ exceptions do not work. Small changes are required to the CFE (which break correctness in the exception handler) to compile the exception handling library (and thus the C++ standard library).</li>
+<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
+appropriate nops inserted to ensure restartability.</li>
</ul>
speaking this is not a bug in the IA64 back-end; it will also be encountered
when building C++ programs using the C back-end.)</li>
-<li>There are a few ABI violations which will lead to problems
-when mixing LLVM output with code built with other compilers,
-particularly for C++ and floating-point programs.</li>
+<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
+ABI compliant layout of v-tables</a>. In particular, it just stores function
+pointers instead of function descriptors in the vtable. This bug prevents
+mixing C++ code compiled with LLVM with C++ objects compiled by other C++
+compilers.</li>
-<li>Vararg functions are not supported.</li>
+<li>There are a few ABI violations which will lead to problems when mixing LLVM
+output with code built with other compilers, particularly for floating-point
+programs.</li>
+
+<li>Defining vararg functions is not supported (but calling them is ok).</li>
</ul>
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="sparcv8">Known problems with the SPARC-V8 back-end</a>
+</div>
+
+<div class="doc_text">
+
+<ul>
+<li>Many features are still missing (e.g. support for 64-bit integer
+arithmetic). This back-end is in pre-beta state.</li>
+</ul>
+</div>
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="additionalinfo">Additional Information</a>
<div class="doc_text">
-<p>A wide variety of additional information is available on the LLVM web page,
-including <a href="http://llvm.cs.uiuc.edu/docs/#maillist">mailing lists</a> and
-<a href="http://llvm.cs.uiuc.edu/pubs/">publications describing algorithms and
+<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.
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>
<p>If you have any questions or comments about LLVM, please feel free to contact
-us via the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">mailing
+us via the <a href="http://llvm.org/docs/#maillist"> mailing
lists</a>.</p>
</div>
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src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
- <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
+ <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
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