maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

various updates. 

llvm-svn: 102051
This commit is contained in:
Chris Lattner 2010-04-22 05:41:35 +00:00
parent 05bf00938b
commit 656db16db4
1 changed files with 75 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

129
llvm/docs/ReleaseNotes.html
View File

@ -29,10 +29,10 @@
</div>
<!--
<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.7
<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
release.<br>
You may prefer the
<a href="http://llvm.org/releases/2.6/docs/ReleaseNotes.html">LLVM 2.6
<a href="http://llvm.org/releases/2.6/docs/ReleaseNotes.html">LLVM 2.7
Release Notes</a>.</h1>-->
<!-- *********************************************************************** -->
@ -383,7 +383,7 @@ organization changes have happened:
</p>
<ul>
<li>LLVM has a new <a href="http://llvm.org/Logo.html">official Logo</a>!</li>
<li>LLVM has a new <a href="http://llvm.org/Logo.html">official logo</a>!</li>
<li>Ted Kremenek and Doug Gregor have stepped forward as <a
href="http://llvm.org/docs/DeveloperPolicy.html#owners">Code Owners</a> of the
@ -396,7 +396,7 @@ organization changes have happened:
<li>The LLVM web pages are now checked into the SVN server, in the "www",
"www-pubs" and "www-releases" SVN modules. Previously they were hidden in a
largely inaccessible old CVS server.</p>
largely inaccessible old CVS server.</li>
<li><a href="http://llvm.org">llvm.org</a> is now hosted on a new (and much
faster) server. It is still graciously hosted at the University of Illinois
@ -414,11 +414,11 @@ organization changes have happened:
<p>LLVM 2.7 includes several major new capabilities:</p>
<ul>
<li>This release includes initial support for the <a
<li>2.7 includes initial support for the <a
href="http://en.wikipedia.org/wiki/MicroBlaze">MicroBlaze</a> target.
MicroBlaze is a soft processor core designed for Xilinx FPGAs.</li>
<li>LLVM 2.7 includes a new LLVM IR "extensible metadata" feature. This feature
<li>2.7 includes a new LLVM IR "extensible metadata" feature. This feature
supports many different use cases, including allowing front-end authors to
encode source level information into LLVM IR, which is consumed by later
language-specific passes. This is a great way to do high-level optimizations
@ -426,26 +426,26 @@ organization changes have happened:
href="http://blog.llvm.org/2010/04/extensible-metadata-in-llvm-ir.html">
Extensible Metadata Blog Post</a> for more information.</li>
<li>LLVM 2.7 encodes <a href="SourceLevelDebugging.html">debug information</a>
<li>2.7 encodes <a href="SourceLevelDebugging.html">debug information</a>
in a completely new way, built on extensible metadata. The new implementation
is much more memory efficient and paves the way for improvements to optimized
code debugging experience.</li>
<li>LLVM 2.7 now directly supports taking the address of a label and doing an
<li>2.7 now directly supports taking the address of a label and doing an
indirect branch through a pointer. This is particularly useful for
interpreter loops, and is used to implement the GCC "address of label"
extension. For more information, see the <a
href="http://blog.llvm.org/2010/01/address-of-label-and-indirect-branches.html">
Address of Label and Indirect Branches in LLVM IR Blog Post</a>.
<li>LLVM 2.7 is the first release to start supporting APIs for assembling and
<li>2.7 is the first release to start supporting APIs for assembling and
disassembling target machine code. These APIs are useful for a variety of
low level clients, and are surfaced in the new "enhanced disassembly" API.
For more information see the <a
href="http://blog.llvm.org/2010/01/x86-disassembler.html">The X86
Disassembler Blog Post</a> for more information.</li>
<li>LLVM 2.7 includes major parts of the work required by the new MC Project,
<li>2.7 includes major parts of the work required by the new MC Project,
which aims to rework our handling of low-level machine code. A few targets
have been refactored to support it, and work is underway to support a native
assembler in LLVM. This work is not complete in LLVM 2.7, but you has made
@ -468,17 +468,17 @@ Address of Label and Indirect Branches in LLVM IR Blog Post</a>.
expose new optimization opportunities:</p>
<ul>
<li>LLVM IR now supports a 16-bit "half float" data type through two new <a
href="LangRef.html#int_fp16">intrinsics</a> and APFloat support.</li>
<li>LLVM IR supports two <a href="LangRef.html#fnattrs">new function
<li>LLVM IR now supports a 16-bit "half float" data type through <a
href="LangRef.html#int_fp16">two new intrinsics</a> and APFloat support.</li>
<li>LLVM IR supports two new <a href="LangRef.html#fnattrs">function
attributes</a>: inlinehint and alignstack(n). The former is a hint to the
optimizer that a function was declared 'inline' and thus it might be useful
to increase the chances the the inliner actually inline it. The later
optimizer that a function was declared 'inline' and thus the inliner should
weight it higher when considering inlining it. The later
indicates to the code generator that the function diverges from the platform
ABI on stack alignment.</li>
<li>The new <a href="LangRef.html#int_objectsize">llvm.objectsize</a> intrinsic
allows the optimizer to infer the sizes of memory objects in some cases.
This intrinsic is used to implement the GCC __builtin_object_size
This intrinsic is used to implement the GCC <tt>__builtin_object_size</tt>
extension.</li>
<li>LLVM 2.7 has pre-alpha support for <a
href="http://llvm.org/docs/LangRef.html#t_union">unions in LLVM IR</a>.
@ -501,47 +501,50 @@ release includes a few major enhancements and additions to the optimizers:</p>
<ul>
<li>Inliner reuses arrays allocas when inlining multiple callers to reduce stack usage.</li>
<li>Instcombine is now a library, has its own IRBuilder to simplify itself.</li>
<li>Better code size analysis in loop unswitch, inliner code split out to a new
CodeMetrics class for reuse.</li>
<li>Many changes to the pass ordering for improved optimization
effectiveness.</li>
<li>BasicAA improved to be less dependent on "type safe" pointers, it can now look
through bitcasts more aggressively.</li>
<li>GVN PHI Translation improvements. blog post: http://blog.llvm.org/2009/12/advanced-topics-in-redundant-load.html</li>
<li>New SCEV AA pass: -scev-aa</li>
<li>Target data now has notion of 'native' integer data types which optimizations can use.</li>
<li>Opt now works conservatively if no target data is set (is this fully working?)</li>
<li>New Analysis/InstructionSimplify.h interface for simplifying instructions that don't exist.</li>
<li>The inliner reuses now merges arrays stack objects in different callees when
inlining multiple call sites into one function. This reduces the stack size
of the resultant function.</li>
<li>The -basicaa alias analysis pass (which is the default) has been improved to
be less dependent on "type safe" pointers. It can now look through bitcasts
and other constructs more aggressively, allowing better load/store
optimization.</li>
<li>The load elimination optimization in the GVN Pass [<a
href="http://blog.llvm.org/2009/12/introduction-to-load-elimination-in-gvn.html">intro
blog post</a>] has been substantially improved to be more aggressive about
partial redundancy elimination and do more aggressive phi translation. Please
see the <a
href="http://blog.llvm.org/2009/12/advanced-topics-in-redundant-load.html">
Advanced Topics in Redundant Load Elimination with a Focus on PHI Translation
Blog Post</a> for more details.</li>
<li>The module <a href="LangRef.html#datalayout">target data string</a> now
includes a notion of what the 'native' integer data types a for the target,
which allows various optimizations to use. This helps mid-level
optimizations avoid promoting complex sequences of operations to data types
that are not natively supported (e.g. converting i32 operations to i64 on
a 32-bit chip).</li>
<li>The mid-level optimizer is now conservative when operating on a module with
no target data. Previously, it would default to SparcV9 settings, which is
not what most people expected.</li>
<li>Jump threading is now much more aggressive at simplifying correlated
conditionals and threading blocks with otherwise complex logic. CondProp pass
removed (functionality merged into jump threading).</li>
<li>New SSAUpdater and MachineSSAUpdater classes for unstructured ssa updating,
changed jump threading, GVN, etc to use it which simplified them and speed
them up.</li>
conditionals and threading blocks with otherwise complex logic. It has
subsumed the old "Conditional Propagation" pass, and -condprop has been
removed from LLVM 2.7.</li>
<li>The -instcombine pass has been refactored from being one huge file to being
a library of its own. Internally, it uses a customized IRBuilder to clean
it up and simplify it.</li>
<li>The optimal edge profiling pass is reliable and much more complete than in
2.6. It can be used with the llvm-prof tool but isn't wired up to the
llvm-gcc and clang command line options yet.</li>
<li>
The Optimal Edge Profiling implementation in 2.6 was more a proof of
concept. The current implementation (the one that will go into 2.7) is
now stable and (as far as my tests go) bug free.
<li>A new experimental alias analysis implementation, -scev-aa, has been added.
It uses LLVM's Scalar Evolution implementation to do symbolic analysis of
pointer offset expressions to disambiguate pointers. It can catch a few
cases that basicaa cannot, particularly in complex loop nests.</li>
The profiling with instrumentation via "opt" and analysis via the tool
"llvm-prof" should Work As Expected (TM).
Two things are missing:
*) Still missing is the modification of all -std-compile-opt passes to
update the profiling information according to the changes made to the
CFG, I'm planning to do this after my master thesis is finished. This
will enable all passes to use the ProfileInfo if available and base
decisions on that information.
*) GCC has the options "-pg", "-fprofile-arcs" and "--coverage" that
insert profiling code and "-fprofile-use" to use them the next time
during compilation. I guess this options should also work properly in
llvm-gcc and clang?</li>
<li>As usual, there are countless minor optimization improvements and bug fixes,
and the default pass ordering has been tweaked for improved optimization
effectiveness.</li>
</ul>
@ -670,7 +673,25 @@ href="http://blog.llvm.org/2010/04/arm-advanced-simd-neon-intrinsics-and.html">
</p>
<ul>
<li>The llvm/Support/Regex.h header exposes a platform independent regular
<li>The optimizer uses the new CodeMetrics class to measure the size of code.
Various passes that use thing (like the inliner, loop unswitcher, etc) all
use this to make more accurate estimates of the code size impact of various
optimizations.</li>
<li>A new <a href="http://llvm.org/doxygen/InstructionSimplify_8h-source.html">
llvm/Analysis/InstructionSimplify.h</a> interface available for doing
symbolic simplification of instructions (e.g. <tt>a+0</tt> -&gt; <tt>a</tt>)
without requiring the instruction to exist. This centralizes a lot of
ad-hoc symbolic manipulation code scattered in various passes.</li>
<li>The optimizer now uses a new <a
href="http://llvm.org/doxygen/SSAUpdater_8h-source.html">SSAUpdater</a>
class which efficiently supports
doing unstructured SSA update operations. This centralized a bunch of code
scattered through various passes (e.g. jump threading, lcssa, loop rotate,
etc) for doing this sort of thing. The code generator has an similar
<a href="http://llvm.org/doxygen/MachineSSAUpdater_8h-source.html">
MachineSSAUpdater</a> class.</li>
<li>The <a href="http://llvm.org/doxygen/Regex_8h-source.html">
llvm/Support/Regex.h</a> header exposes a platform independent regular
expression API. Building on this, the <a
href="TestingGuide.html#FileCheck">FileCheck</a> utility now supports
regular exressions.</li>