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Code Issues Projects Releases Wiki Activity

more prose, some organization improvements.

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@ -66,6 +66,13 @@ It includes many features and refinements from LLVM 2.1.</p>
</div>
<!-- Unfinished features in 2.2:
Index Set Splitting not enabled by default
Machine LICM
Machine Sinking
LegalizeDAGTypes
-->
<!--=========================================================================-->
<div class="doc_subsection">
<a name="deprecation">Deprecated features in LLVM 2.2</a>
@ -92,10 +99,10 @@ llvm 2.2, and will be redesigned or removed in llvm 2.3.</p>
LLVM 2.1, llvm-gcc 4.2 was beta). Since LLVM 2.1, the llvm-gcc 4.2 front-end
has made leaps and bounds and is now at least as good as 4.0 in virtually every
area, and is better in several areas (for example, exception handling
correctness). We strongly recommend that you migrate from llvm-gcc 4.0 to
llvm-gcc 4.2 in this release cycle because <b>LLVM 2.2 is the last release
that will support llvm-gcc 4.0</b>: LLVM 2.3 will only support the llvm-gcc
4.2 front-end.</p>
correctness, support for Ada and FORTRAN). We strongly recommend that you
migrate from llvm-gcc 4.0 to llvm-gcc 4.2 in this release cycle because
<b>LLVM 2.2 is the last release that will support llvm-gcc 4.0</b>: LLVM 2.3
will only support the llvm-gcc 4.2 front-end.</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
@ -104,7 +111,7 @@ 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 2.2 release. If you are interested in
this project, please see the web site.</p>
this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
</div>
@ -115,51 +122,30 @@ this project, please see the web site.</p>
<div class="doc_text">
<p>Scott Michel contributed Cell backend</p>
<p>Dale contributed full support for long double on x86/x86-64 (where it is 80
bits) and on Darwin PPC/PPC64 (where it is 128 bits).</p>
<p>Ada, gfortran</p>
<p>
debug improvements -O0
Gordon: GC Revamp. docs/GarbageCollection.html
Kaleidoscope: docs/tutorial
Gordon: C and Ocaml Bindings
Christopher Lamb: Multiple address spaces.
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="optimizer">Optimizer Improvements</a>
</div>
<div class="doc_text">
<p>Some of the most noticable feature improvements this release have been in the
optimizer, speeding it up and making it more aggressive. For example:</p>
<p>LLVM 2.2 includes several major new capabilities:</p>
<ul>
<li>Scott Michel contributed an SPU backend, which generates code for the
vector coprocessors on the Cell processor. (Status?)</li>
<li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis (which is
not enabled by default) to be several orders of magnitude faster, implemented
Offline Variable Substitution and Lazy Cycle Detection.</li>
<li>llvm-gcc 4.2 has significantly improved support for the GCC Ada (GNAT) and
FORTRAN (gfortran) frontends. Duncan has the llvm-gcc 4.2 GNAT front-end
supporting almost all of the ACATS testsuite (except 2 tests?). The llvm-gcc
4.2 gfortran front-end supports a broad range of FORTRAN code, but does <a
href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
Devang: LoopIndexSplit is enabled by default.
<li>Dale contributed full support for long double on x86/x86-64 (where it is 80
bits) and on Darwin PPC/PPC64 (where it is 128 bits). In previous LLVM
releases, llvm-gcc silently mapped long double to double.</li>
Dan Gohman: LSR improvements for SSE intrinsics and
<li>Gordon rewrote most of the <a href="GarbageCollection.html">Accurate Garbage
Collection</a> code in the code generator, making the generated code more
efficient and adding support for the Ocaml garbage collector metadata
format.</li>
Evan added simple exit value substitution to LSR.
Anton added readnone/readonly attributes for modeling function side effects
and Duncan hooked up GCC's pure/const attributes to use them and enhanced alias
analysis to use them.
</ul>
<li>LLVM now includes a new set of detailed <a
href="tutorial/index.html">tutorials</a>, which explain how to implement a
language with LLVM and shows how to use several important APIs.</li>
</div>
@ -170,33 +156,79 @@ analysis to use them.
<div class="doc_text">
<p>foci of this release was performance tuning and bug
fixing. In addition to these, several new major changes occurred:</p>
<p>We 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>Owen contributed Machine Loop info, domintors, etc. Merged dom and
postdom.</li>
<li>Owen refactored the existing LLVM dominator and loop information code to
allow it work on the machine code representation. He contributed support for
dominator and loop information on machine code and merged the code for forward
and backward dominator computation.</li>
<li>Dan added support for emitting debug information with .file and .loc on
targets that support it</li>
<li>Dan added support for emitting debug information with .file and .loc
directives on that support it, instead of emitting large tables in the .s
file.</li>
<li>Evan physical register dependencies in the BURR scheduler</li>
<li>Evan extended the DAG scheduler to model physical register dependencies
explicitly and have the BURR scheduler pick a correct schedule based on the
dependencies. This reduces our use of the 'flag' operand hack.</li>
<li>Evan added initial support for register coalescing of subregister
references.</li>
<li>Rafael Espindola implemented initial support for a new 'byval' attribute,
which allows more efficient by-value argument passing in the LLVM IR. Evan
finished support for it and enabled it in the X86 (32- and 64-bit) and C
backends.</li>
<li>The LLVM TargetInstrInfo class can now answer queries about the mod/ref and
side-effect behavior of MachineInstr's. This information is inferred
automatically by TableGen from .td files for all instructions with
patterns.</li>
<li>Evan implemented simple live interval splitting on basic block boundaries.
This allows the register allocator to be more successful at keeping values in
registers in some parts of a value's live range, even if they need to be spilled
in some other block.</li>
<li>The new MachineRegisterInfo.h class provides support for efficiently
iterating over all defs/uses of a register, and this information is
automatically kept up-to-date. This support is similar to the use_iterator in
the LLVM IR level.</li>
<li>The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler,
more consistent, and better documented.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="optimizer">Optimizer Improvements</a>
</div>
<div class="doc_text">
<p>In addition to a huge array of bug fixes and minor performance tweaks, LLVM
2.2 supports a few major enhancements:</p>
<ul>
<li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis to be
several orders of magnitude faster, implemented Offline Variable Substitution
and Lazy Cycle Detection. Note that Andersen's is not enabled in llvm-gcc by
default.</li>
<li>Dan Gohman contributed several enhancements to Loop Strength Reduction (LSR)
to make it more aggressive with SSE intrinsics.</li>
<li>Evan added support for simple exit value substitution to LSR.</li>
<li>Evan EXTRACT_SUBREG coalescing support</li>
<li>Evan enhanced LSR to support induction variable reuse when the induction
variables have different widths.</li>
variables have different widths.</li>
<li>Rafael Espindola byval support, finished by Evan for x86 (32/64).</li>
<li>mod/ref info for machineinstrs, inferred from .td files</li>
<li>Evan: Live interval splitting on MBB boundaries.</li>
Efficient iteration over use/defs of registers like llvm ir.
The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler, more
consistent, and better documented.
</ul>
</div>
@ -217,28 +249,11 @@ consistent, and better documented.
<li>Bruno: MIPS PIC support.</li>
<li>Arnold Schwaighofer: X86 tail call support.</li>
<li>Dale darwin/x86-64 and darwin/ppc eh</li>
<li>Evan: darwin/x86 debug info</li>
<li>Evan: darwin/x86 debug info, improvements at -O0?</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="llvmgccimprovements">llvm-gcc Improvements</a>
</div>
<div class="doc_text">
<p>New features include:
</p>
<ul>
<li>.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="coreimprovements">LLVM Core Improvements</a>
@ -260,6 +275,13 @@ consistent, and better documented.
<li>Duncan moved parameter attributes off of function type and onto functions
and calls, which makes it much easier to add attributes to a function in a
transformation.</li>
<li>Christopher Lamb: Multiple address spaces.</li>
<li>Gordon: C and Ocaml Bindings</li>
<li>Anton added readnone/readonly attributes for modeling function side effects
and Duncan hooked up GCC's pure/const attributes to use them and enhanced alias
analysis to use them.</li>
</ul>
</div>