forked from OSchip/llvm-project
more prose, some organization improvements.
llvm-svn: 46921
This commit is contained in:
Chris Lattner
parent
a273586b53
commit
2b8a52e259
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@ -66,6 +66,13 @@ It includes many features and refinements from LLVM 2.1.</p>
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</div>
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<!-- Unfinished features in 2.2:
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Index Set Splitting not enabled by default
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Machine LICM
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Machine Sinking
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LegalizeDAGTypes
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-->
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="deprecation">Deprecated features in LLVM 2.2</a>
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@ -92,10 +99,10 @@ llvm 2.2, and will be redesigned or removed in llvm 2.3.</p>
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LLVM 2.1, llvm-gcc 4.2 was beta). Since LLVM 2.1, the llvm-gcc 4.2 front-end
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has made leaps and bounds and is now at least as good as 4.0 in virtually every
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area, and is better in several areas (for example, exception handling
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correctness). We strongly recommend that you migrate from llvm-gcc 4.0 to
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llvm-gcc 4.2 in this release cycle because <b>LLVM 2.2 is the last release
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that will support llvm-gcc 4.0</b>: LLVM 2.3 will only support the llvm-gcc
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4.2 front-end.</p>
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correctness, support for Ada and FORTRAN). We strongly recommend that you
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migrate from llvm-gcc 4.0 to llvm-gcc 4.2 in this release cycle because
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<b>LLVM 2.2 is the last release that will support llvm-gcc 4.0</b>: LLVM 2.3
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will only support the llvm-gcc 4.2 front-end.</p>
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<p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
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a set of new 'llvm native' front-end technologies for the LLVM optimizer
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@ -104,7 +111,7 @@ nicely, and it has advanced source-to-source analysis and transformation
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capabilities. If you are interested in building source-level tools for C and
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Objective-C (and eventually C++), you should take a look. However, note that
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clang is not an official part of the LLVM 2.2 release. If you are interested in
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this project, please see the web site.</p>
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this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
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</div>
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@ -115,51 +122,30 @@ this project, please see the web site.</p>
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<div class="doc_text">
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<p>Scott Michel contributed Cell backend</p>
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<p>Dale contributed full support for long double on x86/x86-64 (where it is 80
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bits) and on Darwin PPC/PPC64 (where it is 128 bits).</p>
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<p>Ada, gfortran</p>
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<p>
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debug improvements -O0
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Gordon: GC Revamp. docs/GarbageCollection.html
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Kaleidoscope: docs/tutorial
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Gordon: C and Ocaml Bindings
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Christopher Lamb: Multiple address spaces.
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="optimizer">Optimizer Improvements</a>
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</div>
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<div class="doc_text">
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<p>Some of the most noticable feature improvements this release have been in the
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optimizer, speeding it up and making it more aggressive. For example:</p>
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<p>LLVM 2.2 includes several major new capabilities:</p>
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<ul>
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<li>Scott Michel contributed an SPU backend, which generates code for the
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vector coprocessors on the Cell processor. (Status?)</li>
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<li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis (which is
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not enabled by default) to be several orders of magnitude faster, implemented
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Offline Variable Substitution and Lazy Cycle Detection.</li>
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<li>llvm-gcc 4.2 has significantly improved support for the GCC Ada (GNAT) and
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FORTRAN (gfortran) frontends. Duncan has the llvm-gcc 4.2 GNAT front-end
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supporting almost all of the ACATS testsuite (except 2 tests?). The llvm-gcc
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4.2 gfortran front-end supports a broad range of FORTRAN code, but does <a
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href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
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Devang: LoopIndexSplit is enabled by default.
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<li>Dale contributed full support for long double on x86/x86-64 (where it is 80
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bits) and on Darwin PPC/PPC64 (where it is 128 bits). In previous LLVM
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releases, llvm-gcc silently mapped long double to double.</li>
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Dan Gohman: LSR improvements for SSE intrinsics and
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<li>Gordon rewrote most of the <a href="GarbageCollection.html">Accurate Garbage
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Collection</a> code in the code generator, making the generated code more
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efficient and adding support for the Ocaml garbage collector metadata
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format.</li>
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Evan added simple exit value substitution to LSR.
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Anton added readnone/readonly attributes for modeling function side effects
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and Duncan hooked up GCC's pure/const attributes to use them and enhanced alias
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analysis to use them.
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</ul>
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<li>LLVM now includes a new set of detailed <a
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href="tutorial/index.html">tutorials</a>, which explain how to implement a
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language with LLVM and shows how to use several important APIs.</li>
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</div>
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@ -170,33 +156,79 @@ analysis to use them.
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<div class="doc_text">
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<p>foci of this release was performance tuning and bug
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fixing. In addition to these, several new major changes occurred:</p>
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<p>We put a significant amount of work into the code generator infrastructure,
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which allows us to implement more aggressive algorithms and make it run
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faster:</p>
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<ul>
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<li>Owen contributed Machine Loop info, domintors, etc. Merged dom and
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postdom.</li>
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<li>Owen refactored the existing LLVM dominator and loop information code to
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allow it work on the machine code representation. He contributed support for
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dominator and loop information on machine code and merged the code for forward
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and backward dominator computation.</li>
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<li>Dan added support for emitting debug information with .file and .loc on
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targets that support it</li>
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<li>Dan added support for emitting debug information with .file and .loc
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directives on that support it, instead of emitting large tables in the .s
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file.</li>
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<li>Evan physical register dependencies in the BURR scheduler</li>
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<li>Evan extended the DAG scheduler to model physical register dependencies
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explicitly and have the BURR scheduler pick a correct schedule based on the
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dependencies. This reduces our use of the 'flag' operand hack.</li>
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<li>Evan added initial support for register coalescing of subregister
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references.</li>
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<li>Rafael Espindola implemented initial support for a new 'byval' attribute,
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which allows more efficient by-value argument passing in the LLVM IR. Evan
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finished support for it and enabled it in the X86 (32- and 64-bit) and C
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backends.</li>
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<li>The LLVM TargetInstrInfo class can now answer queries about the mod/ref and
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side-effect behavior of MachineInstr's. This information is inferred
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automatically by TableGen from .td files for all instructions with
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patterns.</li>
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<li>Evan implemented simple live interval splitting on basic block boundaries.
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This allows the register allocator to be more successful at keeping values in
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registers in some parts of a value's live range, even if they need to be spilled
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in some other block.</li>
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<li>The new MachineRegisterInfo.h class provides support for efficiently
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iterating over all defs/uses of a register, and this information is
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automatically kept up-to-date. This support is similar to the use_iterator in
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the LLVM IR level.</li>
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<li>The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler,
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more consistent, and better documented.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="optimizer">Optimizer Improvements</a>
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</div>
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<div class="doc_text">
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<p>In addition to a huge array of bug fixes and minor performance tweaks, LLVM
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2.2 supports a few major enhancements:</p>
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<ul>
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<li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis to be
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several orders of magnitude faster, implemented Offline Variable Substitution
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and Lazy Cycle Detection. Note that Andersen's is not enabled in llvm-gcc by
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default.</li>
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<li>Dan Gohman contributed several enhancements to Loop Strength Reduction (LSR)
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to make it more aggressive with SSE intrinsics.</li>
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<li>Evan added support for simple exit value substitution to LSR.</li>
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<li>Evan EXTRACT_SUBREG coalescing support</li>
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<li>Evan enhanced LSR to support induction variable reuse when the induction
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variables have different widths.</li>
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variables have different widths.</li>
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<li>Rafael Espindola byval support, finished by Evan for x86 (32/64).</li>
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<li>mod/ref info for machineinstrs, inferred from .td files</li>
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<li>Evan: Live interval splitting on MBB boundaries.</li>
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Efficient iteration over use/defs of registers like llvm ir.
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The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler, more
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consistent, and better documented.
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</ul>
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</div>
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@ -217,28 +249,11 @@ consistent, and better documented.
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<li>Bruno: MIPS PIC support.</li>
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<li>Arnold Schwaighofer: X86 tail call support.</li>
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<li>Dale darwin/x86-64 and darwin/ppc eh</li>
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<li>Evan: darwin/x86 debug info</li>
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<li>Evan: darwin/x86 debug info, improvements at -O0?</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="llvmgccimprovements">llvm-gcc Improvements</a>
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</div>
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<div class="doc_text">
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<p>New features include:
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</p>
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<ul>
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<li>.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="coreimprovements">LLVM Core Improvements</a>
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@ -260,6 +275,13 @@ consistent, and better documented.
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<li>Duncan moved parameter attributes off of function type and onto functions
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and calls, which makes it much easier to add attributes to a function in a
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transformation.</li>
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<li>Christopher Lamb: Multiple address spaces.</li>
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<li>Gordon: C and Ocaml Bindings</li>
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<li>Anton added readnone/readonly attributes for modeling function side effects
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and Duncan hooked up GCC's pure/const attributes to use them and enhanced alias
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analysis to use them.</li>
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</ul>
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</div>
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