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crank out notes
llvm-svn: 37218
This commit is contained in:
Chris Lattner
parent
8d3963308c
commit
ac84cb2264
@ -72,16 +72,23 @@ and .bc formats within the 2.x release series, like we did within the 1.x
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series.</li>
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<li>There are several significant change to the LLVM IR and internal APIs, such
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as a major overhaul of the type system, the completely new bitcode file
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format, etc.</li>
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format, etc (described below).</li>
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<li>We designed the release around a 6 month release cycle instead of the usual
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3-month cycle. This gave us extra time to develop and test some of the
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more invasive features in this release.</li>
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<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end.</li>
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<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end. Users are required to
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upgrade to llvm-gcc4. llvm-gcc4 includes many features over
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llvm-gcc3, is faster, and is <a href="CFEBuildInstrs.html">much easier to
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build from source</a>.</li>
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</ol>
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<p>Note that while this is a major version bump, this release has been
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extensively tested on a wide range of software. It is easy to say that this
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is our best release yet, in terms of both features and correctness.</p>
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is our best release yet, in terms of both features and correctness. This is
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the first LLVM release to correctly compile and optimize major software like
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LLVM itself, Mozilla/Seamonkey, Qt 4.3rc1, kOffice, etc out of the box on
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linux/x86.
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</p>
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</div>
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@ -93,26 +100,27 @@ series.</li>
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<!--_________________________________________________________________________-->
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<div class="doc_subsubsection"><a name="majorchanges">Major Changes</a></div>
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<div class="doc_text">
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<p>blah
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</p>
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<p>Changes to the LLVM IR itself:</p>
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<ul>
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<li>llvm-gcc3 is now officially unsupported. Users are required to
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upgrade to llvm-gcc4. llvm-gcc4 includes many features over
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llvm-gcc3, is faster, and is much easier to build.</li>
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<li>Integer types are now completely signless. This means that we
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have types like i8/i16/i32 instead of ubyte/sbyte/short/ushort/int
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etc. LLVM operations that depend on sign have been split up into
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separate instructions (<a href="http://llvm.org/PR950">PR950</a>).</li>
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separate instructions (<a href="http://llvm.org/PR950">PR950</a>). This
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eliminates cast instructions that just change the sign of the operands (e.g.
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int -> uint), which reduces the size of the IR and makes optimizers
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simpler to write.</li>
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<li>Arbitrary bitwidth integers (e.g. i13, i36, i42, etc) are now
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supported in the LLVM IR and optimizations. However, neither llvm-gcc nor
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the native code generators support non-standard width integers
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(<a href="http://llvm.org/PR1043">PR1043</a>).</li>
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<li>Integer types with arbitrary bitwidths (e.g. i13, i36, i42, i1057, etc) are
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now supported in the LLVM IR and optimizations (<a
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href="http://llvm.org/PR1043">PR1043</a>). However, neither llvm-gcc
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(<a href="http://llvm.org/PR1284">PR1284</a>) nor the native code generators
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(<a href="http://llvm.org/PR1270">PR1270</a>) support non-standard width
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integers yet.</li>
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<li>'type planes' have been removed (<a href="http://llvm.org/PR411">PR411</a>).
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<li>'Type planes' have been removed (<a href="http://llvm.org/PR411">PR411</a>).
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It is no longer possible to have two values with the same name in the
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same symbol table. This simplifies LLVM internals, allowing significant
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speedups.</li>
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@ -121,36 +129,36 @@ series.</li>
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@ instead of % (<a href="http://llvm.org/PR645">PR645</a>).</li>
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<li>The LLVM 1.x "bytecode" format has been replaced with a
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completely new binary representation, named 'bitcode'. Because we
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plan to maintain binary compatibility between LLVM 2.x ".bc" files,
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this is an important change to get right. Bitcode brings a number of
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advantages to the LLVM over the old bytecode format. It is denser
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completely new binary representation, named 'bitcode'. The <a
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href="BitCodeFormat.html">Bitcode Format</a> brings a
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number of advantages to the LLVM over the old bytecode format: it is denser
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(files are smaller), more extensible, requires less memory to read,
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is easier to keep backwards compatible (so LLVM 2.5 will read 2.0 .bc
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files), and has many other nice features.</li>
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<li>Support was added for alignment values on load and store
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instructions (<a href="http://www.llvm.org/PR400">PR400</a>). This
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allows the IR to express loads that are not
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sufficiently aligned (e.g. due to pragma packed) or to capture extra
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alignment information. </li>
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<li>Load and store instructions now track the alignment of their pointer
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(<a href="http://www.llvm.org/PR400">PR400</a>). This allows the IR to
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express loads that are not sufficiently aligned (e.g. due to '<tt>#pragma
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packed</tt>') or to capture extra alignment information.</li>
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</ul>
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<li>LLVM now has a new MSIL backend. llc - march=msil will now turn LLVM
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<p>Major new features:</p>
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<ul>
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<li>A number of ELF features are now supported by LLVM, including 'visibility',
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extern weak linkage, Thread Local Storage (TLS) with the <tt>__thread</tt>
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keyword, and symbol aliases.
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Among other things, this means that many of the special options needed to
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configure llvm-gcc on linux are no longer needed, and special hacks to build
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large C++ libraries like Qt are not needed.</li>
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<li>LLVM now has a new MSIL backend. llc -march=msil will now turn LLVM
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into MSIL (".net") bytecode. This is still fairly early development
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with a number of limitations.</li>
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<li>Support has been added for 'protected visibility' in ELF.</li>
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<li>Thread Local Storage with the __thread keyword was implemented along
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with added codegen support for Linux on X86 and ARM.</li>
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<li>ELF symbol aliases supported has been added.</li>
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<li>Added support for 'polymorphic intrinsics', allowing things like
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llvm.ctpop to work on arbitrary width integers.</li>
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</ul>
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</div>
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@ -162,29 +170,20 @@ Improvements</a></div>
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</p>
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<ul>
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<li>Precompiled Headers (PCH) support has been implemented.</li>
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<li>Precompiled Headers (PCH) are now supported.</li>
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<li>Support for external weak linkage and hidden visibility has been added.</li>
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<li>Packed structure types are now supported , which allows LLVM to express
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unaligned data more naturally.</li>
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<li>Inline assembly support has been improved and many bugs were fixed.
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The two large missing features are support for 80-bit floating point stack
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registers on X86 (<a href="http://llvm.org/PR879">PR879</a>), and support for inline asm in the C backend (<a href="http://llvm.org/PR802">PR802</a>).</li>
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<li>Ada support, such as nested functions, has been improved.</li>
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<li>"<tt>#pragma packed</tt>" is now supported, as are the various features
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described above (visibility, extern weak linkage, __thread, aliases,
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etc).</li>
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<li>Tracking function parameter/result attributes is now possible.</li>
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<li>Its is now easier to configure llvm-gcc for linux.</li>
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<li>Many internal enhancements have been added, such as improvements to
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NON_LVALUE_EXPR, arrays with non-zero base, structs with variable sized
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fields, VIEW_CONVERT_EXPR, CEIL_DIV_EXPR, nested functions, and many other
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things. This is primarily to supports non-C GCC front-ends, like Ada.</li>
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<li>Many enhancements have been added, such as improvements to NON_LVALUE_EXPR,
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arrays with non-zero base, structs with variable sized fields,
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VIEW_CONVERT_EXPR, CEIL_DIV_EXPR, and many other things.</li>
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<li>Improved "attribute packed" support in the CFE, and handle many
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other obscure struct layout cases correctly.</li>
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<li>It is simpler to configure llvm-gcc for linux.</li>
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</ul>
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@ -193,33 +192,38 @@ Improvements</a></div>
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<!--_________________________________________________________________________-->
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<div class="doc_subsubsection"><a name="optimizer">Optimizer
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Improvements</a></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>The pass manager has been entirely rewritten, making it significantly
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smaller, simpler, and more extensible. Support has been added to run
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FunctionPasses interlaced with CallGraphSCCPasses.</li>
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<li>The <a href="WritingAnLLVMPass.html">pass manager</a> has been entirely
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rewritten, making it significantly smaller, simpler, and more extensible.
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Support has been added to run FunctionPasses interlaced with
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CallGraphSCCPasses, and we now support loop transformations explicitly with
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LoopPass.</li>
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<li>The -scalarrepl pass can now promote unions containing FP values into
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a register, it can also handle unions of vectors of the same size.</li>
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<li>The <tt>-scalarrepl</tt> pass can now promote unions containing FP values
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into a register, it can also handle unions of vectors of the same
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size.</li>
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<li>The predicate simplifier pass has been improved, making it able to do
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simple value range propagation and eliminate more conditionals.</li>
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<li>There is a new new LoopPass class. The passmanager has been
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modified to support it, and all existing loop xforms have been
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converted to use it. </li>
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<li>There is a new loop rotation pass, which converts "for loops" into
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<li>LLVM 2.0 includes a new loop rotation pass, which converts "for loops" into
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"do/while loops", where the condition is at the bottom of the loop.</li>
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<li>The Loop Strength Reduction pass has been improved, and support added
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for sinking expressions across blocks to reduce register pressure.</li>
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<li>ModulePasses may now use the result of FunctionPasses.</li>
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<li>The [Post]DominatorSet classes have been removed from LLVM and clients switched to use the far-more-efficient ETForest class instead. </li>
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<li>The [Post]DominatorSet classes have been removed from LLVM and clients
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switched to use the far-more-efficient ETForest class instead.</li>
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<li>The ImmediateDominator class has also been removed, and clients have been switched to use DominatorTree instead.</li>
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<li>The ImmediateDominator class has also been removed, and clients have been
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switched to use DominatorTree instead.</li>
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<li>The predicate simplifier pass has been improved, making it able to do
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simple value range propagation and eliminate more conditionals.</li>
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</ul>
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@ -235,40 +239,27 @@ New features include:
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</p>
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<ul>
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<li>Support for Zero-cost DWARF exception handling has been added. It is mostly
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complete and just in need of continued bug fixes and optimizations at
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this point.</li>
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<li>Progress has been made on a direct Mach-o .o file writer. Many small
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apps work, but it is not quite complete yet.</li>
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<li>Support was added for software floating point routines.</li>
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<li>DWARF debug information generation has been improved. LLVM now passes
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most of the GDB testsuite on MacOS and debug info is more dense.</li>
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<li>Support was added for software floating point, which allows LLVM to target
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chips that don't have hardware FPUs (e.g. ARM thumb mode).</li>
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<li>A new register scavenger has been implemented, which is useful for
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finding free registers after register allocation. This is useful when
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rewriting frame references on RISC targets, for example.</li>
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<li>Heuristics have been added to avoid coalescing vregs with very large live
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ranges to physregs.</li>
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ranges to physregs. This was bad because it effectively pinned the physical
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register for the entire lifetime of the virtual register (<a
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href="http://llvm.org/PR711">PR711</a>).</li>
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<li>Support now exists for very simple (but still very useful)
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rematerialization the register allocator, enough to move
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instructions like "load immediate" and constant pool loads.</li>
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<li>Significantly improved 'switch' lowering, improving codegen for
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<li>Switch statement lowering is significantly better, improving codegen for
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sparse switches that have dense subregions, and implemented support
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for the shift/and trick.</li>
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<li>The code generator now has more accurate and general hooks for
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describing addressing modes ("isLegalAddressingMode") to
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optimizations like loop strength reduction and code sinking.</li>
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<li>The Loop Strength Reduction pass has been improved, and support added
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for sinking expressions across blocks to reduce register pressure.</li>
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<li>Added support for tracking physreg sub-registers and super-registers
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in the code generator, as well as extensive register
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allocator changes to track them.</li>
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@ -278,6 +269,37 @@ New features include:
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</ul>
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<p>
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Other improvements include:
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</p>
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<ul>
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<li>Inline assembly support is much more solid that before.
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The two primary features still missing are support for 80-bit floating point
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stack registers on X86 (<a href="http://llvm.org/PR879">PR879</a>), and
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support for inline asm in the C backend (<a
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href="http://llvm.org/PR802">PR802</a>).</li>
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<li>DWARF debug information generation has been improved. LLVM now passes
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most of the GDB testsuite on MacOS and debug info is more dense.</li>
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<li>Codegen support for Zero-cost DWARF exception handling has been added (<a
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href="http://llvm.org/PR592">PR592</a>). It is mostly
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complete and just in need of continued bug fixes and optimizations at
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this point. However, support in llvm-g++ is disabled with an
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#ifdef for the 2.0 release (<a
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href="http://llvm.org/PR870">PR870</a>).</li>
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<li>The code generator now has more accurate and general hooks for
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describing addressing modes ("isLegalAddressingMode") to
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optimizations like loop strength reduction and code sinking.</li>
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<li>Progress has been made on a direct Mach-o .o file writer. Many small
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apps work, but it is still not quite complete.</li>
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</ul>
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<p>In addition, the LLVM target description format has itself been extended in
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several ways:</p>
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@ -303,44 +325,39 @@ Improvements</a></div>
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<div class="doc_text">
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<p>X86-Specific Code Generator Enhancements:
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<p>X86-specific Code Generator Enhancements:
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</p>
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<ul>
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<li>The MMX instruction set is now supported through intrinsics.</li>
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<li>The scheduler was improved to better reduce register pressure on
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X86 and other targets that are register pressure sensitive</li>
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<li>Linux/x86-64 support has been improved.</li>
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X86 and other targets that are register pressure sensitive.</li>
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<li>Linux/x86-64 support is much better.</li>
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<li>PIC support for linux/x86 has been added.</li>
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<li>Support now exists for the GCC regparm attribute, and code in the X86
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backend to respect it.</li>
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<li>Various improvements have been made for the X86-64 JIT, allowing it to
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generate code in the large code model</li>
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<li>The X86 backend now supports the GCC regparm attribute.</li>
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<li>LLVM now supports inline asm with multiple constraint letters per operand
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(like "ri") which is common in X86 inline asms.</li>
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<li>Early support has been added for X86 inline asm in the C backend.</li>
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<li>Added support for the X86 MMX instruction set.</li>
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</ul>
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<p>ARM-Specific Code Generator Enhancements:
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</p>
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<p>ARM-specific Code Generator Enhancements:</p>
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<ul>
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<li>Several improvements have been made to the ARM backend, including basic
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inline asm support, weak linkage support, static ctor/dtor support and
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many bug fixes.</li>
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<li>There are major enhancements to the ARM backend, including support for ARM
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v4-v6, vfp support, soft float, pre/postinc support, load/store multiple
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generation, constant pool entry motion (to support large functions),
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and enhancements to ARM constant island pass.
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</li>
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<li>Added support for Thumb code generation (an ARM subtarget).</li>
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<li>More aggressive size analysis for ARM inline asm strings was
|
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implemented.</li>
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<li>The ARM code generator is now stable and fully supported.</li>
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<li>There are major new features, including support for ARM
|
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v4-v6 chips, vfp support, soft float point support, pre/postinc support,
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load/store multiple generation, constant pool entry motion (to support
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large functions), and inline asm support, weak linkage support, static
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ctor/dtor support and many bug fixes.</li>
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<li>Added support for Thumb code generation (<tt>llc -march=thumb</tt>).</li>
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<li>The ARM backend now supports the ARM AAPCS/EABI ABI and PIC codegen on
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arm/linux.</li>
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<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li>
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</ul>
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<p>Other Target-Specific Code Generator Enhancements:
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</p>
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<p>PowerPC-specific Code Generator Enhancements:</p>
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<ul>
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<li>The PowerPC 64 JIT now supports addressing code loaded above the 2G
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@ -350,19 +367,7 @@ Improvements</a></div>
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functional now. llvm-gcc and static compilation are not fully supported
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yet though.</li>
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<li>Many bugs fixed for PowerPC 64.</li>
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<li>Support was added for the ARM AAPCS and EABI ABIs and PIC codegen on
|
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arm/linux.</li>
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<li>Several bugs in DWARF debug emission on linux and cygwin/mingw were fixed.
|
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Debugging basically works on these targets now.</li>
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<li>Support has been added for the X86-64 large code model to the JIT,
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which is useful if JIT'd function bodies are more than 2G away from
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library functions.</li>
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<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li>
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<li>Many PowerPC 64 bug fixes.</li>
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</ul>
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@ -414,7 +419,7 @@ internal changes. If you are programming to the C++ API, be aware of the
|
||||
following major changes:</p>
|
||||
|
||||
<ul>
|
||||
<li>Pass registration is slightly different in LLVM 2.0 (you now needs an
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||||
<li>Pass registration is slightly different in LLVM 2.0 (you now need an
|
||||
intptr_t in your constructor), as explained in the <a
|
||||
href="WritingAnLLVMPass.html#basiccode">Writing an LLVM Pass</a>
|
||||
document.</li>
|
||||
|
||||
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