<div class="doc_text">
-<p>LLVM 1.8 includes a brand new llvm-gcc, based on GCC 4.0.1. This version
+<p>LLVM 1.7 includes a brand new llvm-gcc, based on GCC 4.0.1. This version
of llvm-gcc solves many serious long-standing problems with llvm-gcc, including
all of those blocked by the <a href="http://llvm.org/PR498">llvm-gcc 4 meta
bug</a>. In addition, llvm-gcc4 implements support for many new features,
including GCC inline assembly, generic vector support, SSE and Altivec
-intrinsics, and several new GCC attributes. In addition, llvm-gcc4 is
+intrinsics, and several new GCC attributes. Finally, llvm-gcc4 is
significantly faster than llvm-gcc3, respects -O options, its -c/-S options
-correspond to GCC's (they emit native code).</p>
+correspond to GCC's (they emit native code), supports Objective C/C++, and
+it has debugging support well underway.</p>
-<p>If you can use it, llvm-gcc4 is offers significant new functionality, and we
+<p>If you can use it, llvm-gcc4 offers significant new functionality, and we
hope that it will replace llvm-gcc3 completely in a future release.
Unfortunately, it does not currently support C++ exception handling at all, and
it only works on Apple Mac OS/X machines with X86 or PowerPC processors.
and targets the 32-bit SPARC ABI.</p>
<p>The LLVM 1.7 release is the last release that will include the LLVM "SparcV9"
-backend, which was the very first LLVM native code generator. In 1.8, it will
-be removed, replaced with the new SPARC backend.</p>
+backend, which was the very first LLVM native code generator. It will
+be removed in LLVM 1.8, being replaced with the new SPARC backend.</p>
</div>
executed as scalar operations.</p>
<p>Because llvm-gcc3 does not support GCC generic vectors or vector intrinsics,
-so llvm-gcc4 must be used.</p>
+llvm-gcc4 must be used.</p>
</div>
</div>
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="optimizernew">Optimizer
+Improvements</a></div>
+
+<div class="doc_text">
+<ul>
+<li>The Loop Unswitching pass (<tt>-loop-unswitch</tt>) has had several bugs
+ fixed, has several new features, and is enabled by default in llvmgcc3
+ now.</li>
+<li>The Loop Strength Reduction pass (<tt>-loop-reduce</tt>) is now enabled for
+ the X86 and Alpha backends.</li>
+<li>The Instruction Combining pass (<tt>-instcombine</tt>) now includes a
+ framework and implementation for simplifying code based on whether computed
+ bits are demanded or not.</li>
+<li>The Scalar Replacement of Aggregates pass (<tt>-scalarrepl</tt>) can now
+ promote simple unions to registers.</li>
+<li>The Reassociation pass (<tt>-reassociate</tt>) can now
+ factor expressions, e.g. turning "A*A+A*B" into "A*(A+B)".</li>
+<li>Several LLVM passes are <a href="http://llvm.org/PR681">significantly
+faster</a>.</li>
+</ul>
+</div>
+
+<!--_________________________________________________________________________-->
+<div class="doc_subsubsection"><a name="codgennew">Code Generator
+Improvements</a></div>
+
+<div class="doc_text">
+<ul>
+<li>LLVM has a new prepass (before register allocation) list scheduler, which
+ supports bottom-up and top-down scheduling, pluggable priority functions and
+ pluggable hazard recognizers. The X86 backend uses this to reduce register
+ pressure and RISC targets schedule based on operation latency.</li>
+<li>The tblgen-based target description framework introduced in LLVM 1.6 has
+ several new features, useful for targets that can fold loads and stores into
+ operations, and features that make the .td files more expressive.</li>
+<li>The instruction selector is significantly faster in 1.7 than in 1.6.</li>
+<li>The X86, Alpha and Itanium backends use new DAG-DAG instruction selectors,
+ making them easier to maintain and generate slightly better code.</li>
+<li>The X86 backend now supports generation of Scalar SSE code for scalar FP
+ expressions. LLVM provides significantly better performance with Scalar SSE
+ instructions than it does with the Intel floating point stack
+ instructions.</li>
+<li>The Itanium backend now has a bundling pass, which improves performance
+ by ~10% and reduces code size (previously it unconditionally inserted a stop
+ bit after every instruction).</li>
+</ul>
+</div>
<!--_________________________________________________________________________-->
<div class="doc_subsubsection"><a name="othernew">Other New Features</a></div>
<div class="doc_text">
<ul>
-<li>foo</li>
+<li>The Mac OS/X PowerPC and X86 backends now have initial support for
+ Darwin DWARF
+ debugging information, however, debug info generation has been disabled for
+ the 1.7 release in llvmgcc4.</li>
+<li>LLVM includes the new <a href="docs/CommandGuide/html/llvm-config.html">
+ llvm-config</a> utility, which makes it easier to build and link programs
+ against the LLVM libraries when not using the LLVM makefiles.</li>
+<li>LLVM now supports first class global ctor/dtor initialization lists, no
+ longer forcing targets to use "__main".</li>
+<li>LLVM supports assigning globals and functions to a particular section
+ in the result executable using the GCC section attribute.</li>
+<li><a href="ExtendingLLVM.html">Adding intrinsics to LLVM</a> is now
+ significantly easier.</li>
+<li>llvmgcc4 now fully supports C99 Variable Length Arrays, including dynamic
+ stack deallocation.</li>
+
</ul>
</div>
<div class="doc_text">
<ul>
+<li>The official LLVM URL is now <a href="http://llvm.org/">
+ http://llvm.org/</a>.</li>
<li>The LLVM intrinsics used to be overloaded based on type: for example,
<a href="LangRef.html#int_ctpop"><tt>llvm.ctpop</tt></a> could work with any
integer datatype. They are now separated into different intrinsics with
<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>
+<li>none yet</li>
</ul>
</div>
<p>
llvm-gcc3 has many significant problems that are fixed by llvm-gcc4. See
those blocked on the <a href="http://llvm.org/PR498">llvm-gcc4 meta bug</a>.
-Two signicant ones include:</p>
+Two major ones include:</p>
<ul>
<li>With llvm-gcc3,
<div class="doc_text">
<ul>
-<li>None yet</li>
+<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
+ support the 64-bit SPARC ABI (-m64).</li>
</ul>
</div>
projects / oota-llvm.git / blobdiff