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llvm-svn: 52107
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Chris Lattner 2008-06-08 22:59:35 +00:00
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@ -195,6 +195,14 @@ bugs in C and Objective-C code.</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>LLVM 2.3 includes a huge number of bug fixes, performance tweaks and minor
improvements. Some of the major improvements and new features are listed in
this section.
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="majorfeatures">Major New Features</a>
@ -261,15 +269,20 @@ bugs in C and Objective-C code.</p>
<div class="doc_text">
<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end.</p>
<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support
for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
<p>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
front-end. Objective-C now works very well on Mac OS/X.</p>
<p>
<ul>
<li>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
front-end. Objective-C now works very well on Mac OS/X.</li>
<p>Fortran EQUIVALENCEs are now supported by the gfortran front-end.</p>
<li>Fortran EQUIVALENCEs are now supported by the gfortran front-end.</li>
<p>llvm-gcc 4.2 includes many other fixes which improve conformance with the
relevant parts of the GCC testsuite.</p>
<li>llvm-gcc 4.2 includes many other fixes which improve conformance with the
relevant parts of the GCC testsuite.</li>
</ul></p>
</div>
@ -283,16 +296,18 @@ relevant parts of the GCC testsuite.</p>
<p>New features include:
</p>
Common linkage?
Atomic operation support, Alpha, X86, X86-64, PowerPC. "__sync_synchronize",
"__sync_val_compare_and_swap", etc
<ul>
<li>The C and Ocaml bindings have received additional improvements. The
bindings now cover pass managers, several transformation passes, iteration
over the LLVM IR, target data, and parameter attribute lists.</li>
<li>LLVM IR now directly represents "common" linkage, instead of representing it
as a form of weak linkage.</li>
<li>LLVM IR now has support for atomic operations, and this functionality can
be accessed through the llvm-gcc "__sync_synchronize",
"__sync_val_compare_and_swap", and related builtins. Support for atomics are
available in the Alpha, X86, X86-64, and PowerPC backends.</li>
<li>The C and Ocaml bindings have extended to cover pass managers, several
transformation passes, iteration over the LLVM IR, target data, and parameter
attribute lists.</li>
</ul>
</div>
@ -309,15 +324,18 @@ LLVM 2.3 optimizers support a few major enhancements:</p>
<ul>
<li>Loop index set splitting on by default.<p>
This transformation hoists conditions from loop bodies and reduces loop's
iteration space to improve performance. For example, <p>
<li><p>Loop index set splitting on by default.
This transformation hoists conditions from loop bodies and reduces a loop's
iteration space to improve performance. For example,</p>
<pre>
for (i = LB; i &lt; UB; ++i)
if (i &lt;= NV)
LOOP_BODY
</pre>
is transformed into
<p>is transformed into:</p>
<pre>
NUB = min(NV+1, UB)
for (i = LB; i &lt; NUB; ++i)
@ -325,7 +343,7 @@ for (i = LB; i &lt; NUB; ++i)
</pre>
</li>
<li>LLVM includes a new <tt>memcpy</tt> optimization pass which removes
<li>LLVM now includes a new <tt>memcpy</tt> optimization pass which removes
dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs
return slot optimization. The LLVM optimizer now notices long sequences of
consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li>
@ -333,14 +351,12 @@ consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li>
<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
<tt>memset</tt> is now more aggressive.</li>
<li>The aggressive dead code elimination (ADCE) optimization has been rewritten
<li>The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten
to make it both faster and safer in the presence of code containing infinite
loops. Some of its prior functionality has been factored out into the loop
deletion pass, which <em>is</em> safe for infinite loops.</li>
deletion pass, which <em>is</em> safe for infinite loops. The new ADCE pass is
no longer based on control dependence, making it run faster.</li>
<li>Several optimizations have been sped up, leading to faster code generation
with the same code quality.</li>
<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm
functions for C-based languages, has been rewritten to be a FunctionPass
instead a ModulePass. This allows it to be run more often and to be
@ -354,6 +370,10 @@ deletion pass, which <em>is</em> safe for infinite loops.</li>
<li>Several corner case bugs which could lead to deleting volatile memory
accesses have been fixed.</li>
<li>Several optimizations have been sped up, leading to faster code generation
with the same code quality.</li>
</ul>
</div>