remove anders-aa from mainline, it isn't maintained and is

tantalyzing enough that people keep trying to use it.

llvm-svn: 97483
This commit is contained in:
Chris Lattner 2010-03-01 19:24:17 +00:00
parent 80263e5905
commit 5ea3e65929
6 changed files with 2 additions and 2974 deletions

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@ -403,7 +403,7 @@ implementing, you just override the interfaces you can improve.</p>
href="#basic-aa">basicaa</a></tt> and <a href="#no-aa"><tt>no-aa</tt></a>
passes) every alias analysis pass chains to another alias analysis
implementation (for example, the user can specify "<tt>-basicaa -ds-aa
-anders-aa -licm</tt>" to get the maximum benefit from the three alias
-licm</tt>" to get the maximum benefit from both alias
analyses). The alias analysis class automatically takes care of most of this
for methods that you don't override. For methods that you do override, in code
paths that return a conservative MayAlias or Mod/Ref result, simply return
@ -703,25 +703,6 @@ loads and stores to be eliminated.</p>
non-address taken globals), but is very quick analysis.</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="anders-aa">The <tt>-anders-aa</tt> pass</a>
</div>
<div class="doc_text">
<p>The <tt>-anders-aa</tt> pass implements the well-known "Andersen's algorithm"
for interprocedural alias analysis. This algorithm is a subset-based,
flow-insensitive, context-insensitive, and field-insensitive alias analysis that
is widely believed to be fairly precise. Unfortunately, this algorithm is also
O(N<sup>3</sup>). The LLVM implementation currently does not implement any of
the refinements (such as "online cycle elimination" or "offline variable
substitution") to improve its efficiency, so it can be quite slow in common
cases.
</p>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
<a name="steens-aa">The <tt>-steens-aa</tt> pass</a>
@ -855,7 +836,7 @@ pointer.</p>
<div class="doc_text">
<p>These passes are useful for evaluating the various alias analysis
implementations. You can use them with commands like '<tt>opt -anders-aa -ds-aa
implementations. You can use them with commands like '<tt>opt -ds-aa
-aa-eval foo.bc -disable-output -stats</tt>'.</p>
</div>

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@ -75,7 +75,6 @@ perl -e '$/ = undef; for (split(/\n/, <>)) { s:^ *///? ?::; print " <p>\n" if !
<tr><th colspan="2"><b>ANALYSIS PASSES</b></th></tr>
<tr><th>Option</th><th>Name</th></tr>
<tr><td><a href="#aa-eval">-aa-eval</a></td><td>Exhaustive Alias Analysis Precision Evaluator</td></tr>
<tr><td><a href="#anders-aa">-anders-aa</a></td><td>Andersen's Interprocedural Alias Analysis</td></tr>
<tr><td><a href="#basicaa">-basicaa</a></td><td>Basic Alias Analysis (default AA impl)</td></tr>
<tr><td><a href="#basiccg">-basiccg</a></td><td>Basic CallGraph Construction</td></tr>
<tr><td><a href="#codegenprepare">-codegenprepare</a></td><td>Optimize for code generation</td></tr>
@ -202,80 +201,6 @@ perl -e '$/ = undef; for (split(/\n/, <>)) { s:^ *///? ?::; print " <p>\n" if !
Spadini, and Wojciech Stryjewski.</p>
</div>
<!-------------------------------------------------------------------------- -->
<div class="doc_subsection">
<a name="anders-aa">Andersen's Interprocedural Alias Analysis</a>
</div>
<div class="doc_text">
<p>
This is an implementation of Andersen's interprocedural alias
analysis
</p>
<p>
In pointer analysis terms, this is a subset-based, flow-insensitive,
field-sensitive, and context-insensitive algorithm pointer algorithm.
</p>
<p>
This algorithm is implemented as three stages:
</p>
<ol>
<li>Object identification.</li>
<li>Inclusion constraint identification.</li>
<li>Offline constraint graph optimization.</li>
<li>Inclusion constraint solving.</li>
</ol>
<p>
The object identification stage identifies all of the memory objects in the
program, which includes globals, heap allocated objects, and stack allocated
objects.
</p>
<p>
The inclusion constraint identification stage finds all inclusion constraints
in the program by scanning the program, looking for pointer assignments and
other statements that effect the points-to graph. For a statement like
<code><var>A</var> = <var>B</var></code>, this statement is processed to
indicate that <var>A</var> can point to anything that <var>B</var> can point
to. Constraints can handle copies, loads, and stores, and address taking.
</p>
<p>
The offline constraint graph optimization portion includes offline variable
substitution algorithms intended to computer pointer and location
equivalences. Pointer equivalences are those pointers that will have the
same points-to sets, and location equivalences are those variables that
always appear together in points-to sets.
</p>
<p>
The inclusion constraint solving phase iteratively propagates the inclusion
constraints until a fixed point is reached. This is an O(<var>n</var>³)
algorithm.
</p>
<p>
Function constraints are handled as if they were structs with <var>X</var>
fields. Thus, an access to argument <var>X</var> of function <var>Y</var> is
an access to node index <code>getNode(<var>Y</var>) + <var>X</var></code>.
This representation allows handling of indirect calls without any issues. To
wit, an indirect call <code><var>Y</var>(<var>a</var>,<var>b</var>)</code> is
equivalent to <code>*(<var>Y</var> + 1) = <var>a</var>, *(<var>Y</var> + 2) =
<var>b</var></code>. The return node for a function <var>F</var> is always
located at <code>getNode(<var>F</var>) + CallReturnPos</code>. The arguments
start at <code>getNode(<var>F</var>) + CallArgPos</code>.
</p>
<p>
Please keep in mind that the current andersen's pass has many known
problems and bugs. It should be considered "research quality".
</p>
</div>
<!-------------------------------------------------------------------------- -->
<div class="doc_subsection">
<a name="basicaa">Basic Alias Analysis (default AA impl)</a>

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@ -66,7 +66,6 @@ Almost dead code.
llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
ABCD, SCCVN, GEPSplitterPass
MSIL backend?
AndersAA -> Unsupported, zap after branch.
-->
@ -734,7 +733,6 @@ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
experimental.</li>
<li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
supported value for this option. The ELF writer is experimental.</li>
<li>The implementation of Andersen's Alias Analysis has many known bugs.</li>
</ul>
</div>

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@ -79,13 +79,6 @@ namespace llvm {
//
FunctionPass *createScalarEvolutionAliasAnalysisPass();
//===--------------------------------------------------------------------===//
//
// createAndersensPass - This pass implements Andersen's interprocedural alias
// analysis.
//
ModulePass *createAndersensPass();
//===--------------------------------------------------------------------===//
//
// createProfileLoaderPass - This pass loads information from a profile dump

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@ -46,7 +46,6 @@ namespace {
(void) llvm::createAggressiveDCEPass();
(void) llvm::createAliasAnalysisCounterPass();
(void) llvm::createAliasDebugger();
(void) llvm::createAndersensPass();
(void) llvm::createArgumentPromotionPass();
(void) llvm::createStructRetPromotionPass();
(void) llvm::createBasicAliasAnalysisPass();

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