[polly] r264398 - www; Drop memory access documentation
Tobias Grosser via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 25 06:04:19 PDT 2016
Author: grosser
Date: Fri Mar 25 08:04:19 2016
New Revision: 264398
URL: http://llvm.org/viewvc/llvm-project?rev=264398&view=rev
Log:
www; Drop memory access documentation
This is an old google summer of code project that has been replaced completely
by our new AST generator.
Removed:
polly/trunk/www/documentation/memaccess.html
Modified:
polly/trunk/www/documentation.html
Modified: polly/trunk/www/documentation.html
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/www/documentation.html?rev=264398&r1=264397&r2=264398&view=diff
==============================================================================
--- polly/trunk/www/documentation.html (original)
+++ polly/trunk/www/documentation.html Fri Mar 25 08:04:19 2016
@@ -29,8 +29,6 @@ individual pieces of Polly</a>
</li>
<li><a href="documentation/passes.html">A list of the LLVM passes available
in Polly</a></li>
-<li><a href="documentation/memaccess.html">Polly - Memory access optimizations
-</a></li>
<li><a href="doxygen/">Doxygen documentation</a></li>
<li><a href="docs/">New SPINX based documentation (early stage)</a></li>
</ul>
Removed: polly/trunk/www/documentation/memaccess.html
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/www/documentation/memaccess.html?rev=264397&view=auto
==============================================================================
--- polly/trunk/www/documentation/memaccess.html (original)
+++ polly/trunk/www/documentation/memaccess.html (removed)
@@ -1,128 +0,0 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
- "http://www.w3.org/TR/html4/strict.dtd">
-<!-- Material used from: HTML 4.01 specs: http://www.w3.org/TR/html401/ -->
-<html>
-<head>
- <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
- <title>Polly - Memory access optimizations</title>
- <link type="text/css" rel="stylesheet" href="../menu.css">
- <link type="text/css" rel="stylesheet" href="../content.css">
-</head>
-<body>
-<div id="box">
-<!--#include virtual="../menu.html.incl"-->
-<div id="content">
- <!--*********************************************************************-->
- <h1>Memory access optimizations</h1>
- <!--*********************************************************************-->
-<p><em>WARNING: This project was part of the Google Summer of Code 2011.
-Tt is currently not finished, but it is in the design and implementation stage.
-The Ideas/Plans described here may not yet be implemented in Polly and may be
-changed during the actual implementation.</em></p>
-
-This project adds memory access transformations to Polly. In many cases
-changing the memory access pattern yields to better data locality or removes
-dependences that would otherwise block transformations.
-
-<p>An examples which uses this feature is given below.</p>
-
-Consider the following loop
-<pre>
-for (i = 0; i < 8; i++)
- sum += A[i];
-</pre>
-Through memory access transformations this loop can be executed in parallel.
-It can be transformed to
-<pre>
-<em>// Create and initialize an array 'tmp' with size 4</em>
-for (i = 0; i < 8; i++)
- tmp[i % 4] += A[i];
-sum = tmp[0] + tmp[1] + tmp[2] + tmp[3];
-</pre>
-
-Optimizers like PluTo can schedule the code such that an outer, parallel
-loop is created:
-<pre>
-parfor (ii = 0; ii < 4; ii++) {
- tmp[ii] = 0;
- for (i = ii * 2; i < (ii+1) * 2; i++)
- tmp[ii] += A[i];
- }
-sum = tmp[0] + tmp[1] + tmp[2] + tmp[3];
-</pre>
-
-<h2>TODO</h2>
-<h3>Step 1</h3>
-Polly exports its polyhedral description in a JSCoP file. Define how memory
-layout transformations are expressed in Polly and in the JSCOP file.
-Example:
-
-<p>Consider the following loop.</p>
-<pre>
-for (i = 0; i < 12; i++)
- A[i] = 0;
-</pre>
-In the JSCOP file the memory accesses are represented as follows.
-<pre>
-"accesses": [{
- "kind": "write",
- "relation": "{ Stmt[i] -> A[i] }"
-}]
-</pre>
-To perform a transformation we generate the following code:
-<pre>
-for (i = 0; i < 12; i++)
- A[0] = i;
-</pre>
-The representation in the JSCoP file is:
-<pre>
-"accesses": [{
- "kind": "read",
- "relation": "{ Stmt[i] -> A[0] }"
-}]
-</pre>
-We need to detect this access function change.
-
-<h3>Step 2</h3>
-Update the code generation module to reflect the access function change made
-in Step 1.
-<h3>Step 2.1 Code generation for a constant</h3>
-In the JSCOP file an access function which has variables is changed to a
-constant. Code is generated to reflect this change. Let the content of original
-JSCOP file be:
-<pre>
-"accesses" : [{
- "kind" : "read",
- "relation" : "{ Stmt_for_body[i0] -> MemRef_A[i0] }"
-}]
-</pre>
-The transformed JSCOP file is:
-<pre>
-"accesses" : [{
- "kind" : "read",
- "relation" : "{ Stmt_for_body[i0] -> MemRef_A[10] }"
-}]
-</pre>
-Code is generated for this change.
-<h3>Step 2.2 Code generation for coefficients</h3>
-The coefficients of induction variables are changed here. Let the original
-JSCOP file be:
-<pre>
-"accesses" : [{
- "kind" : "read",
- "relation" : "{ Stmt_for_body3[i0, i1] -> MemRef_A[32i0+i1] }"
-}]
-</pre>
-The transformed JSCOP file is:
-<pre>
-"accesses" : [{
- "kind" : "read",
- "relation" : "{ Stmt_for_body3[i0, i1] -> MemRef_A[16i0+2i1+5] }"
-}]
-</pre>
-Code is generated for this change.
-</div>
-</div>
-</body>
-</html>
-
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