[llvm-commits] CVS: llvm/docs/BytecodeFormat.html

[Reid Spencer]

Changes in directory llvm/docs:

BytecodeFormat.html updated: 1.34 -> 1.35
---
Log message:

Document compressed bytecode details.


---
Diffs of the changes:  (+29 -2)

Index: llvm/docs/BytecodeFormat.html
diff -u llvm/docs/BytecodeFormat.html:1.34 llvm/docs/BytecodeFormat.html:1.35
--- llvm/docs/BytecodeFormat.html:1.34	Sat Nov  6 18:59:57 2004
+++ llvm/docs/BytecodeFormat.html	Mon Nov  8 02:55:21 2004
@@ -580,30 +580,57 @@
 other blocks because there is no identifier and no block length at the start
 of the block. Essentially, this block is just the "magic number" for the file.
 </p>
+<p>There are two types of signatures for LLVM bytecode: uncompressed and
+compressed as shown in the table below. </p>
 <table>
   <tbody>
     <tr>
       <th><b>Type</b></th>
-      <th class="td_left"><b>Field Description</b></th>
+      <th class="td_left"><b>Uncompressed</b></th>
+      <th class="td_left"><b>Compressed</b></th>
     </tr>
     <tr>
       <td><a href="#char">char</a></td>
       <td class="td_left">Constant "l" (0x6C)</td>
+      <td class="td_left">Constant "l" (0x6C)</td>
     </tr>
     <tr>
       <td><a href="#char">char</a></td>
       <td class="td_left">Constant "l" (0x6C)</td>
+      <td class="td_left">Constant "l" (0x6C)</td>
     </tr>
     <tr>
       <td><a href="#char">char</a></td>
       <td class="td_left">Constant "v" (0x76)</td>
+      <td class="td_left">Constant "v" (0x76)</td>
     </tr>
     <tr>
       <td><a href="#char">char</a></td>
       <td class="td_left">Constant "m" (0x6D)</td>
+      <td class="td_left">Constant "c" (0x63)</td>
+    </tr>
+    <tr>
+      <td><a href="#char">char</a></td>
+      <td class="td_left">N/A</td>
+      <td class="td_left">'0'=null,'1'=gzip,'2'=bzip2</td>
     </tr>
   </tbody>
 </table>
+<p>In other words, the uncompressed signature is just the characters 'llvm'
+while the compressed signature is the characters 'llvc' followed by an ascii
+digit ('0', '1', or '2') that indicates the kind of compression used. A value of
+'0' indicates that null compression was used. This can happen when compression
+was requested on a platform that wasn't configured for gzip or bzip2. A value of
+'1' means that the rest of the file is compressed using the gzip algorithm and
+should be uncompressed before interpretation. A value of '2' means that the rest
+of the file is compressed using the bzip2 algorithm and should be uncompressed
+before interpretation. In all cases, the data resulting from uncompression
+should be interpreted as if it occurred immediately after the 'llvm'
+signature (i.e. the uncompressed data begins with the 
+<a href="#module">Module Block</a></p>
+<p><b>NOTE:</b> As of LLVM 1.4, all bytecode files produced by the LLVM tools
+are compressed byte default. To disable compression, pass the 
+<tt>--disable-compression</tt> option to the tool, if it supports it.
 </div>
 <!-- _______________________________________________________________________ -->
 <div class="doc_subsection"><a name="module">Module Block</a> </div>
@@ -1865,7 +1892,7 @@
 <a href="mailto:rspencer at x10sys.com">Reid Spencer</a> and <a
  href="mailto:sabre at nondot.org">Chris Lattner</a><br>
 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
-Last modified: $Date: 2004/11/07 00:59:57 $
+Last modified: $Date: 2004/11/08 08:55:21 $
 </address>
 </body>
 </html>