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describe extensions to the .bc format for function/global alignment

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24217 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2005-11-06 07:20:25 +00:00
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docs/BytecodeFormat.html
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@ -992,12 +992,16 @@ platform independent module).<br>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection"><a name="globalvar">Global Variable Field</a>
</div>
<div class="doc_text">
<p>Global variables are written using an <a href="#uint32_vbr">uint32_vbr</a>
that encodes information about the global variable and a list of the
constant initializers for the global var, if any.</p>
that encodes information about the global variable, an optional extension vbr,
and a an optional initializers for the global var.</p>
<p>The table below provides the bit layout of the first <a
href="#uint32_vbr">uint32_vbr</a> that describes the global variable.</p>
<table>
<tbody>
<tr>
@ -1025,8 +1029,43 @@ follows. </td>
</tr>
</tbody>
</table>
<p>When the Linkage type is set to 3 (internal) and the initializer field is set
to 0 (an invalid combination), an extension word follows the first <a
href="#uint32_vbr">uint32_vbr</a> which encodes the real linkage and init flag,
and can includes more information:</p>
<table>
<tbody>
<tr>
<th><b>Type</b></th>
<th class="td_left"><b>Description</b></th>
</tr>
<tr>
<td><a href="#bit">bit(0)</a></td>
<td class="td_left">Has initializer? Indicates the real value of the "Has
initializer" field for the global. </td>
</tr>
<tr>
<td><a href="#bit">bit(2-4)</a></td>
<td class="td_left">Linkage type: Indicates the real value of the "linkage
type" field for the global.</td>
</tr>
<tr>
<td><a href="#bit">bit(4-8)</a></td>
<td class="td_left">The log-base-2 of the alignment for the global.</td>
</tr>
<tr>
<td><a href="#bit">bit(9-31)</a></td>
<td class="td_left">Currently unassigned.</td>
</tr>
</tbody>
</table>
<p>The table below provides the format of the constant initializers for
the global variable field, if it has one.</p>
the global variable field, if it has one (indicated by the "Has initializer"
field).</p>
<table>
<tbody>
<tr>
@ -1048,7 +1087,8 @@ numbers of the global variable's constant initializer.</td>
</div>
<div class="doc_text">
<p>Functions are written using an <a href="#uint32_vbr">uint32_vbr</a>
that encodes information about the function and a set of flags.</p>
that encodes information about the function and a set of flags. If needed,
an extension word may follow this first field.</p>
<p>The table below provides the bit layout of the <a
href="#uint32_vbr">uint32_vbr</a> that describes the function.</p>
@ -1074,9 +1114,33 @@ href="#uint32_vbr">uint32_vbr</a> that describes the function.</p>
Block</a> in the bytecode file for the function.</td>
</tr>
<tr>
<td><a href="#bit">bit(5-)</a></td>
<td><a href="#bit">bit(5-30)</a></td>
<td class="td_left">Type slot number of type for the function.</td>
</tr>
<tr>
<td><a href="#bit">bit(31)</a></td>
<td class="td_left">Indicates whether an extension word follows.</td>
</tr>
</tbody>
</table>
<p>If bit(31) is set, an additional <a href="#uint32_vbr">uint32_vbr</a> word
follows with the following fields:</p>
<table>
<tbody>
<tr>
<th><b>Type</b></th>
<th class="td_left"><b>Description</b></th>
</tr>
<tr>
<td><a href="#bit">bit(0-4)</a></td>
<td class="td_left">The log-base-2 of the alignment for the function.</td>
</tr>
<tr>
<td><a href="#bit">bit(5-31)</a></td>
<td class="td_left">Currently unassigned.</td>
</tr>
</tbody>
</table>