Add support for embedded metadata to LLVM. This introduces two new types of
Constant, MDString and MDNode which can only be used by globals with a name
that starts with "llvm." or as arguments to a function with the same naming
restriction.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68420 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/LangRef.html b/docs/LangRef.html
index cac8fc7..457a56a 100644
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -65,6 +65,7 @@
<li><a href="#globalconstants">Global Variable and Function Addresses</a></li>
<li><a href="#undefvalues">Undefined Values</a></li>
<li><a href="#constantexprs">Constant Expressions</a></li>
+ <li><a href="#metadata">Embedded Metadata</a></li>
</ol>
</li>
<li><a href="#othervalues">Other Values</a>
@@ -1847,6 +1848,14 @@
large arrays) and is always exactly equivalent to using explicit zero
initializers.
</dd>
+
+ <dt><b>Metadata node</b></dt>
+
+ <dd>A metadata node is a structure-like constant with the type of an empty
+ struct. For example: "<tt>{ } !{ i32 0, { } !"test" }</tt>". Unlike other
+ constants that are meant to be interpreted as part of the instruction stream,
+ metadata is a place to attach additional information such as debug info.
+ </dd>
</dl>
</div>
@@ -2015,6 +2024,35 @@
</dl>
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="metadata">Embedded Metadata</a>
+</div>
+
+<div class="doc_text">
+
+<p>Embedded metadata provides a way to attach arbitrary data to the
+instruction stream without affecting the behaviour of the program. There are
+two metadata primitives, strings and nodes. All metadata has the type of an
+empty struct and is identified in syntax by a preceding exclamation point
+('<tt>!</tt>').
+</p>
+
+<p>A metadata string is a string surrounded by double quotes. It can contain
+any character by escaping non-printable characters with "\xx" where "xx" is
+the two digit hex code. For example: "<tt>!"test\00"</tt>".
+</p>
+
+<p>Metadata nodes are represented with notation similar to structure constants
+(a comma separated list of elements, surrounded by braces and preceeded by an
+exclamation point). For example: "<tt>!{ { } !"test\00", i32 10}</tt>".
+</p>
+
+<p>Optimizations may rely on metadata to provide additional information about
+the program that isn't available in the instructions, or that isn't easily
+computable. Similarly, the code generator may expect a certain metadata format
+to be used to express debugging information.</p>
+</div>
+
<!-- *********************************************************************** -->
<div class="doc_section"> <a name="othervalues">Other Values</a> </div>
<!-- *********************************************************************** -->