[docs] PR15254: Add "AST" to the lexicon.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175077 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/Lexicon.rst b/docs/Lexicon.rst
index 10821f4..11f1341 100644
--- a/docs/Lexicon.rst
+++ b/docs/Lexicon.rst
@@ -15,6 +15,21 @@
**ADCE**
Aggressive Dead Code Elimination
+**AST**
+ Abstract Syntax Tree.
+
+ Due to Clang's influence (mostly the fact that parsing and semantic
+ analysis are so intertwined for C and especially C++), the typical
+ working definition of AST in the LLVM community is roughly "the
+ compiler's first complete symbolic (as opposed to textual)
+ representation of an input program".
+ As such, an "AST" might be a more general graph instead of a "tree"
+ (consider the symbolic representation for the type of a typical "linked
+ list node"). This working definition is closer to what some authors
+ call an "annotated abstract syntax tree".
+
+ Consult your favorite compiler book or search engine for more details.
+
B
-