[OpenCL][Docs] Describe internals of TableGen builtins
Add a high level explanation of the `-fdeclare-opencl-builtins` option.
Differential Revision: https://reviews.llvm.org/D96150
diff --git a/clang/docs/OpenCLSupport.rst b/clang/docs/OpenCLSupport.rst
index 716ce99..bf5aea1 100644
--- a/clang/docs/OpenCLSupport.rst
+++ b/clang/docs/OpenCLSupport.rst
@@ -114,6 +114,8 @@
OpenCL builtins
---------------
+**Clang builtins**
+
There are some standard OpenCL functions that are implemented as Clang builtins:
- All pipe functions from `section 6.13.16.2/6.13.16.3
@@ -129,6 +131,28 @@
enqueue query functions from `section 6.13.17.5
<https://www.khronos.org/registry/cl/specs/opencl-2.0-openclc.pdf#171>`_.
+**Fast builtin function declarations**
+
+The implementation of the fast builtin function declarations (available via the
+:ref:`-fdeclare-opencl-builtins option <opencl_fast_builtins>`) consists of the
+following main components:
+
+- A TableGen definitions file ``OpenCLBuiltins.td``. This contains a compact
+ representation of the supported builtin functions. When adding new builtin
+ function declarations, this is normally the only file that needs modifying.
+
+- A Clang TableGen emitter defined in ``ClangOpenCLBuiltinEmitter.cpp``. During
+ Clang build time, the emitter reads the TableGen definition file and
+ generates ``OpenCLBuiltins.inc``. This generated file contains various tables
+ and functions that capture the builtin function data from the TableGen
+ definitions in a compact manner.
+
+- OpenCL specific code in ``SemaLookup.cpp``. When ``Sema::LookupBuiltin``
+ encounters a potential builtin function, it will check if the name corresponds
+ to a valid OpenCL builtin function. If so, all overloads of the function are
+ inserted using ``InsertOCLBuiltinDeclarationsFromTable`` and overload
+ resolution takes place.
+
.. _opencl_addrsp:
Address spaces attribute
@@ -239,6 +263,8 @@
<https://lists.llvm.org/mailman/listinfo/cfe-dev>`_ or via `Bugzilla
<https://bugs.llvm.org/>`__.
+.. _opencl_fast_builtins:
+
Fast builtin function declarations
----------------------------------
