1 files changed, 11 insertions, 5 deletions

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index cd72cc963e..b98332b3f6 100644
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -822,6 +822,12 @@ example:
     computing edge weights, basic blocks post-dominated by a cold
     function call are also considered to be cold; and, thus, given low
     weight.
+``builtin``
+    This indicates that the callee function at a call site should be
+    recognized as a built-in function, even though the function's declaration
+    uses the ``nobuiltin'' attribute. This is only valid at call sites for
+    direct calls to functions which are declared with the ``nobuiltin``
+    attribute.
 ``nonlazybind``
     This attribute suppresses lazy symbol binding for the function. This
     may make calls to the function faster, at the cost of extra program
@@ -835,11 +841,11 @@ example:
     This attribute disables prologue / epilogue emission for the
     function. This can have very system-specific consequences.
 ``nobuiltin``
-    This indicates that the callee function at a call site is not
-    recognized as a built-in function. LLVM will retain the original call
-    and not replace it with equivalent code based on the semantics of the
-    built-in function. This is only valid at call sites, not on function
-    declarations or definitions.
+    This indicates that the callee function at a call site is not recognized as
+    a built-in function. LLVM will retain the original call and not replace it
+    with equivalent code based on the semantics of the built-in function, unless
+    the call site uses the ``builtin`` attribute. This is valid at call sites
+    and on function declarations and definitions.
 ``noduplicate``
     This attribute indicates that calls to the function cannot be
     duplicated. A call to a ``noduplicate`` function may be moved