diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -9369,6 +9369,12 @@
 pointer may not be unique. The order in which memory is allocated (ie.,
 which way the stack grows) is not specified.
 
+If the returned pointer is used by :ref:`llvm.lifetime.start <int_lifestart>`,
+the returned object is initially dead.
+See :ref:`llvm.lifetime.start <int_lifestart>` and
+:ref:`llvm.lifetime.end <int_lifeend>` for the precise semantics of
+lifetime-manipulating intrinsics.
+
 Example:
 """"""""
 
@@ -18114,6 +18120,11 @@
 byte of the object or it is a stack object that is already alive, it simply
 fills all bytes of the object with ``poison``.
 
+Detection of the underlying object of ``ptr`` depends on the pattern matching
+in the stack coloring algorithm that is used in the optimization pipeline.
+``ptr`` is conservatively considered as a non-stack-allocated object if
+the stack coloring algorithm cannot conclude that ``ptr`` is a stack-allocated
+object.
 
 .. _int_lifeend:
 
@@ -18151,6 +18162,11 @@
 byte of the object, it is equivalent to simply filling all bytes of the object
 with ``poison``.
 
+Detection of the underlying object of ``ptr`` depends on the pattern matching
+in the stack coloring algorithm that is used in the optimization pipeline.
+``ptr`` is conservatively considered as a non-stack-allocated object if
+the stack coloring algorithm cannot conclude that ``ptr`` is a stack-allocated
+object.
 
 '``llvm.invariant.start``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^