Document that dllexported symbols are preserved by optimization passes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196523 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index f7f83dba696ae65f62bd01cbcd72f87a9031dd91..9adbea5e9ee3d3a2d9b1b33d348e1582cad9dd91 100644 (file)
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -289,7 +289,9 @@ symbols from (to) DLLs (Dynamic Link Libraries).
     pointer to a pointer in a DLL, so that it can be referenced with the
     ``dllimport`` attribute. On Microsoft Windows targets, the pointer
     name is formed by combining ``__imp_`` and the function or variable
-    name.
+    name. Since this linkage exists for defining a dll interface, the
+    compiler, assembler and linker know it is externally referenced and
+    must refrain from deleting the symbol.
 
 It is illegal for a function *declaration* to have any linkage type
 other than ``external``, ``dllimport`` or ``extern_weak``.
@@ -501,8 +503,8 @@ variables defined within the module are not modified from their
 initial values before the start of the global initializer.  This is
 true even for variables potentially accessible from outside the
 module, including those with external linkage or appearing in
-``@llvm.used``. This assumption may be suppressed by marking the
-variable with ``externally_initialized``.
+``@llvm.used`` or dllexported variables. This assumption may be suppressed
+by marking the variable with ``externally_initialized``.
 
 An explicit alignment may be specified for a global, which must be a
 power of 2. If not present, or if the alignment is set to zero, the