[llvm] r196523 - Document that dllexported symbols are preserved by optimization passes.

[Yunzhong Gao]

Author: ygao
Date: Thu Dec  5 12:37:54 2013
New Revision: 196523

URL: http://llvm.org/viewvc/llvm-project?rev=196523&view=rev
Log:
Document that dllexported symbols are preserved by optimization passes.


Modified:
    llvm/trunk/docs/LangRef.rst

Modified: llvm/trunk/docs/LangRef.rst
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/LangRef.rst?rev=196523&r1=196522&r2=196523&view=diff
==============================================================================
--- llvm/trunk/docs/LangRef.rst (original)
+++ llvm/trunk/docs/LangRef.rst Thu Dec  5 12:37:54 2013
@@ -289,7 +289,9 @@ symbols from (to) DLLs (Dynamic Link Lib
     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
 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