Bring back note about not supporting global register variables.

This was accidentally removed in r260506, even though we only support
non-allocatable global register variables. The general (allocatable) case
is explicitly not supported.

Differential Revision: https://reviews.llvm.org/D27473

llvm-svn: 289455

diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 26c8521..96b7ac9 100644 (file)
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1830,6 +1830,10 @@ extensions are not implemented yet:
      ...
      local_function(1);
 
+-  clang only supports global register variables when the register specified
+   is non-allocatable (e.g. the stack pointer). Support for general global
+   register variables is unlikely to be implemented soon because it requires
+   additional LLVM backend support.
 -  clang does not support static initialization of flexible array
    members. This appears to be a rarely used extension, but could be
    implemented pending user demand.