Add an address space for the X86 SS segment.

Patch by Michael LeMay (michael.lemay@intel.com)

Differential Revision: http://reviews.llvm.org/D17093

llvm-svn: 268431
diff --git a/llvm/docs/CodeGenerator.rst b/llvm/docs/CodeGenerator.rst
index 347a372..a84645d 100644
--- a/llvm/docs/CodeGenerator.rst
+++ b/llvm/docs/CodeGenerator.rst
@@ -2197,9 +2197,9 @@
 the specified segment.  LLVM address space 0 is the default address space, which
 includes the stack, and any unqualified memory accesses in a program.  Address
 spaces 1-255 are currently reserved for user-defined code.  The GS-segment is
-represented by address space 256, while the FS-segment is represented by address
-space 257. Other x86 segments have yet to be allocated address space
-numbers.
+represented by address space 256, the FS-segment is represented by address space
+257, and the SS-segment is represented by address space 258. Other x86 segments
+have yet to be allocated address space numbers.
 
 While these address spaces may seem similar to TLS via the ``thread_local``
 keyword, and often use the same underlying hardware, there are some fundamental