Index: lib/Target/X86/X86ISelDAGToDAG.cpp
===================================================================
--- lib/Target/X86/X86ISelDAGToDAG.cpp
+++ lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -727,6 +727,8 @@
       case 257:
         AM.Segment = CurDAG->getRegister(X86::FS, MVT::i16);
         return false;
+      // Address space 258 is not handled here, because it is not used to
+      // address TLS areas.
       }
 
   return true;
@@ -1424,11 +1426,13 @@
     return false;
   X86ISelAddressMode AM;
   unsigned AddrSpace = Mgs->getPointerInfo().getAddrSpace();
-  // AddrSpace 256 -> GS, 257 -> FS.
+  // AddrSpace 256 -> GS, 257 -> FS, 258 -> SS.
   if (AddrSpace == 256)
     AM.Segment = CurDAG->getRegister(X86::GS, MVT::i16);
   if (AddrSpace == 257)
     AM.Segment = CurDAG->getRegister(X86::FS, MVT::i16);
+  if (AddrSpace == 258)
+    AM.Segment = CurDAG->getRegister(X86::SS, MVT::i16);
 
   SDLoc DL(N);
   Base = Mgs->getBasePtr();
@@ -1473,11 +1477,13 @@
       Parent->getOpcode() != X86ISD::EH_SJLJ_LONGJMP) { // longjmp
     unsigned AddrSpace =
       cast<MemSDNode>(Parent)->getPointerInfo().getAddrSpace();
-    // AddrSpace 256 -> GS, 257 -> FS.
+    // AddrSpace 256 -> GS, 257 -> FS, 258 -> SS.
     if (AddrSpace == 256)
       AM.Segment = CurDAG->getRegister(X86::GS, MVT::i16);
     if (AddrSpace == 257)
       AM.Segment = CurDAG->getRegister(X86::FS, MVT::i16);
+    if (AddrSpace == 258)
+      AM.Segment = CurDAG->getRegister(X86::SS, MVT::i16);
   }
 
   if (matchAddress(N, AM))
Index: test/CodeGen/X86/movss.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/movss.ll
@@ -0,0 +1,8 @@
+; RUN: llc < %s -march=x86 | FileCheck %s
+
+define i32 @foo(i32 addrspace(258)* %p) {
+entry:
+; CHECK: movl	%ss:
+  %tmp = load i32, i32 addrspace(258)* %p
+  ret i32 %tmp
+}