Implement initial-exec TLS model for 32-bit PIC x86

This fixes a TODO from 2007 :) Previously, LLVM would emit the wrong
code here (see the update to test/CodeGen/X86/tls-pie.ll).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156611 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86MCInstLower.cpp b/lib/Target/X86/X86MCInstLower.cpp
index b578e8d..54bfce1 100644
--- a/lib/Target/X86/X86MCInstLower.cpp
+++ b/lib/Target/X86/X86MCInstLower.cpp
@@ -160,6 +160,7 @@
   case X86II::MO_INDNTPOFF: RefKind = MCSymbolRefExpr::VK_INDNTPOFF; break;
   case X86II::MO_TPOFF:     RefKind = MCSymbolRefExpr::VK_TPOFF; break;
   case X86II::MO_NTPOFF:    RefKind = MCSymbolRefExpr::VK_NTPOFF; break;
+  case X86II::MO_GOTNTPOFF: RefKind = MCSymbolRefExpr::VK_GOTNTPOFF; break;
   case X86II::MO_GOTPCREL:  RefKind = MCSymbolRefExpr::VK_GOTPCREL; break;
   case X86II::MO_GOT:       RefKind = MCSymbolRefExpr::VK_GOT; break;
   case X86II::MO_GOTOFF:    RefKind = MCSymbolRefExpr::VK_GOTOFF; break;