[MC][Target] Implement support for R_X86_64_SIZE{32,64}.

Differential Revision:	D7990
Reviewed by:	rafael, majnemer

llvm-svn: 231216
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 709dc6b..049113c 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -192,6 +192,7 @@
   case VK_GOTPAGE: return "GOTPAGE";
   case VK_GOTPAGEOFF: return "GOTPAGEOFF";
   case VK_SECREL: return "SECREL32";
+  case VK_SIZE: return "SIZE";
   case VK_WEAKREF: return "WEAKREF";
   case VK_ARM_NONE: return "none";
   case VK_ARM_TARGET1: return "target1";
@@ -311,6 +312,7 @@
     .Case("gotpageoff", VK_GOTPAGEOFF)
     .Case("imgrel", VK_COFF_IMGREL32)
     .Case("secrel32", VK_SECREL)
+    .Case("size", VK_SIZE)
     .Case("l", VK_PPC_LO)
     .Case("h", VK_PPC_HI)
     .Case("ha", VK_PPC_HA)