Index: include/llvm/MC/MCExpr.h
===================================================================
--- include/llvm/MC/MCExpr.h
+++ include/llvm/MC/MCExpr.h
@@ -188,6 +188,7 @@
     VK_GOTPAGE,
     VK_GOTPAGEOFF,
     VK_SECREL,
+    VK_SIZE,      // symbol@SIZE
     VK_WEAKREF,   // The link between the symbols in .weakref foo, bar
 
     VK_ARM_NONE,
Index: lib/MC/MCExpr.cpp
===================================================================
--- lib/MC/MCExpr.cpp
+++ 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)
Index: lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
===================================================================
--- lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
+++ lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
@@ -123,6 +123,9 @@
         case MCSymbolRefExpr::VK_DTPOFF:
           Type = ELF::R_X86_64_DTPOFF64;
           break;
+        case MCSymbolRefExpr::VK_SIZE:
+          Type = ELF::R_X86_64_SIZE64;
+          break;
         }
         break;
       case X86::reloc_signed_4byte:
@@ -144,6 +147,9 @@
         case MCSymbolRefExpr::VK_DTPOFF:
           Type = ELF::R_X86_64_DTPOFF32;
           break;
+        case MCSymbolRefExpr::VK_SIZE:
+          Type = ELF::R_X86_64_SIZE64;
+          break;
         }
         break;
       case FK_Data_4:
Index: test/MC/ELF/relocation.s
===================================================================
--- test/MC/ELF/relocation.s
+++ test/MC/ELF/relocation.s
@@ -34,6 +34,10 @@
         movl  $_GLOBAL_OFFSET_TABLE_, %eax
         movabs  $_GLOBAL_OFFSET_TABLE_, %rax
 
+        movq    $foo@SIZE + 32, %rax             # R_X86_64_SIZE64
+        movq    $foo@SIZE, %rax                  # R_X86_64_SIZE64
+        movq    $foo@SIZE - 32, %rax             # R_X86_64_SIZE64
+
 // CHECK:        Section {
 // CHECK:          Name: .rela.text
 // CHECK:          Relocations [
@@ -62,6 +66,9 @@
 // CHECK-NEXT:       0x98 R_X86_64_PC32 foo 0xFFFFFFFFFFFFFFFB
 // CHECK-NEXT:       0x9D R_X86_64_GOTPC32 _GLOBAL_OFFSET_TABLE_ 0x1
 // CHECK-NEXT:       0xA3 R_X86_64_GOTPC64 _GLOBAL_OFFSET_TABLE_ 0x2
+// CHECK-NEXT:       0xAE R_X86_64_SIZE64 foo 0x20
+// CHECK-NEXT:       0xB5 R_X86_64_SIZE64 foo 0x0
+// CHECK-NEXT:       0xBC R_X86_64_SIZE64 foo 0xFFFFFFFFFFFFFFE0
 // CHECK-NEXT:     ]
 // CHECK-NEXT:   }