Fix absolute recording of differences of symbols in two sections. Reduced from ctor_dtor_count-2.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121152 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MachObjectWriter.cpp b/lib/MC/MachObjectWriter.cpp
index d31ecef..1eb7c1c 100644
--- a/lib/MC/MachObjectWriter.cpp
+++ b/lib/MC/MachObjectWriter.cpp
@@ -884,6 +884,17 @@
       // FIXME: Currently, these are never generated (see code below). I cannot
       // find a case where they are actually emitted.
       Type = macho::RIT_Vanilla;
+    } else if (SD->getSymbol().isVariable()) {
+      const MCExpr *Value = SD->getSymbol().getVariableValue();
+      int64_t Res;
+      bool isAbs = Value->EvaluateAsAbsolute(Res, Layout, SectionAddress);
+      if (isAbs) {
+        FixedValue = Res;
+        return;
+      } else {
+        report_fatal_error("unsupported relocation of variable '" +
+                           SD->getSymbol().getName() + "'");
+      }
     } else {
       // Check whether we need an external or internal relocation.
       if (doesSymbolRequireExternRelocation(SD)) {