Add a common error checking for some invalid expressions.

This refactors a bit of duplicated code and fixes an assertion failure
on ELF.

llvm-svn: 306035

1 files changed, 13 insertions, 4 deletions

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 8ccdd3f5f41..758c4c708f3 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -193,14 +193,23 @@ bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
   // FIXME: This code has some duplication with recordRelocation. We should
   // probably merge the two into a single callback that tries to evaluate a
   // fixup and records a relocation if one is needed.
+
+  // On error claim to have completely evaluated the fixup, to prevent any
+  // further processing from being done.
   const MCExpr *Expr = Fixup.getValue();
+  MCContext &Ctx = getContext();
+  Value = 0;
   if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) {
-    getContext().reportError(Fixup.getLoc(), "expected relocatable expression");
-    // Claim to have completely evaluated the fixup, to prevent any further
-    // processing from being done.
-    Value = 0;
+    Ctx.reportError(Fixup.getLoc(), "expected relocatable expression");
     return true;
   }
+  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
+    if (RefB->getKind() != MCSymbolRefExpr::VK_None) {
+      Ctx.reportError(Fixup.getLoc(),
+                      "unsupported subtraction of qualified symbol");
+      return true;
+    }
+  }
 
   bool IsPCRel = Backend.getFixupKindInfo(
     Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;