Add an assertion and prefer a crash over an infinite loop.

llvm-svn: 226588

Author: adrian-prantl

llvm/lib/IR/DebugInfo.cpp

@@ -527,12 +527,15 @@ bool DISubprogram::Verify() const {
         while ((IA = DL.getInlinedAt()))
           DL = DebugLoc::getFromDILocation(IA);
         DL.getScopeAndInlinedAt(Scope, IA);
+        assert(Scope && "debug location has no scope");
         assert(!IA);
         while (!DIDescriptor(Scope).isSubprogram()) {
           DILexicalBlockFile D(Scope);
           Scope = D.isLexicalBlockFile()
                       ? D.getScope()
                       : DebugLoc::getFromDILexicalBlock(Scope).getScope();
+          if (!Scope)
+            llvm_unreachable("lexical block file has no scope");
         }
         if (!DISubprogram(Scope).describes(F))
           return false;