Revert r137134. It breaks some code as Eli pointed out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137135 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/CBackend/CBackend.cpp b/lib/Target/CBackend/CBackend.cpp
index e4ecb9e..5b9a0a2 100644
--- a/lib/Target/CBackend/CBackend.cpp
+++ b/lib/Target/CBackend/CBackend.cpp
@@ -1817,7 +1817,7 @@
     Out << "\n\n/* Global Variable Declarations */\n";
     for (Module::global_iterator I = M.global_begin(), E = M.global_end();
          I != E; ++I)
-      if (I->isDeclaration()) {
+      if (!I->isDeclaration()) {
         // Ignore special globals, such as debug info.
         if (getGlobalVariableClass(I))
           continue;