[clang-offload-bundler] Fix global constants cleanup in clang-offload-bundler (intel#4356)

Author: AlexeySachkov

clang/test/Driver/clang-offload-bundler-tgtsym.c

@@ -25,9 +25,13 @@
 
 const __attribute__((opencl_constant)) char const_as[] = "abc";
 
+extern void my_printf(__attribute__((opencl_constant)) const char *fmt);
+
 extern void undefined_func(void);
 
 void foo(void) {
+  // We aim to create a gep operator in LLVM IR to have a use of const_as
+  my_printf(&const_as[1]);
   undefined_func();
 }
 

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

@@ -653,6 +653,7 @@ class ObjectFileHandler final : public FileHandler {
             // Do not add globals with constant address space to the tgtsym.
             if (!GV.isDeclaration() && !GV.hasLocalLinkage() &&
                 GV.getAddressSpace() == 2) {
+              GV.replaceAllUsesWith(UndefValue::get(GV.getType()));
               GV.dropAllReferences();
               GV.eraseFromParent();
               UpdateBuf = true;