[OpenMP][FIX] Remove AssertingVHs that outlive their values

[jdoerfert]

Summary

The map with AssertingVHs has been moved into the OpenMPIRBuilder which extended their lifetime.
On NVIDIA this will cause an assertion. This simply removes the AssertingVH wrapper.

[jdoerfert]

Committed via 61339427961a4399174e3e69240de7d1ad403046

clang/test/OpenMP/target_codegen_ref_assertion_vh.cpp

+// REQUIRES: nvptx-registered-target
+//
+// Test target codegen - host bc file has to be created first.
+// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple powerpc64le-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm-bc %s -o %t-ppc-host.bc
+// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple nvptx64-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda %s -fopenmp-is-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o %t.final
+// expected-no-diagnostics
+
+#pragma omp begin declare target
+constexpr int A[] = {1,2,3,4,5};
+int f(int i) { return A[i]; }
+#pragma omp end declare target

llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h

public:
   /// Add a new region that will be outlined later.
   void addOutlineInfo(OutlineInfo &&OI) { OutlineInfos.emplace_back(OI); }
 
   /// An ordered map of auto-generated variables to their unique names.
   /// It stores variables with the following names: 1) ".gomp_critical_user_" +
   /// <critical_section_name> + ".var" for "omp critical" directives; 2)
   /// <mangled_name_for_global_var> + ".cache." for cache for threadprivate
   /// variables.
-  StringMap<AssertingVH<Constant>, BumpPtrAllocator> InternalVars;
+  StringMap<Constant*, BumpPtrAllocator> InternalVars;
 
   /// Create the global variable holding the offload mappings information.
   GlobalVariable *createOffloadMaptypes(SmallVectorImpl<uint64_t> &Mappings,
                                         std::string VarName);
 
   /// Create the global variable holding the offload names information.
   GlobalVariable *
   createOffloadMapnames(SmallVectorImpl<llvm::Constant *> &Names,