[OpenMP] Compiler crashes when using use_device_ptr in an inheriting class

[jhuber6]

Currently, we crash on an assertion when we try to use a member from a parent class. This is caused by an assertion that the initializer of the variable is a this clause, which isn't true in this case as it is actually a cast.

class A {
public:
  double *ptr;
  virtual void foo() = 0;
};

class B : public A {
public:
  virtual void foo() override;
};

void B::foo() {
#pragma omp target data use_device_ptr(A::ptr)
  {}
}

$ clang bug.cpp -fopenmp --offload-arch=sm_80 --offload-device-only -S -emit-llvm -o -
clang-17: /root/llvm-project/clang/lib/CodeGen/CGStmtOpenMP.cpp:7149: void clang::CodeGen::CodeGenFunction::EmitOMPUseDevicePtrClause(const clang::OMPUseDevicePtrClause&, clang::CodeGen::CodeGenFunction::OMPPrivateScope&, const llvm::DenseMap<const clang::ValueDecl*, clang::CodeGen::Address>&): Assertion `isa<CXXThisExpr>(ME->getBase()) && "Base should be the current struct!"' failed.

The AST dump for the problematic expression shows

MemberExpr 0x5558ae7245b0 'double *' lvalue ->ptr 0x5558ae7053d0
`-ImplicitCastExpr 0x5558ae724590 'class A *' <UncheckedDerivedToBase (A)>
  `-CXXThisExpr 0x5558ae724580 'class B *' implicit this

This bug is reproducible from the following link https://godbolt.org/z/Kand715qs.

[llvmbot]

@llvm/issue-subscribers-clang-codegen

[llvmbot]

@llvm/issue-subscribers-openmp

[jhuber6]

Proposed fix https://reviews.llvm.org/D144873