A common post condition of the various visitor functions in CodeGen is that instructions, that do not return any values, simply return a nullptr Value as a sentinel. This has not been the case however for calls to some builtins returning void, as well as for an initializer expression of the form `void()`. This would then lead to ICEs in CodeGen on code relying on nullptr being returned for void values, which is eg. the case for conditional expressions [0].
This patch fixes that by returning nullptr Values for intrinsics known not to return any values as well as for a scalar initializer returning void.
Fixes https://github.com/llvm/llvm-project/issues/53127
[0] 266ec801fb/clang/lib/CodeGen/CGExprScalar.cpp (L4849-L4892)
Differential Revision: https://reviews.llvm.org/D136548
