Another constexpr empty class tweak
Improved constexpr handling for empty class types by checking for empty fields during subobject initialization.
This commit optimizes the handling of constexpr (compile-time constant) empty classes by refining the conditions for omitting subobject constructors. It now checks for empty fields, preventing unnecessary constructor omission for non-potentially-overlapping fields of empty class types. This tweak improves code generation efficiency for constexpr contexts involving empty classes.
In Details
The change modifies init_subob_ctx in constexpr.cc to check is_empty_field instead of a broader condition. This ensures that subobject constructors are not unnecessarily omitted for non-potentially-overlapping fields of empty class types within constexpr evaluations. This is a targeted fix within the constexpr machinery, relevant to those working on compile-time evaluation within GCC.
For Context
In C++, constexpr allows certain expressions and functions to be evaluated at compile time, potentially leading to faster code execution. Empty classes are classes with no members. This commit tweaks how GCC handles the creation of empty classes within constexpr contexts. By more precisely determining when constructors can be omitted, it optimizes the generated code, potentially leading to slight performance improvements when using empty classes in compile-time computations.