https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93487
--- Comment #3 from pskocik at gmail dot com --- The gist of this along with https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93540 is "please make trivial aggregates (i.e., aggregates, which are ultimately a native type) a true zero-cost abstraction". I feel like we shouldn't have to pay for `struct Int { int _; };` (or a union of int with some <= types) over `int`, but on gcc (contrast with clang), you effectively have to: ///////////////////// int intfunc(void); int intfuncwrap(void) { return intfunc(); } => jmp 5 <intfuncwrap+0x5> ///////////////////// struct Int { int x; }; struct Int intfuncwrap2(void) { return (struct Int){intfunc()}; } => push rax call 6 <intfuncwrap2+0x6> pop rdx ret ///////////////////// Clang has been doing this right since clang 3 (and Compiler Explorer doesn't have an older version): https://gcc.godbolt.org/z/VSUHs_ . Here's a related, but opposite, example where a trivial (one-member) union gets optimized better than its contained type when used directly: https://gcc.godbolt.org/z/egXRjJ . These trivial type wrappings shouldn't affect codegen positively or negatively, but they do on gcc.
