https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104539
Bug ID: 104539 Summary: Failed to inline a very simple template function when it's explicit instantiated. Product: gcc Version: 11.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: cassio.neri at gmail dot com Target Milestone: --- Consider: template <int> //inline int f() { return 0; } int g() { return f<0>() + 1; } Using -O3, I'd expect f to be inlined in g and this is indeed the case: g(): mov eax, 1 ret However, if f is explicit instantiated: template unsigned f<0>(); then we get a function call (or a jmp if tail call optimisation is possible) g(): sub rsp, 8 call int f<0>() add rsp, 8 add eax, 1 ret A (quite unusual, IMHO) workaround is declaring f as inline: template <unsigned n> inline unsigned f() { return n; } https://godbolt.org/z/TarsTY3zb