https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119387
--- Comment #17 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:a926345f22b500a2620adb83e6821e01fb8cc8fd commit r15-9189-ga926345f22b500a2620adb83e6821e01fb8cc8fd Author: Patrick Palka <ppa...@redhat.com> Date: Thu Apr 3 16:33:46 2025 -0400 c++: P2280R4 and speculative constexpr folding [PR119387] Compiling the testcase in this PR uses 2.5x more memory and 6x more time ever since r14-5979 which implements P2280R4. This is because our speculative constexpr folding now does a lot more work trying to fold ultimately non-constant calls to constexpr functions, and in turn produces a lot of garbage. We do sometimes successfully fold more thanks to P2280R4, but it seems to be trivial stuff like calls to std::array::size or std::addressof. The benefit of P2280 therefore doesn't seem worth the cost during speculative constexpr folding, so this patch restricts the paper to only manifestly-constant evaluation. PR c++/119387 gcc/cp/ChangeLog: * constexpr.cc (p2280_active_p): New. (cxx_eval_constant_expression) <case VAR_DECL>: Use it to restrict P2280 relaxations. <case PARM_DECL>: Likewise. Reviewed-by: Jason Merrill <ja...@redhat.com>
