https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126906
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Aldy Hernandez <[email protected]>: https://gcc.gnu.org/g:454e3ba345c2263563562b489bdb81fcc8e71105 commit r17-3348-g454e3ba345c2263563562b489bdb81fcc8e71105 Author: Aldy Hernandez <[email protected]> Date: Sun Aug 16 18:50:54 2026 +0000 Report failed block copies in the backward threader [PR126906] When back_jt_path_registry::duplicate_thread_path fails, the registered path is dropped silently: the dump shows "Registering jump thread" with no matching outcome. Every other way a thread dies is reported, the profitability FAILs, and the registry's other drops via cancel_thread. Report why the copy failed through cancel_thread like everywhere else. gcc/ChangeLog: PR tree-optimization/126906 * tree-ssa-threadupdate.h (back_jt_path_registry::duplicate_thread_path): Add failure_reason argument. * tree-ssa-threadupdate.cc (back_jt_path_registry::duplicate_thread_path): Set FAILURE_REASON on the two failing exits. (back_jt_path_registry::update_cfg): Cancel the path with the reason when duplicate_thread_path fails.
