https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70847
Patrick Palka <ppalka at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |ppalka at gcc dot gnu.org --- Comment #8 from Patrick Palka <ppalka at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #7) > Created attachment 38636 [details] > gcc7-pr70847.patch > > Untested fix. Wouldn't that cause us to fully fold only the first occurrence of a shared tree and miss folding subsequent occurrences? If we have a CALL_EXPR whose 1st and 2nd arguments share the same tree f (x * 0, x * 0); then IIUC with the patch only the 1st argument would get folded, giving f (0, x * 0); Not sure if this is an actual issue in practice, but if it is, it may be workable by maintaining the pset ourselves in cp_fold_r and doing something like if (pset->add (*stmt_p)) *walk_subtrees = 0; That way *stmt_p will still be set by cp_fold() even when it's a tree that's alraedy been visited.