https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78343
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- Previously handled by the loop_depth check I guess. Note that in void record_temporary_equivalences (edge e, class const_and_copies *const_and_copies, class avail_exprs_stack *avail_exprs_stack) { ... /* Record the simple NAME = VALUE equivalence. */ tree rhs = edge_info->rhs; record_equality (lhs, rhs, const_and_copies); /* We already recorded that LHS = RHS, with canonicalization, value chain following, etc. We also want to record RHS = LHS, but without any canonicalization or value chain following. */ if (TREE_CODE (rhs) == SSA_NAME) const_and_copies->record_const_or_copy_raw (rhs, lhs, SSA_NAME_VALUE (rhs)); we eventually (as in this case) record the same equality twice given record_equality performs canonicalization: Optimizing block #4 1>>> STMT 1 = i_6 le_expr quant_3(D) 1>>> STMT 1 = i_6 ge_expr quant_3(D) 1>>> STMT 1 = i_6 eq_expr quant_3(D) 1>>> STMT 0 = i_6 ne_expr quant_3(D) 0>>> COPY quant_3(D) = i_6 0>>> COPY quant_3(D) = i_6 Optimizing statement sum_2 = quant_3(D) * quant_3(D); Replaced 'quant_3(D)' with variable 'i_6' Replaced 'quant_3(D)' with variable 'i_6' in the IL we have a non-canonical compare: <bb 3>: # i_11 = PHI <i_6(7), 0(6)> i_6 = i_11 + 1; if (i_6 != quant_3(D)) IVOPT transforms if (quant_3(D) > i_6) goto <bb 6>; to if (i_6 != quant_3(D)) goto <bb 6>; (both just as side-notes, not really relevant to this PR).