https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94589
--- Comment #25 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:f1c777f40aa0b6941efc7440495a8d7e0cc2a1bb commit r12-964-gf1c777f40aa0b6941efc7440495a8d7e0cc2a1bb Author: Jakub Jelinek <ja...@redhat.com> Date: Fri May 21 10:39:50 2021 +0200 tree-optimization: Improve spaceship_replacement [PR94589] On Wed, May 19, 2021 at 01:30:31PM -0400, Jason Merrill via Gcc-patches wrote: > Here, when genericizing lexicographical_compare_three_way, we haven't yet > walked the operands, so (a == a) still sees ADDR_EXPR <a>, but this is after > we've changed the type of a to REFERENCE_TYPE. When we try to fold (a == a) > by constexpr evaluation, the constexpr code doesn't understand trying to > take the address of a reference, and we end up crashing. > > Fixed by avoiding constexpr evaluation in genericize_spaceship, by using > fold_build2 instead of build_new_op on scalar operands. Class operands > should have been expanded during parsing. Unfortunately this slightly changed the IL and spaceship_replacement no longer pattern matches it. Here are 3 improvements that make it match: 1) as mentioned in the comment above spaceship_replacement, for strong_ordering, we are pattern matching something like: x == y ? 0 : x < y ? -1 : 1; and for partial_ordering x == y ? 0 : x < y ? -1 : x > y ? 1 : 2; but given the == comparison done first and the other comparisons only if == was false, we actually don't care if the other comparisons are < vs. <= (or > vs. >=), provided the operands of the comparison are the same; we know == is false when doing those and < vs. <= or > vs. >= have the same behavior for NaNs too 2) when y is an integral constant, we should treat x < 5 equivalently to x <= 4 etc. 3) the code punted if cond2_phi_edge wasn't a EDGE_TRUE_VALUE edge, but as the new IL shows, that isn't really needed; given 1) that > and >= are equivalent in the code, any of swapping the comparison operands, changing L[TE]_EXPR to G[TE]_EXPR or vice versa or swapping the EDGE_TRUE_VALUE / EDGE_FALSE_VALUE bits on the edges reverses one of the two comparisons 2021-05-21 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/94589 * tree-ssa-phiopt.c (spaceship_replacement): For integral rhs1 and rhs2, treat x <= 4 equivalently to x < 5 etc. In cmp1 and cmp2 (if not the same as cmp3) treat <= the same as < and >= the same as >. Don't require that cond2_phi_edge is true edge, instead take false/true edges into account based on cmp1/cmp2 comparison kinds.
