Here's a brief summary on the patch: v4 (this version): - In process_bb's condition-prediction code: update equivalence-heads if value-numbers have changed, otherwise some chances can be lost.
v3 (a few minor updates): - Simplify function record_equiv_from_prev_phi_1 by removing an argument. - Fixed two small bugs that can lead to losing optimize opportunities. - Link: https://gcc.gnu.org/pipermail/gcc-patches/2021-December/586687.html v2: - Use equivalence-heads (disjoint set) to represent temporary equivalences. - Improved performance by reducing predicates-recording. - The last version and some discussion: https://gcc.gnu.org/pipermail/gcc-patches/2021-December/586116.html - Earlier discussion: https://gcc.gnu.org/pipermail/gcc-patches/2021-October/580688.html - The patch: https://gcc.gnu.org/pipermail/gcc-patches/2021-September/579607.html v1: - The initial patch (use a hashmap to store temporary equivalences): https://gcc.gnu.org/pipermail/gcc-patches/2021-June/573603.html - Updates (fixed some code-style issue) and some explanation: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575531.html - Reply from Richard: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/576185.html If the patch is considered, a following step I'm thinking is to teach PRE pass with the temporary equivalences. Currently regression test pr68619-4.c fails with the patch, because a variable's value number turns to constant, and its equivalent's head is lost in the AVAIL set. I think with this change, more partial redundancies can be found. Thanks, Di Zhao --- Extend FRE with temporary equivalences. 2021-12-24 Di Zhao <diz...@os.amperecomputing.com> gcc/ChangeLog: PR tree-optimization/101186 * tree-ssa-sccvn.c (VN_INFO): remove assertions (there could be a predicate already). (dominated_by_p_w_unex): Moved upward. (vn_nary_op_get_predicated_value): Moved upward. (is_vn_valid_at_bb): Check if vn_pval is valid at BB. (lookup_equiv_head): Lookup the "equivalence head" of given node. (lookup_equiv_heads): Lookup the "equivalence head"s of given nodes. (vn_tracking_edge): Extracted utility function. (init_vn_nary_op_from_stmt): Insert and lookup by "equivalence head"s. (vn_nary_op_insert_into): Insert new value at the front. (vn_nary_op_insert_pieces_predicated_1): Insert as predicated values from pieces. (fold_const_from_equiv_heads): Fold N-ary expression of equiv-heads. (push_new_nary_ref): Insert a back-reference to vn_nary_op_t. (val_equiv_insert): Record temporary equivalence. (vn_nary_op_insert_pieces_predicated): Record equivalences instead of some predicates; insert back-refs. (record_equiv_from_prev_phi_1): Record temporary equivalences generated by PHI nodes. (record_equiv_from_prev_phi): Given an outgoing edge of a conditional expression taken, record equivalences generated by PHI nodes. (visit_nary_op): Add lookup previous results of N-ary operations by equivalences. (insert_related_predicates_on_edge): Some predicates can be computed from equivalences, no need to insert them. (process_bb): Add lookup predicated values by equivalences. (struct unwind_state): Unwind state of back-refs to vn_nary_op_t. (do_unwind): Unwind the back-refs to vn_nary_op_t. (do_rpo_vn): Update back-reference unwind state. * tree-ssa-sccvn.h (struct nary_ref): hold a lists of references to the nary map entries. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr68619-2.c: Disable fre. * gcc.dg/tree-ssa/pr71947-1.c: Disable fre. * gcc.dg/tree-ssa/pr71947-2.c: Disable fre. * gcc.dg/tree-ssa/pr71947-3.c: Disable fre. * gcc.dg/tree-ssa/pr71947-5.c: Disable fre. * gcc.dg/tree-ssa/pr71947-7.c: Disable fre. * gcc.dg/tree-ssa/pr71947-8.c: Disable fre. * gcc.dg/tree-ssa/pr71947-9.c: Disable fre. * gcc.dg/tree-ssa/vrp03.c: Disable fre. * gcc.dg/tree-ssa/ssa-fre-100.c: New test. * gcc.dg/tree-ssa/ssa-fre-101.c: New test. * gcc.dg/tree-ssa/ssa-fre-102.c: New test. * gcc.dg/tree-ssa/ssa-pre-34.c: New test.
v4-tree-optimization-101186.patch
Description: v4-tree-optimization-101186.patch
