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Fri, 12 Sep 2025 12:20:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id KAETMSYQxGjNeQAAD6G6ig (envelope-from ); Fri, 12 Sep 2025 12:20:54 +0000 Date: Fri, 12 Sep 2025 14:20:54 +0200 (CEST) From: Richard Biener To: gcc-patches@gcc.gnu.org cc: RISC-V Subject: [PATCH] Avoid VMAT_ELEMENTWISE for negative stride SLP MIME-Version: 1.0 Message-Id: <20250912122054.CF6FE136DB@imap1.dmz-prg2.suse.org> X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCPT_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[tree-vect-stmts.cc:url, imap1.dmz-prg2.suse.org:helo, imap1.dmz-prg2.suse.org:mid] X-Spam-Level: X-Spam-Score: -4.30 X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_VALIDITY_RPBL_BLOCKED, RCVD_IN_VALIDITY_SAFE_BLOCKED, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces~patchwork=sourceware.org@gcc.gnu.org The following makes us always use VMAT_STRIDED_SLP for negative stride multi-element accesses. That handles falling back to single element accesses transparently. Bootstrap and regtest running on x86_64-unknown-linux-gnu. * tree-vect-stmts.cc (get_load_store_type): Use VMAT_STRIDED_SLP for negative stride accesses when VMAT_CONTIGUOUS_REVERSE isn't applicable. --- gcc/tree-vect-stmts.cc | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc index 6168ac07b40..76c07b406b0 100644 --- a/gcc/tree-vect-stmts.cc +++ b/gcc/tree-vect-stmts.cc @@ -2026,6 +2026,7 @@ get_load_store_type (vec_info *vinfo, stmt_vec_info stmt_info, without permutation. */ if (! SLP_TREE_LOAD_PERMUTATION (slp_node).exists ()) first_dr_info = STMT_VINFO_DR_INFO (SLP_TREE_SCALAR_STMTS (slp_node)[0]); + if (STMT_VINFO_STRIDED_P (first_stmt_info)) /* Try to use consecutive accesses of as many elements as possible, separated by the stride, until we have a complete vector. @@ -2089,15 +2090,10 @@ get_load_store_type (vec_info *vinfo, stmt_vec_info stmt_info, (vinfo, stmt_info, vectype, vls_type, 1, &neg_ldst_offset); else - { - /* Try to use consecutive accesses of DR_GROUP_SIZE elements, - separated by the stride, until we have a complete vector. - Fall back to scalar accesses if that isn't possible. */ - if (multiple_p (nunits, group_size)) - *memory_access_type = VMAT_STRIDED_SLP; - else - *memory_access_type = VMAT_ELEMENTWISE; - } + /* We can fall back to VMAT_STRIDED_SLP since that does + not care whether the stride between the group instances + is positive or negative. */ + *memory_access_type = VMAT_STRIDED_SLP; } else if (cmp == 0 && loop_vinfo) {