https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104601
--- Comment #12 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:9251b457eb8df912f2e8203d0ee8ab300c041520 commit r12-7371-g9251b457eb8df912f2e8203d0ee8ab300c041520 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Feb 24 15:29:02 2022 +0100 sccvn: Fix visit_reference_op_call value numbering of vdefs [PR104601] The following testcase is miscompiled, because -fipa-pure-const discovers that bar is const, but when sccvn during fre3 sees # .MEM_140 = VDEF <.MEM_96> *__pred$__d_43 = _50 (_49); where _50 value numbers to &bar, it value numbers .MEM_140 to vuse_ssa_val (gimple_vuse (stmt)). For const/pure calls that return a SSA_NAME (or don't have lhs) that is fine, those calls don't store anything, but if the lhs is present and not an SSA_NAME, value numbering the vdef to anything but itself means that e.g. walk_non_aliased_vuses won't consider the call, but the call acts as a store to its lhs. When it is ignored, sccvn will return whatever has been stored to the lhs earlier. I've bootstrapped/regtested an earlier version of this patch, which did the if (!lhs && gimple_call_lhs (stmt)) changed |= set_ssa_val_to (vdef, vdef); part before else if (vnresult->result_vdef), and that regressed +FAIL: gcc.dg/pr51879-16.c scan-tree-dump-times pre "foo \\\\(" 1 +FAIL: gcc.dg/pr51879-16.c scan-tree-dump-times pre "foo2 \\\\(" 1 so this updated patch uses result_vdef there as before and only otherwise (which I think must be the const/pure case) decides based on whether the lhs is non-SSA_NAME. 2022-02-24 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/104601 * tree-ssa-sccvn.cc (visit_reference_op_call): For calls with non-SSA_NAME lhs value number vdef to itself instead of e.g. the vuse value number. * g++.dg/torture/pr104601.C: New test.
